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Dwarf Junipers

Why do I have brown areas near the tips of my dwarf Japanese junipers? This has been occurring the last few years. They are supposed to be drought resistant”

“It’s hard to diagnose without seeing the plants or their location,” says Matt Warrick, sales associate in tree and shrubs at Gethsemane Garden Center, Chicago. “Your plants may be in a situation that’s too dry. With the type of drought we had this past summer, even if a plant is drought-tolerant, it would have needed supplemental watering.”

Other factors that affect junipers are poor drainage, insufficient light, fungal disease, and insufficient acidity in the soil. Any of these conditions could cause needle browning.


Slugs

I am sick of slugs. Perhaps if I knew their life cycle I could get rid of them. Where do they go over winter? Where do they come from? What is the best way to get rid of them?

Slugs are gastropods belonging to the mollusk class. They have lungs and can breathe air and live one year. At nightime, to conserve moisture, they feed by biting tissue with a rasping mouth underneath their body. They move by sliding over slime secreted by a large muscular foot and constantly lose water from this slime production and evaporation.

To make matters worse, they are hermaphrodites having both male and female organs and can deposit egg-like clusters of 1/8 inch pearls in soil where they overwinter. Their growth is activated by rising soil humidity and temperature in the spring, according to Ed Valauskas, Manager of Library and Plant Information Services at the Chicago Botanic Garden.

Even if your soil is relatively slug free, they can come in from a neighbor’s yard or live in the soil of container-grown plants. If you garden in very sandy, fast draining soil, you will probably not have many of these pests, but in heavy clay soil, slugs find constant moisture that suits their life style.

Slugs feed on plants with moisture in them, especially hosta, ligularia, dahlia and begonia leaves, lettuce, strawberries and tomatoes. They hide by day and feed at night or on gray, damp days. Go outside with a flashlight after 10 p.m. and look for them under boards, rocks or pots and destroy them.

Laurie Skrzenta of Laurie’s Landscape, a Downers Grove hosta grower, keeps the hosta area dry and doesn’t water them because slugs do not live in dry locations. She depends on rainfall and maintains that hostas can exist without supplemental water. Laurie also suggested using coarse sand as a mulch. Another possibility is to sprinkle sand in the center of your dormant hostas since this is where the slugs lay their eggs.

There are many home remedies to get rid of slugs including beer, ammonia water, ice water, and yeast water. Gardener Anna Hevrdejs, Woodridge, suggests sprinkling corn meal around slug areas. Slugs like to eat it, then die. Replace it after a rain. She also claims that sweet woodruff planted around hostas restrains the slug population.

Chemical metaldehyde or methiocarb pellets are useful but they can be attractive to dogs and children. They are very toxic. Much safer is a copper strip laid around the areas to be protected, although this is not practical in an ornamental garden.


Coneflowers

I thought that purple coneflowers were insect proof, but now I see some aphids at the bud and tiny flies. What is wrong?

Purple coneflower (Echinacea purpurea) is a common native perennial that grows best in sandy or well-draining soil and full sun. If you are not giving your plant these growing conditions, certain insects can attack your plants.

Aphids are sometimes visible on buds, and as sucking insects they cause stunted and deformed leaves. Spider mites are tiny insects that often multiply in hot, dry conditions. Spider mites feed on sap and cause yellowish leaves. Thrips are barely visible, tiny insects causing bud malformation.


I've got green worms!

What is the green worm that eats my roses and columbine every year?

It is hard to diagnose your problem without seeing the caterpillar. There are several green worms that bother roses, and one can be controlled with Bt (Bacillus thuringiensis) but rose slug, for example, cannot. Proper identification is necessary before applying any control method. Do not use an insecticide for anything that"s not on on the product label. Do not use any insecticide as a preventive measure. It doesn"t work and ends up being harmful to the environment and a waste of your money.

Green worm on your columbine could be an inch worm or canker worm. If the caterpillar loops up in the center or arches as it moves along, it could be a looper or cabbage worm. Leaf miners, which are usually white or pink, tunnel in the leaves. “To eliminate insects, use insecticidal soap,” said Nancy Clifton, Chicago Botanic Garden Plant Information Specialist.

For an exact diagnosis, consult your local University of Illinois Extension service or collect a specimen and bring it to the Plant Information Service at the Chicago Botanic Garden or the Morton Arboretum.


Tree Position

What is the correct distance from my house to plant a tree? What is the correct distance from the lot line to plant a tree?

It depends on the size of the tree you are planting. A small tree such as a serviceberry (Amelanchier) or a dwarf flowering crab could be planted as close as four to five feet from the house. For a birch tree, a distance of six to eight feet would be the minimum.

