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Azaleas

I received a beautiful flowering azalea plant during the holidays. I would like to continue growing it over winter. Will I be able to bring it into bloom next year?

Trying to get azaleas to flower in the home is difficult and time consuming because the light in a house is lower than that in the greenhouse where it originated. But if you would like to try to keep your plant growing, follow these directions.

To keep an azalea flowering after you get it, give it water-soluble acid fertilizer at quarter-strength. Keep it in a cool, shaded location, away from heat-releasing light bulbs or hot air vents.

After flowering, remove the withered flowers and keep the plant in a cool, sunny location. Water as needed to keep from wilting. In summer, sink the pot in the garden in a semi-shaded spot. Water and fertilize regularly. Acid fertilizers will help to maintain proper soil pH and keep the foliage from yellowing. Before July 1, shape the plant if needed. Keep the plant outdoors as long as possible in the fall. The plant may need protection from early light frosts but should be brought in before heavy frosts or freezes occur.

Once the plant is indoors, place it in a cool area, 40-50 degrees. An unheated porch, cold frame or similar area is good. Flower buds develop during the cold period. About 6-8 weeks of cold are needed for bud development. Do not fertilize during this time and only water enough to keep the plant from wilting. Buds should develop and swell. In January, move the plant into a cool sunny area, about 60 degrees. Flowering should begin in a few weeks. If temperatures are excessively high during this period, buds often develop poorly and new shoots will grow right past the buds, hiding them. Additional humidity is helpful to keep the calyx on the flower moist and easier to open.

Even if your plant doesn’t rebloom, all is not lost. Azaleas are known to be air purifiers.


Powdery Mildew

My lilac had a grayish blight on the leaves this summer. What caused this and how can I prevent it?

Your lilac had powdery mildew, a common fungal disease. It occurs in late summer in humid weather, especially if your plant is located in a damp, shady area. While unsightly, it does not damage the plant since it only affects the outermost leaf cell layer. If it really bothers you, spray the leaves with a sulfur fungicide early in the season. If mildew appears late in the season, spray again.

Newer varieties of lilac are more disease resistant than the common lilac. Improving air circulation by pruning out any dead branches will also help to reduce mildew, advises Joan Barczak, owner of Blumen Gardens, Sycamore.


Planting Tulips

Is there a best time to plant tulips? I see them at the garden centers in late summer but I am afraid that it is too early to plant them. If I wait too long, I might forget all about them.

Fall bulb planting should wait until soil temperatures drop to 55 degrees or cooler. This usually occurs when nighttime temperatures drop to 50 degrees or lower for two weeks or more. While waiting to plant, store the tulips in a cool, dark place away from direct sunlight—but don’t forget them. After planting, water the bulbs well, advises the Netherlands Flower Bulb Information Center.

If you plant grape hyacinth bulbs amidst your tulips, they will come up early in the fall and serve to mark the position of your tulips.


Container Plants for Fall

Besides mums, what are a few other plants you would recommend for containers for fall color?

Jackie Weiss, garden center manager, Linton’s Enchanted Gardens, Elkhart, Ind.

Dwarf or miniature sunflowers add a bright, sunny pop of color to any container. Mix them with pink celosia, ornamental kale, dwarf ornamental grass and ornamental peppers for a special autumn arrangement. The kale is a great addition as the colors get brighter with colder temperatures. Ornamental pepper can also be taken in and kept as a houseplant through the winter months. Or use aster through October and plant in the garden before the soil freezes. Comes in many colors.

Tracy Bordis, product line specialist, Lurvey Garden Center, Des Plaines, Ill.

The rudbeckias ‘Indian Summer’, ‘Prairie Sun’ and ‘Becky Cinnamon Bicolor’ all have beautiful large flowers. Herbs and leafy vegetables like Swiss chard ‘Bright Lights’, mustard ‘Red Giant’, bronze-leaved fennel and variegated sage all add fun textures. Plectranthus ‘Mona Lavender’ combines nicely with ornamental kale and cabbage. Also plant trailing pansies like those in the ‘Cool Wave’ series at the edge of planters and hanging baskets. Another creative way to add interest to fall planters is with preserved and dried botanicals, sticks or accents.

Zannah Crowe, horticulturist, Monches Farm, Colgate, Wisc.

Our favorite addition to autumn containers – hands down – is ornamental kale. As the temperatures drop, the leaf color intensifies and the plant actually becomes more attractive. We frequently pair ornamental kale with late season grasses as well as decorative gourds and squash tucked amongst the foliage to celebrate the abundance of the harvest season. Your visitors may still be enjoying your kale peeking through the early snow on Thanksgiving Day!


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.


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.


Raising Lawn Level

I want to raise the level of my lawn as much as 2 feet in places. I now have a large quantity of somewhat composted wood chips and I am wondering if I can use them as fill to raise the ground level and provide a good soil in which to sow a lawn.

“It is not a good idea to use only wood chips to raise the grade of an area,” says Greg Stack, University of Illinois extension educator, horticulture. While wood chips may raise the grade for a while, over time they will decompose and eventually the site will sink. Even using them as fill and putting soil over them is not a good idea.

“I would not use straight compost by itself to raise the lawn level, but mix it with soil,” adds Stack.


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.


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


Climbing Hydrangea

What does it take to make a climbing hydrangea flower? Ours was planted 3 years ago and is growing energetically. It’s in a protected nook near the patio and gets very little direct sunlight, but doesn’t act sun starved. We gave it a shot of slow release fertilizer on planting, and once since. Somewhat inadvertently it gets plenty of water, since the hose spigot is nearby and leaks, but drainage does not seem to be the problem. It now fully occupies an 8-foot trellis but shows no interest in flowering. Is it youth, lack of sun, too much or too little fertilizer, bugs, lack of pruning or what? When do these plants bloom and what conditions do they like?

Climbing hydrangea (Hydrangea anomala subsp. petiolaris) is a choice vine with rich, vigorous, dark green foliage, growing ultimately to 20 feet high and 10 feet wide. The extra moisture it gets is good, and it can bloom in shade. Brent Horvath, president and grower at Intrinsic Gardens, Hebron, has seen it blooming beautifully under a canopy of trees.

After weighing all the cultural factors you described, Horvath has concluded that your vine may be immature and will need a couple more years before it flowers. Climbing hydrangea matures very slowly, especially when it’s sold in 2 gallon containers.


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