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Hibiscus

I am growing my potted tropical hibiscus indoors for the winter. The leaves are starting to yellow and fall off. Should I give the plant iron and should I fertilize it? Do I cut it back, and if so, when?

Hibiscus leaves turn yellow in response to the change in environment. The older leaves fall off first. If the leaves are chronically pale yellow with green veins, the plant could be lacking iron, but in your case, it is probably the change in growing conditions that is affecting the plant. When the days get longer in February or March, prune it to shape it, or cut it down to force good bottom growth.”

“Don’t panic; the plant expresses itself dramatically,” reassures Mike Geimer, owner of Geimer Greenhouses, Long Grove. “Don’t be timid pruning it.”


What are some good plant/tree choices to hide unattractive views?

I’d like to block an unattractive view of my neighbor’s house/yard. What are some good plant/tree choices to hide unattractive views?

John Eskandari, owner, The Urban Plantsman, Chicago

Two evergreens for sun are Thuja occientalis ‘Wintergreen’ and Picea pungens ‘Fastigiata’. Both are moderate to fast growers. For shadier locations, Picea abies ‘Cuppressina’ does remarkably well.

A deciduous tree that would work nicely is Fagus sylvatica ‘Dawyck’. It comes in green, gold, red and purple leaved varieties. They work well in shadier spots but the red and purple leaves are less intense in shade.

In smaller areas, I like Amelanchier laevis ‘Cumulus’. It’s a more upright form of serviceberry providing nice spring blooms, edible berries, and golden fall color. It is adaptable to both sun and shade.

Chrissie Sieff, nursery manager, Platt Hill Nursery, Bloomingdale

Whenever I am asked this question, my customers usually have something in mind such as ‘Emerald Green’ arborvitae (Thuja occidentalis ’Emerald Green’, sometimes labeled ‘Smaragd’). They want a green wall, and they want it instantly! Our dead plant return rate is high on this item, so I try to steer them to hardier choices, such as Viburnum nudum ‘Winterthur’ or Syringa pubescens subsp. patula ‘Miss Kim’.

A strategically placed tree can also do the trick. I love katsura tree (Cercidiphyllum japonicum), river birch (Betula nigra), serviceberry (Amelanchier), and ‘Ivory Silk’ tree lilacs. As you can tell, I’m not a big fan of evergreens.

Andy Wedel, part owner, Wedel’s Nursery, Florist & Garden Center, Kalamazoo, MI

Arborvitae (Thuja spp.) is the first plant we think of, but there are others. It’s hard to pick just one. Fine Line buckthorn (Rhamnus frangula ‘Ron Williams’) is a columnar-shaped deciduous shrub with yellow fall color. Evergreen, drought-tolerant upright junipers such as Juniperus chinensis ‘Blue Point’ are great in sunny spots. Some other columnar trees include ‘Crimson Sentry’ maple (Acer platanoides ‘Crimson Sentry’), Red Fox katsura (Cercidiphyllum japonicum ‘Rotfuchs’), and columnar hornbeam (Carpinus spp., cvs.).


Variegated Sedum

I have a large variegated sedum with pink flowers that I have had for years. I noticed that it has started to send up some all-green shoots. Why is it doing this and how can I keep my plant variegated?

All variegated plants contain a combination of green cells with chlorophyll and white tissue with no chlorophyll, which produces the green and white effect. Variegated plants are genetically unstable, so sometimes the tissues revert to all-green cells and send up solid green shoots from the base of the plant. Because these shoots contain more chlorophyll than the variegated tissue, they are more vigorous. Thus they can quickly overrun a plant, according to Hortech, a developer and grower of sedums.

Cut the green shoots off at the base of the plant as soon as you see them. It is possible you have induced vigorous growth by giving the plant too much high-nitrogen fertilizer, so it would be wise not to fertilize. It sometimes helps to divide your plant and then choose the most variegated stems for a new plant. Since your sedum, a cultivar of Sedum spectabile, is such a rapid grower, it will quickly become a new clump after division. Newer named cultivars are more genetically stable and do not have this problem.


Azalea

We moved into a house with a lovely azalea that didn’t bloom. We thought it might have been over-pruned. Last fall we did not prune it and now it still hasn’t bloomed. I was hoping to transplant it this year, but it looks rather sickly. Shall we prune it again and give it another year? Can I still transplant it?

Stop pruning your plant since you may have over-pruned it. Evergreen azaleas only need tip pruning in July after their flowers have faded.

Concentrate now on rebuilding the azalea into a healthy plant. Do not transplant a sickly one. Feed your plant regularly with an liquid acidic fertilizer. Keep your plant weeded and its roots moist by using mulch because azaleas are surface rooters. Make sure your plant is situated in soil with good drainage and in a part sun/part shade location.

Try this regime over summer and evaluate your plant next spring, advises Charlene Wooten, manager, Cedar Hill Nursery, Lake Zurich.


