Years ago I had to replace dozens of 'Limerock Ruby' coreopsis plants for my clients. This perennial plant charmed me with the most lovely, profuse little velvet-red daisy-type flowers, and it could handle dry, rocky soils. But even though it was marketed as winter hardy for our region, turns out, it wasn't. For me, this perennial turned out to be a very costly...annual.
Liz Elkin, proprietor of Bloom Landscape Design and Fine Gardening Service, says, "Sometimes a beautiful, bold new flower or shrub will practically leap off the nursery table and jump into my truck. I will bring just one of them home, plant it in my own garden or container, and see how it behaves for a season or two before incorporating it into designs for a client's garden. Sometimes, a robust-looking plant in the nursery or greenhouse turns out to be a total bust in the garden, too weak to handle our heavy local soils. Alternately, sometimes a sweet, small, innocent-looking ground cover will take over the entire garden by the end of its second season."
For all plants, keep your site conditions in mind when you go shopping so that you can select the right plant for the right spot. For instance, do you have shade for most of the day in that spot, or baking sun, or some of both? Does the soil drain well there, or stay wet? And the very important macrocondition: What is your USDA Hardiness Zone, and is the plant you're thinking of buying fully winter hardy to that zone?
There is another major consideration. Orange County Arboretum Horticulturist and Arborist Pete Patel says, "I've observed that the biggest thing new gardeners feel defeated by is wildlife damage, especially from deer." Patel says that unless you have a serious deer fence like the one they have at the Arboretum, deer resistance should be the first consideration for any plant selection (see Resources).
What specifically should we be looking for when we buy annuals, perennials, shrubs, or trees?
Patel and 50 volunteers grow thousands of annuals each year in the Orange County Arboretum greenhouse for the Arboretum, for use in County parks at large, for select nonprofits, and for popular public plant sales three Saturdays in May (May 9, 16, and 23 this year). Patel follows Cornell University annual plant trials to learn about the sturdiness of new industry releases before he invests in seed for his greenhouse program.
Some annuals are marketed by the "Proven Winners" labeling program as being exceptionally beautiful and tough. Among the Proven Winner annuals Patel favors for the Arboretum are the 'Señorita Rosalita' cleomes/spider flowers, 'Playing the Blues' salvia, 'Vertigo' pennisetum grass, and 'Goldilocks Rocks' bidens. Patel says these are plants that will work hard, bloom prolifically, transition well into his fall display, and fill space nicely. "Instead of planting seven marigolds, I can plant one 'Goldilocks Rocks' and it will bush out and occupy the same amount of space," he says.
Patel advises people not to buy perennials only when they are in bloom. "What's it going to look like at the end of summer?" he says. "We all have the capability in our pocket to look at that plant online and find out." If we only buy what's in bloom in May or June, we miss out on many beautiful, deer-resistant, drought-tolerant plants that tend to bloom in late summer or fall.
Patel recommends that we always favor the independent growers. "Their livelihood is based on these plants, so they know them inside and out for your local area. They will come to remember you as the person with the sandy loam or heavy clay or full shade."
When Patel is shopping for perennials, in addition to looking for healthy foliage and absence of insects or fungus, he looks for the little round pellets that indicate a slow-release fertilizer has been applied. He checks the soil mix to see if it is friable and contains compost. "I don't like a perennial (or an annual) that has a huge mass relative to the size of its pot," he says. "When you put that in the ground, you'll be watering it every day. I prefer the more compact plants."
Patel also looks for a vigorous root system but one that has not yet become pot-bound. For economy, he asks, "Are there enough roots such that I can divide that perennial into four? Can that ground cover be chopped four or six ways?"
Shrubs and Trees
With trees and shrubs especially, be sure to consider how much above ground and below ground space is actually available to accommodate the plant at its mature size.
Shrubs should have well-balanced growth, with stems growing up and out, not crossing over one another. They should not be pot-bound, a condition that forces roots to circle around the inside of the pot. Patel will grab the base of the plant and remove it from the pot to be sure. "For shrubs or trees, having circling roots is really detrimental over the life of the plant," he says. One of the indicators that trees or shrubs are pot-bound is that they will fall over in the wind, because their "sail" is too large relative to their constrained root mass.
In addition to looking for healthy foliage and soil and absence of critters, Elkin considers travel conditions for woody plants especially. She says, "I try to pick the most compact, sturdy plant that will travel well and does not have rogue branches or stems sticking out asking to be broken on the way home."
When Patel shops for trees, he makes sure he can see the root flare—the place where the roots begin to flare out. If you can't see the root flare, or can't scratch down through the soil and see it, the tree has been buried under too much soil. This will create problems in the future, because tree roots need to be close to the soil surface to access oxygen.
Structure is really important in trees: Is there a strong central leader (preferred), or are there co-dominant stems that are subject to breakage? Is the branch system well balanced, or are there large branches crossing and rubbing against one another? Are there side branches almost as wide in diameter as the main trunk? If so, those proportionately large branches are prone to rip off under the weight of snow or ice. Patel looks for any wounding on the trunk, and says that if there is a tree protector sleeve, he slides it up to inspect the trunk underneath. Avoid buying trees with trunk wounds.
For both trees and shrubs, Patel looks at the condition of the soil to see if fertilizer and adequate water have been applied. He says, "If it's an evergreen with its root system in burlap sitting in a hot parking lot with no signs of irrigation, or it's one dry container-grown tree in a block of container-grown trees that are wet, these are trees to avoid."
When buying packs of multiple annuals, look for relatively uniform plant size across the pack.
If it’s wilted, keep walking. Even though a good watering could perk up the foliage, the wilting is probably indicative of a cycle of poor plant care, and this plant is stressed.
Beware of clouds of tiny flies, or insects hiding under the leaves.
There should be no fungus or algae on the soil surface.
If the selection is picked over, ask when the next round of annuals will come out of the production greenhouse or be delivered.
Avoid leggy annuals. Good growers keep them pinched and compact.
Bloom Landscape Design and Fine Gardening Service
Cornell Annual Plant Trials Hort.cornell.edu/bglannuals
Deer Resistant Plants List from Mohonk Mountain House
Orange County Arboretum Orangecountyarboretum.org
USDA Plant Hardiness Zone Map Planthardiness.ars.usda.gov