Why Citrus Fruit Drops and Flowers Fail to Develop

lime-flowers-becoming-fruit-2-800 

Is your citrus tree dropping its fruit before they reach full size, or even worse, dropping the flowers before fruit even begin to form?

Trees photosynthesise to produce carbohydrates such as sugars which they store as their energy source. They can only store a finite amount, which they use to drive the growth of new leaves, branches, roots and stem. Fruiting requires a tree to divert its finite energy resources away from these vital activities into the production of flower buds, flowers and fruit.

Fruit development involves pollination followed by fertilization, growth, maturation and ripening. This process takes between 6-7 months in warmer areas, requiring a considerable amount of the trees energy resources as a result.

Trees are capable of managing their own resources, and will re-divert them in cases of emergency…

 

Fruit Drop and Plant Stress

In regions where citrus produce a single crop each year, they go through a specific sequence of growth phases as follows:

  1. Bud formation and flower initiation (mid winter)
  2. Flowering and fruit set (early spring)
  3. Fruit growth – cell division (late spring to early summer)
  4. Fruit growth – cell expansion (mid summer to early autumn)
  5. Fruit maturation (late autumn to winter)

The exception to this is in regions where multiple citrus crops are produced throughout the year. In these cases, different growth phases will be occurring simultaneously.

A citrus tree can manage its crop load quite effectively, and will only carry as much fruit as it can support. It’s natural for all citrus trees to drop excess small fruit and young blossoms in early spring to prevent overproducing. There’s no need to be too concerned about flower drop, as a citrus tree only needs 1% to 2% of the blossoms to produce a good crop, and sometimes even less than 1% is enough.

If a tree gets stressed because it doesn’t receive enough water during hot, dry windy weather, of if it is starved of nitrogen because it hasn’t been given adequate fertilizer, the fruit drop will be much heavier in spring. There can also be a minor amount of fruit drop in summer under stressful conditions.

Solution: Provide sufficient water, and water more often during hot weather and strong winds. Feed citrus with a balanced fertiliser at the start of spring (September in the Southern hemisphere,  March in the Northern hemisphere)

 

Fruit Drop and Potassium Nutrient Deficiency

Where citrus trees are bearing heavy crop loads, fruit drop can be exacerbated by low potassium levels.

Potassium, also known as potash (represented by the chemical symbol K on fertiliser labels which state an N-P-K or nitrogen-phosphorus-potassium ratio) is a primary macronutrient which is necessary for flowering and fruit formation. Next to nitrogen, plants absorb potassium in greater quantity than any other nutrient. Without potassium, trees stop flowering and fruiting, that’s what happens when they’re not fed regularly.

Before any smug horticulturist proclaims to you that potassium is not directly responsible for flowering and fruiting, let me say that as a horticulturist and biochemist, plant chemistry, like the chemistry of all living things is complex, but certain inputs are necessary to produce certain outputs, and the references I’ve cited at the end of this article support my statements!

To get into the science, Potassium (K) is Important for water, nutrient and carbohydrate movement in plant tissues. It also activates enzymes which facilitate complex chemical reactions within the plant – such as the production of starch, protein and adenosine triphosphate (ATP). The role of ATP is to transports the energy necessary for all cellular metabolic activities in all living organisms, and in plants the production of ATP can regulate the rate of photosynthesis.

Potassium also helps regulate the opening and closing of the stomata, the openings or pores on the underside of leaves by which oxygen and carbon dioxide are exchanged with the atmosphere, and the loss of water vapour through transpiration is controlled. It Increases root growth which increases nutrient uptake and improves drought resistance, and also increases resistance to frost, insects and diseases. Optimum levels of potassium levels produce uniform ripening and growth rate of fruit, as well as better food quality, flavour and grade.

Agricultural extension agencies advise that large amounts of potash are needed by most plants, and that a deficiency of potassium or inadequate amounts of the macronutrient lead to stunted plant growth and reduced yields, and that potassium levels affect not only  yield, but fruit size, juice quality and shelf life.

Since potassium plays such a key role with water regulation, a deficiency would clearly increase the stresses associated with fruit drop discussed in the previous section.

Solution: Ensure that citrus trees are fertilised with a balanced fertiliser as previously discussed. Additional potassium can be supplied by using seaweed extract (which is not fertiliser but contains a good amount of potassium), wood ashes (used in tiny quantities only as it’s very alkaline), or sulphate of potash (potassium sulphate) – all these are certified as acceptable in an organic garden.

Don’t ever use potassium chloride as it can be toxic to plants, it’s the cheap nasty alternative that fertiliser manufacturers substitute to save money!

