Plant Lovers' Almanac: Of hardy hibiscus and hordes of hued hydrangeas

I split time this past week between the trees and buildings of Central Park, the droughty piles of fallen planetree leaves in Brooklyn in New York City, the ravaged roses of Manhattan, the lovely lacebark elms at a Brooklyn playground, and then returned westward, to the colorful shrubs of Secrest Arboretum in Wooster, the myriad summer-sweets (Clethra) and their aromas in Northeast Ohio, huge hibiscus flowers, and once again — those hydrangeas.    

Panicled hydrangea

This plant, with the convenient Latin binomial of Hydrangea paniculata, was named from the Greek for “water vessel,” describing the shape of its seed capsules and the loose branching cluster of flowers (panicles). This species is a long-standing gardening favorite, including the peegee moniker for the Hydrangea paniculata “Grandiflora” large-shrub type.

In recent years, though, dozens upon dozens of new selections are available. One of the wonderful aspects of this plant is the progression of flower color among many of the types in the new cultivar trials at Secrest Arboretum. Linen white and creamy white flower clusters have added increasingly lovely pink hues as the flowers progress in recent weeks.

I mentioned “Strawberry Shake” last week. This past Sunday some of my favorites were “Magic Flame” and particularly “Pink Avalanche” with the white descending into pink in the frothy panicles.    

Hibiscus

Hibiscus moscheutos, known as the hardy hibiscus, rose mallow or swamp rose mallow, is a member of the Malvaceae (cotton family).  

They are native perennials often hybridized and sold in a wide range of popular cultivars, with the “Disco-Belle” range of colors, with spectacular, almost dinner-plate-size blossoms leading the surge in popularity starting several decades ago.

Rose mallow is related to the large shrub-size rose of SharonHibiscus syriacus, which is of Korean origin, but much shorter (2 to 4 feet high). The leaves of rose mallows are attractive and three- to five-lobed, but the mid- to late summer flowers are eye-popping.   

Multiple flowers develop daily and as they senesce should be dead-headed to enhance overall plant appearance. In the fall, as plants go dormant, cut back to 3 to 4 inches from the ground to keep plants within bounds the next season.  

Clethra

This genus is of wide distribution, mostly Asian and American origins, with fossils found in Denmark.

Our native C. alnifolia has yielded the most common commercial cultivars, increasingly popular for their pleasant scents and tiny, bell-like flowers.

Check out “Hummingbird” with compact form, and for a little taller plant “Ruby Spice” (4 to 6 feet tall, 3 to 5 feet wide) with ruby-pink flowers.

I am also very fond of C. acuminata, another native shrub, known as cinnamon clethra for its exfoliating cinnamon-colored bark. It is a somewhat bigger plant over time, up to 10 feet tall according to sources, though mine is now 6 feet tall after four years.

It also has a lovely fragrance, and is just blooming now, so the clethras are midsummer dreams.  

Beauty and the Beast

While in New York City I was once again reminded of the problem with overdoing too much of a good thing. Shrub roses that had long-lasting bloom periods became quite the rage in the late 1990s and early 2000s. Beauty, thy name is rose.  

But, as is often the case, lack of diversity oft awakes the savage beast: Monocultures mean vulnerabilities. Rose rosette disease, caused by a plant virus, spread by microscopic eriophyid mites, is devastating.

Along the West Side Highway in Manhattan, just to the east of the Hudson River and across from the 9/11 sites, there is a sad tale of dead and dying roses. Thousands upon thousands of roses. No effective controls in sight.

Diversity is such a must for sustainable landscape maintenance.  

Urban gardening

There are many versions of urban horticulture in New York City. There are big-time, Big Apple efforts: Central Park; the innovative, narrow High Line Park three stories above the urban fray now framed by rising high-rises; Green Thumb, “the largest community garden program in the country with over 500 gardens and 20,000 volunteer gardeners throughout the five boroughs”; Grow to Learn school gardens; on and on.  

New York State is even the ninth state in the country for commercial fruit and vegetable production ($503 million), led of course by — big apples.  

But small versions of urban gardening are sometimes just as inspiring. As I walked along a Ditmas Park-area street in Brooklyn, there was a little table of edible wares, courtesy of “Sparkle Fairy,” a homeowner with a backyard garden, selling her tidily displayed vegetables and fruits, from tomatoes to green beans.

After a short chat, she went back inside and I bought some homegrown blackberries, $2 per bowl, leaving $5 behind. I was about a block down the street when she caught up, eager to give me change. That’s New York City for you, little friendly apples in the Big Apple.  

The Name Game

Finally, back to the Name Game. Names of plants and animals, and people, are ever changing. This fascination with names and relationships and classification should not be surprising.  As I read in Jennifer Hochschild book “Genomic Politics” recently: “Genealogical research is America’s second favorite hobby after gardening.” Reevaluation take many forms, including knowing your ancestors.

In an article in the summer 2022 edition of Audubon magazine, titled “What’s in a Bird Name,” author Ariana Remmel notes that the official naming authority for common names of North American birds, the American Ornithological Society, is working on renaming the 150 of 2,000 birds named with honorifics, to give them more descriptive names.  

One example of this is Wilson's warbler, named for Alexander Wilson, a 17th century naturalist, widely credited as the father of American ornithology. The name of “green black-capt flycatcher,” which Wilson himself named the bird, does bring to the front a more descriptive name for the bird. Perhaps instead of the five American birds named for Wilson, it is better to use descriptive names that help teach us about the birds.

Check out the article, it is quite thought-provoking: After all, do we really want to continue naming the Alaskan long-tailed duck, the “Old Squaw” duck? 

So it goes, we shall always want to name and classify. The 18th century Swedish naturalist Carl Linnaeus, the greatest classifier of his time, though he knew not of DNA and the details of heredity, had the overwhelming impulse to characterize. As he said: “Deus creavit; Linnaeus disposuit” (God created; Linnaeus organized).” 

Jim Chatfield is a horticulture educator and professor emeritus at Ohio State University Extension. If you have questions about caring for your garden and other topics, write to chatfield.1@osu.edu or call 330-466-0270. Please include your phone number if you write.