Garden docs: Garden ideas for starting over after fire damage

Evie asks: My rhododendron leaves are wilting and the entire shrub appears very stressed. This plant was given to me in the spring and seemed healthy. But now it is gradually declining. What should I do?

It sounds like your rhododendron has a parasitic fungus called Phytophthora, or root rot. The fungus attacks the critical water-conducting tissue, which eventually kills the plant. The problem can occur after warm wet weather and in poor draining soil.

Your rhodie may have had an invisible fungus problem when you got it. Dig up the plant and see if the base is brownish. The plant should have an abundance of white feeder roots. Infected roots become blackened and stunted and eventually die. Do not replant in the same location.

One way to prevent the problem is to check the roots of a plant before you buy it. If you see a plant that has stressed leaves, ask a salesperson for permission to examine the roots by tipping the root ball out of the container.

Some species are resistant to root rot but may be hard to find in nurseries. However, many nurseries are willing to make special orders.

One rhododendron that I know is more resistant to Phytophthora is “Caroline.”

In soil that drains adequately, plants have more resistance. When planting, add compost and plant shallow, on a mound. Cover roots with soil because sunburn or exposed roots can leave a rhododendron vulnerable to Phytophthora.

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Howard asks: I have always enjoyed the beauty of native plants in the landscape. Now, after losing our house and garden in the fires, we are starting over with a new landscape. But we're concerned about the flammability of some native plants after our garden loss.

What would be some of your favorite choices if you were in our situation?

There are beautiful natives that aren't necessarily a fire hazard. I am not a purist and combine nonnative plants with the same cultural requirements of native plants such as low water-use plants. It's most important to combine plants that enhance their location/zone such as coastal seascapes, warmer interior landscapes, woodland landscapes and shade exposures. The goal is to provide foliage texture in planting combinations, variations in plant heights and seasonal bloom.

Here are some of my favorites: Penstemon heterophyllus planted in mass; succulents; Dudleya cymosa, planted in multiples and interesting drifts; annual wild flowers that reseed such as California poppies; taller shrubs such as the native Garrya; silk tassel; trees such as Arbutus unedo “Marina,” Italian buckthorn and Rhamnus alaternus, a large shrub or small tree with dark evergreen leaves.

Other favorites include Feija sellowiana, a medium-sized evergreen shrub that has a spring bloom and attracts wildlife; colorful native yarrow; Achillea; millefolia; native beach aster Erigeron glaucus with continuous bloom; wall flowers of many colors that attract butterflies and Mimulus or monkey flower, planted near water features with a bonus of attracting butterflies.

Salvia sonomensis, or creeping sage, is a native plant choice for slopes. Douglas iris planted in mass is good for spring color. And Pacific dogwood or Cornus nuttalii works for a woodland garden.

“Designing California Native Gardens: The Plant Community Approach to Artful, Ecological Gardens,” by Glenn Keator of Sebastopol and Alrie Middlebrook, is an excellent resource for those interested in designing with natives.

Tip for burned slopes: As a temporary measure to reduce erosion, seed the burned area with a fast-growing annual rye grass. The winter rains will help seed germination.

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Matt asks: We have a broadleaf evergreen Pittosporum shrub that has been in the same location for two years. My wife would like to move it. The shrub is healthy and we would hate to lose it. Is it safe to move? If so, how should we do it?

This following is a technique that nurseries and landscapers use to move trees and shrubs:

In January or February, use a sharp, long-edged spade and dig down around the perimeter of the shrub about 2 feet from the main trunk. The roots should be severed. New roots will form inside the severed circle.

In the fall, prepare a new hole where you want to plant the shrub, making it wider but the same depth as the original hole. Go back to the plant, cut a new circle outside of where you previously pruned the roots and carefully remove the shrub, keeping the root ball intact.

Plant as you would any new shrub and water it thoroughly, making sure there are no air pockets near the roots.

Dana Lozano and Gwen Kilchherr are garden consultants. Send your gardening questions to The Garden Doctors, at pdgardendoctor@gmail.com. The Garden Doctors can answer questions only through their column, which appears twice a month in the newspaper and online at pressdemocrat.com.