Even if there are sufficient potassium levels in the soil, they may not be accessible to plants, unless we make certain improvements.

 

Improving Plant Uptake of Potassium

There are several factors that can affect potassium uptake by plants:

  • soil moisture
  • soil aeration and oxygen levels
  • soil temperature

Higher soil moisture levels increase potassium availability to plants by enhancing the movement of potassium to plant roots.

As soils get wetter and closer to saturation, where they become waterlogged, potassium uptake decreases, because air is excluded from wet soils and oxygen levels become very low. Air is necessary for both root respiration and potassium uptake.

All plant physiological activity, including root activity, increase as soil temperature increases, leading to increased potassium uptake, with the optimum soil temperatures being between 16-27°C (60-80°F)

Solution: Water enough but don’t overwater, and mulch the soil in late spring to keep the soil temperatures in the optimum range during very hot weather and to reduce water loss to evaporation.

 

Other Factors

Sometimes there may be several factors causing increased fruit drop in citrus. How does the fruit drop mechanism work in fruit trees?

Fruit drop (also known as fruit abscission) is regulated by the balance of two endogenous (meaning from within) plant hormones, auxin and ethylene. When the ratio of ethylene to auxin is higher, it induces the enzymes which dissolve cell wall components in the abscission zone between the fruit and stem (peduncle) at the button, which separates the fruit from the tree.

Ethylene is produced in response to stress factors such as water stress, physical injuries, frost damage, and decay of the fruit. When the fruit is injured, ethylene gas production is triggered, which may cause fruit to drop.

If citrus trees are planted in poorly drained soil, extended hot, rainy weather in late late summer to early autumn may lead to root root and cause excessive fruit drop in mature trees

Additionally, if the lower branches of the tree canopy are shaded out and don’t receive adequate light, the fruit is quite likely to be shed from those branches. Prune citrus to an open vase shape to ensure good light penetration through the canopy, which is important for even fruit ripening.

 

 

References: 

  • University of Arizona Cooperative Extension – Diagnosing Home Citrus Problems, AZ1492 April 2009 – John Begeman, Glenn Wright
  • University of Georgia Extension – Citrus Fruit for Southern and Coastal Georgia, Bulletin 804, 20154 – Gerard W. Krewer, Bob Westerfield
  • LSU AgCenter – Citrus Problems, 3/21/2015 – Daniel Gill 
  • University of Florida Institute of Food and Agricultural Sciences (IFAS) Extension – Citrus Problems in the Home Landscape, Publication #HS876 – Mongi Zekri and Robert E. Rouse
  • University of Florida Institute of Food and Agricultural Sciences (IFAS) Extension – Citrus Nutrition Management Practices, HS1292 – J. D. Burrow, T. Vashisth, M. Zekri, S. H. Futch, and A. Schumann
  • Virginia Cooperative Extension – VCE Publications / 426 / 426-613, Environmental Horticulture: Guide to Nutrient Management – Diane Relf, Extension Specialist, Horticulture, Virginia Tech
  • University of Minnesota Extension – Potassium for crop production
  • New South Wales Department of Primary Industries – Growing lemons in Australia- a production manual
  • Potassium Nutrition in Plants, Fact Sheet. A&L Canada Laboratories Inc.

 

 

 

Posted in Gardening Information, Pests, Diseases & Problems, What's New! | 2 Comments

For Melbourne Australia readers – Monash Climate Change Survey

Monash-climate-change

The Monash Climate Change Communication Research Hub are running a column under Leader Local Newspapers, featuring local climate stories from everyone across Melbourne to help improve how we understand climate change.

Changing Climates will be the first dedicated climate column in Australian newspapers. It will bring the climate discussion back into the community by publishing your opinions alongside established climate science.

If you live in Melbourne, help us improve how Melbournians understand climate change and share your experience in your local Leader newspaper by completing this quick 5-minute survey link: bit.ly/MonashCC

The answers will not be used for research purposes.

Supported by the Lord Mayor’s Charitable Foundation

 

Posted in Uncategorized, What's New! | Leave a comment

Identifying and Growing Edible Aloe Vera

edible-aloe-vera-barbadensis-800

Aloe vera is a hardy succulent semi-tropical plant which is native to North Africa and the SW Arabian Peninsula, but at the present time can almost be found worldwide. It’s a very tough plant which will grow in poor soil and hot, dry sunny  locations, but can also be grown as an indoor plant in a near a window with bright natural light

The thick leaves contain a gel which is commonly used externally to treat skin irritation, minor burns, sunburns, itching due to allergies and insect bites, sores and skin ulcers. Aloe vera is possibly the oldest and the most used medicinal plant worldwide, its recorded medicinal use dates back historically to well over 2,000 years.

