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  • May garden tips & tasks

    GARDEN EVENTS IN MIDDLE TENNESSEE

    May 20: Master Gardeners of Davidson County Urban Gardening Festival, 9 a.m. - 4 p.m., Ellington Agricultural Center Demonstration Garden. Free admission. www.mgofdc.org; on Facebook at www.facebook.com/mgofdc.

    June 10: Middle Tennessee Daylily Society show and sale, Ellington Agricultural Center’s Ed Jones Auditorium, 440 Hogan Rd. in Nashville. Sale open at 10 a.m.; show opens to the public at 1 p.m. To learn more about the Middle Tennessee Daylily Society, visit www.middletndaylilysociety.org.

    It’s time to plant those tender herbs and vegetable transplants, such as basil, dill, tomatoes, green peppers, hot peppers, eggplant.

    If tomato transplants are already too tall and leggy, you can plant them on their sides and cover the long stems with soil. The stem tips will turn upward, and the buried stems will sprout roots.

    Sow seeds of bush beans and pole beans, cucumbers, sweet corn, melons, okra, field peas, pumpkin, squash and zucchini. Follow the directions on the seed package for planting depth and spacing. Vegetables grow best in full sun.

    Cut the faded blossoms of peonies. Fertilize the plants lightly in late spring or early summer.

    Remember the basics of watering: morning is best, so plants’ leaves have time to dry before evening. Lawns, perennial borders and annuals like to have 1 – 1½ inches of water per week.

    Many indoor plants enjoy a summer vacation outdoors. Give them a cool, shady spot in the yard, and don’t forget to water them.

    Prune thyme frequently so it will stay full and green in the center.

    Weeding is easiest after a rain. If the ground is too dry and you need to weed, soak the bed first with a hose or sprinkler.

    Whether they’re growing in the ground or in pots on the porch, pinch the tips of geraniums from time to time to encourage them to branch out and to produce more flowers. Geraniums in pots benefit from regular feeding with a water-soluble fertilizer.

    Remember that mulch can be a gardener’s best friend. Pine straw or composted leaves are good alternatives to hardwood mulch.

    Harvest herbs as they reach their peak. Dry small leaves on a screen, hang small bunches of long-stemmed herbs in a warm, dry room out of the sunlight.

    Plants growing outdoors in containers dry out quickly when it’s hot. Check them daily, and water as needed.

    Don’t go near hydrangeas with the pruning shears unless all you’re cutting is dead branches. If the bigleaf hydrangeas look like they’re not going to bloom, it could be that the buds were nipped in a late cold snap, or the plant was pruned too late last year.

    As the flowers of Shasta daisies begin to open and then to fade, keep them clipped off. This prolongs the blooming season of daisies (and most other annuals and perennials), and keeps the plants looking better, as well.

    Watch for aphids on shrubs and perennials. A strong blast of water from a hose will remove many of them, or spray with insecticidal soap.

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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

Disappearing columbine

The columbine that I planted about three years ago usually starts coming up in March, but it hasn’t started growing this year. Could something have killed it?

Although it self-seeds, columbine is a short-lived perennial.

Although it self-seeds , columbine is a short-lived perennial.

Columbine (Aquilegia is the botanical name), with its lacy leaves and bell-shaped flowers, is a nice addition to spring gardens. It’s a relatively short-lived perennial, however, that owes any sense of longevity to a habit of prolific self-seeding. The original plant may last only two or three years. Continue reading

Zinnias for summer – and a Book Giveaway!

I love seeing zinnias in a summer garden, and want to plant them in my yard this year. Is it too late to grow them from seeds?

ZinniasYou’d get that great summer zinnia look a little sooner by planting bedding plants, if you can find them, but early May is not too late to plant zinnia seeds. In fact, they get off to a better start if you sow seeds after the soil has warmed, as they sprout and grow quickly.

Sow the seeds in a prepared garden bed (good garden soil in full sun) about ¼-inch deep. Keep the bed moist, and once they’re up, thin the plants to at least six inches apart. This is important to provide good air circulation around the plants; a bed planted too thickly may be more susceptible to powdery mildew when summer’s humidity sets in.

Then, just wait a few weeks for them to start blooming. Butterflies will love them, and you’ll be able to cut flowers for summer bouquets from the time they start blooming until frost knocks them down. The more you cut, the better and bushier the plants will be.

There are dozens of zinnia varieties, tall and short, and a range of colors. Most of the familiar forms are common zinnia, Zinnia elegans, but gardeners who wish to avoid the powdery mildew problem may want to try Z. angustifolia, or narrow-leaf zinnia, which grows in a mounded form. The flowers resemble miniature daisies, and the plant blooms from early summer to frost.

A fun fact that I found at the Rodale’s Organic Life website: when zinnias, which are native to Mexico, were introduced in Europe, the flowers were referred to as “everybody’s flower” because they were so common and easy to grow.

Book Giveaway! Southern Gardener’s Handbook by Troy Marden

©Troy B. Marden

©Troy B. Marden

If you ask Troy Marden about the best plants for a garden, he’ll most likely talk about soil.

“That may not be the answer you expected and it’s usually not the answer most people want to hear,” he says. “People want to plant pretty flowers, trees and shrubs.

“But if you don’t start with your soil – amend it, feed it, nurture it – the results will be lackluster.” That’s especially true here in the south, where we often try to coax a garden out of heavy, wet clay.

Troy is one of the Mid-state’s favorite go-to garden experts, so we listen to what he says. He’s passing along more of his garden knowledge in a new book, Southern Gardener’s Handbook, published this spring. Besides his thorough lesson on soil and how to make it better, he offers his ideas for best practices on watering, fertilizing, understanding microclimates, sun and shade, compost and “greener ways to garden.” This is followed by three hundred full-color plant profiles, organized under ten plant categories from annuals to vines.

