Sturt's Desert Pea

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Trevor Australis

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Sturt's Desert Pea
« on: February 12, 2013, 08:32:39 AM »
I was talking to a friend a few days back as we stood admiring his stand of Sturt's Desert Pea in bloom: two shades of scarlet with black/purple keels and a glorious pink form. He said that he'd collected the seeds from near Roxby Downs in the far northe of South Australia. Then he commented that they don't germinate until after a really heavy rain - say around 4 inches he said, at which time the red pure sand soil is thoroughly saturated. The peas, which may have lain dormant for some years, germinate within days and grow extremely rapidly and begin flowering after only two weeks or so. They rush to produce seed in vegetable anticipation of no further rains arriving to sustain them. He also commented that seed sown in the green also germinates very rapidly. Otherwise he told me the dry seeds need to be nicked with a razor blade or scapel. The technique is to form the point of a pencil into a chisel shape and use this to hold the seed firm while making the nick. Soaking the seeds for 24-48 hrs in water that starts out warm can also help the nicked seeds to swell and commence germinating. I observed his peas were planted on a mound of sharp, fine sand built on a base of rocky rubble. He waters his plants only at the roots by inserting a 7cm tube alongside each plant and placing inside it one spaghetti tube from his irrigation system. He turns the system on as he judges it is needed - usually about once a week. He aims to keep the plants growing strongly until seed pods have swollen and begun to dry off. It is important to bag the pods while they are still greenish yellow o/wise they pop unexpectedly and the seeds are dispersed by ants.  tn
M Land. Arch., B. Sp. Ed. Teacher, traveller and usually climate compatible.

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Alisdair

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Re: Sturt's Desert Pea
« Reply #1 on: February 12, 2013, 09:52:00 AM »
Very interesting! At the MGS meeting in Adelaide last October Greg Kirby gave us an intriguing talk about this capricious, fascinating plant. You and your fellow-Australians will know exactly what it looks like, as it's the state flower of South Australia and stylised representations of the flower crop up all over the place, especially on bank signs.
But here in Europe it's virtually unknown. It is one of the most striking plants we saw in Australia, so here's a picture I took (in the magnificent new botanic garden at Cranbourne):
Alisdair Aird
Gardens in SE England (Sussex); also coastal Southern Greece, and (in a very small way) South West France; MGS member (and former president); vice chairman RHS Lily Group, past chairman Cyclamen Society

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Alisdair

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Greg Kirby's advice on growing Sturt's Desert Pea
« Reply #2 on: February 13, 2013, 02:09:23 PM »
Greg Kirby's talk to the MGS in Adelaide about Sturt's Desert Pea included many useful practical tips. Several underline the points made already by Trevor.
Greg said that it normally grows on rich alkaline soils, often clay, with a pH of around 8, often with iron oxide, phosphorus and potash. As Trevor says, it germinates when the soil is thoroughly wet, with follow-up rain.
Only about 10% of wild-collected seed is viable. If the seed is not fresh, Greg recommended abrading it, and soaking it before sowing - not in boiling water, but 90 deg C for two minutes is good. The soil must be above 20 deg C for germination, and the plants really need temperatures of 32 deg C or above to grow on well. In the Mediterranean Greg thought it unlikely to succeed in the open ground North of a line from Tangier and Tunisia to Cyprus.
The plants can take an amazing amount of heat if given water, and while growing in good heat should be watered at dawn and dusk.
Don't disturb the roots, and don't shade the plants at all - avoid trees and shrubs. If there are mycorrhizal fungi in the soil, the plants should nodulate, but they do respond well to fertiliser, needing need NPK, iron and calcium. Liquid fertilisers give them a good boost.
Greg said that if you can get them you should always plant more than the number you actually want. And in the open ground, grow in a different spot each year.
If the plants are in pots, they must be given nitrogen, and need big pots.
Pests love it, he said, particularly red spider mite.
They can be grafted, and grow well on Colutea rootstocks (back in the 1870s/1880s Clianthus and Sutherlandia were used too).
Interestingly, Greg said that Sturt's Desert Pea used to be cultivated quite widely in Europe (including the UK), certainly from1858 onwards. Yet it's very rarely seen here now.
Alisdair Aird
Gardens in SE England (Sussex); also coastal Southern Greece, and (in a very small way) South West France; MGS member (and former president); vice chairman RHS Lily Group, past chairman Cyclamen Society