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Peony Blight

Last summer my neighbor told me the black spots on my peony were a blight, although my peonies bloomed nicely. What can I do about this?

Your peonies probably have a fungal disease, a common problem. The causes are wet summers with cool damp nights, too much shade, poorly drained soil, or a lack of air circulation. While your neighbor diagnosed your problem as peony blight, which is caused by an air-borne botrytis fungus, the black spots indicate the more common phytophthora blight, according to Walter Schmidtke, nursery manager at Pesche’s Garden Center in DesPlaines.

Early in the spring, young emerging shoots may suddenly wilt and fall over, turn black and show masses of gray-brown botrytis spores. If nothing is done, these spores are carried to developing buds, which turn black.

Black spots on foliage, leaves turning red in summer, and black stripes on the stalk indicate phytophthora. “Plants with these conditions won’t have as much zest” said Schmidtke.

The best protection against recurrence of either blight is good sanitation. In fall, it is important to cut down and throw away all peony foliage, cutting stalks just below the surface of the ground.

If this doesn"t work and you resort to chemicals, the treatment is the same for both diseases. As soon as the shoots emerge in spring, begin spraying with Mancozeb, a copper sulphate solution, and repeat every 7-10 days until buds form, according to University of Illinois Extension. Spray the whole soil area for overwintering spores. In early summer you can spray plants with Daconil, a general purpose fungicide. Cut away any diseased foliage at once.


Miniature Gardening

Miniature gardening is the rage. What enchanting miniature plants work well in a shaded area?

T Biernacki
Many miniature plants grow in shade. Some unusual ones are the 6-inch tall Solomon’s seal (Polygonatum humile ‘Tom Thumb’), the 2-inch tall Ajuga reptans ‘Planet Zork’ and two cultivars of the very slow-growing conifer Cryptomeria japonica: ‘Koshyi’ and ‘Tenjan’. Or look for two European gingers, Asarum forlesii ‘Mercury’ and Asarum takaoi ‘Roundabout’, which are about 3 inches tall. Also: the maidenhair fern (Adiantum venustum), mosses and miniature hostas

M Samios
The best and most obvious answer is miniature and small hostas. From the ever-expanding “mouse” series with ‘Holy Mouse Ears’, ‘Mighty Mouse’ and ‘Giantland Sunny Mouse’ to newbies such as ‘Mini Skirt’, ‘Ladybug’, ‘Baby Booties’ and ‘Little Starlet’… perfection! Add some grass-like carex such as ‘Beatlemania’ for texture, miniature Solomon’s seal (Polygonatum humile) and dwarf heucheras from the Little Cute series, and your garden fairies will be in heaven.

C Bornmann
If you’re planting in the ground, these low-growing perennials will add interest and texture to your garden: Irish and Scotch moss (Sagina sublata and S. subulata ‘Aurea’ – best in part shade), brass buttons (Leptinella squalida) and miniature hostas. Add color with annuals such as polka dot plants (Hypoestes), ‘Strawberry Drop’ coleus and torenia. It’s important to add perennials and annuals into your garden for a longer season of color.


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.


Ground Cover Suggestions

I have a dampish area with poor grass and moss that I would like to change to ground cover, but if I have only one plant, won’t it be boring? Can I get rid of the grass in winter or early spring?

If we have a dry winter or spring, you can smother the grass with a heavy layer of newspapers held down by bricks or stones, or use a product that will kill the grass. Use it according to the label directions. Grass roots are very persistent, so you may have to dig out the remaining roots by hand. The moss will disappear as you aerate the soil and rake in organic material.

When your area is properly prepared, you will have a large choice of low-growing groundcovers.

Kim Schroeder, perennial buyer at Wasco Nursery and Garden Center, St. Charles, suggests the following: lily of the valley (Convallaria majalis), sweet woodruff (Galium odoratum), wild ginger (Asarum canadense), or European ginger (A. europaeum), vinca (Vinca minor), Tiarella, Astilbe-the cultivar ‘Perkio’ is shorter than Astilbe chinensis ‘Pumila’ and violas such as bird’s foot viola (Viola pedata) or sweet white viola (V. blanda).