There is a growing interest in the health benefits of Aloe vera juice currently, and as a result some people are deciding to grow their own plants for the purpose. It’s important to understand that there are different varieties of Aloe vera, and the common variety for burns is not meant to be eaten, it’s just meant to be applied to the skin.

Lets look at the differences between the Aloe vera varieties, so we can distinguish the edible variety from the non-edible one.

 

Which Aloe Vera Variety is Edible?

There is more than one variety of Aloe vera, and Aloe vera barbadensis miller variety is usually mentioned as the most beneficial variety of Aloe vera, and as the edible one. Trying to find this Aloe vera is made much more difficult thanks to the botanists who have made a complete mess of the names!

To quote the San Marcos Growers website article on Aloe vera:

“The scientific name assigned to this aloe has been changed several times in the last few years from Aloe vera to Aloe barbadensis and then back to Aloe vera. It seems that this controversy dates back to the two names being published a couple weeks apart back in April of 1768. In “The Illustrated Handbook of Succulent Plants: Monocotyledons” (Edited by Urs Eggli, Springer-Verlag 2001) L.E. Lewis, the author on the section Aloaceae, lists the plant as Aloe vera (Linné) Burman and notes that Linné (Carl von Linné or Carolus Linnaeus) did not pubish the combinations of Aloe vera as a numbered species and that Gilbert Westacott Reynolds in “The Aloes of tropical Africa and Madagascar” (1966) argued that the name should be A. barbadensis but had overlooked the combination published by N.L. Burman (not later than April 6, 1768), which has priority over Miller’s name [A. Barbadensis]. Lewis cites as reference for this information L.E. Newton’s article “In defence of the name Aloe vera” in the the “Cactus and Succulent Journal of Great Britain” (1979:41-2).”

Currently, according to botanists, all these names refer to the same plant:

  • Aloe vera
  • Aloe barbadensis
  • Aloe vera var. barbadensis
  • Aloe vera var. chinensis

In the real world, horticulturists and growers differentiate the edible and non-edible Aloe vera varieties in a much simpler way, even if it’s not supposedly academically correct.

  • Edible Aloe vera is referred to as Aloe vera barbadensis, Aloe barbadensis or Aloe vera barbadensis var. miller.
  • Non-edible Aloe vera is referred to as Aloe vera var. chinensis

How do we tell the different Aloe vera plants apart?

Aloe vera barbadensis var. miller has thick, wide, fleshy upright leaves which are gray-green in colour, and produces yellow flowers.

Aloe-vera-barbadensis-miller-edible-2
Aloe vera barbadensis var. miller has a green to grey-green colour and a very distinct circular rosette form

 

Aloe-vera-barbadensis-miller-edible-1
Aloe vera barbadensis var. miller closer view of the plant

 

Aloe-vera-barbadensis-miller-edible-3
Aloe vera barbadensis var. miller showing thickness of leaves

 

Aloe-vera-barbadensis-miller-edible-5
Aloe vera barbadensis var. miller showing width of leaves, exceedingly broad at the base

 

Aloe-vera-barbadensis-miller-edible-7
Aloe vera barbadensis var. miller showing width of leaves from underside

 

Aloe-vera-barbadensis-miller-edible-6
Aloe vera barbadensis var. miller plant structure, with few very thick leaves forming a rosette shape

Aloe-vera-barbadensis-miller-edible-8
Aloe vera barbadensis var. miller plant, showing the distinct difference between the spotted younger leaves, and the mature leaves, which have no spots

 

Aloe vera var. chinensis has less thick, narrow spotted leaves and produces orange flowers. This is the Aloe vera variety that is commonly sold for treating burns.

Aloe-vera-chinensis-nonedible-1
Aloe vera var. chinensis has a blue-green colour (not shown well in these photos) and a very different form, somewhat flatter and stacked rather than a rosette

 

Aloe-vera-chinensis-nonedible-2
Aloe vera var. chinensis closer view of the plant

 

Aloe-vera-chinensis-nonedible-3
Aloe vera var. chinensis showing both the mature and young leaves are spotted, leaf markings are retained right through to maturity

 

The tubular yellow or orange flowers of Aloe vera plants are grown high on long stems in spring to summer once the plants reach a certain level of maturity, usually when they’re around four years old.

A more definite way to identify the Aloe vera barbadensis Miller variety is by comparing the young and the mature leaves, they will look different. The pups (baby plants growing at the sides of the parent plant) and young leaves on the mature plants will be ‘spotted’, they will have many white or pale green markings, which will vanish as the plant matures and the leaves get larger and thicker. The leaves are also green or grey-green in colour.

