Hydrangeas of summer

Hydrangeas are great show-stopping shrubs for the summer border, adding both structure and floral power to the landscape. Here are just two (among many) that I am fond of.

I've long admired the simple smooth hydrangea, Hydrangea arborescens, and the cultivar 'Annabelle' really cannot be beat for its bountiful display of rounded blossom clusters. An 'easy keeper', smooth hydrangea intermingles well with other plants, including herbaceous perennials.


















Another common species that is a personal favorite of mine is the oakleaf hydrangea, Hydrangea quercifolia. A more substantial piece of shrubery than H. arborescens, this species also produces robust conical panicles of white flowers, often blushed pinkish. And, like other members of the genus, oakleaf hydrangea flowers can be just as striking after they have dried.






























Both of these species are native to eastern North America, although the natural range of oakleaf hydrangea is restricted to the Southeast (this has not stopped some northerners from growing it as a native species, however). Both can be found in woodlands and thickets, typically in dappled shade, although it is not unusual to see them in very densely forested areas.

A study in leaves...

They come in all shapes and sizes, all sorts of colors and textures.

Some are nondescript and plain,













Tetracentron sinense

while others are bold and outrageous.












Actinidia kolomikta


Some are huge,














Hydrangea quercifolia


others are teeny-tiny.













Acer monspessulanum


Some have fantastical shapes.














Ginkgo biloba (unnamed selection)


They may have two faces,













Croton alabamensis

be needles,













Microbiota decussata

or float on the water.













Nelumbo nucifera


And of course, let's not forget that within these funky structures, water is split asunder using quantum energy, carbon dioxide is cannibalized, and oxygen is generated.

Fascinating machines, these things called leaves.

Vandals...

Is it no wonder this weeping beech (Fagus sylvatica 'Pendula') casts down its branches in such sorrow?

What possesses somebody to carve their name into the bole of a tree? I suppose, like a white-washed wall calls to the graffiti artist, the clean elephantine bark beckons a person to scrawl and to scratch, to cut and to hack. Finished, they lovingly trace the lines and admire their handiwork; arrogant, they later return to fondle the permanence of their actions.

Oh, could I but once catch somebody in this devious act. I would take out my own pen knife and carve my initials into their trunk. Like a tree, their sap would ooze and bleed, infections within would dance in glee. Eventually, their skin would callus, but the scar-tissue would forever remain, marking my brand, my permanence.

Candlestick tree...

While in California the other week, I also saw countless species of Banksia, a Southern Hemisphere shrub/tree with other-worldly flowers and flower clusters.
















I do not know the name of this species I saw at the UC Santa Cruz Arboretum (and I was too afraid of roaming rattlesnakes to go probing at the base of the tree for an accession tag!). But, the inflorescences sure do look a lot like candlesticks, don't they? The bees liked them, too, as can be seen in the close-up.

My horti-botanical roots...

I often am asked how I managed to wind up doing what I do: telling stories about plants, and trees in particular. I tell people it is natural that I do what I do, as my mother is a very able gardener and my father a detective. I was destined to grow up to be a PI: Plant Investigator.

The other day, while en route to California, I recalled one of my very first experiments. It was autumn of 1986 and an assignment in my 7th grade biology class was to design an experiment to test an hypothesis. My teacher, Mr. S. was an excellent one. An earlier project for the class was to make a leaf collection. That was my first exposure using taxonomic keys to identify unknown plants. I got an A+ on the leaf collection, a bound bundle of 30-odd specimens that I still have on my shelf.

But, back to the experiment. There had been two trees that were favorites of mine as a kid, perfect for climbing. One, an old contorted mulberry (Morus alba), not only presented an array of branches from which to perch prostrate upon, but come summer produced an endless supply of sickly-sweet fruits. Oh the hours I would spend up in that tree, reading books, day dreaming, and sharing mulberries with the starlings (which would then fly over my mother's clothesline).

Not far away from the mulberry was the remnants of an old apple (Malus domestica) orchard that had been established in the early 1900s. Like the mulberry tree, many of the apple trees were perfect for climbing. And, by summer's end, they yielded ample yellow apples to eat and share with the horses.

Not yet learned in the botanical sciences and assuming that ANYTHING was possible, I decided to join these two species together in a magical splice, which would fuse and grow and eventually form a hybrid that had the best attributes of both the mulberry and the apple (would I call it a mulapple?). And so, I collected my cuttings and presented my proposal to Mr. S. "Oh, this is all fine and good, Michael, but WHAT is your hypothesis? And what are your treatments?" he asked me.

I responded matter-of-factly, "I want to see if it works, if I can stick the two twigs together in a jar of water and watch them grow together and make a new tree." I had seen my mother root many a houseplant cutting, so of COURSE this would work. At the time, perhaps my command of the birds and the bees needed improvement, for me to think I could create a new species so easily. OR, perhaps I really was precocious and I was attempting a graft-chimera that would span across whole families of plants. Hmmm... I think the former.

