Clammy Locust, Hartweg's locust
Robinia viscosa

Family: Fabaceae or Leguminosae

What it is like

Robinia viscosa is a deciduous Tree growing to 13 m (42ft 8in) at a medium rate. See above for USDA hardiness. It is hardy to UK zone 3. It is in flower from May to June. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects. It can fix Nitrogen. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers dry or moist soil and can tolerate drought. It can tolerate atmospheric pollution.

Height (m): 13

Where it is found

Dry open woodland and hillside scrub to 1200 metres.

South-eastern N. America - Pennsylvania to Alabama.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 0

Medicine

Rating: 0

Other

Rating: 3

Plants produce an extensive suckering root system and can be used for soil stabilization on banks etc. The flowers are a rich source of nectar for bees. Wood - heavy, hard, close-grained. The wood weighs 50lb per cubic foot.

Soil stabilization: Plants that can be grown in places such as sand dunes in order to prevent erosion by wind, water or other agents.

Food Forest: Plants for Edible Forest Gardens and Food Forests.

Nitrogen Fixer: Plants that fix nitrogen in the soil

How it is grown

Succeeds in any soil, preferring one that is not too rich. Requires a well-drained soil, succeeding on dry barren sites. Plants are tolerant of drought and atmospheric pollution. Plants prefer a position in full sun, though they also tolerate light shade. A very hardy plant, tolerating temperatures down to at least -25°c when fully dormant. A fast-growing but short-lived species in the wild. The branches are brittle and very liable to wind damage. When plants are grown in rich soils they produce coarse and rank growth which is even more liable to wind damage. Any pruning should be done in late summer in order to reduce the risk of bleeding. The young branches, seedpods and petioles are covered with dark glandular hairs that exude a clammy sticky substance. Plants sucker freely, especially after coppicing, the suckers have vicious thorns. A very greedy tree, tending to impoverish the soil. Plants in this genus are notably resistant to honey fungus. This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby. For polyculture design as well as the above-ground architecture (form - tree, shrub etc. and size shown above) information on the habit and root pattern is also useful and given here if available. The plant growth habit is a running thicket former forming a colony from shoots away from the crown spreading indefinitely. The root pattern is flat with shallow roots forming a plate near the soil surface. The root pattern is suckering with new plants from underground runners away from the plant.

Propagating it: Seed - pre-soak for 48 hours in warm water and sow the seed in late winter in a cold frame. A short stratification improves germination rates and time. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in the following summer. The seed stores for over 10 years. Suckers taken during the dormant season.

Best place to grow: Woodland Garden Canopy; Secondary;

Habit: Tree

Hardiness: 3-7

Growth: Medium

Soil: Light (sandy), medium, heavy (clay)

Shade: Semi-shade, no shade

Moisture: Dry, moist

Things to keep in mind

Its other names

Local names

Synonyms

R. glutinosa. Sims.