QI have a large clump of Stella de Oro daylilies. How do I divide them?
ADaylilies are favored perennials because they require little maintenance, are cold hardy and have a long blooming season. Stella de Oro is one of the most popular of the daylily cultivars that bloom repeatedly throughout the summer.
Daylilies grow for a number of years before they need to be divided. Declining flower production is often an indicator that the clump should be divided. You also can divide any reasonably sized clump just to have more divisions to plant or to share with friends.
Daylilies can be divided in spring, just as new shoots are emerging, or in late summer to early fall. Don't divide the plants too late in the season, however, or the replanted sections may not have time to reestablish before the ground freezes.
To divide a clump of daylilies, carefully dig up the entire clump using a shovel or spading fork. Daylilies have dense systems of thickened, tuber-like roots that are often tightly bound. There are various methods for dividing clumps, so pick the one that works best for you. You can divide sections using hand tools (dandelion diggers and pronged cultivators may be helpful). If you have two spading forks, you can insert them back-to-back in the clump and wedge off sections of the clumps. I usually resort to the easy method, which is to slice through the clump with a well-sharpened flat-bladed spade. This will inevitably cut open some of the tuber-like roots, but that seems to have little ill-effect on the divisions.
Each division should have at least three or four growing points (where foliage arises). Larger divisions will have more impact on the landscape in a shorter time. Daylily divisions should be replanted as soon as possible, though they can be held for several days if kept cool and moist.
QI want to get rid of the grass around a three-year-old-river birch so I can plant bulbs around it. I layered newspapers, landscape fabric and mulch over the area, which I plan on taking up after six weeks. Is there a better way to get rid of the grass without damaging the tree roots?
AYour grass-killing method will work, but it may take more than six weeks to kill off the grass. There are two faster ways to kill grass, however.
Removing the sod is the most immediate and most laborious of the two ways. Using a sharp, flat-bladed spade, slice through the sod where you want the edge of the bed to be. Then start working the spade, held almost horizontally, under the sod. It's easiest to do this in a kneeling position. Cut through the turfgrass roots, perhaps half an inch under the soil surface. Shake soil out of the stripped pieces of sod, then put the sod in the compost pile. Because the tree roots are growing deeper than half an inch, you should not damage them by stripping sod. Be careful not to injure the tree's trunk.
The second method is to kill the grass with an herbicide. Glyphosate (Roundup is a trade name) kills turfgrass. It also will kill any other green plant you spray it on, so use it cautiously. Protect the tree trunk from the herbicide by wrapping plastic around the trunk, then removing it as soon as the spray has dried. It may take a week or so for the grass to die. Glyphosate does not have any residual action in the soil, so it will not affect the tree roots or the bulbs you plant. Dig holes for bulbs as small as possible, because digging holes is more likely to damage roots than removing the turf.
QI moved here from Hawaii and brought a plumeria with me. It has been outside all summer but I'd like to know how to keep it indoors over winter.
APlumeria (Plumeria sp.) is a tropical plant that is sometimes grown in greenhouses in cold climates. The plants tend to be leggy, but they are grown for their fabulously fragrant flowers. Because they are native to warm, tropical zones, make sure to move the plants indoors well before the first freeze.
Plumerias need lots of light and humidity to survive indoors. They are better suited to greenhouses or conservatories than to home interiors, where there often is not enough light or moisture. Lacking a greenhouse, you may be able to get your plumeria through the winter by placing it in the sunniest spot in your house and running a humidifier near the plant. Mealybugs and scales are fond of plumeria, so patrol regularly for these insect pests.
-- Nancy Rose is a research horticulturist at the Minnesota Landscape Arboretum. She spends her spare time gardening, inside or outside, depending on the weather. To ask her a gardening question, call 612-673-9073 and leave a message. She will answer questions in this column only.