On two occasions, I have purchased potting soil and azalea mix from a local nursery and mixed it 50-50 to grow tomatoes in large pots. This combination was recommended by the nursery.

The tomato plants I purchased looked green and healthy. After planting in the mix, they seemed to weaken, become pale and grow poorly. On one plant, the buds just dried up after blooming.

In the mix, there were a lot of wood chips. I saw a place that grinds pallets and mixes that with dirt. Do you think it's possible this potting mix and azalea mix are mixed with ground-up pallets?

What should one use to grow fine tomatoes?

– Dale Scribner, Sacramento

As they decompose, the wood chips in your soil mix are using the nitrogen in the soil and reducing the amount available for the tomatoes, according to UC master gardeners.

It takes nitrogen to make green growth. In the future, you would have better luck if you bought a good planting mix specifically designed for your container-grown plants.

Note: Potting mix is different than potting soil. A good potting mix usually contains peat moss, compost, vermiculite, perlite and sand. Premium mixes often contain some fertilizer, too. There are many brands available such as Kellogg, Scotts, Black Gold and Super Soil.

It also helps to use a slow-release fertilizer such as Osmocote. This product releases some plant food every time you water.

Using conventional fertilizer with container plants is disadvantageous, as the product is quickly washed out of the pot.

We have a large tulip maple tree in our front yard. During the summer months, its leaves are covered with aphids, and a saplike substance blows out of the tree for approximately three months, covering our cars with sticky stuff.

We like to have clean cars and it is impossible during the summer because of the tree. Is there a treatment or do I cut the tree down?

– Rick Barnes, Sacramento

The issue is not the tree, it's the aphids. Because you are dealing with a large tree, there are several approaches for eliminating the honeydew produced by the aphids in your tree, say UC master gardeners.

Ants are responsible for putting the aphids up the tree. Ants go up the tree to harvest the sweet sap the aphids are sucking out of the leaves. To stop the ants, put a 6-inch band of duct tape around the trunk of the tree about 6 inches above the soil level. Coat this band with Tanglefoot, available at nurseries and home improvement stores. The ants can't cross this sticky substance.

You will have to redo this again when the product is no longer sticky due to dust, water, etc. In conjunction with the Tanglefoot-treated tape, a forceful spray of water or water-soap solution (even on large street trees, when applied with appropriate equipment) will provide sufficient control.

If all else fails, you can treat the tree with a systemic insecticide such as Bayer's Tree and Shrub Insect Control. This product is poured at the base of the tree, where it is absorbed by roots and is then effective for one year.

Because it takes a substantial time for the product to get from the soil level to the growing points in the tree, applications must be made two months before problems are anticipated. Read and follow the directions on the bottle carefully for the quantity to use and the optimal application time.

GARDEN QUESTIONS?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties.

Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h&g@sacbee.com. Please put "Garden Detective" in the subject field and include your postal address. To contact your UC Extension directly, call:

• Sacramento: (916) 875-6913; 9 a.m.-noon and 1-4 p.m. weekdays

• Amador: (209) 223-6838; 10 a.m.-noon Monday through Thursday; email ceamador.ucdavis.edu

• Butte: (530) 538-7201; 8 a.m.-noon and 1-5 p.m. weekdays

• El Dorado: (530) 621-5512; 9 a.m.-noon weekdays

• Placer: (530) 889-7388; 9 a.m.-noon on Tuesdays, Wednesday and Thursdays, or leave a message and calls will be returned

• Nevada: (530) 273-0919; 9 a.m.-noon Tuesdays through Thursday or leave a message

• Shasta, Tehama, Trinity: (530) 225-4605

• Solano: (707) 784-1322; leave a message and calls will be returned

• Sutter, Yuba: (530) 822-7515; 9 a.m.-noon Mondays and Tuesdays and 1-4 p.m. Thursdays

• Yolo: (530) 666-8737; 9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned

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