How to Plant, Grow and Harvest Potatoes

Potatoes (Solanum tuberosum) are a herbaceous, perennial, root-crop plant from the Solanaceae (Nightshade) family that grow to around 60cm (24”) high, and are native to Central and South America. They originated in the Andean highlands almost 10,000 years ago, but have naturalised widely and spread to all continents, growing in climates ranging from temperate to tropical.

When potato plants grow, they produces enlarged underground stems known as the tubers, which store the plant’s food reserves in the form of starch granules, which enable them to survive the cold when the plant dies down above the ground in winter. These starchy tubers are the edible part of the plant, and the portion of the plant used for vegetative plant propagation.

The humble potato is an extremely important cool-season vegetable crop in temperate climates, it ranks as the world’s fourth largest food crop after corn, wheat and rice, and is therefore one of the most important staples in the human diet.

Can You Grow Potato From Seed?

Potatoes do actually produce small red fruit which look like tiny cherry tomatoes, and each of these fruit contain viable seed.

The problem is that potatoes are not true-to-seed, meaning that plants grown from seeds will turn out to be different varieties from their parent plant, they show wide genetic variations, and can have poor vigour and lower yields. The propagation of potatoes from seed is also a very time-consuming and labour-intensive process.

For these reasons, potatoes are usually grown from seed potatoes, these are tubers specifically grown to be disease-free, and will produce healthy plants which are clones of the parent plants.

How to Chit Potatoes and is it Really Necessary?

In many gardening books you’ll read about the practice of chitting potatoes before planting them, which simply means encouraging the potatoes to sprout, that’s all!

To chit potatoes, just place them in an open egg carton or tray, with the ‘rose end’ which has the most buds pointing upwards. Put these potatoes in a well-lit but not sunny location which is frost free, such a a room inside the house, and leave them there for around 6 weeks, after which many strong shoots around 1-2.5cm (1/2 – 1”) will emerge.

Sprouting usually happens accidentally when seed potatoes are kept too long in a warm location, so if sprouts emerge, it’s still okay to plant the potatoes. In fact, it’s better to plant them sooner rather than later if they’ve sprouted, because the tubers will begin to lose moisture more quickly, which will show because they’ll begin to wrinkle and soften. I prefer to plant potatoes with the shoots below the soil level if they’re short, as this protects them from the cold till they harden off.

This practice is meant to give potatoes an early start, and may be useful in extremely cold climates, but is usually unnecessary in most locations, so there’s not need to fuss over this practice.

Do Potatoes Need to Be Cut Before Planting?

Another common practice with potato growing is to cut the seed potatoes into pieces which have at least one or two ‘eyes’ or buds before planting. This is a propagation method use to produce more plants, as each section will sprout for the eyes and develops into a new plant.

Seed potatoes larger than 110 grams (3.9 oz) can be cut into pieces as long as each piece has at least two eyes on each part. The energy stored in the potato tuber will drive the growth of the plant, so it’s counter-productive to cut small seed potatoes, as they won’t grow as strongly.

If potatoes are cut, they need to be planted immediately, preferably into a warm, moist soil, so they don’t dry out from the exposed cut area.

When seed potatoes are planted in cold, wet ground, they shouldn’t be cut, but planted whole.

When Is the Best Time to Plant Potatoes?

Potatoes can be planted from late winter through to late summer, which corresponds to:

• August to February in the southern hemisphere (Australia, New Zealand, etc)
• February to August in the northern hemisphere (US, UK, etc)

Plant seed potatoes directly where they will be grown, and they will be ready to harvest in 15-20 weeks, or 4-5 months.

In Melbourne, Australia, they’re planted in August, the last month of winter, and they’re usually ready to harvest in March, the first month of autumn.

Crop Rotation of Potatoes

Potatoes are members of the Solanaceae family, which includes Eggplants, Capsicums, Chillies and Tomatoes. Being from the same family, these crops are prone to many common pests and diseases, and use up soil nutrients in a similar way.

The practice of crop rotation is used to prevent localised nutrient depletion, and to avoid the build-up of pests and diseases in a garden bed. How do we implement crop rotation when growing potatoes?

• Never plant potatoes in a garden bed that has grown potatoes or any other members of the same family for 3 years in a row.
• Don’t plant root crops in a garden bed previously used to grow root crops (i.e. potatoes after carrots or beetroot).

Ideally, it’s preferable to grow potatoes in a spot where members of the same family were not grown in the last year.

Site Selection and Soil Preparation Potato Growing

Potatoes can be grown in garden beds, or in containers such as large pots 40-50cm (16-20”) wide or even larger 100L (20 gallon) grow bags. Large containers are needed to grow potatoes because they’re root crops which require a good depth and volume of growing medium.

Fill containers with potting mix/potting medium only, don’t use soil, it’s too dense and gets waterlogged in containers! In terms of initial fertilising, a good, premium quality potting mix will usually contain enough fertiliser to last approximately for the first three months, so there’s no need to add any extra fertiliser at the start.

