Harvest pistachios when shell casings loosen

When to harvest pistachios, how to sprout screwbean mesquites and other questions I dealt with this week:

Question: How do we tell when to harvest pistachios?

Answer: When the shell coverings become loose, the time is right. Remove them and dip the nuts in water and spread in the sun to dry. Some shells may split. Or boil the nuts in a salt solution for a few minutes and then let them dry.

Q: How do I sprout screw bean mesquites?

A: Remove the seeds from the pods. Next, scarify the seeds with sandpaper just enough to scar the seed coat and then plant them. Plant several to ensure a good stand.

Did you know the screw bean mesquite was one of the original trees in our valley? Dennis Swartzell of Horticulture Consultants said it, the honey mesquite desert willow, Joshua tree and cat-claw acacia were here when the first explorers came to the valley.

Q: Our shrubs have struggled and, for some unknown reason, they put on a spurt of growth unlike I've experienced in previous years. May I prune them now without harming them?

A: Yes. You can prune shrubs anytime to keep them in check. The hard rain we've had probably brought on the sudden burst of growth. The rain flushed the salts, which were inhibiting your plants' growth. I have a feeling your plants enjoyed the rain more than you did.

Q: How do I control the loopers on cabbage plants?

A: Use Bacillus thuringiensis. It's one of the most effective and safe insecticides used to control larvae such as loopers. The larvae eat the treated foliage and it causes so much irritation in the digestive tract that they can't eat and starve to death. All nurseries sell Bt.

Q: What is eating all my vegetable seedlings as they come out of the ground?

A: I suspect birds or rabbits are doing the damage. Next season, cover your garden with bird netting to deter them.

Q: Why won't my cross vine bloom? Last year it bloomed all summer. I feed it often.

A: I strongly suspect you are overfertilizing and perhaps overwatering it. Sometimes stressing plants brings them into bloom. Those I see on a very strict watering schedule bloom profusely.

Q: Why are my vegetables looking so sad? I worked lots of horse manure in the soil before planting so the soil is in good condition.

A: I'm concerned about the use of horse manure. All manures have salt in them. To overcome this, give your soil a deep soaking to flush away the salts.

Q: We have this large grassy plant that has large feathery blooms on it. Do you know what it is?

A: You're describing pampas grass. It is easy to identify by the tall feather-duster plumes. It's a beautiful ornamental grass when pruned right and in bloom.

Q: When do we harvest our persimmons?

A: We all want to eat persimmons too soon, so they have earned the reputation of being a tart fruit. Wait until the fruit softens to enjoy them more. You may have to put bird netting over the tree to keep the birds out. Like pomegranates, chilling certainly makes the fruit sweeter.

A persimmon tree is extremely attractive in late fall. The leaves turn stunning shades of yellow, orange or red before dropping, leaving the fruit alone hanging on the tree.

Q: My apricot tree suddenly died. What caused it?

A: When a tree suddenly dies, peel back the bark just below the soil line. Look for a brownish-black disease called crown rot. Continually moistening the plant's crown at the soil line activates this soil-borne fungus. It plugs the lifeline of the tree and kills it. To avoid further problems, pull soil away from the trunk and refill it with pea gravel to keep the trunk dry.

Q: We are new to the valley and want to know which plants to consider. Which hardiness zone are we in?

A: According to the U.S. Department of Agriculture, we sit on the edge between zones 8 and 9. The minimum average temperature for the area determines zones. A zone assigned to an individual plant indicates the lowest temperature it can be expected to survive over the winter.

According to Sunset's Western Garden Book, we are in Zone 11, but we can use plants on both sides in zones 10 and 12. You will find a complete description of these zones in the Western Garden Book. I use it as my plant bible. You'll also find the USDA zones described in the garden book.

Linn Mills' garden column appears on Sundays. He can be reached at linnmillslv@gmail.com or 702-526-1495.