Permaculture Plants – Australian Indigo, the Nitrogen Fixing Tree for Small Sites, an Alternative to Tagasaste for Urban Gardens

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In permaculture, tagasaste (tree lucerne) is used as a nitrogen-fixing tree on large sites and rural properties, but it can grow around 5-7m tall and equally wide, which is way too large for smaller urban properties. Luckily for Australian permaculture gardeners, we have a much smaller nitrogen-fixing tree available which works much better in small-scale gardens.

Indigofera australis, also known as Australian Indigo or Austral Indigo, is an attractive ornamental native Australian evergreen shrub varying in size and  habit, growing 1-2m tall and equally wide, more typically closer to 2m tall and wide in size. It’s also from the Fabaceae (legume) family, just like tagasaste, and is a nitrogen-fixing plant, which can be used to increase soil fertility, and as a nurse crop tree to protect growing young trees.

The delicate looking pinnate blue-green foliage can be lightly pruned to create a showy specimen or feature plant in a garden. During spring, bright pink to purple flowers are produced in long spires, which are a good nectar source and attract bees, butterflies, nectar-eating birds and other beneficial insects.

The leaves and stems can be used for making natural dyes, giving a range of colours from soft yellows through to light blues, depending on the plant growing conditions and the dyeing technique used.

The indigenous people of Australia used the crushed leaves of Indigofera australis to throw into the water to kill or stun fish and eels, and also placed roots which were hammered in salt or fresh water to poison fish.

This shrub can be used as a low windbreak, and it will tolerate extended wet periods and saline soils.

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The pink-mauve pea-like flower of Australian indigo is attractive to bees, butterflies and nectar-eating birds

This Australian native shrub is fairly hardy, being reasonably drought tolerant and able to handle light to moderate frosts. It will grow in full sun or light shade in most soil types, ranging from sandy soil to clay loam. It is adaptable to a wide range of climates, from sub-tropical, through to temperate and cool and even semi-arid. It’s best pruned lightly, don’t cut into old wood as it won’t regrow. It can be propagated from seed, division or by taking semi-hardwood cuttings.

Indigofera australis is capable of regenerating after fire, which breaks the dormancy of seeds in the soil, but it can also regrow by suckering from the roots that stay alive below the ground.

It’s easy to grow, and can be grown amongst fruit trees without any problem., I have mine growing in a food forest garden between two young dwarf citrus trees and an apple tree, in a full-sun location, and it flowers prolifically, attracting lots of bees. It’s not phosphorus sensitive like some Australian native plants (such as those from the Proteaceae family) so it doesn’t need any special care or native fertiliser formulations.

 

Propagation

Propagation of Indigofera australis is done from seed, but the seeds have a thick seed coat and seed treatment is required to break the physical dormancy.

Two methods of seeds treatment are described as follows:

  1. Scarifying – the seeds can be scarified by contact with an abrasive surface, such as fine sandpaper.
  2. Hot water treatment – this involves dropping the seeds into a container, filling it with boiling water, then and allowing the seeds to soak in the water overnight as it cools. Seeds that swell larger than their original size can be sown, while seeds which stay floating can be discarded as they’re usually infertile.

After sowing the seeds, germination should take around 3-4 weeks. The season to sow seeds is in late winter to early spring.

Indigofera australis can also be propagated from cuttings, and being evergreen would be propagated using softwood cuttings in early spring.

 

 

About Angelo (admin)

Angelo Eliades is a presenter, trainer, writer, permaculture consultant, urban permaculture pioneer and food forest specialist.
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5 Responses to Permaculture Plants – Australian Indigo, the Nitrogen Fixing Tree for Small Sites, an Alternative to Tagasaste for Urban Gardens

  1. naturewalker7 says:

    Hi Angelo, I love your well thought through articles. Being in the ‘northern climes’ with a foot of snow on the ground today and zone 4-5, it’d be great if you included growing zones with your plants recommendations. The indigo looks wonderful but I’m not sure if it will grow here.

    Thanks a bunch and keep it ALL up! Kristin from Idaho

    On Tue, Dec 10, 2019 at 4:00 AM Deep Green Permaculture wrote:

    > Angelo (admin) posted: ” In permaculture, tagasaste (tree lucerne) is used > as a nitrogen-fixing tree on large sites and rural properties, but it can > grow around 5-7m tall and equally wide, which is way too large for smaller > urban properties. Luckily for Australian permacultur” >

    Like

  2. Colleen says:

    Hello Angelo
    I’m on the Fleurieu Peninsula, near the coast. Are the Australian Indigo and Tagasaste trees fast growing? We would like to plant a windbreak on the western side of our property and also attract bees to our garden. Could you also suggest any other trees that might be suitable to grow in our sandy soil, please? Thanks for your newsletter, so informative!

    Like

    • Angelo (admin) says:

      Hi Colleen, yes, they’re both very fast growing and make excellent windbreaks. and tagasaste are are also fire retardant trees which are planted as firebreaks in bush fire-prone areas. Acacias (wattles) will also establish quickly, they’re also nitrogen fixing, and can provide protection to establish longer-lived trees.

      Liked by 1 person

  3. I believe that they make excellent stock feed as well. Tagaste are certainly a very useful plant!

    Like

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