These choices are not aggressive growers like goutweed (Aegopodium), which grows anywhere and is very difficult to eradicate. You can plant free form areas with one type and another alongside it as contrast. Most of these ground covers bloom at slightly different times to give you a spring-into-summer flowering season.


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.


Tree Planting

What is the best time to plant a tree in northern Illinois?

The two best times to plant a tree are April-May or September-October because the weather is cool and there is a good moisture supply, according to Joni Cotten, nursery stock manager, Hawthorn Gardens in Hawthorn Woods. However, planting times can vary, depending on the plant and its method of growth.

Bare-root trees are planted when dormant. They are less expensive, and the planting hole can be back-filled with soil dug from the hole. Trees that have burlap-covered root balls are generally planted in the cooler months, while trees in containers can be planted at any time. Rhododendrons and evergreens are not planted bare root.

“Birches and oaks are dug in nursery fields and planted in the spring. Oaks especially have a long tap root, so they do best when they have the entire season to grow,” says Cotten.


Japanese Maple

I’m moving to a townhouse with limited direct sunlight. I would like to put a Japanese maple in a north-facing garden but don’t know if it will do well. What are the best kinds? Also, when is the best time to plant a small tree?

Japanese maples are small decorative trees which are becoming more popular as more dependable cultivars come on the market. Even so, an established tree will sometimes succumb in a severe winter. Their light requirements vary.

The trees can grow in a northeast exposure, and 6 hours of sunlight is not too much, according to Jeff Sibley, nursery manager of Red’s Garden Center, Northbrook. They need a moist, well drained, neutral soil, amended with organic matter. They can grow to 8 feet tall in a good location. He says the best planting time is right after Mother’s Day. A protected spot and plenty of moisture are critical elements for survival, even with the newer cultivars.

Sibley recommended the following cultivars of Acer palmatum var. dissectum, a cut-leaf variety, as the most graceful trees:

  • ‘Crimson Queen’ is a small shrubby tree, with finely cut reddish leaves that hold color all summer and turn scarlet before dropping off in the fall.‘Garnet’ is similar to ‘Crimson Queen’ but a somewhat more vigorous grower.‘Bloodgood’ is a vigorous, upright tree with blackish red bark. It has deep red spring and summer foliage, scarlet in the fall.
  • Acer palmatum var. dissectum ‘Viridis’ Lace Leaf Japanese Maple is a small shrub with drooping branches, green bark and pale green, finely divided leaves that turn gold in autumn. It takes shade.

Begonias

I start ‘Dragon Wing’ begonia from seed under grow lights. What other begonias can I use to cross-pollinate with the ‘Dragon Wing’ so I can collect my own seeds?

‘Dragon Wing’ is a unique hybrid type of begonia named to reflect the shape of its leaves. It is created by interspecific crosses of two different begonia species and can lead to interesting new plants, but they are sterile.

It is impossible to say exactly which species will cross and which will not cross. You can try crossing angel wing begonia, a common houseplant, with another species. There is a good chance viable seed will be produced, according to Brian E. Corr, new crops development manager at Ball Horticultural Company, West Chicago.

The American Begonia Society (begonias.org) is a resource for information on hybridizing. The archives of the bi-monthly journal The Begonian would also be helpful.


Trimming Japanese Maple Trees

My split-leaf Japanese maple tree is 15 to 20 years old, about 7 feet high and about 10 feet wide. It is overtaking the corner of the yard. Can I trim it, and at what time of the year?

Trim your tree in late fall to early winter when the tree is dormant. Remove only one-third of the amount you want pruned each year, being careful to retain all its charm.

“Go easy on it,” says Joann Madon, horticulturist, The Growing Place, Aurora and Naperville.


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.


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