Who needs “fruiting and flowering” trees when you have an oak I say! A few times in the past I have seen Tim Kong’s large Valley Oak flowering at the Cow Palace show, but I had never seen one of my own oaks flower until this spring. I am torn between taking off the flowers to keep the tree focused on producing a nice canopy and just sitting back to watch the pretty little things bloom.

Oaks are not renowned for their flowers, but, as is well known, all trees flower in some manner or another. Oak flowers may only happen on a particular bonsai tree once every few years and are so small that many people don’t even think of them as flowers. I admit that oak flowers are not the largest or most colorful but they are still interesting. Oaks flower in two distinct ways: first comes the production of the male(pollen) flowers on long slender stalks called catkins which emerge from mixed buds at the terminal of the branches; second are the female (ovule) flowers, which are located at the base of a leaf on the new branch. The timing of the two stages is staggered on any given tree to prevent self-pollination.

The male flowers, the larger and more obvious of the two types, have no petals making the flowers small and inconspicuous compared to many species. Petals are not neccesary because oaks do not rely on insects or animals for pollination. The catkins contain many flowers each, each flower contains pollen sacks which swell and release the pollen into the wind. The wind carries the pollen to neighboring trees which have already opened their female flowers. The color of the catkins vary by species; in the case of black oaks the catkins are a wine red color, and in the case of my coast live oak they are also a redish color. The structure and appearance of the catkins is roughly similar to that of a wisteria flower stalk except much smaller.
As with the cones on pines, I was concerned with the tree being weakend by it spending too much of its energy making the pollen and acorns. After consulting a book called “The Life of an Oak” by Glenn Keator I am fairly confident that the production of the pollen is already complete, so letting the tree flower will do no further harm. The pollen is produced as the mixed buds, containing the new leaves and the catkins, are forming in the late summer and fall. This clears up a little thing I was puzzling over last fall: all of my younger and smaller live oaks were putting out a flush of new branches while this one was not. It is now clear that this tree was spending its time and effort producing pollen and catkins hidden inside the buds.

I can’t really think of a way of preventing the tree from flowering in the future but I will keep a close eye on the branches to make sure that no acorns are forming since this will indeed take much energy from the tree over the coming seasons. Since I can’t prevent it, I think I’ll just enjoy the flowering and remind myself that it’s still not a “fruiting and flowering” tree.

Tags: oak, spring