Unusual Pea Relatives
What are they?
This is a rather varied group of plants that are all woody members of the Pea Family (Fabaceae) but which differ greatly from the traditional family in not bearing the classic 'pea flowers'. It's interesting to note that at least two of these unusual plants - Kentucky Coffee Tree and Honey Locust - are evolutionary anachronisms, forming part of a group of plants from North America that have lost their natural seed dispersers due to the disappearance of the region's megafauna. Their outsized fruits no longer have natural dispersal mechanisms and the species seem doomed to extinction without help from people.
Where are they found?
These are introduced species that are occasionally used in amenity plantings, as street trees or in other public spaces such as cemeteries and churchyards.
Identification
Each of these species is relatively easy to identify in its own right, due to their combination of unusual leaves, flowers and fruits. Young plants without fruits or flowers may be confusable with other trees that have compound leaves, but close attention to detail should make them identifiable.
Honey Locust Gleditsia triacanthos
Introduced from North America. Popular as an amenity ornamental in public open spaces in urban areas. Flowers May to June. A small to medium-sized tree with leaves which may be pinnate or bipinnate. Flowers inconspicuous, the male and female flowers being borne on separate trees. Male flowers in catkin-like clusters, females in smaller, few-flowered clusters. Female trees later produce impressive, curved or spiralled seed pods, to 45cm in length, beginning green and eventually turning glossy dark brown to blackish. Cultivated trees are typically of the yellowish-leaved cultivar 'Sunburst' which is thornless, but the species is naturally thorny, the thorns long-persistent on the main branches and trunk. There are also green-leaved, thornless forms in cultivation too.
 |
 |
|
 |
| |
|
|
|
 |
 |
 |
 |
| |
|
|
|
Kentucky Coffee Tree Gymnocladus dioica
Introduced from North America as an ornamental. Rare as a street tree or occasional amenity plant. Flowers May to June. Typically a small to medium tree in cultivation (but to 30m in the wild). Leaves large, to one metre in length, bipinnate with both the rachillas (side branches of each leaf) and the individual leaflets appearing in offset pairs. Each leaf has one or two pairs of single leaflets at the base before the leaf subdivides. Leaf petioles swollen, almost sucker-like at the base, where they join the main stem. Male and female flowers appear on separate trees, the females later producing large, conspicuous fruits, though both flowers and fruits are seldom produced in the UK except in the hottest summers.
 |
 |
 |
 |
| |
|
|
|
 |
 |
 |
 |
| |
|
|
|
Silver Wattle Acacia dealbata
Introduced from South-east Australia as a garden ornamental. Rare in amenity plantings in urban areas but becoming more frequent as climate change makes this (and many other species) more able to survive our climate. Flowers February to April. A small to medium, graceful tree. Leaves bipinnate with a feathery appearance due to the tiny, 4-5mm long leaflets. The leaflets are arranged in offset pairs, giving the rachilla (side stalk of the leaf) a zigzag appearance. The central stalk (rachis) of the leaf has tiny, rounded glands. Flowers abundant in late winter/early spring on mature trees.
 |
 |
 |
 |
| |
|
|
|
 |
 |
 |
 |
| |
|
|
|