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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.


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.


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.


Orchids

What causes black spots on my orchid leaves?

There are a number of causes for black spots, depending on the type of orchid.

“In some varieties, like Oncidium ‘Cherry Baby’, the small black spots through the leaf are normal,” says Liese Butler, owner, Oak Hill
Gardens, Dundee.

Black spots on the top of the leaf could be sunburn, caused when sunlight scalds a drop of water that has been left on a leaf. Newer growth of Cattleya orchids can normally have a purplish spot. A black mushy spot and a black stem indicate rot.


Japanese Red Maple

I have a nicely sheltered, rounded 7-foot tall Japanese red maple on the southeast corner of my backyard. Half of the tree has lost its leaves, the formerly red bark is turning gray, and a good-sized square of bark has been stripped off on the side that faces the yard. I sprayed the exposed bark with black pruning spray to close any entry for insects. I have not cut off any of the branches.

Does the winter have any effect on the tree? Should I look for some insect infestation? What should I do now?

“It appears that the tree suffered some kind of injury. Over winter, watch for sun scald on the southern exposure. Use paper tree wrap on the trunk,” advises Mike Geimer, owner of Geimer Greenhouse, Long Grove. If you are fearful of insects, you can use an organic pyrethrum spray. Black pruning spray is not necessary.


Large Tree Replacement

What is the largest tree that one can plant? We are trying to replace some 7- to 8-foot trees that were recently destroyed.

Trees sold at garden centers that are 2.5 to 3 feet tall, with a 2.5 inch diameter trunk, can be planted by hand. A hole for a ‘balled and burlap’ tree with a 5 to 6-inch diameter trunk can be dug by hand without a tree spade.

Any tree with a trunk larger than 6 inches in diameter would need a tree spade to do the moving and digging. Even large trees, such as a 35-foot tall tree with a trunk 9 or 10 inches in diameter can be transplanted with proper equipment. “Spruces 30 feet tall can be installed easily with a tree spade,” according to Greg Oltman, owner, Gro Horticultural Enterprises, Huntley.


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.


Bulbs Over Winter

What is the best way to dig up, clean and store gladiolus and dahlias? What are the little white sacs on glad bulbs?

Gladiolus corms and dahlia tubers are generally dug up after the first frost or before Halloween. Cut off all the stems and foliage, let the plants dry, and shake off all the soil. Make sure each corm and tuber is firm and not rotted. Place them in a box or tray and cover with peat moss. If you know the cultivar name, tag the plant.

Store them in a dark, cool place, checking them over winter. If the dahlia tubers are shriveled, sprinkle a little water on them. Dahlias can be potted up in spring for an early start in the garden.

“The white sacs you see attached to the gladiolus corms are little bulblets. You can remove them or not. If left on the corm, they will grow larger, and may enhance the number of stems on the plant. If you remove them and plant them, it will take at least three years before they flower,” explains Joni Cotton, perennial manager, Hawthorn Gardens, Hawthorn Woods.


Hydrangeas

When is the best time to cut back hydrangeas? How far do I cut them back?

Pruning hydrangeas depends on the species. Oakleaf hydrangea (H. quercifolia) and Peegee hydrangea (H. paniculata), with its well-known cultivars ‘Limelight’ ‘Little Lamb’ and ‘Tardiva’, are woody shrubs that bloom on old wood. Trim them within two to three weeks after flowering. The following year’s primary flower buds form near the top of the stems in late summer. If you wait too long to prune, you will be cutting off flowers on the old stems.

The new bigleaf hydrangea (H. macrophylla) ‘Endless Summer’ is an herbaceous plant that dies to the ground over winter and starts into new growth in spring. It can be cut at any time since it flowers on both old and new wood.

Hydrangea ‘Annabelle’ (H. arborescens) can be trimmed at any time. “It dies back totally to the ground each year so you can keep it trimmed to the size you want,” says Jean Bragdon, garden center manager at Lurvey’s Garden Center, Des Plaines.


Trumpet Vine

Will a trumpet vine growing on a tree harm it?

Trumpet vine (Campsis radicans) is a vigorous vine which can climb to the top of a tree in one season and spreads by suckering roots. It blooms in full sun in clusters of 3-inch-long orange tubes with flaring scarlet lobes.

The vine will not harm an established tree but a young tree could be stressed.

“There may be root competition between the vine and the tree for moisture, especially if your tree needs a lot of water. However, trumpet vines can grow with less moisture. When customers claim their vine does not bloom, it is because they are watering and pampering it too much,” says Lori Harms, greenhouse manager, Countryside Nursery and Garden Center, Crystal Lake.


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questions

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?

What is the largest tree that one can plant? We are trying to replace some 7- to 8-foot trees that were recently destroyed.

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

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