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Tuesday, June 28, 2011

Eucalyptus polyanthemos - Silver Dollar Tree

The silver dollar tree is a pretty common tree in Santa Cruz county. Unlike other Eucalyptus it seems to say where it's planted, does not get too tall and is not a big mess as the bark is not shed in large strips. Creates shade when needed and provides an interesting form and foliage color.

An evergreen tree medium to fast growing to 30 - 60' x 15 - 30' wide. Usually fairly narrow with upright primary scaffold branches and pendulous laterals creating a nice soft weeping effect. Added bonus is the soft bluish color of the foliage.

Leaves are alternate, simple, broadly oval to ovate-lanceolate in shape, 2 - 4" range by 1.5 - 2" wide. Tips vary with leaf shape, either acute, rounded or notched. Leaves have a thick glaucous (waxy) bloom. I have seen some almost round and some narrowly elliptical on the same tree. What fun. Here is an image of some leaves pulled from 2 trees side by side. Rounder leaves are more juvenile.

This is a pretty common leaf shape, size and color. The young stems are thin (that's why they hang) usually red colored or covered with wax.

Small, off white color in panicled umbels of 7. Eucalyptus buds are typically arranged in umbels, ranging from 3 to 7.

You can see the operculum falling off of some of the flowers. The operculum is a term for the sepals and petals that are fused into a "cap" common to all Eucalyptus.

Here is a picture of the flower buds arranged in a panicle (a branched inflorescence) of umbels (all flower stalks from the same place). You will notice the elongating branching inflorescence (the panicle) and the individual flowers coming from the same location (the umbel).

Fruit are small capsules, 1/4" or less, with the valves included below the rim. They seem to constrict a bit at the rim, only slightly. Sitting on a leaf for scale.

The bark of the silver dollar tree is more or less smooth until old then becomes somewhat fibrous. Until then its sort of smooth, mottled colors due to shedding of bark at different times and of different sizes. Bark comes off in fibrous flakes. Brown usually.

Misidentification? There are lots of these around town and according to Matt Ritter they have one of the largest native ranges suggesting that the variability should be huge. So, expect to see some that dont look "normal".

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