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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.


Houseplants

I have houseplants outside that I will need to bring indoors. What is the lowest temperature at which I can leave them outside?

The rule of thumb is when night temperatures are in the 50s, it is time to bring your houseplants indoors, according to horticulturists at Pesche’s garden center, Des Plaines.

To avoid the shock of suddenly bringing plants into a hot dry environment, place them in a shaded area before the heat comes on in the house. Bring in sensitive tropicals such as hibiscus and anthuriums as soon as summer cools down.

Christmas cactus and cymbidium orchids can tolerate chillier temperatures and stay outdoors longer, but move them indoors before the thermometer drops to freezing, says Greg Stack, University of Illinois Extension Educator, Horticulture. Indoors, a cool 50-degree area such as an unheated sun porch will give them the short day situation they need to set flower buds. Stack keeps his Christmas cactus in a cool unused room where the lights aren’t turned on. His plant sets buds and blooms reliably every year, he reports. Christmas cactus buds will dry up in an overheated, dry room.


Birch Trees

I’d like to plant a white bark birch in front of my home in my sunny front yard. What can you tell me about Betula utilis var. Jacquemontii?

The birch, Betula utilis var. Jacquemontii is a tall, narrow tree (to 100 feet) with very white bark that’s native to India. It is subject to borers. The popular weeping white bark birch, B. pendula is also subject to borers in our climate and is not a suitable choice.

“There are better birch choices, so choose what grows well in our area,” advises Ken Morris, vice president of Spring Bluff Nursery in Sugar Grove. Two trees resistant to borers are the paper or canoe birch and the river birch.

Canoe or paper birch (B. papyrifera) has a stout trunk with creamy white bark that peels off in papery layers. It is native to North America. It is the first paper birch bred to resist the bronze birch borer, but it still needs to be monitored and sprayed yearly for the borers. A good cultivar is ‘Renaissance Reflection.’

River birch (B. nigra), native to the eastern United States, is fast growing when young. It can reach more than 50 feet in height. Its bark is a smooth, shiny apricot and, when mature, flakes and curls in cinnamon strips. It tolerates slow drainage and is also resistant to borers. “It’s pretty tough, good and sturdy,” says Morris.

The cultivar ‘Heritage’ was introduced to much acclaim around 15 years ago.

Birch trees need moisture. Do not allow your tree to dry out in your sunny site.


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.


Pre-Chilled Bulbs

I purchased some pre-chilled hyacinths and tulips for forcing but there were no directions with them. Does this mean I don’t have to chill them in the refrigerator, and will they just bloom in the house any time during the winter? The last batch of bulbs became moldy in the refrigerator.

Using pre-chilled bulbs avoids the 12- to 14- week cold treatment that bulbs need for indoor blooming. However, you need to pot up the bulbs in a loose potting mix. Do not cover the bulbs in plastic wrap or paper bags. It will still take 3 or 4 weeks of cold for roots to appear.

Hyacinths kept cool do not need to be potted. They can sprout roots in a saucer of water with the bulb held in place by stones. Check the water level and make sure it just touches the base of the bulb and add water as needed.

The bulbs can be forced as soon as you see roots, or you can hold them in the cold temperature to space out the bud development. Place rooted bulbs in bright light in a cool room, and watch for buds. Rotate the plant so the flowering stem will be erect. “Your previous bulbs rotted because they were not potted up,” says Lori Harms, greenhouse manager, Countryside Nursery, Crystal Lake.


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.


Italian Cypress

Is it possible to plant and grow Italian cypress in the Chicago area? Are our winters too severe for it? If they are, is there an alternative conifer that will provide a similar look?

Italian cypress (Cupressus sempervirens) has dark green foliage and horizontal branches and grows into a dense column 60 feet high in Italy. It is not hardy here.

Paul Jeffers, tree and shrub salesperson, Gethsemane Garden Center, Chicago, suggests substituting a dense, columnar arborvitae, (Thuja occidentalis ‘Fastigiata’). It grows to 25 feet tall and 5 feet wide, but can be kept lower by pruning. The very narrow arborvitae ‘DeGroots Spire’ is another choice. The false cypress Chamaecyparis nootkatensis ‘Green Arrow’, often mistaken for arborvitae, is a tight upright growing plant.


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.”


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.


African Violets

I have twelve beautiful blooming violet plants on my office desk, placed 12 inches from a light source that’s kept burning day and night. I water them from the bottom and let the water remain in the saucer.

No matter what I spray, I continue to have gnats and other insects in my soil. I also occasionally start to get yellow spots on the tips of the leaves and then the spots start going down the leaves. What’s going on here?

A number of factors could be causing your problems.

“Yellow tips indicate your plant is showing stress either from lack of humidity or watering too much; it’s hard to pinpoint,” says Sandy Fuller, Palatine, past president of Barrington Bloomers, who grows 100 African violets under lights in her basement.

Peat-based soil needs to dry out for fungus gnats to disappear. Use a magnifying glass and try to identify them. Gnats eat only decaying plant material and do not damage the plants. If you have mealy bugs, their cottony waxy sac is easy to identify.

Office tap water may be too cold. Let it sit for half a day before using it. If the water is too cold, the plant could rot. Some violets are more sensitive than others to temperature changes.

Repot your plants in African violet soil and use a 20-20-20 fertilizer.


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questions

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?

I plan on saving my amaryllis bulbs that I kept outside over summer, but I noticed red streaks on the inner side of the leaves. What caused that? Will I be able to save my bulbs?

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

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