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  • Upcoming Garden Events

    Sept. 30: The Nashville Herb Society presents Through the Garden Gate: A Glimpse of Edwardian England, 8 a.m. – 3 p.m. at Cheekwood Botanic Hall. Celebrate the gardens, foods and flowers that delighted Downton Abby family and friends at the turn of the 20th century. The event begins with a hearty Edwardian breakfast, followed by three speakers: Marta McDowell on Beatrix Potter’s Gardening Life; Geraldine A. Laufer on Tussie Mussie – Victorian art of expressing yourself in the language of flowers; and Terry White, The English Garden event florist . Registration includes breakfast, box lunch in the garden with music, English tea and cookies. To learn more or to register, visit www.herbsocietynashvlle.org.

    Tips & tasks – September

    Cut the dead tops of coneflowers, but leave enough for goldfinches to enjoy the seeds.

    Plant cool-weather vegetables for a fall crop: spinach, mustard and turnip greens, radishes, leaf lettuce.

    Start a new lawn of cool-season grass, such as fescue, or refurbish or repair establish lawns.

    Don’t let the soil of newly planted grass dry out. New grass needs about an inch of water per week.

    It’s still warm, so continue to water and weed garden beds as needed.

    Remove dead foliage, spent flowers and other garden debris; replenish mulch as needed.

    Continue to harvest produce, which may be getting a boost now from slightly cooler weather. Keep watering sage, rosemary and other perennial herbs so they’ll be in good shape to get through winter.

    Prepare to bring houseplants back indoors: remove dead leaves, scrub soil from the sides of the pots, treat for insects. Bring tropical plants in before nighttime temperatures dip to 55 degrees.

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Care for peonies after they bloom

Now that the peonies have finished blooming, what’s the best thing to do with them – leave them or cut them back? Ours often get an ugly coating of powdery mildew on the leaves in the summer. Is there a way to prevent this?

After they bloom, peonies spend the rest of the summer gathering strength to bloom next year before they die back to the roots in winter. A good first task for the gardener is to cut off the faded flowers. Garden expert P. Allen Smith suggests removing the seed pods and lightly fertilizing in late spring or early summer. But be sure to leave the foliage. After the blooms are gone, the rich green leaves of peony shrubs remain an attractive feature in the garden – except when it develops a case of powdery mildew. Continue reading

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Keep hellebores healthy

I inherited a fairly large garden of hellebores when I moved into my current house. There is a problem with black spots on the leaves that I researched on the internet. I have cleaned out the dead leaves from the winter to improve their appearance and air circulation. What is the best way to deal with this problem?

Hellebore-webIf you’ve cut off the dead leaves of the hellebores and gotten any infected foliage around the plants cleaned up and destroyed, you’ve already gotten a good start on controlling the problem by non-chemical means. Leaf spot disease seems to be a fairly common affliction of Helleborus, caused by a fungus, and the first line of defense is to avoid spreading it around, and keep the area inhospitable to fungal growth.

Continue reading

Roses may be at risk for fungal disease

My rose bush is developing little black spots on some of the leaves. What’s causing this, and what can I do about it?

Yellow rose

Roses may develop diseases that affect the foliage.

For questions on roses, I always go to the helpful experts at the Nashville Rose Society, and their Web site. It looks like there are at least two fungal diseases that cause black spots on the leaves of roses: one appropriately called black spot, and the other, anthracnose. You can tell the difference by looking at the edges of the spots. Black spot has the feathery margins, which give rise to some of its other names: leaf blotch or star sooty mold.

Both make a rose look really bad for awhile, which is why people who are serious about growing fancy, beautiful roses stick to a rigid schedule of spraying. Fungicides are to ward off the ugly fungal diseases, pesticides to keep away chewing and sucking bugs.

Both blackspot and anthracnose overwinter on the plant and develop during a cool, moist spring. The best way to minimize the risk of developing diseases is with preventive maintenance: Clean up dead leaves and decaying matter around rose bushes, prune out diseased canes, make sure the rose bush is in a place that has good air circulation, and water in the morning, to give the foliage plenty of time to dry during the day. Fungicides, applied on a regular schedule in early spring, can help prevent infection.

