A Report of the Good, the Bad, and the Untested
by Carol Edwards for the Capitol Hill Garden Club
At the 2011 University of Maryland Extension Master Gardener Annual Training Day, Alan Summers gave an enlightening lecture on new cultivars. Mr. Summers is a former Maryland nursery owner, who had often seen his customers frustrated when trying to choose from among the many cultivars of particular plants. In this article, I share his advice, which I hope you will find as helpful as I have. But, let me first set the context with my experience.
As you probably know, many new cultivars of popular perennials, shrubs, and tress become available on the retail market every year. I read about these plants in gardening magazines or catalogs. They seem so appealing. As I spy one of these introductions in our local nurseries, I always read the label, which generally provides information essential to my purchasing decisions. When it comes to plants, I may be an impulse buyer, but I am a responsible impulse buyer!
Here is the big problem. How reliable is the information on the label or, for that matter, in the magazine or blog article? For instance, what specific traits, if any, have been tested prior to market release? Has this cultivar been subjected to growing conditions and practices similar to mine? Has the testing been done by a party with a major financial interest in the sale of the plant? Have the trials included a large number of plants or only a few? I could go on, but you see where I am headed.
The lack and poor quality of plant testing have led to some colossal failures recently. For example, some of the recent Echinacea (coneflower) cultivars have proved to be very disappointing—subject to leggy, spindly growth and color reversion. Some red cultivars of coreopsis (tickseed) have been unable to winter over reliably north of zone 8. (We are located in zone 7.)
So, how is a gardener to know whether to believe the label? Truthfully, there is no way to know with new introductions, particularly those not developed through non-profit research facilities. You can take the plunge, risking the loss of your investment, or wait a few years and track how the cultivar performs locally.
To conduct due diligence, Mr. Summers recommends consulting with staff at local garden centers. (As big-box stores replace dedicated garden centers as the primary source for retail plant material, reliable advice is growing more difficult to obtain. That’s another article, however.) Ask specific questions, such as how long other customers have grown the cultivar. Does it hold its color and shape? Do the flowers or stems flop over? Is it winter hardy? Will it take heat and humidity? Are the mature plant dimensions accurate as described? How fast does the plant grow? Who tested the cultivar? What was the purpose for developing the cultivar (particularly important when assessing agricultural plants)?
With those questions and more in mind, here are some of Mr. Summers’ observations about particular cultivars and some of his favorites.
For those of you that have property in or north of zone 6, avoid Encore and Marshy Point azaleas and the ‘Dazzle’ or ‘Fili’ series of crape myrtles.
Although cultivars are often not as dwarf as described on the plant label, the red azalea ‘Bixby,’ the ‘Flutterby Petit’ series of butterfly bush, Rose of Sharon ‘Lil Kim,’ Hydrangea macrophylla ‘Mini Penny,’ and forsythia ‘Golden Peep’ seem to stay small reliably. The new cultivar of Russian sage (Perovskia atriplicifolia), ‘Lacy Blue’ stays less than 24 inches tall.
Mr. Summers' favorite crape myrtles are in the ‘Whitcomb’ series.
The flowers of Hydrangea arborescence ‘Ryan Gainey’ do not flop as do many of this plant’s cultivars, such as ‘Incrediball.’
Notable cultivars of Hydrangea macrophylla include ‘Penny Mac’ and ‘Double Delights Perfection’ with its improved reblooming capability. The new lilac (Syringa), ‘Bloomerang,’ will show some reblooming in the fall.
Hydrangea paniculata ‘Bombshell’ forms a mound and remains fairly small.
Thuja (arborvitae) ‘Steeplechase’ is denser and fuller than the popular ‘Green Giant.’
Although the red and orange thornless flowering quinces (Chaenomeles) hold their color, the pink does not. Neither does the yellow Knockout rose.
The ‘Double Play’ series of Spirea has larger blooms than other cultivars.
He likes the Pieris japonica (Japanese andromeda) ‘Katsura,’ with maroon new growth and ‘Passion Frost,’ variegated and pink flowered.
Among the best of the boxwood (Buxus) cultivars are ‘Chicagoland Hardy,’ ‘True Spreader,’ and the popular substitute for English boxwood, ‘Vardar Valley.’
His favorite recent hollies (Ilex) are the dense, tall and berried ‘Centennial Girl’ and ‘Red Beauty.’
He also touts the new colors of butterfly bush (Buddleia), ‘Grande Vanilla,’ ‘Peach Cobbler,’ ‘Sweet Marmalade,’ ‘Miss Ruby,’ ‘Tangerine Dream,’ and ‘Miss Molly’ (dark fuchsia).’
The ‘Showoff Starlet’ forsythia flowers all the way down to the base of the plant year after year.
If you are in the market for a deciduous azalea, Mr. Summers recommends ‘My Mary.’
So there you have it. Of Mr. Summers’ recommended cultivars, I grow ‘My Mary’ and agree that it is a forgiving, lovely azalea, with its small trumpet shaped yellow and red flowers. I have also tried ‘Katsura,’ the absolutely stunning Japanese andromeda that, alas, needs better drainage than I gave it.
I hope this article will be the start of information sharing about recent introductions. Have you tried any of these or other new cultivars? What have your experiences been?
