Pollination: Let's talk about sex—flower sex, that is. Flowers contain a plant's reproductive organs, which include the anthers and the stigma. For the plant to produce seed—which is how most plants reproduce—the tiny dust-like grains of pollen contained in the anthers (or male organs) must reach the stigma, where they burst open and release sperm that fertilize the eggs within the ovary (the female organ). Fertilized (or pollinated) eggs grow up to become seeds.
Some types of plants are self-fertile, meaning that the eggs that they produce can be pollinated by their own pollen; others have distinct male and female flowers, and you must grow both to get seed. The majority of plants, however, have flowers with both types of organs yet still grow best when they are cross-fertilized with pollen from another nearby plant of the same species. The pollen in those cases gets from the anthers of one plant to the stigma of another carried either by the wind (anemophilous pollination) or by insects (entomophilious pollination). Flowering plants are generally pollinated by bees, butterflies and moths, which are attracted by the sight and scent of flowers.
Annuals and biennials that produce and drop seeds
where they are growing, which then sprout and grow into full-grown plants themselves are "self-seeding," explains Nona Koivula of All-America Selections in Chicago. Hollyhocks, for example, self-seed so efficiently that you might think they are perennials because they keep growing in the same place year after year; in fact, they are biennials that drop seed which stays dormant through the winter and comes up the following spring in the same place. Unfortunately, many of the peskiest annual weeds like dandelions are efficient self-seeders, too—if you want to get rid of them for good, you have to pull these weeds before they develop their seeds and drop them where they will germinate the next year.
You can find out all you need to know about your soil's pH
with a simple soil test—which you can perform with a kit you buy or you can get from a soil laboratory. (Lab tests are inexpensive and give you lots of other worthwhile information about your soil.) The result of the pH test will be a number: if that number is below 7, your soil is acidic; if it is above 7, the soil is alkaline. What that tells you is how hospitable your soil is to specific plants. Some, like azaleas, prefer acidic (often referred to as "sour") soil; others, like cool-season grasses, grow best in alkaline (or "sweet") soil. Many like the soil close to the neutral pH of 7.
You can alter your pH by adding lime to acidic soil or sulfur to alkaline soil. Or you can just add compost! "A soil's pH seems to be less important to plants when the soil is rich in organic matter—the plants still grow well even if the pH isn't quite what they prefer," elaborates Elaine Ingham, Ph.D., an associate professor of soil ecology at Oregon State University. "Unless the pH is extreme in one direction, you're better off adding compost to the soil than trying to balance the pH with other amendments."
Sport: Most of the new plant varieties that find their way into nurseries and garden centers are the result of years of careful breeding and selection of the best specimens from trials. But sometimes that marvelous creator known as Accident can bypass all the years of work when a plant develops a new and desirable trait as the result of a spontaneous mutation in its cells. If that trait remains within new plants grown either from its seed or from a piece of the original plant, the new plants get a new name and are known as "sports." A sport will be identical to the original in every way except the one trait.
Plants that don't reproduce by seed often spread by stolons, or underground stems on which new plants grow. Zoysiagrass is a familiar plant that reproduces by stolons; many weeds do, too. When pulling these weeds, you must be sure to get all the stolons as well as the roots and leaves
Sucker: "A sucker is a bud that forms and grows into a branch in the crotch between another branch and the main stem," says Richard Racusen, Ph.D., professor of plant biology at the University of Maryland, "and it can crowd out the original branch if left to grow." That's why you hear (or read) advice suggesting that you remove the suckers from trees and other plants.