• Enter your email address to follow this blog and receive notifications of new posts by email.

  • Upcoming events in Middle Tennessee

     

    Save the Date: Perennial Plant Society’s 30th Plant Sale is April 4, 2020, 9 a.m. – 1 p.m. at the new Expo 3 Building at The Fairgrounds Nashville. Here’s where you can find the newest varieties of perennials, shrubs, vines and annuals from local growers, along with long-time, never-fail favorites, ready for spring planting. Learn more at the PPS website.

     

  • Categories

  • Archives

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

Summer is hard on the lawn

QUESTION: Our lawn has looked great all summer – until now! The grass is turning brown in patches, even though I water it regularly. What’s wrong?

Grass brown patchFor lawn-lovers, the middle of summer often brings disappointment to those who carefully cultivate that carpet of green. I’ve written about the problem here before, but here at mid-summer, it bears repeating.

In Middle Tennessee (Zone 7A, where The Garden Bench calls home), fescue seems to be the preferred type of lawn. It’s a cool-season grass, and it has a tendency to go dormant and turn brown when the weather is hot and dry. It often perks up again when the weather gets cooler.

But lawns can also suffer from brown patch, a fungal disease that can affect fescue lawns. It starts with small brown patches, or a ring of brown grass that gets larger over time. The plant may be green at soil level, but individual blades of grass will be brown.

Before you resort to a fungicide, it’s a good idea to know exactly what the problem might be. I’m not a lawn expert, so when I wrote about this before, I pointed to the popular garden guru and author Walter Reeves’s web site, which provides quite a bit of information about lawn fungus, blights and molds. Here it is again.

In general, lawns do well with about an inch of water a week. They don’t need to be watered every day, but water deeply about once a week if it doesn’t rain. It’s also a good idea to cut the grass higher; when grass is cut too short, it leaves the lawn vulnerable to more weeds and diseases.

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.

Evergreens turning ever-brown

QUESTION: We are seeing many evergreen trees — Leyland cypress and others — with big sections of brown limbs. Is that due to the drought? Or is there some other problem affecting the trees?

The drought this summer plays a big part in the browning of Leyland cypress, but it’s not the whole story. Alan Windham, at UT Extension’s Soil, Pest and Plant Center says the branch dieback is the result of a one-two punch: drought and seirdium canker, a fungus that appears on branches or stems and in branch axils and causes the branch to die. “I’ve seen more damage this month than I can remember in several years,” Windham says.

I found a good description of seirdium canker at the Web site of North Carolina State University’s Plant Pathology Extension: The cankers are brown or purple sunken patches on the bark, and may be accompanied by a flow of resin. Affected branches may be scattered randomly throughout the tree; they turn a reddish-brown color, in striking contrast to the green, healthy foliage. The fungus can be spread by splashes of rainwater or water from sprinklers, or it can travel from branch to branch on unclean pruning tools.

There are no chemicals recommended to control the canker. Brown branches should be pruned and destroyed as soon as possible. Prune at least an inch below the canker, and sterilize the pruning tools between cuts by dipping them in rubbing alcohol or a solution of 1 part chlorine bleach to 9 parts water. Plants that are severely affected should be removed and destroyed. Watering by drip irrigation during drought can help prevent problems, Windham says.

Upright arborvitae are also having trouble due to the drought. Windham explains: Plants have different strategies to survive: some plants sacrifice older leaves to protect new shoots; some have waxy leaves, some plants roll their leaves or close up to prevent water vapor from escaping.

“Then you have plants like arborvitae, where it’s all or nothing. It’s as if the plant is saying, ‘We’re going for broke. Everything survives or nothing survives.’ Well, this strategy didn’t work out too well for many arborvitae I have seen.”

In this case, the only solution is to remove the dead trees and start again.