With Aloe vera var. chinensis the spotted leaves will not change as they mature, the young and the mature leaves look the same, with the only difference being in their size. The leaves are a different colour, more of a blue-green.

As a side-by-side comparison, I cut a mature leaf of Aloe vera var. chinensis (it’s the narrow leaf, the non-edible variety that’s applied to the skin only), against a mature leaf of Aloe vera barbadensis var. miller growing in a large pot.

aloe-vera-varieties-comparison-chinensis-barbadensis-1
On the left, a leaf of non-edible Aloe vera var. chinensis compared to a leaf of edible Aloe vera barbadensis var. miller. Note the difference in thickness, colour and the leaf markings.

 

aloe-vera-varieties-comparison-chinensis-barbadensis-2
On the front, a narrow spotted mature leaf of non-edible Aloe vera var. chinensis compared to a much wider plain-coloured mature leaf of edible Aloe vera barbadensis var. miller behind it.

 

Growing Aloe Vera

Aloe vera grows in full sun to part shade, is very drought tolerant, and will tolerate cold, it’s hardy to -2°C (28°F). It grows naturally in hot, humid climates with high rainfall, in well drained soils with high organic matter. It does best with an annual rainfall of 500mm or more.

Even though Aloe vera will grow in most soil types, it doesn’t like ‘wet feet’, where the soil stays wet and soggy for long periods, especially during colder weather. Dig in compost before planting to help with drainage in clay and other water-retentive soils.

In locations which are too shady, Aloe vera plants becomes weak and vulnerable to disease, so it’s best to ensure they get sufficient light when grown outdoors.

When growing Aloe vera in a pot or container, it’s important to use a very well draining potting mix such as ‘cactus and succulent mix’, and most gardeners use terracotta pots to grow them in because they drain much better. Water frequently in hot, dry extreme weather as Aloe vera plants growing in pots can get quite burnt and wilted if they are in a harsh, exposed open position and their water supply runs short.

Indoors, Aloe vera is often grown in the kitchen or bathroom for emergencies to deal with minor burns and skin irritations. It will grow well near a bright window which receives midday and afternoon sun. Let the pot dry out before rewatering, and ensure that the pot doesn’t sit submerged in a saucer of water. Avoid placing plants too close to the glass as there isn’t much air circulation and a lot of localised heat build up when a strong sun shines through. The non-edible Aloe vera var. chinensis is a much better plant for growing indoors on a kitchen bench, as it’s a much smaller plant and can be kept quite compact.

With both Aloe vera varieties, harvest the older outer leaves when required. If you need to create more plants, give the plants time to grow and they’ll multiply prolifically, whether in a pot or in the ground. Gently pull up the offshoots or pups growing around the parent plant and repot them, that’s all there is to it! Propagating Aloe vera is very easy and enjoyable, and a great way to create an endless amount of plants!

 

 

Posted in Gardening Information, Health & Wellbeing, What's New! | Tagged , , , , , , , | 13 Comments

Can You Grow Grapes From Seed? Garden Mythbusting!

flame-seedless-grape-ripening

Plant propagation is the practice of creating new plants from old using a variety of techniques such as seed sowing, grafting, taking cuttings, division, marcotting, ground layering, and even tissue cell culture. Some gardeners may wonder why there’s such a wide range of propagating techniques. There are reasons, there are always reasons…

True to Seed or Not?

It sounds ideal to be able to enjoy a fruit or berry, and if we find any seeds, to plant them and create a new plant of our own from which we can harvest the exact same variety of tasty treats. Works fine with tomatoes, as any seed saver would attest to!

Unfortunately, Nature is more complicated than that. Many productive plants are not true to seed, meaning that the seeds from a particular variety of fruit for example will grow into a tree which WILL NOT produce the same fruit as the parent tree, but something which may look or taste completely different.

Why? Plants need to produce genetic variation and diversity in their offspring to ensure survival of future generations. There are exceptions, some plants and trees will grow ‘true to seed’, producing exactly the same fruit or berries as the parent plant, and therefore can be grown from seed, which we’ve discussed in the previous article – The Difference Between Seedling, Grafted and Cutting Grown Fruit Trees.

At this point you’re probably wondering how it works with grapes, so here’s the definitive explanation!

 

Growing Grapes from Seed?

Grapes come in both seeded and seedless varieties, so it stands to reason that seedless grapes need to be propagated by any means other than seed, and the industry standard method of propagation is the use of hardwood cuttings in late winter.

Seeded grapes do contain viable seeds, and planted in autumn will produce grape vine seedlings in spring. They need to be planted early because they require cold stratification, exposure to cold temperatures which will cause the seed to break out of dormancy.

