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Rose Rosette Disease (RRD)

What is rose rosette disease? I lost two antique roses and removed a hedge of multiflora roses that were supposed to be undesirable. How bad is it?

Rose rosette disease is a plant killer of unknown origin and no known cure. It is known to plant pathologists, but unknown to most rose gardeners in this area.

The disease is believed to be caused by a virus or virus-like pathogen that has been spreading through much of the wild rose population in the Midwest, probably transmitted by a mite introduced to the U. S. to eradicate multiflora roses. It is lethal to the wild multiflora rose and potentially lethal to many rose species and cultivars.

Symptoms of rose rosette disease are highly variable, depending on the species or cultivar. Some of the more recognizable symptoms include rapid elongation of new shoots forming witches brooms, or clustering of small branches with distorted leaves of conspicuous red pigmentation and distorted flowers.

David Robson, Springfield, extension educator, horticulture with the University of Illinois, reports that it is all over our area. Mike Geimer, owner of Geimer Greenhouse, Long Grove, reports coming across RRD in a Long Grove garden. One plant in a bed of Flower Carpet roses caught his eye because of its uncharacteristic red clumping stems. He looked up the symptoms on the internet, identified it as RRD and advised immediate removal of the plant. Also important, warns Geimer: “Always sterilize pruning shears.”

Kathy Hallgren, Sycamore, is worried about the future of old roses. Two summers ago she noticed some peculiarly rampant irregular, hyper-thorny pink growth with irregular leaves on an antique Alba rose.

After researching the symptoms, Hallgren determined the irregularities were from RRD. “I dug out the plant and burned it. Once I learned that multiflora roses could be the culprit, I removed them even though they were healthy. This summer I saw it on one of my ‘William Baffin’ roses so cut it down and burned it. This disease means business,” says Hallgren.

No effective control is available for existing rose rosette disease. All cultivated roses are potentially susceptible. Be on the lookout for it. Early detection is the key to effective cultural control. If the disease is recognized early and the rose is removed, it is possible to save other roses in the garden and hopefully curb the spread of RRD.


Fruit Trees

I am interested in growing fruit trees in my suburban DuPage County yard. Can sweet cherries be grown here? Can you suggest varieties of apples, pears, peaches, apricots and plums that are hardy and disease resistant?

Sweet cherries are not hardy in this area. Some fruit trees are sensitive to winter cold and spring frost damage to the buds. Early flowering apricots are the most sensitive, followed by peaches. Pears and sour cherries bloom later and are less sensitive to late frosts.

Apples are the least sensitive to frost damage. Apple scab and apple maggot are common pests. Fruit trees require a regular schedule of spraying for pest control.

For a backyard fruit tree grower, tree size is important. Dwarf fruit trees bear full-sized fruit earlier than standard sized trees. Most fruit cultivars need two different varieties to cross- pollinate and produce fruit.

Midwest Fruit Explorers is a non-profit amateur backyard fruit-growing group. For more information about fruit growing, see www.midfex.org.


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.


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.


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.


What plants do you predict will be best sellers this year? Why?

What plants do you predict will be best sellers this year? Why?

Bryon Angerman, nursery manager, Alsip Home & Garden, St. John, Ind. and Frankfort, Ill.

I believe these two compact hydrangeas will be hot plants this year. First is Invincibelle Wee White® hydrangea, a compact and reblooming white variety of ‘Annabelle’ hydrangea. Its dwarf habit of 18-24 inches and versatile adaptability to full-sun to part-shade planting locations will yield three to four months of continuous flowers on sturdy stems. It’s sure to become a staple in every landscape. Also look for Mini Mauvette hydrangea for similar habits with pinkish purple flowers.

Molly Hornbaker Blogg, nursery manager, Hornbaker Gardens, Princeton.

Hydrangea Little Quick Fire will be a best seller this year. It blooms early with pure white flowers turning to pink, then rose. Its more
compact size, at 4-5 feet and fits into most urban gardens better than most other panicle hydrangeas. Hosta ‘Autumn Frost’ is an attention grabbing plant with powder blue leaves and showy yellow margins. Last year’s Perennial of the Year, Asclepias tuberosa, should continue to be a big seller because of its gorgeous orange flowers and because it is a host for monarch caterpillars.

Jennifer Brennan,horticulture information specialist, manager of education, Chalet, Wilmette.

