I get ideas for this column in many ways, often from readers. This week's topic was stimulated by a telephone call from Carl Orndorff, a local nurseryman for more than 70 years, who's still going strong at age 91. He called to remind me to tell you that now's the time to divide and move irises and daylilies and to plant biennials from seed. Thanks, Carl. Here we go.

Daylilies

Daylilies can be divided in several ways. They grow in clumps. Dig the entire clump out of the ground. Knock or wash as much soil off the roots as possible. Divide where the roots pull apart easily. Plant healthy roots that have at least three large eyes or buds on them. Place them about three inches deep in soil that has been amended with lots of compost. Site in full sun.

Add kelp, fish emulsion or other organic, low-nitrogen growth stimulant. Look for sea-life-based materials at your garden center. Some of the ones you can pick are Bio-Plex, Coast of Maine Fermented Salmon Organic Fertilizer, Neptune's Harvest Liquid Seaweed Food and Ocean-Gro Plant Food.

Water newly divided daylilies as you replant them and during dry periods. Adding compost to soil and mulching the surface will go a long way toward conserving moisture. The daylilies will leaf out in spring and grow two to three "scapes," the stems that produce blooms, by next season. Each scape will have several flowers on it.

If you don't wish to divide your daylilies by hand, another method is to dig the clump and simply slice or cut pieces from the main root ball with a spade. Make the pieces three to four inches across and as deep as the existing roots. Transplant the pieces as described above and they will thrive. But the most efficient way to thin them for your greatest yield is to clean the roots and divide them by hand.

Irises

Many varieties of iris, such as dwarf crested (Iris cristata) and Japanese iris, don't need to be divided if your intent is for them to grow like a ground cover. But when rhizomes, including Siberian or bearded irises, grow into a tight mass or clump after many years you will want to divide them for better flowering. Bearded types are among the most popular, and regular division of them will discourage disease and the very destructive iris borer.

Bearded irises have a distinctive fan of leaves that grow from shallow, fleshy roots called rhizomes. Also called German irises, they're considered by many enthusiasts to be the showiest of the late-spring flowers. Their four-foot size makes them the primary attention-getters of the landscape when in bloom, and so many hybrids have been developed that they're available in every color but true red. To get them to continue producing showy flowers, divide them now.

When you dig bearded iris, the soil usually falls away from the roots, and they'll divide rather easily. Keep only the one-year rhizomes, which are the roots that are attached to the fan of leaves. Dispose of all older root pieces. This will keep your irises free of borers. The one-year rhizome for transplanting should be about three to four inches long and must have at least one large fan of leaves attached. It's all right if there are a couple of smaller fans as well. Cut the fans in half and transplant them to a new location in full sun, making sure that the eye or bud on the rhizome is within half an inch of the soil surface.

Use a generous amount of compost to lighten the soil and ensure drainage for iris beds. Drainage is the most important consideration in preventing the root-rot diseases they get.

Siberian irises are more disease-resistant and less particular about how you transplant them. They do not have to be divided and will flower in spring and develop very showy, tight clumps of foliage that look good throughout the growing season.

If you want to divide them to make more plants, dig the entire clump. It will be a tight mass. Knock as much of the soil from the roots as you can. Look for natural divisions to get the most from your plant, but you may have to slice them apart. Use a curved-edge cutting tool, such as a linoleum knife, to separate tightly bound rhizomes. Transplant pieces that have at least three leaves and place them in the soil at about the depth they were growing on the parent plant.

Biennials

Orndorff considers biennials to be a very misunderstood group of plants. They are defined as plants that bloom a year after they are sown, and then go to seed and die. Sow the seed now for foliage growth this season and flowers next year. Or buy them as started plants at the garden center next spring.

This group of plants is so confusing that you may find them being sold as annuals or perennials. But they don't die with the first freeze like annuals or come back stronger one year after another the way perennials do. Biennials will self-sow their second year, thus propagating themselves.

Biennials that can be sown now are hollyhocks (Alcea), forget-me-nots (Myosotis sylvatica), hesperis, foxgloves (Digitalis), larkspurs (Delphiniums), sweet Williams (Dianthus barbatus) and pansies. You can't easily transplant them from a planting bed, so they should be sown where you ultimately want them to be growing.

Many garden centers don't stock these seeds. You may have to call around or purchase seeds from catalogues. A few places you can order from are Thompson & Morgan, 1-800-274-7333; Seeds of Change, 505-438-8080 and W. Atlee Burpee & Co., 1-800-888-1447. Put a rush on your order, so you can plant within the week and hope for rain.

Here are seed-planting guidelines:

* Dig an inch of compost into the top two to three inches of soil.

* Scatter the seeds lightly where you want them to grow.

* Very lightly slide an upside-down leaf rake over the planting bed to barely cover the seed.

* Sprinkle with water when planting and irrigate lightly three times a week through dry periods.

* Protect the roots of the young plants in winter with a mulch of aged leaves or bark.

You'll enjoy these biennials next year. When they go to seed at the end of their blooming period, give them a chance to return annually. They may not grow back as the showy hybrids that you first planted but will usually flower again and, perhaps, surprise you the following year with a new color or form.

Lerner is president of Environmental Design in Capitol View Park, Md. His e-mail address is lernscap@erols.com