Garden Detective

For the past few years, we have been bothered by flies that go around and around in circles in our covered entryway. We have sprayed and sprayed, using the strength strong enough to kill mosquitoes, and still they are here. What causes this, and what can we do to encourage them to do this dance someplace else?

At what time of the year do we need to prune our fruit trees? We have blueberry bushes and tangerine, apple, Asian pear and fig trees. We also have a tofu factory near us. Is it OK to use the ground soy bean waste as a fertilizer for our fruit trees?

We are overrun with voles out here in Lincoln. Any suggestions on how to get rid of these nasty creatures?

I gave up on my orchard because of codling moths. Three dormant sprayings does nothing noticeable. The only year I got significant Asian pears, apples and walnuts was when I nuked the trees with toxic chemicals repeatedly. I know I could put paper bags on the fruit and after two hours of that I'd have saved $15 worth of fruit, not quite minimum wage. Do you have any organic methods that work to suggest? I also have pistachio trees and almonds, which I assume are also victims of moths.

Garden events

I've spotted nutgrass in our lawn. What's the best way to eradicate it?

I planted queen palms about a year and a half ago. Some are turning yellow. This happened last year when the weather turned cooler. Is it the weather? What can I do to keep them nice and green with cooler weather on the way?

Five years ago, we built a redwood deck around a large sycamore tree. We left plenty of room for the trunk. But now the roots are pushing the deck up. Can I shave part of those roots down? It would only be 2 or 3 inches off of about 6 inches of root.

How do I get rid of oxalis growing in my creeping thyme ground cover? I've tried and tried to pull it out, but I am losing the battle.

What is the best dwarf tangerine, seeded or seedless, for Yolo County, sun to part shade?

We planted a lot of iris around our yard 20 years ago, and the plants continue to bloom and expand. Should I be cutting off the stems and leaves each year? Do I need to dig up the rhizomes and separate them? Do they need fertilizer?

We're having problems with tree roots growing under the driveway and part of the garage. They've caused the driveway and part of the garage floor to crack and break. Should we cut them?

Seven years ago I purchased and planted a Bartlett pear tree. Since planting, it has produced only a few blossoms in one small area of the tree. The foliage looks great, but obviously the tree will never produce fruit unless it blossoms. Is this common with the Bartlett? What might I do for next year to encourage this tree to perform as was intended?

Our Japanese maple receives a lot of afternoon sun, since we had to remove a fruitless mulberry that shaded it. Since then, we've noticed some die-back at the tips of some of the upper branches.

Our four 45-year-old pomegranate trees produce quite well in spite of their age, but recently some of the fruit has been splitting open.

Only about 10 of my 100 gladiolus plants produced nice blooms. The rest look like they've been burned. I planted 30 new bulbs this past spring, and they look awful, too. Is there a disease affecting glads this year?

The leaves of my camellia are falling off. Is this normal?

Q: Last year, and again this year, our tomatoes have very few leaves and are producing very little fruit.

I have a gophers in my beautiful green lawn. Any solution to get rid of them?

1. Water early in the day to conserve water and minimize plant disease.

What's the best way to water raised garden beds? We have run soaker hose throughout the bed. Is that the best choice?

Q: Each year, the leaves on my potted Brugmansia (angel's trumpet) get mottled, turn yellow, die and fall off. Spider mites? I did see some webbing and minuscule dots, much too small to see with the naked eye. I have put on approximately four applications of Bayer Advanced Rose and Flower Care, which says it kills spider mites. I also spray the underside of the leaves every day when I water it. The leaf wash seems to be helping some. Is there any other systemic product I can use for this problem? Because the plant is under stress, it's not flowering like it should.

I recently moved into a home where the flower beds are completely overrun by Bermuda grass and other "volunteers." How can I get control?

Q: Three years ago my tomato plants grew, gave me a few tomatoes, then started dying from the bottom of the plant to the top.

