Garden Doctor: How do I revive frostbitten foliage?

Question: Help! So many of my plants and shrubs look terrible from the recent days of 20-degree weather and frostbite damage. Is it OK to prune and cut back now?

Answer: Yes, gardens in our area do look somewhat wounded due to recent freezing weather. The local paper tells the story; quite a few mornings were in the mid-20 degree category. This will damage tropical, succulent and other tender plants. From 29 to 32 degrees is the range for “frost” and 28 degrees and below is actual freezing.

No, do not prune or cut back any tender plants that have frost/freeze damage! “Tender” refers to the inability of the plant to withstand freezing temperatures. A plant designated “hardy” will withstand freezing temperatures because it is dormant. The dead stems act as insulators against future freezes. Pruning frost-damaged plants too early will encourage new tender growth that can be lost to future freezes. You might also prune off parts that would recover and grow when spring comes.

Wait until all danger of frost has passed, then proceed to check each plant. Scrape your fingernail or a sharp object on the stem of the plant. If it is green, there still is life in the plant. Prune back until you reach the green area. If the scratch reveals brown or hard stems, try going farther down toward the base of the plant until you reach a green area. If the plant is dead all the way to the base of the plant, you may cut it off at the ground, but take care not to damage new growth, which may be just below or at the soil surface. Plants that do not show new growth in the spring can be removed and placed in the compost pile.

Protect tender plants with covers such as old sheets or frost cloth available at most garden centers, or place potted plants in a protected patio or garage. Do not use plastic bags or sheets; plastic will not insulate the plant sufficiently to prevent freezing. The temperature around plants can be raised a few degrees by stringing the old-type Christmas lights (not LED) among the branches.

Garden workshops

* Grape pruning: 10 a.m.-noon Saturday, Feb. 16, Woodland Community College Greenhouse Orchard Area, 2300 E. Gibson Road, Woodland. Both spur and cane grape pruning techniques will be demonstrated in the college vineyard, and you can learn how to start your own grapevines from cuttings. Other winter and spring grape-growing tips will be discussed. In case of rain, the class will be taught in the college greenhouse.

* How much water is enough?: 10 a.m. Saturday, Feb. 23, Grace Garden, United Methodist Church of Davis, 1620 Anderson Road, Davis. Grace Garden is a project of the Yolo Master Gardeners that provides fresh produce to needy families. See if you’d like to volunteer here.

* Succulents and cacti, California natives: 9:30-10:30 a.m. and 11 a.m.-noon Saturday, March 2. Workshops will cover two approaches to “green” your garden, making it more sustainable and waterwise.

Question: I have a bed of Algerian ivy, years old that is growing vigorously. I want to replace it with another garden. When would be the best time to do this? What steps should I take to eradicate the vines, and how soon after that can I plant other perennials?

Answer: This is an excellent time to eradicate Algerian ivy. Because of its tenacious nature, getting rid of the ivy should be looked at as a two- to three-year project, but don’t dismay. This doesn’t mean that you can’t go ahead with your plans.

The best way to rid your area of the ivy is by hand pulling and digging. You can speed up the process by pruning heavily before you dig and pull. (If you use an herbicide on the ivy when there is still foliage, the leaves fall off, but the chemical doesn’t make it to the roots.)

As you dig, look for the fine, hairy roots on the main root. Persistence is the key here; watch for ivy that will resprout and then can easily be pulled. In about 24 months you’ll be free of the ivy, or have it under control so that maintenance is easy. Your new plants can go in as soon as you have cleaned off all visible traces of ivy, taking extra care where your plants actually will be placed.

Another method is to mow or cut the ivy and follow it with an appropriate application of an herbicide such as glyphosate. Applying it to open cuts will allow uptake into the roots. Even this process will need repeated mowing/cutting and application of the herbicide.

Herbicides are not inexpensive and you will need more than a single application. Read and follow the directions exactly. This information will tell you how soon you can plant after application. When using an herbicide, note your surrounding plants because the herbicide can (and probably will) kill these as well. Lastly, be sure to protect yourself when applying any chemical by wearing the appropriate protective clothing and eye coverings and then laundering afterwards..

The Garden Doctor had success with a project very much like this one, replacing a 50-foot bed of Algerian ivy with a waterwise strip of cotoneaster, Oregon grape, and osmanthus. The bonus was several dozen aluminum and glass beverage containers that were also revealed and recycled when the ivy was removed. Now the bed is mulched, and the plants offer eye appeal without the worry about what might be hiding under that ivy.

— Send questions, addressed to the “Garden Doctor,” by email to mgyolo@ucdavis.edu, voice mail to 530-666-8737 or regular mail to UCCE Master Gardeners, 70 Cottonwood St., Woodland, CA 95695. Be sure to include your contact information, because any questions not answered in the Garden Doctor column will be answered with a phone call or email to you. You can request the Yolo Gardener newsletter delivered by email and learn more about the Master Gardener program in Yolo County at http://ceyolo.ucdavis.edu/Gardening_and_Master_Gardening.