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.


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.


Staking Plants

I dislike staking perennials. Is there anything I can do to avoid it?

There are several techniques you can use to limit time spent on this chore, but it is difficult to totally

avoid staking some plants.

First and foremost, the old adage “right plant, right place” means full sun perennials need to be grown in full sun for tight upright growth. If they are too shaded, the plant will stretch or bend toward the sun and grow in a loose habit. Growing plants a little closer together also helps because it enables plants to support each other.

The best remedy to avoid staking is to cut some tall plants down by one-half in June. That will delay flowering in helenium, monarda, platycodon, chrysanthemum and aster, but the plants will remain upright. If you really want to eliminate cutting back, grow dwarf versions of these plants.”
Short, thin branches from forsythia or dogwood (known as “pea staking” in England) can be placed around the perimeter of newly emerging plants to help keep the stems upright. Some garden centers have begun selling bundles of branches for this purpose. In a short time, the shrub cuttings are covered by emerging shoots. This technique works well with fine foliage such as baby’s breath or flax.

There are numerous staking supports from bamboo to iron rebar rods. Wire staking supports are available in full, half and even quarter circles to support single stems. Peony hoops can be left in place over winter and will support not only peonies but boltonia, baptisia, and even errant tomatoes.

Some plants always need to be staked. Giant dahlia tubers need a heavy stake dug into the hole at planting time. That prized, single-stemmed iris, lily, or delphinium can get blasted in a storm, and then it’s too late to save it.

Remember: the time to stake plants is during the cooler days of spring when plants are growing rapidly and not on humid July days. Staking should be done unobtrusively and subtly for plants to retain their natural grace.


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.


Fresh Figs

I recently moved to Chicago from Houston and I miss fresh picked figs. Is there any way to grow figs in Chicago short of installing a greenhouse? Will sunny windows do? I’m desperate.

Figs (Ficus carica) are handsome plants with smooth gray bark and large lobed leaves which can grow into gnarled trees in warm climates. In Illinois, with winter die-back, they are grown as shrubs. They should be sited where they get some protection from the wind in winter.

You do not need a greenhouse to grow figs, and a sunny window would not be appropriate. Grow a fig cultivar suitable for this climate. While most figs are rated to winter hardiness zone 4, the problem comes because our growing season is too short to ripen fruit, which may take until September or October in a cool summer. Sometimes we have an early frost. If so, pick unripened figs and let them ripen in the house.

Alana Mezo, senior horticulturist for the fruit and vegetable island at the Chicago Botanic Garden, recommends ‘Chicago Hardy’ fig, the variety they grow. They have 10 or 12 plants there growing in a row and, through trial and error, have decided not to protect them over winter because rodents chew roots and stems in wrapped plants and set back their growth. Their figs are multi-stemmed, die back to the ground when unprotected, and get off to a slow start in the spring, delaying fruiting.

However, if you do not have a rodent problem, tie the stems together, wrap burlap around the tied stems, and cover the base with a basketful of leaves. With this protection, your plants will have a head start in spring, and you should have figs ripen a month earlier than unprotected plants, at least by late August.

Another method of winter protection is to root prune in a half semi-circle around the plant, lay it down and cover the plants with leaves over winter.

If you grow a fig in a large container, you can wheel it into an unheated garage and store it over winter. Watch it to see if it needs moisture. Your plant does need a dormant cold period, but not a freeze. This is an “iffy” process according to Mezo.

A fig grower in Highwood claims that rubbing olive oil on the fig hastens ripening, but Mezo has not tried this yet.


Winter Mulch

Must I mulch my garden and, if so, when is the best time to apply it? What are the best materials to use?

Perennial gardens usually come through the winter better when given some sort of protection, although many gardeners leave their established gardens unprotected save for deer netting to keep deer off newly emerging greens in spring. Plants new to your garden can be protected by mulch during the first winter and may not need it after that.

Mulch is used in winter not to keep the plants warm, but to keep the ground at an even temperature and prevent plants from heaving out of the soil during periods of alternate freezing and thawing. Thus it is applied after the ground freezes. If mulch is applied before the ground freezes, it can smother the plants.

The simplest mulch is a loose layer of oak leaves, which do not mat down and rot. Ground-up leaves are ideal, and even dried grass can be used. Or apply straw left over from Halloween decorating.

Use only a few inches of mulch and keep it light enough not to smother the plants. Deer netting helps to hold mulch in place until it is wet enough not to blow around. In spring, as soon as the plant starts to grow, remove the mulch gradually, a little at a time over several days. Don’t wait too long because if the shoots are too tall, you may damage them as you pull off the mulch. Work the mulch into the soil with a trowel afterwards.

Heucheras, astrantias and recently planted perennials may heave even if mulched. Push any dislodged plants back into the soil. Mulch also protects the evergreen rosettes of biennial hollyhock, foxglove, Canterbury bells and sweet William from snow and ice damage.


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