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Wednesday, June 29, 2011

Robinia pseudoacacia - Black Locust

The Black Locust is an old school tree. It has been in commerce for years. The black locust tree traveled across the US with migrating easterners using the fast growing, drought tolerant tree for lumber and fence posts. Old trees are very attractive and tough looking.  They have an upright, open crown, a straight trunk and the foliage often restricted to the ends of the coarse branches. Makes a nice contrast with the attractive rough bark. You are much more likely to encounter the pink flowered one than the species in Santa Cruz. There are a few old species on the corner of N Branciforte Ave and Goss.

The black locust has alternate, odd pinnately compound leaves, 6-14" long with 7-19 leaflets. The leaflets are about 1.5-2" long, entire margins, sort of oblong-shaped.

Stems are brown, smooth, often with sharp stipular spines at the base of the leaves. Spines seen on vigorous shoots.

Flowers are very attractive. Each pea-like flower is off white, and very fragrant.

Fruit is a 3-4" brown pea-pod. Generally produced in high quantities, and looking pretty bad once the foliage drops off.

Bark is very deeply furrowed and a wonderful contrast, especially in winter with snow. Not around here anyway.

Misidentification: not sure, students usually have a problem with so many pinnately compound leaves.

Locations: Great ones on Branciforte and Goss, old school ones.

Lots of cultivars abound as well,

There is a 'Decaisneana' with very light pink flowers at 7341 Soquel Dr on the side of the lot. Shown below. Most likely a hybrid Robinia X ambigua.

'Frisia' - Is a beautiful tree in the right place. I first saw this tree at  Buchart Gardens and was blown away. Tried it many times up north in the cold and heat, and would not do well, but here it seems to be great. There is one at 136 Mar Monte in La Selva Beach. The image below is not the one on Mar Monte.

Robinia X ambigua idahoensis  Rose colored flowers, more commonly planted in SC than the others, found along River St near Mission. Bark is smooth, and usually one or two vertical cracks on the trunk. Not sure what the real name is, or if there is a difference between this one and 'Purple Robe'.

'Tortuosa' - A dwarf twisted form, this plant may  be 10' tall with a dense twisted branches. Two nice ones on Monterey Blvd in Capitola, 729 and 230 Junipero Ct (2 doors up).

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