If you've ever admired a plant and not known where to get it, or if you've ever wanted to save money on plants, you need to know about cuttings.

Most people think that plants come from seeds, and they do. But seeds are only one method for reproducing plants, and it's not the one employed at most nurseries. Here's why:

It requires two plants to make a seed, a mother and a father. The plant that grows from that seed will have some of its mother's traits and some of its father's traits. To get a plant that's an exact replica of the plant with the best characteristics, most nurseries use stem cuttings -- and you can, too.

It's surprisingly easy to propagate new plants by taking stem cuttings, but there are a few caveats. For one thing, cuttings vary widely in how long they take to produce roots. Roses tend to produce roots quickly, so they're a great plant to practice on. Junipers are very slow to produce roots and oak cuttings will probably never produce roots no matter how patient you are.

The kindest cut

The type of cutting that works for most plants is a softwood cutting, which should be taken in late spring or early summer.

To take a softwood cutting, make your cut 3 to 6 inches from the end of a branch. Remove the leaves from the bottom 2 inches of the cutting, then treat the leafless end of the cutting with a rooting hormone. (Garden centers stock several rooting hormones, including Dip'N Grow and Hormodin Rooting Compound. Be sure to follow package instructions. Each kind is used a bit differently.)

After you've treated the cutting, insert the treated end into moist potting soil to a depth of 2 inches. (It's best to use a potting soil that doesn't have added fertilizers. Fertilizers aren't useful to the cutting until it has developed roots.)

If you're taking a single cutting, start it in a 4- to 6-inch pot. If you're trying to root several cuttings, a common technique is to take a 12-inch-square plastic tray, poke drainage holes in the bottom and fill it with potting soil. Place the cuttings in a lightly shaded area.

Cuttings need to be kept moist but not wet. To do so, mist the cuttings with a spray bottle three or four times a day and cover them with clear plastic to help hold in moisture.

Check your cuttings every two weeks or so to see if they've developed roots. Give the cuttings a gentle tug. If there's some resistance, they've developed roots. Carefully brush a bit of soil away to see how developed the roots are.

As soon as the cuttings have three or four roots that are more than an inch long, they can be transplanted into individual pots filled with potting soil. Now you can give your cuttings a light dose of a slow-release fertilizer. Again, be sure that your potting soil is kept moist, but not wet, for the first couple of weeks after transplanting, and keep the cuttings out of full sun.

In a few weeks, your plants should be just like any plant you'd buy at a garden center. You can plant them in the garden or use them in a container display.

Nothing makes us gardeners feel quite as successful as propagating our own plants. But here's another caveat: It's not legal to propagate all plants.

Some plants are protected by patents, making it illegal to reproduce them -- even by taking cuttings -- without a license. The good news is that many plants, especially those that have been around a while, were never patented or have patents that have expired. A few -- including the popular Sven, Ole and Lena shrub roses -- have active patents, so don't try your newfound propagating skills on them.

Jeff Gillman is an associate professor of horticulture at the University of Minnesota. He's also the author of "How Trees Die," "The Truth About Garden Remedies" and "The Truth About Organic Gardening" (Timber Press, $12.95).