Carol T. Bradford: Why Plants Wilt

Portulaca Rio Grande Orange is an annual. It is a cultivated variety of the garden weed purslane. The flowers close in the afternoon. The leaves and stems are edible, as is the weed. They are tasty pickled. Pinch off a few leafy stems, rinse and dry, then drop them into a jar of leftover sweet pickle juice. Keep them in the refrigerator and eat within a few days. (Carol T. Bradford)
Large flowered clematis vines have stems that are exceptionally and unusually fragile.

Dear Carol: I am having a problem with my clematis. I don't know why. It's been absolutely beautiful every year for about six years, very prolific. I cut it down to a few inches in the spring and it was beautiful until a couple of weeks ago when I noticed it was thinning out with the blooms and getting brown stems. I am wondering if when the lawn service spread fertilizer or weed killer on the lawn if that might be the killer. However, none of the other flowers around is affected. -- D.N., Cazenovia.

Dear D.N.: I've had a couple of questions this week about wilting plants, so I want to start with the reasons that plants wilt. Plant stems have tubes running up their length, the xylem, that carry water from the roots to the leaves. Water is lost from the leaf surfaces by transpiration into the atmosphere. Cells also use water in photosynthesis. So a constant supply of water is needed. If the water supply isn't adequate, the plant first shuts down on transpiration, as best it can. If that's not enough, then it begins to wilt. Plants die if they dry out too much.

One reason for a plant's wilting is that the soil is too dry. The roots can't take in enough water to replace the water that is lost through the leaves. Solution: water the plant. It will often make a miraculous recovery. Don't let this happen if you can help it.

But say you water the plant and it doesn't recover. The plant may be too far gone. That's usually OK. It will probably grow back from the stems, crown or roots. It sacrificed the leaves, but isn't quite dead yet. Don't let this happen too often either.

Another possibility is that the roots have been damaged. This wilting, paradoxically, can be caused by overwatering. Excess water rots the roots so they aren't able to take up water. Root rot can be fatal. Dig the plant up and take a look. If the roots are brown and mushy, and there is a swampy smell, that's the trouble. If the plant will root from cuttings, take some quickly and discard the rotted crown and roots.

Newly dug and replanted perennials, shrubs and trees wilt because they have lost most of their roots and the remaining ones can't support the top growth. That's why we try not to dig in hot weather.

Finally, plants wilt because the xylem tubes are either damaged or blocked. Fungal and bacterial diseases can block the tubes. There are zillions of these pathogens that cause wilt diseases.

Wilt happens from physical damage. Bunnies, insects and voles gnaw on stems. Everything above the damage dies. People (and weed whackers) break stems, and that is what happened to the clematis vines. Large flowered clematis vines have stems that are exceptionally and unusually fragile. The plant will be fine next year, just be extra careful working around them.

Carol Bradford gardens in Syracuse. Email your gardening questions and your location to her at: