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Winter Mulch

Must I mulch my garden and, if so, when is the best time to apply it? What are the best materials to use?

Perennial gardens usually come through the winter better when given some sort of protection, although many gardeners leave their established gardens unprotected save for deer netting to keep deer off newly emerging greens in spring. Plants new to your garden can be protected by mulch during the first winter and may not need it after that.

Mulch is used in winter not to keep the plants warm, but to keep the ground at an even temperature and prevent plants from heaving out of the soil during periods of alternate freezing and thawing. Thus it is applied after the ground freezes. If mulch is applied before the ground freezes, it can smother the plants.

The simplest mulch is a loose layer of oak leaves, which do not mat down and rot. Ground-up leaves are ideal, and even dried grass can be used. Or apply straw left over from Halloween decorating.

Use only a few inches of mulch and keep it light enough not to smother the plants. Deer netting helps to hold mulch in place until it is wet enough not to blow around. In spring, as soon as the plant starts to grow, remove the mulch gradually, a little at a time over several days. Don’t wait too long because if the shoots are too tall, you may damage them as you pull off the mulch. Work the mulch into the soil with a trowel afterwards.

Heucheras, astrantias and recently planted perennials may heave even if mulched. Push any dislodged plants back into the soil. Mulch also protects the evergreen rosettes of biennial hollyhock, foxglove, Canterbury bells and sweet William from snow and ice damage.


Asparagus

Can I grow asparagus from seed? I saved the little red berries from my plants.

You can grow asparagus from seed. I have done so many times, but it takes three or more years for a crop, and growing from seed usually gives inferior plants. Better crops come from hybrid plants.

If the red berries from the female plant have dried over winter, there should be two or three black seeds inside. Clean them off and prepare your seed bed for planting.

Asparagus needs full sun and a sandy loam soil raked smooth. After the danger of frost is past, bury the seeds at a depth two times its diameter and keep the bed moist. In the third year you can lightly cut the pencil-thin stalks. There are often volunteers of female plants between rows you that can transplant. However, it is best to start asparagus by buying roots so you have a small crop the first year. Most varieties sold are male.


Siberian Iris

My Siberian iris ‘Gracilis’ plants have only one bloom per clump. I have five 3 to 5 year-old clumps that are 8 to 10 inches wide. They do not appear to be crowded. All are planted in a moist area. Why is there only one bloom per clump?

“Iris bloom is directly proportional to the amount of sun received,” proclaimed Chuck Simon, Hinsdale, past president of the Northern Illinois Iris Society, who grows 10,000 rhizomes of 1,000 to 1,500 iris varieties. Iris need 4 to 5 hours of sun, but full sun is best. Another cause of bloom failure could be iris borers, which eat mature fans and cause only minor increases in plant growth. Spray with Cygon 2E in spring when eggs of borers hatch in order to break their life cycle. When transplanting iris, make sure the roots remain moist. Grow them in moist but not wet soil. In the first year after planting, water them religiously. Once past that point, they are very hardy. Simon, a master iris judge, referred to the American Iris Society checklist for any special cultural conditions affecting bloom and discovered that this variety is very old. Iris siberica ‘Gracilis’ was introduced in 1927.


Fruit Trees

I am interested in growing fruit trees in my suburban DuPage County yard. Can sweet cherries be grown here? Can you suggest varieties of apples, pears, peaches, apricots and plums that are hardy and disease resistant?

Sweet cherries are not hardy in this area. Some fruit trees are sensitive to winter cold and spring frost damage to the buds. Early flowering apricots are the most sensitive, followed by peaches. Pears and sour cherries bloom later and are less sensitive to late frosts.

Apples are the least sensitive to frost damage. Apple scab and apple maggot are common pests. Fruit trees require a regular schedule of spraying for pest control.

For a backyard fruit tree grower, tree size is important. Dwarf fruit trees bear full-sized fruit earlier than standard sized trees. Most fruit cultivars need two different varieties to cross- pollinate and produce fruit.

Midwest Fruit Explorers is a non-profit amateur backyard fruit-growing group. For more information about fruit growing, see www.midfex.org.


Japanese Red Maple

I have a nicely sheltered, rounded 7-foot tall Japanese red maple on the southeast corner of my backyard. Half of the tree has lost its leaves, the formerly red bark is turning gray, and a good-sized square of bark has been stripped off on the side that faces the yard. I sprayed the exposed bark with black pruning spray to close any entry for insects. I have not cut off any of the branches.

