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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.


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.


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.


Cold Frames

With all the emphasis on growing fresh vegetables, I think I should use a cold frame but I am not sure what to do or how to go about it. Any ideas?

Cold frames are simply four walls with a window or plastic sheet on top. They range from simply placing four bales of straw in a square with an old window atop them to more deluxe mini-greenhouses with aluminum frames, plastic panels and automatic vents using solar energy to open and close them automatically.

Before building a cold frame, study garden supply and greenhouse catalogs to determine your needs and how fancy you want your cold frame to be. Do you prefer a permanent installation or an easily disassembled frame?

A basic plan for building a cold frame is taught by Chicago Botanic Garden’s senior horticulturist Heather Sherwood. Create four walls from plywood or bricks. Add a transparent lid (plastic sheeting or an old window) for light to enter. Place the lid on an angle. Place the frame against a building, facing south. Make sure there is good drainage. Open the frame when it gets above 60 degrees. Rabbits don’t usually get into the box but chipmunks may squeeze in.

Cold frames are used for extending the growing season, starting plants early, for storing bonsai or protecting semi-hardy plants over winter. The soil in the frame depends on how you will use it. The frame can be set on existing soil when you are storing plants, or fill it with straw to protect bonsai. Locate it conveniently against the house near a back door for easy access, especially if you envision running out to cut some salad greens when snow is on the ground.

Use a cold frame to get a head start on the gardening season. In early spring, start flats of lettuce, radishes, parsley, pansies and other cool-weather plants in the house, and place them in the cold frame in March, depending on the weather. If you plan on planting directly into the cold frame, fill it with a seed starting soil mix and an inch of compost worked into the top 3 inches of the soil. This will help keep the soil loose and aid moisture retention. The plants will be small in the cold frame and can be grown close together. Also use the cold frame to harden off house-grown seedlings.
Don’t forget to check on your plants regularly because winter sun is strong and plants dry up easily. Use it for a head start on the gardening season.


Good Annuals for Shade

Now that bedding impatiens (I. walleriana) are not recommended because of impatiens downy mildew, what are three good annuals for shade?

Chris Williams, production manager, K&W Greenery, Janesville, Wisc.

I like New Guinea Impatiens. They make nice bushy plants that are full of large colorful flowers and are easy to grow. You also get a large color selection with New Guineas. The SunPatiens and Bounce impatiens are fairly new plants, and they are recommended for sun as well as shade. Then there’s coleus. Who doesn’t like its colorful foliage? Many varieties grow upright, but others also spread. Torenia, also known as wishbone flower, has trumpet-like flowers of white, yellow, rose and purple that cover nicely mounded, low-growing plants.


Karen Wedel, manager of the outdoor floral department, Wedel’s Nursery, Garden Center, Kalamazoo, Mich.

One of my favorites is begonia. Tuberous varieties have large colorful blooms; wax begonias are good for mass planting. I’m also a fan of the big leaf, 16-20 inch tall Whopper series with large waxy leaves and summer-long flowers.
Another idea is coleus and caladiums. They come in different foliage colors, work great in gardens and containers. They are both also easy-care.
Finally, torenia or wishbone flower, named for the small “wishbone” inside the mouth of the pink, yellow or blue-purple flowers. Blooms all summer. Some varieties will trail.

Kevin DeBoer, manager, Big John’s Farm Market and Greenhouse, Chicago Heights

My favorite is Dragon Wing begonias. They’re usually sold in 4½ inch pots or hanging baskets. At my house I removed them from the baskets, then planted them in the ground in full shade. They turned out awesome! Plain wax leaf begonias are also good.
In addition, I like coleus. They don’t produce flowers, but they have many different vibrant leaf colors. In full shade New Guinea Impatiens will flower sparingly, but if you put them in some sun, they will flower more.


Russian Sage

Our Russian sage (Perovskia) is full and bountiful but will not stay upright. Is there anything we can do? Is there a way to split some off when it has outgrown its space? Should it be trimmed back in fall or spring?

The normal growing habit of Russian sage is to open in the center, according to Tina Pansic, staff horticulturist at Chalet Nursery, Wilmette, who says this is a common complaint. Russian sage must be grown in full sun and can be supported by pea stakes (willow or dogwood branches) or commercial wire stakes. A new cultivar, ‘Little Spire’ is shorter and will stay upright. Your plant can be divided by breaking up the root system with a spade as the bottom stems get woody.Wait until spring to cut the plant to the ground. Plants that are cut back in autumn suffer more winterkill. Pansic cuts her perovskia halfway down in late summer to control the spreading, and then cuts it to the ground the following spring


Low Light House Plants

We have a skylight in the bathroom over our Jacuzzi tub with an area around the tub that is quite large. What plants can we grow there, and what care do they need? Can we grow orchids?

Use plants that grow in low light such as pothos, philodendron, peace lily (Spathiphyllum), Chinese evergreen (Aglaonema), any type of dracaena, and include lady palm (Rhapis) for height. It would be possible to grow moth orchids (Phalaenopsis).

“While the bathroom will give you good humidity, your plants must be watered thoroughly. The peace lily needs to be kept evenly moist. Feed monthly with an all-purpose houseplant fertilizer,” advises Elizabeth Hoffman, manager, West End Florist, Evanston.


Frost

I have a Japanese maple that was hit by frost. Some of the leaves are curled and brown. Will they fall off and new leaves grow? Is there anything I can do to help the tree? What is the best method to prevent this from ever happening again?

Your tree will recover from the frost damage. Adventitious (secondary) buds at the nodes will send out new leaves. Make sure that your tree is sited correctly in a sheltered location and protected from harsh winds, advises Susan Eyre, Rich’s Foxwillow Pines Nursery, Woodstock. If your tree is fully leafed out and a hard frost is predicted, you could drape your tree with plastic, a tarp or some other covering overnight.


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.


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.


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