“I wrote this guide as comprehensive, but approachable,” Troy says. “Interesting enough for the more seasoned gardener, but easy enough to understand for those who might be getting their hands dirty for the first time.”

southern gardeners handbookThe Giveaway: Here at The Garden Bench, we are giving away two copies of Southern Gardener’s Handbook from the publisher, Cool Springs Press.

Leave a comment at the end of this post about your favorite May blooms – or just say “Count me in!” Respond by 6 p.m. Friday, May 15, 2015, and your name will go into a drawing to win one of two copies of Troy Marden’s Southern Gardener’s Handbook.

Small space, big returns: It’s possible to grow edibles and ornamentals even if you don’t have a plot of soil that you can call a garden. In Saturday’s Tennessean, master gardener Mary Boyd discusses several ways to garden in small spaces. Master Gardeners of Davidson County is getting ready for its annual Urban Garden Festival on May 16.

Plant peonies in spring or fall

Question: I have a flower bed in a spot that gets morning sun, and I want peonies in my garden. Can I plant them now?
peonies gbYes, early spring is a good time to plant peony rhizomes. They can also be planted in the fall. Once they’re established, peonies are finicky about being moved, so it’s a good idea to make sure the new flower bed is in good shape before you put them in the ground.
Peonies prefer a spot in full sun or with light afternoon shade, with good drainage, and away from the roots of trees and shrubs that would compete for water and nutrients. They can be susceptible to powdery mildew, so make sure they are not crowded and there is good air circulation in the bed.
Work plenty of organic matter and a high-phosphate fertilizer into the soil, and set the roots 1 inch deep.
Peonies may not bloom the first year they are planted, but they should bloom every year after that.

In the garden this week

It’s spring in Middle Tennessee (Zone 7a on the USDA Plant Hardiness Zone map, where The Garden Bench calls home). Here are a few late-March tasks on our gardening to-do list:

  • Replenish mulch around roses, azaleas and other shrubs.
  • Dig and divide, hardy mums, daylilies that have gotten too crowded.
  • Set out transplants of herbs that can stand up to a few more chilly days: parsley, cilantro, sage, chives, oregano are among the garden and kitchen favorites.
  • Trim buddleia or cut it back before new leaves emerge.
  • Last chance to mow over winter-browned liriope; new shoots are beginning to come up from the roots.

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.

Powdery problems

I have three peonies. Two are fine, but the third, in a different location, is completely covered with powdery mildew. How does that happen? Should I do something about the one that’s covered? Or just leave it and hope for the best?

Powdery mildew (which affects all kinds of plants in the landscape) can be a problem when weather conditions are right and cultural conditions are less than perfect. It’s a fungus that thrives in warm weather when the humidity is high. It becomes more of a problem for plants that are growing in damp, shady places and overcrowded conditions.

It’s a common disease and you’ll know when it hits: look for patches of gray-white, powder-like growth. It usually appears on the tops of leaves but can also be seen on the bottoms of leaves, and on young stems, buds and flowers. It likes the young, succulent parts of plants.

At the UT Extension Soil, Plant and Pest Center, expert Alan Windham (who frequently provides answers to questions here) says the peony should survive with no problem. It’s a good idea to remove any dead or dying foliage and destroy it (don’t put it in the compost; that probably won’t kill the fungus spores), and clean up around the area.

Windham is more worried about downy mildew in beds of impatiens, which we mentioned in this column several weeks ago. “There are lots of cases coming in from all over the state; it’s been found in nearly every state east of the Mississippi,” he says.

Watch for plants that are losing leaves, that don’t flower, and that have white growth on the undersides of the leaves, he advises. The disease can be extremely damaging, so pull up, bag and dispose of infected plants to keep it from spreading.

Bad news this year, but even bigger implications for next year regarding availability, use by commercial landscapers and their general viability as a bedding plant, he said. Does that mean the ubiquitous impatiens won’t be among the gardener’s favorite go-to shade annual next year?

“Begonias, SunPatiens and New Guinea impatiens are going to be in high demand,” he says.

If you haven’t seen the Soil, Pest and Plant Center’s Facebook page, check it out here. “We’re putting lots of good stuff up,” Windham says.

 

Prevent powdery mildew

QUESTION: How do I keep my beautiful zinnias from getting powdery mildew? It may be too late for this year, but what should I do different next year?

Powdery mildew is a fungus that thrives when nights are moderately cool and foliage stays damp. It travels by airborne spores, and appears as gray or white splotches on leaves, stems and flowers of susceptible plants, such as zinnias. A mild case is merely unattractive; a severe case of powdery mildew can cause distorted shoots and leaves, misshapen flowers or can prevent flowering altogether.

The best defense is to give zinnias room to grow without crowding, which allows air to circulate better around the plants, and water only in the morning, so the foliage has time to dry before nightfall. Cut back on the use of high-nitrogen fertilizer, which produces succulent new growth that is a major powdery mildew magnet. Grow them in full sun; hot temperatures (above 90 degrees) inhibit the growth of mildew.

There are fungicides available that should be applied as soon as you begin to spot the mildew (so yes, probably too late for this year), but I always suggest trying the good-cultural-practices method first. The University of Tennessee Extension has a short list in a publication about powdery mildew here. If you decide to go that route, be sure to read and follow directions on the product label.

Zinnias are not the only things plagued by powdery mildew. Lilacs, roses, crepe myrtles and other woody ornamentals, and many herbaceous ornamentals and bedding plants are also targets when weather conditions favor the fungus.