I have two 3-year-old rose of Sharon plants, about 20 feet apart. One blooms every year. The other plant forms about 100 buds and looks healthy, but it has not bloomed in the last two years. The buds are solidly closed and look as if they are rotting from the inside out. There does not seem to be any sign of insects on the plant. What is this problem?
From the description it sounds like your plant is infected with botrytis blight, a fungus disease that attacks buds before they open, according to Jim Schuster, extension educator, horticulture, University of Illinois. Your plant needs to be treated with a fungicide early in the season. Remove all diseased portions of the plant and any residue on the ground, as the fungus lives over winter in discarded material.
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.
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.
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.
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.
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 keep seeing photos of interesting plants I’d like to grow, but they’re labeled zone 6 and I’m in zone 5. What can I do to successfully overwinter these marginal plants? I’d like to try them, but I don’t want to waste my money.
“Pushing a plant past the limits of its hardiness is not for the average gardener,” says Marie Dvorak of The Planter’s Palette in Winfield, “but plants can sometimes be successfully overwintered by siting them in a special microclimate such as a sheltered southern exposure.” Another tip comes from horticulturist Ann Hancock at Michigan State University, where they are trialing perennials that the English firm Blooms of Bressingham is introducing in the U.S. Hancock explains that the best way to keep perennials that are tender in Zone 5 or that are rated for Zone 6 is to grow them in raised beds with good drainage because poorly drained wet soils will cause the roots to rot. In addition, it is important to check perennial beds for plants that have heaved out of the soil through repeated freezing and thawing. Replace them in the soil and protect with mulch.
One example of a marginally hardy plant that will be getting attention this year is ‘Flamenco’, a new cultivar of Tritoma (Kniphofia, red-hot poker) that has just been named an All-America Selections Winner for 1999. Tritomas should have their foliage tied upright so water does not remain in the crown, said Hancock.
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.
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.
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.
I thought that purple coneflowers were insect proof, but now I see some aphids at the bud and tiny flies. What is wrong?
Purple coneflower (Echinacea purpurea) is a common native perennial that grows best in sandy or well-draining soil and full sun. If you are not giving your plant these growing conditions, certain insects can attack your plants.
Aphids are sometimes visible on buds, and as sucking insects they cause stunted and deformed leaves. Spider mites are tiny insects that often multiply in hot, dry conditions. Spider mites feed on sap and cause yellowish leaves. Thrips are barely visible, tiny insects causing bud malformation.
What is Chicagoland Gardening’s reprint policy?
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?
Where can I send a letter to the editor?