Garden Docs: Cover crops, worms keep your garden happy

Kevin F. of Sebastopol asks: Can you suggest a few potato varieties that I could harvest throughout the growing season? I don’t like to have potatoes all at one time, and it would be nice to enjoy different varieties.

Answer: Early varieties that mature in less than 90 days are perfect for any garden: Cherry Red, Viking Purple, Irish Cobbler, Caribe and Red Norland.

Midseason varieties mature in 100 days or so, and include Yukon Gold and Red LaSoda, which are often the top-producing potatoes in warm climates.

Late varieties need 110 days or more of growing time and typically produce a heavy crop of tubers that store well. All Blue and Butte are all-purpose potatoes that perform well.

Elongated fingerling potatoes vary in their maturation times and come in a range of colors and sizes. None of them are very early, but the late-maturing fingerlings will size up earlier if you pre-sprout the seed potatoes before you plant them. French Fingerling is one to try.

Kamala R. of Santa Rosa asks: What is a cover crop, and when would we use it?

Answer: There are three main ways to improve soil: grow cover crops, mulch (cover) the surface with any organic material, and/or dig in organic soil amendments such as compost, grass clippings, rotted manure or wood chips. They all have their advantages, but cover cropping is the method least practiced by home gardeners.

A cover crop is any plant that is grown for the primary purpose of improving the soil. Since the early 1900s, farmers have used cover crops to restore the fertility to land low in organic matter. In addition to helping feed soil with organic matter, cover crops prevent erosion, suppress weeds and create soilborne nutrients by using the power of the sun.

Christine of Santa Rosa asks: What is vermicompost, and what do you do with it?

Answer: Vermicompost, or compost made by earthworms, is seven times richer in plant nutrients compared to compost created mostly by fungi and bacteria in your compost pile. Studies have shown that small amounts mixed into the soil suppress diseases, slugs and many harmful insects. Studies have also shown that when 10 percent of the volume of potting soil used to grow seedlings is vermicompost, many plants grew better. Whether they were houseplants, annuals, perennials or vegetables, the results were amazing. It’s easy to entice worms to work their magic in your garden directly. Or you can make vermicompost in enclosed bins, or do both. In addition to improving the soil fertility with their castings (a mixture of manure and slime emitted through the worms’ skin), worms improve soil physically by opening airways and drainage holes as they travel.

Ellen of Windsor asks: What is sunscald on fruit trees, and how can I prevent it? I heard its bad and can kill trees.

Answer: Sunny winter days heat up the trunks of the fruit trees, which then cool rapidly in the evening. These swings in temperature can cause expansion and contraction of the bark, which then cracks and peels. Fruit tree trunks then become more susceptible to insect damage and disease because of this damage done to the tree. White latex paint can be used instead of tree guards to prevent sun damage. White paint reflects back the winter sun and prevents the bark from warming, thus keeping the back intact. It’s a good idea to dilute to one-half strength with water. Start from the bottom of the tree, from the soil line, and paint the trunk all the way up to the first branches. That should be high enough. As the months pass, the paint will slowly disappear, and no other application is needed.

Gwen Kilchherr and Dana Lozano 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.

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