Henry Homeyer: Plants I want to try, with a little help from Prof. Dirr

Even though it came out in 2011, I only recently got my own copy of “Dirr’s Encyclopedia of Trees & Shrubs.” It’s 950 pages of information about 3,700 species of woody plants — with more than 3,500 color photos. I have decided to read it cover to cover by April, though I am skimming the parts about plants for Zones 7 to 9. And since I own it, I am underlining and highlighting relevant info about plants that I want to try. I’d like to share a few of my ideas for purchases with you.

I’ve filled up most of my sunny places, so things that do well and bloom in shade are of interest to me. In the back of the book are lists of plants that do well in various conditions. It lists 225 plants that do well in shade (though some are outside our climatic zone).

First on my list of shade lovers to buy is bottlebrush buckeye (Aesculus parviflora). Dirr calls it “truly one of the best native shrubs for late spring and early summer.” It is hardy to Zone 4 and “flowers almost as prolifically in shade as in sun.” The blossoms are 8 to 12 inch long, bottlebrush-shaped white inflorescences similar to those on horse chestnut trees — they are “cousins” in the same genus. But it is an understory plant, growing to be just 8 to 12 feet high and 8 to 15 feet wide. And although it likes moist, well-drained soils best, it will grow almost anywhere.

Next, for both the bark and the blooms, I want to buy a Japanese clethra (Clethra barbinervis). It is a Zone 5 plant (good to minus 20) that requires shade and moisture-retentive soil for success. I have plenty of moist, shady areas near my stream that would easily harbor a 10- to 20-foot-tall shrub or small tree. The small blossoms are displayed in hanging panicles in July and August — a time when few other shrubs are blooming. The bark is exfoliating (it peels, exposing different colors of bark), which means it will be interesting to look at in winter.

I’ve always loved Franklinia (Franklinia alatamaha) for its bark, which has interesting vertical fissures and for its 3-inch fragrant white blossoms in July and August. It will grow in shade and likes moist, well-drained soils. But Dirr warns that poorly drained soils generally prove fatal. It is a shrub or small tree, 10 to 20 feet high and 6 to 15 feet wide.

Franklinia was originally found in 1770 in Georgia, named after Ben Franklin, and disappeared from the wild by 1790. It is, according to Dirr, “a somewhat persnickety landscape plant.” Does that deter me? Well it has so far, but now that USDA has reclassified my area as Zone 5, and Dirr says this is a Zone 5 plant, maybe I should try it. I have not seen it succeed in New Hampshire or Vermont, which should warn me not to spend too much on my experiment. If you have grown it, please let me know how it did, and where you grew it.

Another tree that interests me is paw-paw (Asimina triloba). This is a small understory tree that produces edible fruit with a somewhat tropical flavor — a bit like bananas. I have only seen — and tasted — it in the Athens, Ohio, area but Dirr says it is hardy to Zone 5. It does well in moist, well-drained soils in shade to full sun. Dirr says it will sucker (send out roots from the mother plant) so that it creates colonies. I have never seen the flowers, but he describes them as “lurid purple flowers that creep out of hairy brown buds before the leaves come out in April or May.”

Why is it that we see so few of these more unusual shrubs and trees? It may be that nurseries are unwilling to try things that no one has ever heard of. Or it may be that some growers have tried them, and the plants did not do well. Soil type (sandy, loam or clay) and soil pH (level of acidity) are important, but so are microorganisms. It may be that the bacteria and fungi in the soil along a stream bank in Ohio are very different than along my own stream.

My grandfather was not an educated man, but a wise one who was an organic gardener long before it was fashionable. He once told my sister, “When you transplant something, bring along enough soil so that it will remember where it came from.” What he was saying, I think, is that you should bring along enough soil to inoculate your soil with the microorganisms from the site where it thrived.

Professor Dirr’s book is fun reading, too. He is opinionated and comes out with occasional wild statements — “with the right amount of imagination they (the flowers of Colutea arborescens) conjure visions of Yosemite Sam,” for example. So get your library to order a copy — or order your own.

Henry Homeyer can be reached at P.O. Box 364, Cornish Flat, NH 03746, or henry.homeyer@comcast.net, or visit Gardening-Guy.com.