Sounds good? So what’s the problem then? Well, to put it bluntly, there is a lot of inaccurate, cut-and-pasted misinformation all over the internet, especially on the topic of growing grapes from seed! Let’s look at an example which is probably the worst offender in this respect, which has been doing the rounds in the Permaculture world for the last decade –  enter the ubiquitous Concord fox grape!

 

Mythbusting Concord Grape Propagation

The permaculture community is quite fond of Concord grapes almost as much as they are of swales and herb spirals, and there are so many discussions centred around growing this grape variety from seed.

What’s so special about this grape you may ask? The Concord grape is a native American grape variety, it’s Vitis labrusca ‘Concord’ which is a different species to the European grape Vitis vinifera. It’s a cold tolerant and tough grape variety which is used for making grape juice and grape jelly. By the end of the 19th century (i.e.e the 1800s), it was the most commonly planted grape in the US. These purple grapes are thick-skinned with large seeds. The pulp, which is sweet, with a strong grape flavour, separates easily from the skin but clings to the seeds. Once the first truly successful commercial grape in the US, by today’s standards of cultivated grapes, it falls way short.

So let’s look at the history of the Concord grape to get the facts straight!

The Concord grape, Vitis labrusca ‘Concord’ is a cultivated variety of the US native wild grape Vitis labrusca hybridized (crossed) with the European grape Vitis vinifera, being genetically one-third of the latter by parentage.

To quote the University of Arkansas, Division of Agriculture, Research & Extension article Plant of the Week: Grape, Concord:

“But by lucky happenstance a resident of Concord, Massachusetts named Ephriam W. Bull (1805-1895) raised a grape seedling in his garden that tolerated the vagaries of the American climate. Bull planted a few native fox grapes, Vitis labrusca, for decoration around his new home about 1840. After raising seedlings from two generations of these plants he selected a form with large fruit he named ‘Concord.’ ”

This clearly tells us that the Concord grape variety was developed from a wild fox grapes seedling, which was then crossed with other wild fox grapes seedlings to produce this cultivated variety. It’s actually the same way all new grape varieties are always produced.

So what does this tell us? Well, to cross seedlings, they need to be different. Therefore, wild, seed-grown fox grapes have different qualities and properties from plant to plant, it’s what we call genetic variation in biology.

What happens if we take seeds from a Concord grape and plant them? We’d create new genetic fox grape variants, WHICH ARE NOT CONCORD GRAPES! They will be some other form of Vitis labrusca or hybrids of them. Think about it, if it was possible to sow fox grape seeds and create the same tasting fox grape, it would have been impossible for Ephriam W. Bull to create a new variety in the first place, as they grapes would never change… And the seedlings are all different, and it really does matter that they’re different, as he apparently had to evaluate more than 22,000 seedlings to find the variety which would be named the Concord grape. If it didn’t matter, he obviously would not have gone to that much trouble!

To throw some more facts into the circle from another credible source, this time from the Missouri Botanical Garden, Vitis labrusca ‘Concord’ article:

“‘Concord’ will not come true from seed, however, and is propagated asexually (cuttings and grafting).”

Looking up many of the University Agriculture Extension Services, I can only find that grapes are propagated by various means, except by seed, for example, from Agricultural Extension Service, The University of Tennessee article Grape Growing in Tennessee (PB 1475):

“Most grapevines, with the exception of V.vinifera varieties, are grown on their own roots. V.vinifera varieties are especially sensitive to root phylloxera, which is a threat throughout the country.Therefore, these vines are grafted onto resistant rootstocks.American bunch varieties and French-American hybrid varieties may be propagated by cuttings… Layering is the surest way to propagate all grape varieties. How-ever, it is seldom used except for varieties that do not root readily from cuttings, such as with muscadines and Cynthiana. “

Note, the reference to grafting V.vinifera (European) varieties for protection against root phylloxera is only applicable to certain locations and soil types around the world, such as Tennessee in the US. European grapes grow just fine on their own roots in Australia for example, and this is how they’re grown commercially and in viticulture.

This should hopefully settle the matter and clear up a lot of the misinformation on the subject.

 

Seed Grown Grapes?

To summarize, technically, we can grow grape vine seedlings from seed, but they aren’t the same variety as the parent vine. It’s a genetic gamble on what they will turn out to be, so unless we have plenty of space to waste and are happy to wait at least two or three years to find out what the grapes taste like, it’s kind of pointless, as the grapes may not be very palatable, or may not be edible.

So, unless you’re attempting to breed a new grape variety, don’t grow grape vines from seed, grow them from hardwood cuttings or graft them if they can’t grow on their own roots in your location.