Does the winter have any effect on the tree? Should I look for some insect infestation? What should I do now?

“It appears that the tree suffered some kind of injury. Over winter, watch for sun scald on the southern exposure. Use paper tree wrap on the trunk,” advises Mike Geimer, owner of Geimer Greenhouse, Long Grove. If you are fearful of insects, you can use an organic pyrethrum spray. Black pruning spray is not necessary.


Peonies

Do the ants on my peony flowers help buds to open, or is this an old wives’ tale? What are the extremely tiny, microscopic yellow wormy looking bugs crawling on my pink peony flowers? My peonies are beautiful, but I don’t want all these bugs.

Peony buds exude a sweet viscous sap that attracts ants. The ants do not generally affect the opening of peony buds. The old tale could have arisen because ants are occasionally seen eating large transparent drops of sap on the buds.

The tiny worms you describe are common yellow thrips, which are attracted to light-colored flowers. Thrips suck juice from buds, petals and leaves. Their triangular bodies are too small and move too fast to be hosed off the plant. A systemic insecticide should be used to prevent plant injuries.

“Peonies are such old time nostalgic favorites that people excuse their shortcomings,” says Mary Ellen Murphy, perennial plant specialist, Pesche’s Garden Center, Des Plaines. “To use the flowers indoors in cut arrangements, pick them when the buds are soft and show color, and then rinse the stems outside with a hose to remove insects.”


Perennial Pinchback

Is there an overall rule about when to pinch back my leggy plants?

“The reason plants are pinched back is to obtain compact and bushier growth. This is generally done three times during a growing season, or you can apply the 6 nodes rule,” says Jennifer Brennan, horticulturist, Chalet Nursery, Wilmette.

After 6 weeks of growth, trim back half of the growth, or wait until you see 6 nodes on the plant stem to trim back to get more branching. For plants that respond, such as chrysanthemums, use the 6 node criterion.


Osteospermum

Can you tell me if the African daisy Osteospermum ‘Springstar Aurora’ can be winterized here? It is a healthy plant?

Those South African daisies could never endure a frigid winter here and should be considered annuals. Their daisy-like flowers with blue centers open only in sunlight and bloom best in early summer or later when summer days cool down. They can be seed-grown under lights.


Cabbage Worms

We are first-time gardeners and have planted Brussels sprouts and green and red cabbage that we are trying to grow organically. There are black egg sacs and small green worms eating the leaves. Is there an organic product we can use on the cabbage?

Egg sacs can be washed off with a hose.

There are several organic methods you can use to deter cabbage worms. Lightweight polypropylene row covers, placed over a row of plants and supported by hoops, will block wind and insects while permitting light, air and rain to reach the plants. Hold down the row covers with soil, stones or bricks.

Another organic method uses pots of mint growing between cabbage plants. The mint odor is said to deter cabbage moths. Don’t let the mint take root, however; it will take over your garden. Rotenone dust is considered organic, as it leaves no poisonous residue on plants. The use of hot pepper spray is an irritant to insects and worms, but also to your skin and eyes. Bacillus thuringiensis (Bt) is a specific biological control that is fatal to cabbage worms if ingested. Note that it can be harmful to certain butterfly larvae.


Overwintering Clivia

After a summer outside, my clivia has returned indoors. Last year it had only one puny flower. What treatment should I give it over winter to bring it into bloom?

A. Clivia miniata, sometimes known as Kaffir lily, a South African native, is a member of the amaryllis family. When growing clivia, it is important to observe seasonal changes. During short winter days, stop fertilizing entirely until spring, and stop watering also.

“Treat your plant like a cactus,” says Steve Butcher, tropical plant specialist at Sid’s Garden Center in Palos Hills. “You can keep it completely dry for a couple of weeks up to the point of shriveling before watering. Keep your plant in a cool place; 55 to 65 degrees is ideal, but that’s hard to achieve in many homes. It does not need a brightly lit location.”

When the days lengthen, move the plant into a brighter location and increase watering. There are no hard-and-fast rules on watering. The frequency depends on the pot size and the root mass. Use a water-soluble, high-phosphorus fertilizer every second or third watering. After you see buds, reduce fertilizer to once per month. Root bound plants flower better.

Following this regime last winter, Editor Carolyn Ulrich reported five bloom stalks on one of her plants in February. Other plants bloomed in March but one didn’t bloom until June. Clivia are considered a winter-flowering houseplant, but bloom time will vary. Be patient.


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