When planting potatoes in the garden, select a sunny garden location where members of the same Solanaceae family haven’t been grown for the past year.

Loosen the soil to a depth of around 25cm (10”), mixing in compost to improve soil structure and manure or some form of balanced fertiliser to restore fertility. Add twice as much compost as manure, and mix in to make the soil more friable (loose) so the roots can push more easily through the soil.

How to Plant Potatoes, a Step-by-Step Guide

In these instructions the photos show container planting, but I’ll also explain planting in the ground, as it’s not that different.

For container planting, you’ll just need a hand trowel, but for garden bed planting, you’ll probably need a garden spade.

Step 1. Prepare the Planting Holes or Furrows

Potatoes need to be planted below the soil, but not too deep.

• In containers, just use the hand trowel to make a hole 10 cm (4”) deep.
• For garden beds, make long furrows or trenches 10 cm (4”) deep, spaced 75 cm (30”) apart.

Step 2. Place Tubers Into Planting Holes or Furrows

When planting potatoes, make sure that the rose end of the potato with the most eyes (buds) is facing upwards.

• In containers, place the potato into the planting hole, so that the shoots are just below the level of the potting mix.
• For garden beds, place seed potatoes 25cm (10”) apart along the trench. If you like, you can also sprinkle some balanced fertiliser high in phosphorus between the evenly spaced potatoes at this point.

A few gardening tips. Small potatoes such as these Kipfler potatoes can be spaced fairly closely in containers, as pictured below.

Also, when planting potatoes in the ground, if you’re not into digging, or practise no-dig gardening, and your soil is rich and friable, or was prepared previously in late winter, you can use a large bulb planter to make the holes for the potato tubers, as they’re not too dissimilar to flower bulbs.

Step 3. Cover Seed Potatoes With Soil

Gently cover the potatoes with soil till they are completely below the soil, and don’t compact down the soil above them, leave it loose so the shoots can easily push through the soil.

Step 4. Water In

Water the planted seed potatoes to settle them into the soil and provide them with the moisture they need.

Use a watering can with a rose fitting or a hose fitting that provides a gentle shower setting to water in the potatoes, avoid too much pressure as you don’t want to wash away the top soil level and uncover them.

After a few weeks, the potato plants will emerge from the soil and begin to grow! This photo was taken three weeks after planting.

Once the plants shoot up, they will start growing rather quickly and put on lots of new growth in weeks. This photo was take one week later.

Feeding Potatoes, Choosing the Right Fertiliser

Once the potatoes are planted, it’s just a matter of waiting for them to shoot up from the ground once the weather warms up.

To care for the plants and support their growth, add a solid (powder, pellet or prill) slow-release fertiliser at the start of spring when the plants start growing, and to maximise productivity, add fertiliser every 6-8 weeks during the growing season. Liquid fertilisers should only be used as a top-up supplementary feed, they wash out easily and aren’t long-acting.

The nutrient phosphorus is used by plants for root formation, stem growth, and fruiting, so it’s particularly important to all root crops, including potatoes. It’s best to use a balanced fertiliser which will normally contain ample phosphorus, but will also provide all necessary nutrients in the right amounts.

Fertilisers such as chicken manure or blood & bone are particularly phosphorus-rich, and are great for use around root crops.

Companion Plants for Potatoes

Many plant do much better in the garden when grown alongside other plants, these plants are referred to as good companions in the practice of companion planting.

Conversely, some plants are detrimental to each other’s health when grown close together, and can also spread diseases to each other, so are best kept apart from each other, these are known as bad companions.

Good Companions: Broad Beans, Cabbage, Eggplant, Foxgloves, Green Beans, Horseradish, Marigolds, Nasturtiums, Peas, Sweetcorn

Bad Companions: Apples, Cherries, Cucumbers (with any but not early crops), Pumpkins, Sunflowers, Tomatoes, Raspberries, Rosemary

When Are Potatoes Harvested?

Potatoes are usually ready to harvest in 15-20 weeks, or 4-5 months after they’re planted. Depending on the timing, potatoes can be harvested early while the plant is still growing in midsummer, which is the month of January in the southern hemisphere or July in the northern hemisphere.

To harvest potatoes early, dig along the side of the plant and work through the soil sideways until potatoes are found, then harvest a only few potatoes without disturbing the rest of the plant. This is easier when potatoes are mounded or grown in mesh frames.

Normally, when the weather cools down and the potato plants die down, the potatoes are then ready to harvest, as all the nutrients have been diverted from the plants into the tubers.

References

• The Encyclopedia of Food and Health, 2016 – Potato Plant and Tubers by P. Padmanabhan and G. Paliyath
• The Encyclopedia of Food and Health, 2016 – Potatoes and Related Crops: Role in the Diet by S. Turner
• Government of Western Australia, Department of Primary Industries and Regional Development, Agriculture and Food division – Mid West potatoes: soil and fertiliser management, December 2014