Protect Cold-sensitive Plants | Print |  E-mail
Thursday, 29 November 2012 13:07

112912reBy Buzz Bertolero

The Dirt Gardener

Q: We have two mandevilla plants in containers on our patio and we’re concerned about how best we can protect them from the cold weather. Would it be a good idea to completely wrap the plants with plastic?

A: Keeping a mandevilla wrapped up like an Egyptian mummy all winter long is not recommended. When they’re unwrapped in the spring, you’ll find an ugly mess from the decaying tissue and mold from the moisture that couldn’t escape.

Instead, I’d apply Bonide Wilt Stop. Wilt Stop is a liquid that forms a protective barrier when dried between the leaves and the cold temperatures and still allows the leaves to breath. I like to call it “Chap Stick” for plants.

You should also protect citrus, bougainvilleas, hibiscus, jade and other cold-sensitive plants.

Cold is a desiccant which means it pulls moisture out of the leaves causing the plant cells to collapse, and turns the foliage and stems a brown or black color.

You could also move these containers as close to a structure as possible and cover them with a protective plant blanket available at your favorite garden center. This is the most effective way to capture the escaping heat.

A string of holiday lights on the plants and under the plant blanket is another method of warming the cold air.

Clear plastic is not recommended unless it’s kept off the leaves. The cold will travel through the plastic sheeting. Once the freeze or frost warnings have come down, you can remove the covering. Normally, we have three to four frost warnings per winter.

Our coldest nighttime temperatures are just before sunrise. The extent of the damage is determined by how long the temperatures stay at or below freezing after the sun rises.

It’s recommended to water those rain-protected plants every three to four weeks. Water stress is the primary reason why container plants suffer more damage than a similar plant in the ground.

It is inevitable that once every 15 to 25 years there will be a killing frost. Hence, the above precautions will not be sufficient.

And, finally, you don’t prune off the frost damage until mid March as it acts as an additional covering from late-season cold weather.

Q: Do you have any suggestions for preventing moss from growing on my composition roof?

A: There are several brands of moss-prevention products. You need to read the labels carefully, as some products are for use around plants while others are effective only on a structure.

Bonide Moss Max can be used on both.

Moss is a plant that produces spores. The spores remain viable for long periods of time. They germinate and thrive in cool, damp weather, going dormant when it’s dry. You’ll need to make repeat applications to control the moss.

Buzz Bertolero is Executive Vice President of Navlet’s Garden Centers and a California Certified Nursery Professional. His web address is and you can send questions by email to This e-mail address is being protected from spambots. You need JavaScript enabled to view it or to 360 Civic Drive, Ste. “D,” Pleasant Hill, CA 94523, and on Facebook at



Weekly specialty items listings, garage sales, and much more!


Current Ads


If you would like to place a Classified Ad, call Patrick at 510-614-1558.

Real Estate

Get the latest in housing news and services delivered to you in full color PDF.


Browse this weeks gallery