Considering grape vines will fruit for many decades, and are quite cheap to buy, perhaps it may be way easier to just buy a growing grape vine of known variety from a garden nursery! They will pay for themselves many times over in their lifetime.

Want to propagate your own grape vine? It’s very easy.

 

How to Grow Grape Vines from Cuttings

Grapes can be propagated from cuttings taken in late winter, this prevents the cuttings from drying out during the drier winter periods.

  1. Use year old growth material for cuttings, which has matured at the end of the growing season. The wood at the end of a cane should be well matured and hardened off, without green tips. Cuttings should have at least 3-4 buds, but not more than 6-7. A good length is around 30cm (12”).
  2. To identify the top and bottom of the cutting, cut the top fairly flat and the bottom end (root side of the plant) at a sharp angle, as the cuttings won’t root if planted upside-down! It also makes it easier to push them into the propagating medium.
  3. Dip the bottom ends of the cuttings into rooting hormone – this is optional and not necessary.
  4. Fill a deep pot with a suitable propagating medium such as potting mix (or dig a narrow trench in the ground and loosen the soil if propagating in the ground). TIP: Coconut coir also works really well as a propagating medium.
  5. Take each cutting and push it into the propagating medium so that only the top two buds are unburied.
  6. Keep the propagating medium/potting mix barely moist and locate the pots of cuttings in a sheltered, protected location which preferably gets morning sun and dappled midday sun to prevent the cuttings from drying out when the leaves first emerge in spring.

You can also take very short cuttings with only one bud known as vine eyes. Make a cut 6mm (1/4”) above a bud, then make another cut 5cm (2”) below it to complete the cutting. It’s a way of making a limited amount of propagating material go much further to produce more cuttings.

Note: vine eye cuttings with their single bud only do not take root as easily as the larger 3-4 bud cuttings.
image

When propagating grapes, it’s more efficient and productive to put many vine cuttings into a larger wide container, rather than potting up cuttings singly.

When the cuttings put out their new leaves and begin to develop a decent root system, they can be transplanted into their own pots and left to grow on there. Don’t be inpatient and attempt to repot the cuttings too early, as too much root disturbance can cause the cuttings to fail. It is advisable to let the cutting grow in their pots for a year to develop really strong roots before planting them out into the groundin late winter.

 

 

Posted in Gardening Information, Permaculture, What's New! | Tagged , , , , , , , , , , | 3 Comments

Gardening Calendar (Australian Temperate Climate) – April

April brings us well into autumn, and the days are now getting shorter. While the soil is still warm, it’s a good time to plant trees, shrubs, and herbs, as their roots will have a chance to take hold before winter.

This is also the last chance to harvest fruit such as apples and pears (if they are ripe) before they’re damaged by frost. (To tell if an apple or pear is ripe, lift the fruit up gently in the palm of your hand, and give it a slight twist. Ripe fruit will come away easily with the stalk still attached to the fruit).

Things to Do This Month:

  • Plant new trees, shrubs, climbers, annuals and perennials.
  • Gather and compost autumn leaves.
  • Divide overgrown perennials, collect their seeds, prune those that have finished flowering,
  • Relocate evergreen shrubs (can be done either in autumn and early spring).
  • Prune tall shrubs to reduce their height to better resist winter winds.
  • Collect and sow seeds from berry producing trees and shrubs.
  • Propagation of hardwood cuttings is done in autumn – prune off 30cm long shoots of current season’s growth, cut off the soft growing tip, cut off the bottom end below a bud, and dip end into rooting hormone. Make a ‘slit trench’ by pushing a spade into soil and rocking it back and forth. In clay soil, add some coarse sand for drainage. Put cuttings in so 2/3 is below the soil, and press the soil down around them. Cuttings will root and be ready to plant next autumn.
  • Dig in cool season green manures that were sown in early autumn (such as rapeseed, broad beans, fenugreek, linseed, lupins, mustard, oats, subclover, and vetch) before they flower.
  • Prune brambleberries after they finish fruiting – cut out the canes that fruited, and tie in the newly grown canes to the support wires on the berry trellises.
  • Blackcurrants (and brambleberries) can be pruned from now till winter time.
  • Continue planting garlic, strawberry runners and shallot bulbs.
  • Harvest and store root crops – continue lifting beetroot and carrots and finish lifting potatoes. Leave parsnips in ground, they need some cold to taste the best.
  • Cut down asparagus foliage that has turned yellow (if it wasn’t done in March) and top-dress the asparagus crowns with compost or manure.
  • Empty compost bins into the garden to prepare soil for next season.
  • Cover ponds with netting to prevent autumn leaves rotting in the water. Also, feed the fish less food, as they are less active as the days shortens and uneaten food will foul the water.

