Robinia pseudoacacia 'UMBRACULIFERA' mop-head acacia, black locust

Umbraculifera is a dwarf variety of black locust that originated in Austria in 1813. It makes deciduous, 25-30 cm long, pinnate leaves, composed of up to 23 elliptical or oval leaflets. They emerge light green and mature to a slightly darker shade of green, but never too dark. And since black locust lacks a gene common to most other native deciduous trees that tells them to stop growing at the end of the season, black locusts keep producing new leaves until the autumn. Therefore, their canopies are constantly a combination of darker, mature leaves and young, bright green leaves. Another plus is that they last exceptionally long. In warm, urban environment they remain on the trees often into December and fall off only after the arrival of really strong frosts.

Umbraculifera belongs among top five favourites suitable for small gardens and narrow streets as it has a compact, spherical crown that commonly grows to between 2 and 4 meters in width and slightly less in height. Only in open ground with unlimited root space they get slightly larger. Another advantage is the fact that it doesn't bloom, so don't expect a pile of withered, rotting flowers down on the ground as you can see under common, white-flowered locust. Standard trees always need a strong support for the first 3 years after planting before they establish. Also, during that time don't let the lawn grow close to the trunk – keep the area above roots clean and ideally mulched.

Locusts are not fussy about soil type, they even tolerate road salt but can’t cope with boggy or wet ground. They do not suffer from pests or common diseases, but we have seen trees with dead parts of the crown, most likely caused by a fungal disease hidden in the wood. The compact shape of the crown is natural without pruning, yet it can be done in early spring if you want to keep the crown size smaller. Fertilizing makes no sense. Fully hardy to min. -34 °C (USDA one 4).

Last update 07-12-2008; 24-01-2024