Siberian peashrub

Siberian peashrub: how do you recognise it?

Habit

Upright shrub or small tree 3–4 m high and about 3 m wide, with grey-green branches.

Leaves

Pinnate, with 4–6 pairs of oval leaflets 1–2.5 cm long; fresh green, yellow in autumn. Deciduous.

Flowers

Yellow pea flowers about 2 cm long, singly or in small clusters beneath the leaves, in May.

Fruit

Narrow brown pods 3–5 cm long that split open in summer.

Spines

The stipules at the base of the leaves often become small, hard spines.

Roots

Deep, with nodules in which bacteria fix nitrogen from the air.

Flowering: May · Plants: March–April and October–November · Pruning: June

Why grow it?

• Extremely hardy and drought tolerant: ideal for poor, dry sandy soil.
• Fixes its own nitrogen, so fertiliser is unnecessary.
• Yellow pea flowers in May, loved by bees and bumblebees.
• A sturdy windbreak or informal hedge in an open spot.
• Finely pinnate leaves give it an airy, light character.
• The weeping forms make attractive small trees for a small garden.

Siberian peashrub: where does it grow best?

• Full sun; in shade it grows sparse and flowers poorly.
• Any free-draining soil: sand, loam or clay, acid to chalky. Poor sandy soil is no problem.
• Dry to moderately moist; it dislikes wet, stagnant soil.
• Withstands strong wind: suitable as a windbreak in an exposed spot.
• As a single shrub allow 2.5–3 m; in a hedge or windbreak, 50–70 cm between plants.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Dry or normal

Size

4 m tall, 3 m wide

Hardiness

Hardy (to -40 °C)

Goes well with

• Lilac: Flowers at the same time and is just as hardy.
• Lavender: Fragrant purple underplanting on dry soil.
• Catmint: Blue clouds at its feet in summer.
• Blue oat grass: An ornamental grass for the same dry, sunny spot.

Siberian peashrub: when and how to plant it?

Plant in March–April and October–November.

1. Plant in March–April or October–November, when the soil is not frozen.
2. Dig a hole twice as wide as the root ball; extra fertiliser or compost is not needed.
3. Set the plant at the same depth as in the pot; on a grafted tree, keep the graft union above ground.
4. Firm the soil well and water thoroughly.
5. Stake a standard for the first few years.
6. Mulch around the base to suppress weeds and retain moisture.

Care

Water

Only in dry spells during the first year. After that it fends for itself.

Feeding

Not needed: it makes its own nitrogen.

Hedge

Clip a hedge once a year, straight after flowering.

Standard

On a grafted weeping form, remove shoots growing from the stem or below the graft as soon as you see them.

Seedlings

Seedlings may come up around the shrub; pull them out while they are small.

Tip: Plant it in the driest, poorest spot in the garden, where other shrubs give up: thanks to its own nitrogen it grows there without fertiliser.

Siberian peashrub: when to prune it?

Pruning months: June.

When: After flowering, in June. It needs little pruning.

How:

• Shorten overlong shoots to just above a side shoot to keep the shape.
• Remove dead, damaged and crossing branches.
• Clip a hedge or windbreak to shape, with the base slightly wider than the top.
• Rejuvenate an old, bare shrub by cutting a few old stems back low; it reshoots well.

Caution: Prune a weeping form only lightly and do not cut all the hanging shoots to the same length, or it will lose its natural shape.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Soak the seed overnight in lukewarm water and sow in spring in a tray or an outdoor seedbed. It germinates readily.

Softwood cuttings

In June–July, 10 cm cuttings from young shoots, in moist cutting compost under plastic. They root within a few weeks.

Siberian peashrub: how does it get through the winter?

Hardy to −40 °C.

• Extremely hardy, to about −40 °C: no protection is ever needed in Belgium.
• Even in a pot it can stay outdoors; just make sure it drains well.
• Wet soil in winter is the only real risk.

Diseases and pests

• Aphids: On young shoots in spring. Ladybirds usually deal with them; otherwise hose them off.
• Wet feet: Yellow leaves and dying shoots on heavy, wet soil. Move it to a drier, free-draining spot.
• Seedlings: Many seedlings sometimes come up under and around the shrub. Pull them out while young.
• Wild shoots: On grafted weeping forms, upright shoots sometimes grow from the stem. Cut them off at the base straight away.

Through the year

• March: Plant.
• April: Plant. Water young plants in dry weather.
• May: In flower. Bees and bumblebees.
• June: Prune after flowering. Take softwood cuttings.
• July: Pods ripening. Pull out seedlings.
• August: Pods split open. Collect seed.
• October: Plant. Yellow autumn colour.
• November: Plant.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• On the prairies of Canada and the United States it was planted on a large scale as a windbreak around fields and farms.
• On warm summer days the ripe pods split open with an audible snap, flinging out their seeds.
• Like peas and beans, it lives together with bacteria in root nodules that fix nitrogen from the air.