Undeveloped Pacific Dogwood Flowers


Recently I was admiring the red autumn leaves of the Pacific dogwood  (Cornus nuttallii) along the Falls Loop Trail at Burney Falls State Park CA. The red leaves provide a beautiful contrast to the dark conifers in their natural habitat. I noticed what looked like undeveloped flowers. That made me curious. Do the Pacific dogwood flower buds form in the summer or fall and overwinter?

The Pacific dogwood’s showy “blossom” is actually a dense head of small, yellowish-green Pacific dogwood flowers surrounded by 4 to 6 showy, white petal-like bracts. The bracts of Pacific dogwood are not notched at the ends with greenish tips like its eastern cousin. A photograph of the flowers and bracts can be seen in my previous post, “Pacific Dogwood” 05/07/15.

The Pacific dogwood flower cluster partially forms in the summer. The bracts are situated just below the immature, button-like cluster and remain in an undeveloped state until the following spring when they grow large and showy as the flowers also develop and open. In the photographs the bracts are visible below the flower head.

Pacific dogwood wood is extremely hard, strong and close-grained. Native Americans used dogwood for bows, arrows, harpoons and other implements. Shuttles for textile mills were once made from dogwood because the wood’s ability to remain smooth under continuous use. Golf club heads and piano keys were also once made of dogwood. Now the wood is primarily used only for aesthetically ornamental purposes.

There are several explanations for the origin of the name dogwood. One says that in Medieval times in northern Europe the wood from a local Cornus species was used for skewers or “dags”. Dagwood evolved to dogwood. Other common names for C. nuttallii are mountain dogwood, western dogwood, and California dogwood. The genus name, Cornus, means “horn” in reference to the hard, hornlike wood.

The fungus, Discula destructiva, was introduced into New England and Washington State in the 1970s. D. destructiva causes anthracnose disease in dogwoods. The fungus appears as tan spots and blotches on the dogwood leaves. When the entire leaf is infected the fungus proceeds to the twigs and eventually the trunk where cankers produce split and buckled bark. Healthy dogwood trees are able to survive the fungal attack. However, those dogwoods stressed by drought or disease succumb to anthracnose disease.

David Douglas was the first botanist to observe Pacific dogwood. But Douglas mistook this species for the Eastern dogwood and did not identify it as a new species. Thomas Nuttall, a member of the second Wyeth Expedition to the Northwest,  in September of 1834 was the first to identifiy and describe Pacific dogwood as a new species.

In the spring I will return to see the beautiful white dogwood “flowers” that arise from these overwintering immature bracts and button heads.

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