My mature golden delicious apple tree has what looks like fire blight. It has badly infected the tree, turning the terminal 4 to 6 inches of many twigs brown and dead.

Green kyllinga is infiltrating my front lawn, which is a mix of Bermuda and Kentucky bluegrass. The kyllinga seems impossible to eradicate. What do you suggest?

Last year, the skins on my tomatoes – and I've grown tomatoes for 30 years – were tough. They tasted good. What did I do wrong? I don't want tough tomatoes this year.

Last year, my Brandywine tomatoes had lots of blooms but no fruit. They looked healthy and got sunshine all day, but I got one tomato from four plants at the end of July.

Arthur M. Shapiro, professor of evolution and ecology at the University of California, Davis, responds to a recent "Garden Detective" column:

Colonial bentgrass is overtaking my lawn, and I've been told the only way to get rid of it is to kill the entire lawn and start over. Is this true?

Last year the buds and the tiny lemons on my dwarf Meyer lemon tree turned hard and black as spring turned to fall.

How can I make seed tapes for the garden like I see in mail-order catalogs? The rows look so neat, and there's not much thinning to do.

When should lilacs be pruned? Should I thin out the bushes leaving only the main branches? The blooms are getting higher and higher.

I made the mistake of planting Swiss chard and rhubarb without noting the confusing double label that came with the plant. I didn't know which was which, so I have torn out the plants.

Last year's yellow jacket population was almost unmanageable, with many nests all around the eaves and doors to our house in Lincoln.

Is there a product that can be sprayed on mondo grass to kill weeds but not the mondo grass?

I have six hydrangeas planted on the north side of the house that were cut back severely by our lawn and garden service. They used to bloom profusely, but last year we had only two blooms. What can I do?

Q: I have a long row of mature cannas in my backyard, and they've become an incredibly invasive pest. I've tried herbicide with no luck. I cannot dig them out without destroying a retaining wall. Can you help?

My dwarf myrtle shrubs have grown to 36 inches tall. Some are very woody. Can I cut them down to 20 inches without killing them? Is now a good time?

Q: My bird of paradise is 2 years old, and during the recent cold spell the leaves turned brown. I cut the stalks back about 6 inches below their leaves. Now half the stalks have turned brown or yellow. They seem very strong, but nothing new has grown back. I give them iron and fertilizer, and they get plenty of water and sunlight. Any suggestions?

Q: We have a salt-chlorinated pool and want to plant grass near it. Will the salt cause any problems?

Q: I have a few redwood trees in my yard, and wonder whether they'll produce seeds and whether the seeds are rare or common.

Q: Should we stake and tie up oleander bushes? Our pink bush was drooping, so my husband had our gardener tie it up. In time, the branches were disfigured and had to be cut off. It seems to be weak and I don't know that binding it all up is doing it any good. Will it get stronger and grow up straight as all the others are doing?

Q: The birch trees in my front lawn were planted some 35 to 40 years ago. One of the trees (the largest, about 18 inches in diameter and closest to the house) has developed a fungus at its base.

Q: Our neighbor's "Aptos Blue" redwood isn't doing well. Many branches are dying and turning brown. Our trees are fine except for the one adjacent to the sick neighbor's tree.

How do I get rid of ants in my garden? I've been a little afraid to use ant stakes because of the sprinkler spraying it and the chemical getting into the ground where the garden is growing.

Q: Bits of my neighbor's oleander blow into an area of my garden where I would like to plant herbs. As I regularly water the herbs, will the toxicity of the oleander flowers leach into the soil where they have landed? Will they then penetrate the herb plants, making the herbs unsafe to eat?

Q: Is it OK to prune an ornamental Japanese flowering cherry tree? A friend said not to because they are prone to infection and rot from pruning cuts. Also, this year our dwarf Satsuma mandarin had lots of growth but almost no fruit. Perhaps some of the branches are suckers or sprouts? How should we prune this tree to maximize fruit yield?