Distance from the lot line does not matter as long as it doesn’t interfere with power or sewer lines. You should check with your village before planting. Closeness to the neighbor’s lot line is not an issue, because neighbors have the right to trim back any overhanging branches, according to Matt Zerby, partner in Wasco Nursery, St. Charles.


Tree Planting

What is the best time to plant a tree in northern Illinois?

The two best times to plant a tree are April-May or September-October because the weather is cool and there is a good moisture supply, according to Joni Cotten, nursery stock manager, Hawthorn Gardens in Hawthorn Woods. However, planting times can vary, depending on the plant and its method of growth.

Bare-root trees are planted when dormant. They are less expensive, and the planting hole can be back-filled with soil dug from the hole. Trees that have burlap-covered root balls are generally planted in the cooler months, while trees in containers can be planted at any time. Rhododendrons and evergreens are not planted bare root.

“Birches and oaks are dug in nursery fields and planted in the spring. Oaks especially have a long tap root, so they do best when they have the entire season to grow,” says Cotten.


Rose of Sharon - Botrytis Blight

I have two 3-year-old rose of Sharon plants, about 20 feet apart. One blooms every year. The other plant forms about 100 buds and looks healthy, but it has not bloomed in the last two years. The buds are solidly closed and look as if they are rotting from the inside out. There does not seem to be any sign of insects on the plant. What is this problem?

From the description it sounds like your plant is infected with botrytis blight, a fungus disease that attacks buds before they open, according to Jim Schuster, extension educator, horticulture, University of Illinois. Your plant needs to be treated with a fungicide early in the season. Remove all diseased portions of the plant and any residue on the ground, as the fungus lives over winter in discarded material.


Cycas

I have a cycas palm and am not sure how much direct sunlight or water it needs. It has light brown marks developing on the leaves. What is causing this, and how do I care for my plant?

Cycas palms or sago palms (Cycas revoluta) are tough house or patio plants. They are neither palms nor ferns but primitive cone-bearing relatives of conifers. A rosette of green feather-like leaves, 2 to 3 feet in height, grows from a central point at the top of a single trunk.

Cycas need bright light and should be kept relatively moist with weekly watering. However, prolonged rainy spells can cause fungal leaf spot disease.

“The shiny brown spots are probably caused by scale,” says Jeff Frohn, sales associate at Geimer Greenhouses, Long Grove. “It can be treated with fish oil, vegetable oil or an all-in-one insecticide spray,” adds Mike Geimer, owner, Geimer Greenhouses.


White Pine Trees

I have lost four 12-15 foot tall white pine trees over the last year. All had the same symptoms, browning needles at the bottom that continued up to the top. Can you tell me what pest is killing the white pines? I am also losing an Austrian pine now. It is experiencing the same symptoms.

White pines in this area are very rarely troubled by disease. They are, unfortunately, highly susceptible to high pH problems, or soil alkalinity, and are utterly intolerant of salt, according to Rich Eyre of Foxwillow Pines, Woodstock. The browning needles could also indicate the plant is getting too much water or has poor drainage.If environmental problems are not the issue for your white pines, consult an expert. Betty Lockwood, Plant Information Specialist at the Chicago Botanic Garden, suggested you bring them a sample branch to check on disease and bring in an arborist for an on site visit to check your growing conditions. Or take a 12-inch sample of an affected tree to your local extension office.Austrian pine is very tolerant of environmental conditions but is prone to certain diseases—diplodia tip blight and dothistroma needle blight, both caused by a fungus. Only an arborist or a laboratory can provide an accurate diagnosis. If you bring in a 12-inch sample for diagnosis, be sure to sterilize your pruning shears with denatured alcohol after cutting the diseased wood.


Trimming Japanese Maple Trees

My split-leaf Japanese maple tree is 15 to 20 years old, about 7 feet high and about 10 feet wide. It is overtaking the corner of the yard. Can I trim it, and at what time of the year?

Trim your tree in late fall to early winter when the tree is dormant. Remove only one-third of the amount you want pruned each year, being careful to retain all its charm.

“Go easy on it,” says Joann Madon, horticulturist, The Growing Place, Aurora and Naperville.


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questions

What is the correct distance from my house to plant a tree? What is the correct distance from the lot line to plant a tree?

I have a large variegated sedum with pink flowers that I have had for years. I noticed that it has started to send up some all-green shoots. Why is it doing this and how can I keep my plant variegated?

What is the green worm that eats my roses and columbine every year?

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