Taproot: The first root that many plants put down when they germinate grows straight down into the soil and is like a stem that all the other roots grow from—this root is called the "taproot" and its like a major artery in the human body. When transplanting, take care not to break the taproot or you severely hamper the plant's chances of surviving the move.
Tissue culture: When scientists and nurseries want to reproduce a lot of one plant very quickly and inexpensively, they can take a piece of that plant—literally, a few cells—and grow them in a laboratory into replicas of the original plant. That process of reproducing a plant in the laboratory is known as "tissue culture" and it's "a valuable tool for researchers and other plant people," insists Dennis Stimart, Ph.D., a professor of plant genetics and physiology at the University of Wisconsin. "However, the plants that come out of tissue culture can be unreliable," he adds, declining to give specific examples for fear of making home gardeners overreact to them. For our part, we've heard gardeners express frustration about the reliability of tissue cultured plants such as hostas (they turn out different rather than identical to the varieties they came from) and so we can recommend that you look for conventionally reproduced plants whenever possible, which Dr. Stimart does not disagree with.
Your average plant has two sets of chromosomes. To enhance certain qualities in some species, scientists have bred triploids (which have three sets of chromosomes) and tetraploids (four sets of chromosomes), reveals Dennis Stimart, Ph.D., a professor of plant genetics and physiology at the University of Wisconsin. What do gardeners need to know about triploids and tetraploids? "Triploids are typically sterile," so they don't produce viable seed
, answers Dr. Stimart. "The flowers on tetraploids are generally bigger than those on other varieties of that species, but there are fewer of them and the plant generally grows slower than the types with two sets of chromosomes."
Variegated: Leaves that have different colors are variegated—"if those different colors are genetically induced and not caused by pests, diseases or nutritional deficiencies," adds Wallace Pill, Ph.D., professor of horticulture at the University of Delaware. Variegation is most often white or yellow, but it can also be bluish or reddish, depending on the plant. Those colors can change due to light or soil conditions; some plants outgrow the variegation altogether.