My patient teacher insisted that while my ideas were all fine and dandy, what I was doing was solely an observation. It wasn't an experiment with a testable hypothesis. So, to the drawing board I returned. I went home that day and climbed atop Mr. Mulberry. And I thought. And thought some more. And then I saw my dad cleaning out the barn, scooping endless shovelfulls of horse manure out onto the pile in the nearby barnyard. Knowing that some of this would eventually find its way to the vegetable garden, I began to formulate my perfect experiment...

Why not test if the cuttings would root better in water or a manure-soil concoction? I rushed inside, grabbed paper and pen, and rewrote my proposal. I clearly stated what my anticipated results would be and what my hypothesis was: the splices placed in the manure would root together perfectly, far better than those in water. The next day, I presented my ideas to Mr. S., and he proudly nodded his head and agreed that my ideas were grounded in experimental science. I had a testable hypothesis.

I went home that day, collected two sets of cuttings (1 from each tree), and bound them together with a rubber band. One bundle I placed in a mason jar filled with water. The other I stuck in a 5-gallon bucket that I had filled with the ripest-smelling, freshest horse manure I could find. (Note: I know that I only had 1 replicate for each treatment, but give me a break, I was 10 years away from my first course in Statistical Design of Experiments!)

I waited.... And waited... And waited some more. Weeks went by and yet nothing happened. No roots formed in EITHER treatment, let alone join together and hybridize. I waited some more. The twigs began to soften... and then rot... and then stink, particularly the manure treatment. Imagine a 5-gallon bucket full of wet manure and no drainage...


I eventually threw the whole thing away, but I wrote up what I observed. My hypothesis was half correct, I suppose. The cuttings in the water didn't root, as I surmised. But, neither did the other treatment. I got an 'A' on the project. I had followed the rules, designed an experiment, and tested my hypothesis. The goal of an experiment is to refute your hypothesis (or somebody else's); it is impossible to ever prove one correct.

An experiment never fails.



Cercidiphyllum japonicum

From the Redwood Forests....

I've been on hiatus the past week or so. The annual conference of the American Public Garden Association took me to sunny San Francisco, CA. I've been going to this annual meeting (which is held in a different city each year) since 2000, and I must say that this year's was the very best yet. The sessions and speakers were outstanding, the food delicious, the field trips to other gardens amazing, and the company exceptional.

This was my first trip to the West Coast, and I must admit I was completely bowled over by the plant material. The moderate climate affords them to cultivate an enormous diversity of plants from not only other Mediterranean climates, but also temperate and subtropical ones. The vast majority of species I encountered (both in the wild and in the various gardens) were completely foreign to me, at least outside of books. In fact, the first thing I did once I got there was purchase a fieldguide to the trees of the Bay area.

Of course one of the most distinguishing native trees is the coast redwood, Sequoia sempervirens, which reaches heights of over 350 feet. Standing in their presence not only gave me goosebumps, but made me appreciate the role of fog in the ecophysiology of trees such as these. The Bay area experiences a complete summer drought, which would normally severely compromise the growth of arboreal specimens like the coast redwood. However, as the daily fog blanket rolls in from the ocean, the tree canopies intercept the moisture which then drips along the branches and trunk, reaching the soil below and mitigating the lack of precipitation. The photo below was taken mid-morning in Muir Woods, just as the fog was lifting.




















Another California native is Cupressus macrocarpa (the Monterey cypress). This species' native range is actually limited to two small populations in CA, however it is widely cultivated as an ornamental and as a timber tree (and has become weedy in the eyes of some). It is instantly recognized by its flat-topped, picturesque form, as can be seen in this silhouette photo from the expertly curated San Francisco Botanical Garden at Strybing Arboretum.





















And then things get weird... By that I mean those crazy plants from the Southern Hemisphere. It is very safe to say that here in the Northeastern US, we cannot cultivate anything out of doors from the Southern Hemisphere -- at least not over a winter. Thus, it was a dazzling treat to experience the wide array of South African plants, including the red and yellow pincushion proteas (Leucospermum cordifolium) growing in the University of California, Santa Cruz Arboretum. The fist-sized flowers are brilliantly colored, and very tactile, with stiff styles (female organs) that feel like hairbrush bristles.















Perhaps the most amazing part of the trip was a visit to Quarryhill Botanic Garden, about an hour's drive north of San Francisco. I think I am still speechless. All of the plant material in the garden has been collected from the wild in Asia, and nothing in the garden is older than 16 years. Despite the young age, the garden is lush with sizeable and maturing specimens. I've visited many plant collections before, but nothing like this. Already, it represents one of the finest collections of Asian plants in the world -- I cannot wait to see how it develops in the future. Plant conservation is an integral part of the work at Quarryhill, and one of their rarest species is the maple, Acer pentaphyllum (below). Only a few plants remain in the wild (SW Sichuan), and because of human impact, their future does not look bright. However because of the efforts of Quarryhill, the National Geographic Society has recently funded a project to protect the plants before they are completely extirpated. Kudos for Botanic Gardens!















California was amazing, introducing me to her own native flora as well as a vast array of other plants that make up an incredibly rich palette. Now, if only I could remember 5% of what I saw growing there!