Vegetables and Herbs to Sow:

Sow in April Harvest (weeks)
Beetroot ds 7-10
Broad beans d 12-22
Burdock d 17-18
Carrot d 12-18
Chives ds 7-11
Corn Salad d 5-8
Endive ds 10-11
Florence Fennel d 14-20
Garlic d 17-25
Kale d 7-9
Kohlrabi d 7-10
Lettuce ds 8-12
Mizuna d 35-50 days
Mustard greens d 5-8
Oregano s 6-8
Pak Choy d 6-11
Parsley ds 9-19
Peas d 9-11
Radish d 5-7
Rocket d 21-35 days
Shallots d 12-15
Silverbeet ds 7-12
Snow Peas d 12-14
Spinach d 5-11
Swedes d 10-14
Turnip d 6-9

Key:
d = sow directly into ground
s = sow in seed tray
ds = sow directly into ground or seed tray

Download printable PDF version of Gardening Calendar (Australian Temperate Climate) – April

Posted in Gardening Calendar, What's New! | Tagged | Leave a comment

How to Grow Pandan in Temperate Climates

pandan-plant-800

Pandan plant (Pandanus amaryllifolius) (Chinese Name : 班兰) is a tropical plant native to South East Asia. It’s a perennial evergreen tree with fragrantly-scented leaves, growing into a small shrub 1 – 1.6 m tall when the leaves are harvested often, or a small tree 2 – 4.5 m tall in it’s tropical native habitat. Picking the leaves prevents it from growing into a tree form and keeps it small. The plant eventually forms an upright trunk, with a canopy of long, strappy leaves with thick aerial roots hanging down from the trunk.

 

How Pandan is Used

Pandan leaves are used in South-East Asian cuisine to wrap chicken, pork, fish and glutinous rice before they are barbecued or steamed to impart the distinct and unique flavour, which is described as being a milky-sweet, floral-rose-almond-vanilla-like.The fresh or frozen leaves need to be be bruised or boiled to release their flavour, and dried pandan leaves are described as having little to no flavour at all.

In soups and stews, the leaves are tied in a knot and placed in the food as it’s cooking to give flavour and fragrance. In many dishes the leaves are cut into large pieces and cooked with the food, then removed afterwards, as they are fibrous and inedible. Pandan leaf is also used to flavour curries in Balinese, Malaysian, Sri Lankan and Thai cooking.

Fresh leaves are also used in cakes and other desserts, confectioneries (such as agar jellies) and drinks. The fresh leaves are crushed or boiled to extract the green chlorophyll pigments, which are used to colour foods bright green. Commercially produced pandan extract can also be purchased for the same purpose.

This versatile plant is also used medicinally, infusions of the leaf are used as a calming sedative for restlessness, while infusions of pandan leaf in coconut oil are rubbed on the skin to treat rheumatism. The roots contain the compound 4-hydroxybenzoic acid which is a potential anti-diabetic drug.

More than just culinary, pandan leaves have pest repellent properties too, they contain the compound 2-acetyl-1-pyrroline which is a repellant to the American cockroach (Periplaneta americana) and German cockroach (Blattella germanica).

 

Growing Conditions for Pandan

pandan-plants-tubestock

Being a tropical plant, pandan doesn’t like too much sun or wind, and is best grown in a protected, part-shade position. A position that gets direct morning sun and a bit of dappled midday sun is ideal, but keep it away from hot afternoon sun! It’s also drought and frost tender, which means that the plant wont survive dry conditions or low temperatures, so keep the soil moist during the warm seasons and protect it from the cold. In fact, if the temperature falls below 10 C°(50 F°), the plant is best moved indoors for protection in cooler climates, as the plant is damaged by temperatures of 7 C°(44.6 F°) and below.

In its natural environment, pandan prefers light well drained, moderately fertile soils. In cooler climates, grow pandan in a pot with a good quality potting mix.

Temperate Climate Warm Season: Since tropical plants grow in climates which have hot, wet, humid summers and drier cool seasons, ensure that the pandan plant is kept moist (but not wet) during hot weather periods. Do not sit the plant pot in a saucer of water, that will rot out the roots. You can use a spray bottle to mist the leaves on hot days to maintain humidity around the plant, or sit the plant on a humidity tray (see below) to maintain humidity around the plant. Having other plants around the pandan will also provide protection from winds and increase the humidity levels. Locate the plant on the east side of the house where it will mainly get morning sun, use shade-cloth (50% screening grade) to reduce the effects of sun and wind when the plant is in a more exposed location.

