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Cucumbers

The foliage on our cucumber plants is starting to wither and turn yellow. They get plenty of water and I feed them regularly. What could be wrong?

“The plants may be getting too much water. They can tolerate fairly dry soil,” says Tim Norris, owner Spring Bluff Nursery, Sugar Grove. There are other possible causes for yellowing foliage as well. The cucumber beetle may have fed on the plants when they were small and transmitted bacterial wilt, which later plugs the vascular tissue. To prevent the beetle from feeding on young plants, use row covers until the plants get larger. A stressed plant is also open to attack by bacterial wilt.


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.


Types of Fruit Trees

I am going to be planting five dwarf fruit trees; two ‘Bartlett’ pears, one ‘Cresthaven’ peach, and two ‘Honeycrisp’ apples. Could you give me some feedback on them?

If you buy young container fruit trees, plant them very early in the spring to lessen transplanting shock (as soon as the soil can be worked and before the buds break). Plant the tree at the level it was in the pot, adding a layer of top mulch.

“Wrap the trunk in paper or plastic tree wrap to prevent deer and rabbit damage. Protect the trunk from voles with fine wire mesh at the base,” says Tim Norris, president of Spring Bluff nursery, Sugar Grove.

‘Bartlett’ pear is subject to fire blight and also needs a pollinator for good fruit production. ‘Patten’ and ‘Parker’ are two pear cultivars Norris recommends. Two different cultivars will give you better cross-pollination.

‘Honeycrisp’ apples are an excellent choice for this area. They grow up to 20 feet tall on semi-dwarf root stock. They can be pollinated by any member of the Malus family, including a nearby flowering crab tree.

‘Cresthaven’ peach, while hardy here, may not bear fruit, depending on how cold the winters are. When the temperature goes down to zero, ‘Cresthaven’ peach loses all its flower buds. Norris suggests growing ‘Reliance’ peach instead. It needs a long growing season. Last spring (2008) was a cool one and peaches did not bear much fruit. Peaches are not long-lived trees. By the time the tree is bearing fruit, you will need to start growing another tree.


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.


What are your three favorite “all-but-forgotten” perennials that every garden should include? Why do you like them?

What are your three favorite “all-but-forgotten” perennials that every garden should include? Why do you like them?

Jan Sorensen, Native Plant Specialst, Wasco Nursery & Garden Center, St. Charles

Anemone tomentosa ‘Robustissima’ is a late season plant for sun to part shade and a wide range of soils. Deer and rabbit resistant with few pests or diseases. The fuzzy texture and gray-green leaves of Stachys byzantina ‘Helene von Stein’ complement other sun plants wonderfully. Leaves mask brown lower foliage of asters. The 3 to 5-foot tall Baptista australis and PRAIRIEBLUES cultivars offer gorgeous blue and purple flowers and they attract butterflies. They like full to part shade and tolerate poor soils.

Elizabeth Hoffman, owner, West End Florist and Garden Center, Evanston.

My three favorite forgotten perennials are plumbago, bergenia and Stokes’ aster. Plumbago (Ceratostigma plumbaginoides) is a ground cover with sky blue flowers in fall and red leaves. Intersperse it with spring bulbs for three seasons of interest. Bergenia (Bergenia cordifolia) is versatile, handling conditions from moist sunny areas to dry shade. It is rabbit and deer resistant. When you rub your two fingers on either side of the leaf you can make it squeak (hence another common name: pig squeak). The long-blooming and easy-care Stokes’ aster (Stokesia laevis) is fairly pest and disease free. Rabbits tend not to eat it, and it attracts butterflies.

Rich Massat, co-owner,The Growing Place, Naperville and Aurora

Three favorites of ours are pasque flower (Pulsatilla vulgaris), Laddie peony (Paeonia peregrina) and balloon flower (Platycodon grandiflorus). Pasque flower blooms very early in spring with extremely soft leaves and silvery green buds. Red, white or purple flowers; purple seems to have more vigor. The ferny-leaved Laddie peony also blooms very early with red flowers. It’s a hybrid of Paeonia peregrina and P. tenuifolia. Balloon flower is named for blue, pink or white flowers that start out looking like a balloon and open to look like a star. They have a long blooming period in summer.


Compost Bin

I’d like to start composting. Do you have any advice on what kind of bin to purchase/build so that it is successful in the Chicago climate?

Compost, decayed organic matter, improves soil structure, porosity and density and creates a better root system. It increases moisture retention and nutrients while adding significant quantities of organic matter to the soil. It is such a valuable addition to garden soil that it is worth the effort to collect and store waste vegetative material until it decomposes.

Compost bins range from low to high tech. A compost heap can be as simple as a pile of leaves stored at the rear of your garden. The most costly composter is a revolving two-tumbler device with a rotator drum that separates new material from finished material and discharges the final product.

Ideally, if you are saving a mix of unshredded plant material that includes flower stems, large leaves and small branches, a three-bin system works best. Stake out three 36-inch square cages using fence rails, lattice or steel wire. Raw material goes into the first bin. When it is partially decomposed, aerate it and shift it to the second bin, and put the most highly decomposed matter into the final bin. With that method, you can keep adding fresh material as the season progresses.

Do not put any diseased plants in the pile. Keep it in a concave shape to hold rainwater, and aerate it occasionally. As the pile “cooks,” it will heat up during the summer. An interior temperature of 180 degrees will kill bacteria but is not often attainable; 120 degrees is more likely for a mix of green and dried leaves.


Mandevilla

I brought my mandevilla plant into the house to overwinter. How best can I keep it? Will it flower? Can I root pieces of it?

Mandevilla is a tropical vine requiring high light. Keep it in the sunniest part of your home. It will not flower over winter because the light intensities will not be great enough to bring on flowers and many of the leaves will fall off. It is best to keep it in a semi-dormant stage by trimming it back, withholding fertilizer and allowing it to dry out between waterings. Mandevilla is prone to aphids, white fly and mealy bugs, but don’t treat the plant preventively with an insecticide. It doesn’t work, and it also adds unnecessary chemicals to your indoor air. Treat a bug problem only if one develops. One preventive measure that does work is to give your houseplants a periodic shower or spritz them with a hand spray in the kitchen sink.

When the days are longer in early spring, begin feeding it with a 20-20-20 plant food to encourage new growth and then switch to a 20-30-20 formula. “It’s hard to propagate in winter, but in spring when your plant gets a burst of new growth, you can try to root cuttings,Ôø‡Ôø‡Ôø‡ advised Susan Izenstark, tropical specialist at Jamaican Gardens, Morton Grove.


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.


Voles

How can I get rid of voles? I think they are doing a lot of damage to my bulbs.

Voles are mice-like rodents that gnaw on roots and bulbs. They are hard to control.

There are repellents on the market that you can try—Deer Off, Moletox, and a new product named Shot Gun Repel. The latter repellent was designed specifically to protect bulbs from chipmunks, moles, voles and mice. Treat the bulbs before storing or planting. Remove old skin and soil, and then spray thoroughly until wet. Allow the bulbs to dry before storing or planting.


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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