Being at a retail garden center and nursery, I get to hear customers’ requests and questions about plants for their gardens. Being on the board of the Perennial Plant Association for 6 years, I get to hear hybridizers and growers claims about the “BEST” plants. It is wonderful when the claims of the hybridizers and growers match the requests of the gardeners and designers. The other fact that is worth stating is that the plants are trialed much better than in the past, so there is proof from many areas of the country that the recommended plants will perform and survive.

The first plant that I expect to be a good seller is one that has been selected by the members of the Perennial Plant Association as the Perennial Plant of the Year for 2018. It is Allium ‘Millenium’. Allium ‘Millenium’ is one of the very best ornamental onions. Unlike spring-blooming Allium bulbs, this hybrid Allium blooms in mid to late summer with large large 2 inch rose-purple, globe-shaped flowers over shiny deep green strappy, grassy foliage. Mature plants have dozens of globes covering this perennial plant. Allium ‘Millenium’ attracts butterflies and bees love it as well, but deer and rabbits stay away. This Allium is good for winter hardiness Zones 5-9; prefers full sun to part shade and is 10-12 inches tall.

The
second plant is a flowering perennial Echinacea. It is Echinacea KISMET™ Raspberry and it is different due to sheer flower number and a fabulous habit. It blooms first year, early in the season, with large flowers and continues until a hard frost. It is a great plant! I saw it in trials in the Chicago area and in Colorado. It attracts butterflies and hummingbirds. It is a wonderful cut flower with a great fragrance. It is deer resistant. It is hardy from Zone 4 to zone 10. It forms an upright mound that is 16 inches tall by 24 inches wide, up to 18 inches in flower. It is a beautiful hot pink color that blooms June, July, August, September and October. And, it likes average well drained soil in full sun.

The third plant is a hybrid of a native grass. Native plants are one of the strongest trends in gardening these days. The natural beauty of native Blue Grama Grass is raised to a higher level in Bouteloua gracilis ‘Blonde Ambition’. Its allure includes an abundance of horizontal seed heads, which resemble elegant, petite flags. They emerge chartreuse and transform to blonde. These exquisite blooms hover above thin, blue-green, two-foot stems. ‘Blonde Ambition’ was named a 2011 Plant Select® Winner for its resistance to pests, exceptional performance in low water conditions, retail appeal, and long-lasting attractiveness in gardens and containers. It pops right back up after snowfall. Bouteloua gracilis‘ Blonde Ambition’ was discovered and introduced by David Salman of High Country Gardens. It is easily grown in average, dry to medium, well-drained soils in full sun. It tolerates a wide range of soils, except poorly-drained, wet ones. It is hardy from Zone 3 to Zone 10. It is a tufted, warm season, Missouri native grass noted for its distinctive arrangement of mosquito larvae-like seed spikes which hang from only one side of its flowering stems. It is native to prairies, plains, open rocky woodlands and along railroad tracks. It has narrow, bluish-gray leaf blades (to 1/4 inch wide) that typically form a dense clump growing 12-15 inches tall. Foliage turns golden brown in autumn, sometimes also developing interesting hues of orange and red. Inflorescences of blond colored flowers appear on arching stems above the foliage in early to mid-summer, typically bringing the total height of the clump to 20 inches tall.

All three of these should be at the top of the selling lists for the 2018.


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.


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.


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.


Pre-Chilled Bulbs

I purchased some pre-chilled hyacinths and tulips for forcing but there were no directions with them. Does this mean I don’t have to chill them in the refrigerator, and will they just bloom in the house any time during the winter? The last batch of bulbs became moldy in the refrigerator.

Using pre-chilled bulbs avoids the 12- to 14- week cold treatment that bulbs need for indoor blooming. However, you need to pot up the bulbs in a loose potting mix. Do not cover the bulbs in plastic wrap or paper bags. It will still take 3 or 4 weeks of cold for roots to appear.

Hyacinths kept cool do not need to be potted. They can sprout roots in a saucer of water with the bulb held in place by stones. Check the water level and make sure it just touches the base of the bulb and add water as needed.

The bulbs can be forced as soon as you see roots, or you can hold them in the cold temperature to space out the bud development. Place rooted bulbs in bright light in a cool room, and watch for buds. Rotate the plant so the flowering stem will be erect. “Your previous bulbs rotted because they were not potted up,” says Lori Harms, greenhouse manager, Countryside Nursery, Crystal Lake.


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