Temperate Climate Cool Season: When the weather begins to cool down, it’s important to reduce the amount of water, keep the soil just moist, as tropical plants dislike wet soil in cold weather. When overnight temperatures fall to 10 C°(50 F°) or below, bring the plant indoors. When day and night temperatures remain cold, keep the plant indoors until the weather warms up again. Make sure that the plant pot is placed in a location which receives good light during the day, don’t place it too close to the window, as it’s colder near the glass in winter, especially at night!

It’s important to choose the right indoor location for growing pandan, most houses have heating systems, such as ducted heating, which blows hot, dry air – this will provide the warmth but dry out and kill a pandan plant. Either choose a room with good light and no heating duct, such as a laundry perhaps, or use a humidity tray to keep the humidity levels high around the plant. Once again, you can use a spray bottle to lightly mist the plant leaves to maintain humidity levels around the plant, or sit the plant on a humidity tray to maintain humidity around the plant. If the pandan plant is kept in a cold room, don’t wet the leaves as water will sit in the spaces between the leaves and the stem, become cold water and rot the stem.

 

How to Make a Humidity Tray

Constructing a humidity tray is very simple, just take a plastic tray which can hold water, fill it with stones or pebbles, then add water below the level the top of the stones or pebbles, so that a plant pot sitting on the surface is kept out of the water below.

Water evaporating from the wet stones will increase the humidity around the plant, it’s that simple!

 

humidity-tray

For the plastic tray, a deep plastic pot saucer works well, the one pictured below is filled with scoria, which is a porous volcanic rock. Shiny pebbles work just as well, it makes no difference

humidity-tray-plant-saucer-with-scoria

 

Larger plastic trays can hold much more plants, and aggregating a number of plants together helps retain the humidity around them.

humidity-tray-with-scoria

 

Here’s a pandan potted up and sitting on a humidity tray. This can be placed near a well-lit window indoors, and an occasional topping up of the water is all that’s required. A regular misting would also help in heated areas with warm dry air, just keep the plant away from the heating ducts and the flow of air coming from them.

pandan-humidity-tray-with-scoria

To create even more humidity around the plant, use a clear plastic storage tub, place the humidity tray and the plant inside it, the surrounding walls of the container will retain a lot more humidity around the plant.

Pandan-humidity-tray-storage-tub

For those who want to go a step further, it’s possible to raise the temperature a bit more too! An electric heat mat for raising plants seedlings can be used, just sit it under the humidity tray, it will warm  the water, increase evaporation and create a nice warm humid microclimate for the pandan plant.

 

References:

National Parks Board, Singapore.Government, Flora & Fauna Web, Pandanus amaryllifolius Roxb.

 

Posted in Gardening Information, What's New! | Tagged , , , , , , , , | 4 Comments

Apple Tree Problems – Sun Scald

granny-smith-apple-sun-scald

Sun scald is not a disease, but damage caused to apples and many other fruit, caused by high temperatures and strong sunlight in summer.

Typically, sun scald damage appear on sun-exposed side, which is usually towards the direction of the midday to afternoon sun. The cells die in the sunburnt area, forming an irregularly shaped reddish-brown patch which is sunken below the surface of the fruit. The flesh underneath the damaged area also turns a brown colour. Fruit with sun scalded damage tend to drop prematurely.

Fruit are more likely to be damaged by sun-scald in hot, dry weather with continuously strong sunlight, especially in young trees where there is not much foliage covering the fruit. Heavy pruning which reduces leaf cover over fruit will cause sun scald, as will poor quality soils which don’t retain moisture, causing the tree to dry out and burn more easily.

The best way to prevent sun scald is by shading, having some form of protection from the hot west afternoon sun. This can be in the form of dappled shade provided by other trees, or by frames and structures supporting shadecloth (use 50% shading rated shadecloth for plants and trees, higher ratings are for humans only, and don’t allow sufficient light through for plants).

Fruit protection bags and tree netting covers made of insect exclusion netting with a fine 2mm mesh provide approximately 20% shade and can also protect fruit from sun scald.

Ensure that trees receive adequate nutrition so that they can put out adequate new leafy growth to protect the fruit, feed with a balanced fertilizer in at the start of spring and autumn.

Mulching the soil in late spring to prevent water evaporation from the soil is very helpful in maintaining fruit trees in general, and can reduce damage to fruit due to moisture shortage.

Another method for preventing sun scald in extremely hot dry weather is increasing the humidity around trees. This is achieved by watering the soil surface (don’t water the leaves as this may promote fungal diseases!)  with a hose, using a gentle spray. The cooling effect reduces the effects of the heat and the risk of fruit damage.

 

 

Posted in Gardening Information, Pests, Diseases & Problems, What's New! | Tagged , , , , | 2 Comments