May is often advertised as the best time for flowers—you know the rhyme, April showers bring… but in Vancouver, May flowers are often just a continuation of April’s bounty. Vancouver is usually cool, and often wet, but otherwise agreeable at this time of the year (unlike western Europe and eastern North America, which can suffer from both late frost and sweltering temperatures in May). Flowers and the tender young growth of all kinds of plants last much longer with cool and humid conditions. At this time, the new growth on a number of trees can be exceedingly ornamental. For example, the emerging leaves of mountain ashes (Sorbusspecies) are often surprisingly bright green. On the other hand, many worm-head trees (Meliosma species) have dull, yellow green leaves, but the vegetative (leaf) buds open at the same time, with the entire year’s leaves all expanding simultaneously. The leaves are both unusual and eye-catching, with upright, hairy leaf stalks and drooping leaflets.
In rhododendrons, new leaves appear immediately following flowering, and again, high humidity and lower temperatures benefit their development. As leaves emerge from their buds, the bud scales generally fall away and expose the unfolding leaves, which stand stiff and straight as the individual leaves unfurl. Many rhododendron leaves are covered with a dense vestiture of hairs on the leaf backs (known as indumentum), and in many cases, the hairs contrast beautifully with the green of the expanding leaves.
The daphniphyllums (Daphniphyllum species) are also worth a look. Their leaves are not unlike those of some rhododendrons, both in size and shape, and in their clustered arrangement. Immediately after bud-break, the quickly swelling leaf cluster resembles a Belgian endive with its stiffly upright, tightly packed leaves. As the dozen or so upright leaves continue to spread and grow, they gradually redden at the tips, the colour eventually bleeding downward until the leafy crowns are copper and green.
Submitted by Douglas Justic, Associate Director, Horticulture & Collections, April 30, 2014.