“Hydrangea includes some 35 species of small trees, shrubs, or shrubby climbers, found in eastern and southeastern Asia and the Americas. The name comes from the Greek for a water vessel, after the shape of the fruit. Hydrangeas are plants of regions with warm and humid summer climates, the shrubby kinds growing typically in woodland edge habitats, and in Japan, along the coast.
“For gardeners, the distinction between lacecap and mophead is crucial. Plants are naturally lacecaps… with a large number of small fertile florets being surrounded by a corona of larger sterile ones, the latter attracting pollinators. Mutation may result in nearly all the fertile florets being replaced by sterile ones — a turn of events that renders the flowers totally dysfunctional as far as wild plants are concerned but which led to great interest from humanity….“
Let’s wrap up August 2021 with the last of my bluebird hydrangea photos — to be followed in a few days with a selection of my very own beautiful and bulbous mophead hydrangeas; or, as I like to call them: hydrangibles.
“The … flattened clusters of the lacecaps make hydrangea flower morphology easy to see. The bigger, showier florets that tend to dominate or stay to the outer edges are always sterile. The smaller, inner ones are fertile, and with pollination they will produce fat little fruits that lead to chambered seeds. It’s typical to have four or five petals, and between four and ten sepals. Peer closely — the true petals are clearly separate from one another, while the sepals are fused.
“Thus the pollinators, various flies and bees, may have to root around a bit to find the true flowers once they arrive.”
In my previous two posts (see Baby Bluebird … Hydrangeas (1 of 2) and Baby Bluebird … Hydrangeas (2 of 2), I included photographs of some bluebird hydrangeas from my garden shortly after they started their springtime blooming. The images in this post (and the next one) feature some of the same hydrangea plants, photographed a few weeks later as the blooms continued to get larger and more mature. So in the galleries below you’ll see bigger central clusters of tiny flowers, surrounded by the white (or bluish or purplish white) petals that are both larger and more numerous than in the baby bluebirds.
“Garden hydrangeas will turn from pink to blue if the soil is acid and if aluminum is available to them, but it still seems rather magical, and when they were first introduced it was inexplicable. It was initially thought that they might take their color from their surroundings, especially as cuttings from a plant of one color might well turn out the other color when propagated.”
“When the first Asian hydrangea reached maturity in The Royal Botanic Gardens, Kew, in the late 1700s, the flowers caused a sensation when their original colour gradually changed — as if by magic.
“Widely believed to be unique to hydrangeas, this chromatic instability is one of the plant’s most memorable characteristics, and it comes down to the availability of aluminium ions in the soil.
“Acid soils … contain aluminium ions in a form that the plant can absorb and then use to produce the pigment for blue blooms. Alkaline soils … and those that are high in phosphate ‘lock up’ the aluminium so the ions are unavailable to the plant. As a result, the same variety will produce flowers that are pink or mauve. The more acid your soil is, therefore, the more clear and intense the blue colour will be.
“Hydrangeas can take several years to settle into a site and assume their ultimate colour, but giving them a dose of ‘free’ aluminium in the form of potassium aluminium sulphate (potash alum) can speed up the process — but take care not to overdo it, as the plant may suffer.”
I’ve never actually tried the color-change trick on my hydrangeas, being content instead to let nature do its thing and produce whatever colors the plant thinks most appropriate. I’m actually not even sure if you can change the colors of hydrangeas of the lacecap variety; though I would say that the color variations I see even in these baby bluebirds suggest it might work.
The photos in this post and the previous one are all from three shrubs of the same kind, planted near each other four springs ago — yet some of the blooms show blue colors only, while others include bits of color in the pink/purple ranges. The bluer ones are planted farther back in my garden, where the soil is thicker (I had to build it up quite a bit to work around the ground-level roots of some pine trees) and that extra soil tends to absorb and store more water. Rainwater — we’ve had tons of rain this year — is slightly acidic, so I pretend to know what I’m talking about and say that lots of rain with its acidic content soaking into thicker soil causes the plant to produce more blue blooms, whereas water running off those in the front of the garden reduces the acidity (producing more pink and purple).
“A thoroughly graceful and elegant hydrangea, the flowers of Bluebird take a classic lacecap form; shapely and understated with large, clear sterile florets around the periphery of a woad-blue dome of fertile blooms.
“The larger flowers are sometimes sparse, but their paucity serves only to emphasize their individual exquisiteness. As in a design, the space around something can be crucial, enhancing it and enabling the observer to fully appreciate the focal point. And should the plant be cruelly criticized for lack of impact, the fact that the flowers are scented should more than repair this deficiency.
“The blue colour is reasonably stable with variations in soil pH, too, although it can be more mauve or even pale pink on a very alkaline site. In autumn, the large sterile florets turn to face downwards and are infused with magenta and mulberry, complemented by the foliage, which turns copper-bronze towards the end of the season.
“The shrub is compact enough to suit small gardens and will also do well in containers. Like all serrata cultivars, it is moderately cold-tolerant but does not find exposed or coastal sites conducive, nor is it a fan of full sun.”
The galleries below feature a few close-up photos of Bluebird hydrangeas in my garden. I took these photos early in the spring, just as the first white petals began to appear, then set them aside while working through and posting many of the spring and summer photos (especially the lily photos) that I had taken at Oakland Cemetery’s gardens. This and the next blog post — and several others whose photos I’m still working on — returned me from Oakland to my own back yard where I crept daily among the ferns and hostas to photograph my hydrangeas in their progression to summer from spring. Hydrangeas are mostly desiccated now; here in the southeast they tend to bloom early then lose most of their floweriness by late June or early July.
The lacecap hydrangeas have an interesting structure and biology, having developed a natural variation of the typical design of a flower. The central clusters of tiny buds are properly the plant’s fertilizable flowers; they’ll open a handful at a time (as you can see in the third and last trio of photos below) for pollinators such as bees (and occasionally hummingbirds) that flit from cluster to cluster. The white (or light-bright blue or purple) petals that emerge and often surround the clusters have no reproductive function but still they have a job to do: they’re brightly colored to attract the attention of pollinators who are more likely to notice their luminosity than the mix of darker hues among clusters of flowers.
Can’t you just see the little white petals waving at the birds and the bees?