Green flowers may be caused by aster yellows

I had purple coneflowers this summer that never turned purple. Many of the flowers were green. What causes this?

coneflower

Coneflowers are one of the many species that may be affected by a disease called aster yellows.

There is a disease called aster yellows that may be affect coneflowers and many other species. Several years ago, I learned from Extension agent Bob Ary that the condition, which is an infection of a phytoplasma spread by leafhoppers, can cause a variety of symptoms: green flowers,  stunting, yellowing, abnormal shoots, tiny leaves that emerge from the seed heads.

In most cases, a plant infected with aster yellows will eventually die, but even if the plant lives, there is the chance that the condition could spread to other plants by any insect that feeds on the plant.

Aster yellows can’t be cured, and it’s not practical to try to control leafhoppers, Ary said. Garden experts say that the disease is sporadic enough that it may only affect a few plants in a bed. When you remove the plant, it’s also a good idea to remove nearby weeds that may be secondary sources of the disease.

Garden events in Middle Tennessee

Sept. 7 – Beekeeping 101, backyard beekeeping basics, 10 a.m. – noon at WarnerParkNatureCenter. This adult-level class is led by Vera Vollbrecht, Melissa Donahue, and Dganit Eldar. Call to register, 352-6299.

Sept. 17 – Perennial Plant Society meets at Cheekwood in Botanic Hall, speaker is landscape designer Marty DeHart on “Problem Area Perennials.” Refreshments at 6:30, meeting at 7, open to the public.

Sept. 21 – Oct. 31: Cheekwood Harvest Fall Festival includes scarecrows along the garden paths, a pumpkin patch, guided garden tours and nearly 5,000 autumn-hued chrysanthemums in the Robertson Ellis Color Garden, planted specifically for Cheekwood Harvest. The full schedule is at www.cheekwood.org

Sept. 21 and 22: The Tennessee Gesneriad Society annual show and sale at Cheekwood in Botanic Hall. There will be many rare and unusual plants on display as well as for sale.  Hours on Saturday September 21 are 9:30a.m.-4:30p.m., and on Sunday September 22 are 11:00a.m.-4:30 p.m. For more info, call Julie at 615-364-8459.

Sept. 26:  Middle Tennessee Hosta Society meets at Cheekwood in the Potter Room; speaker is David Bates of Bates Nursery on shrubs that tolerate shade for use in hosta gardens. The meeting is at 6:30 and is open to the public.

Sept. 28: Welcoming Fall Wildflower Hike at ShelbyBottomsNatureCenter. A short naturalist-led hike for all ages, 10 – 11 a.m. Call (862-8539) or email (shelbybottomsnature@nashville.gov) to register.

At WarnerParkNatureCenter, Deb Beazley leads adults on a stroll through a meadow to enjoy the fall wildflowers, 9 – 11 a.m. Call 352-6299 to register.

Lovely roses, ugly leaves

QUESTION: I have two rose bushes and the flowers are beautiful, but there are small, irregular holes in some of the older leaves. My neighbor’s roses have black spots on the leaves. What causes these things?

rose redThere seem to be so many things that can bug roses: aphids, spider mites, Japanese beetles, thrips. Blackspot, anthracnose, mildew.

Damage to leaves is most often caused by insects. If you find holes in the leaves of your rose bushes, most likely they have been visited by the chewing kind. One likely suspect may be the little caterpillars known as rose slugs, the larva of an insect called a sawfly.

A little research reveals that the adult lays her eggs on the leaf surface, and when the larvae hatch they move to the underside of the leaf and begin feeding, creating holes between the veins. Finally, the larva drops to the ground, and later emerges as an adult sawfly, ready to begin the cycle again. There can be six generations a year.

Rose holesThe best method for eradication is to pluck these things off the leaves when you see them. Examine the undersides of the leaves, particularly, for the ¾-inch, lime green caterpillars. If you feel you must spray something, a pyrethrin product is advised.

The black spots on rose leaves could be one of several possibilities: Anthracnose is a fungal disease that causes black spots that later turn purple or brown. It thrives where conditions are moist. Downy mildew begins with irregular purplish spots that turn black. The most common, though, is a condition called blackspot, another fungus that thrives in moist conditions.

