that contains silt, sand and clay—the major components of well-balanced soil—is called "loam." The ideal proportions of those components for gardening, notes Wayne Honeycutt, Ph.D., a USDA soil scientist at the University of Maine, are 30 to 50 percent sand, 30 to 50 percent silt and the remainder as clay. "That balance is ideal," he explains, "because in those proportions the soil holds water well but is loose enough for the roots to penetrate the soil easily." Allow us to state the obvious and point out that "sandy loam" has more sand and "clay loam" has more clay—just wanted to be sure that was clear.
Naturalize: You want bulbs that keep coming back for many years and that multiply themselves? Then you want those that "naturalize" in your climate, Kim Tyson of the Netherlands Bulb Co. in Easton, Pennsylvania, tells us. "A bulb that adapts well to the kind of soil you have, your winter and summer temperatures and the amount of light it gets will naturalize in your area," Tyson explains. "Those differ from one place to the next. Most daffodils, for instance, naturalize in the Northeast, but they don't in Florida because it doesn't get cold enough for them in the winter," she continues, "but it gets too cold in the Northeast for paper-whites [a close relative of daffodils], which will naturalize in most parts of the Southeast."
N-P-K: Pop quiz! Remember back in high school chemistry class when you had to learn the Periodic Table of Elements? Each element had a letter or two for a symbol that scientists use as shorthand to write out formulas. So, what did the letters N, P and K represent? You're right, N=nitrogen, P=phosphorus and K=potassium! Give yourself a gold star.
Now, why are we testing your memory of that long-forgotten class when talking about gardening? Because those three elements, N, P and K, are the major nutrients most garden plants require for healthy, productive growth—in varying proportions, depending on the plant and what stage of its development it has reached. And when you look at a bag or bottle of store-bought fertilizer, it will have an N-P-K rating on it that is typically expressed as a ratio, like 2-1-2, which means there are two parts each of nitrogen and potassium to one part of phosphorus.
In contrast to annuals and biennials (see the definitions above), perennials live longer than two years, even through frozen winters. "Some, like columbines, are short-lived perennials that come back for only three or four years," explains Dennis Stimart, Ph.D., a professor of plant genetics and physiology at the University of Wisconsin; "others, such as peonies, come up for decades" even though they look like they've died back in the winter. "And some plants that we think of as annuals, like ornamental peppers
, are really perennials in their native climates," he adds, "but we treat them like annuals because they don't survive winters in the North." Petiole: The part of a leaf's stalk between the bottom of the leaf and the plant's main stem is called the petiole (PET-ee-ole). "It is a vascular conduit between the plants' roots and its leaves," notes Richard Racusen, Ph.D., professor of plant biology at the University of Maryland. "Like humans, plants have two types of tubing that serve different purposes. Both of those reach the leaves through the petiole."
Pinch back: Mom always said that if your sister pinches you, you should not pinch her back, but many gardeners know that pinching back some plants helps direct their growth. "The most common reason for pinching back a plant is to make it bushier," states Wallace Pill, Ph.D., professor of horticulture at the University of Delaware. "When you pinch back the top of certain plants, they will grow more lateral branches and thus become bushier."
Pinching back is easy to do—all you need are a thumb and forefinger and the resolve to trim your plants for their own good. Just get a solid grip with your fingers on the stems you're going to pinch back and firmly pull them off. "If you're advised to do a soft pinch, pull off about a half inch," clarifies Dr. Pill. "For a hard pinch pull off a whole inch."
When should you pinch back a flowering plant? "Before the plant has committed to flowering," he answers. "For example, gardeners often pinch back chrysanthemums in midsummer so the plant will get grow more lateral branches that will produce more flowers. But once the days become shorter mums will form flower buds and it is too late for pinching back to do any good—all of the plant's energy at that point will be devoted to filling out those buds and opening them into flowers."