These diseases overwinter on old leaves that fall to the ground, so it’s good gardening practice to clean up around the base of the shrubs and remove dead foliage. The experts at the Nashville Rose Society recommend a regular fungicide spray schedule beginning in the spring.

With all that can go wrong with roses, why bother growing them? Because if you have the right sun and soil conditions, they can be one of the most rewarding plants in the garden.

Eating extra-local — from your back yard

Find ideas for all that zucchini, that basket full of okra, all those tomates, plus summer garden tips and tasks in the August Garden Calendar at Tennessean.com.

Garden events in Middle Tennessee

August 20: Julie Berbiglia of NPT’s Volunteer Gardener is the speaker at this month’s Perennial Plant Society of Middle Tennessee meeting at Cheekwood’s Botanic Hall. Her topic: “Water Conservation.” Refreshments at 6:30, meeting at 7 p.m. The public is invited. www.ppsmt.org.

August 22: Hosta hybridizer Bob Solburg of Green Hill Farm in Franklinton, N.C. is the speaker at this month’s meeting of the Middle Tennessee Hosta Society at Cheekwood. The meet-and-greet begins at 6:30, meeting at 7 p.m., and Solburg will have plants for sale. www.mths-hosta.com.

Blight sours sweet woodruff

QUESTION: I had a big, fragrant patch of sweet woodruff in a shady raised bed that suddenly began turning gray and dying off in the center. Within a few days almost all of it had turned gray or black, and now there are just a few sprigs left around the edges. What happened?

Sweet woodruffRapid die-off is often an indication of some kind of blight, and a little research into this symptom in sweet woodruff (Galium odoratum) turned up the disease called Rhizoctonia web blight. It’s caused by the fungus Rhizoctonia solani, which is the source of an array of cankers, rots and diseases. Web blight develops in hot, humid weather.

Look closely at the dead and dying plants, and you may be able to see fine webbing that sticks to the leaves and stems and across the surface of the soil. It’s common on sweet woodruff, and also attacks Dianthus, Coreopsis, ferns, hibiscus, goldenrod and yarrow.

I found this information at the web site of the University of Maryland  Extension, where they explain that the blight usually doesn’t kill the roots of the plants, but it’s best to remove dead plants and debris right away.

To reduce the chance of development of the disease, thin the plants out a bit to improve air circulation. Remove mulches and other debris from the area. Cut plant debris at ground level and remove it in the fall.

What’s bugging the squash?

QUESTION: The leaves on some of my squash plants are beginning to wilt. Some of the small squash are rotting. What’s the reason?

squash gbWhen summer squash plants begin to go bad, you can probably blame it on insect pests. Two likely culprits: the squash bug and the squash vine borer.

“When squash leaves wilt and collapse, the squash bug is usually the pest to blame,” says extension agent David Cook. Squash bugs lay small, bronze-colored eggs on the undersides and upper surfaces of the leaves. Nymphs are gray with black legs, and are usually found in groups; adult squash bugs are broad and flat. They pierce the leaves and remove the sap, leaving the leaves wilted. You may also find them on cucumbers, melons and pumpkins.

The best control method is to be on the lookout for the eggs early in the season, and remove any that you find on the plants. (Organic Gardening magazine’s online pest control center suggests gently squishing them before they have a chance to hatch, and squishing any nymphs you may find, as
squash bug eggswell.) If you feel you must spray something, Cook says insecticides labeled for squash bug include bifenthrin, or permethrin. Always read and follow label directions.

If a long branch of the plant — or the entire plant — wilts suddenly, it’s the work of the squash vine borer, the larva of a moth that lays her eggs on the leaf stalks and vines. The eggs hatch in about a week, and the larva bores into the stem of the plant and begins to feed. If you look closely, you may find sawdust-like material near the base of the plant. To try to save the vine, split the stem open and remove the caterpillar. Mound soil up around the wound to encourage roots to grow.

After the larva enters the stem, insecticides are ineffective, so if you choose to use a chemical treatment, you have to start early. Cook says insecticides labeled for squash vine borer include bifenthrin, permethrin, carbaryl and esfenvalerate, and spinosad, which is considered a natural insecticide. Again, be sure to follow label instructions.