Q: About two years ago, possibly three, I had a very tall liquidambar tree cut down and the roots ground. Within a month or two, I had shoots coming up all over the removal site. I called the tree company back and they chopped and ground the area again, this time much deeper and wider.

Before a year passed, a cement walkway lifted a couple of inches on one side and shoots were again coming up all over the place. This time, it was farther from the original site, which was close to the house.

I've had two arborists here and followed their suggestions to apply Roundup with a brush or stump killer. The problem is now worse than ever and shoots continue to sprout even farther away, probably up to 15 feet.

Is there anything I can do to kill these roots once and for all?

– Joyce Norton, Granite Bay A: According to UC Master Gardener Carol Hunter, the basic problem with the continued spreading of roots after tree removal is that the tree is still alive.

Tree roots extend at least as far out as the tree canopy. Have you and an arborist eliminated the possibility that the roots are associated with another tree nearby?

Discontinue watering as far as possible from the tree stump. Depending on the size of the roots, you or a professional can cut the roots. Manual removal, although time-consuming, can be extremely effective. Shoots should be torn off at ground level, not clipped off.

Continue to use the concentrated Roundup application that you have used before. Apply to the sprout foliage with a paintbrush or spray. Before application, score the foliage to improve penetration.

The shoot stems can be cut and the chemical applied directly to the cut. Roundup is a nonselective herbicide, so apply with great caution.

Another possible solution: Root barriers can be created by trenching at least 3 feet deep and inserting a thin layer of concrete, sheet metal or other durable barrier. Any method selected needs to be continued periodically until the tree has died entirely. Q: In a past Garden Detective column titled "Young redwoods need water to become established" (Home & Garden, Jan. 15) you mentioned several conditions that negatively affect redwoods. However, since the tree in question was young, your response dealt mostly with proper irrigation.

I have two redwoods among 20 or so that exhibit many of the same signs as the ailing tree in the article, but I am still at a loss at how to treat the trees. Help!

One other thing: One of the trees has several branches that are actually white, but are vital. Any clues?

– David Favro, Yuba City

A: According to UC Master Gardener Bill Pierce, your trees exhibit the same characteristics as those mentioned in The Bee article because your trees are not getting enough water.

Here in the Valley, established redwoods need to be deeply watered on a monthly basis during the dry season. The most economical way to do this is to use soaker hoses that circle the tree at the drip line.

When you begin, run the water for eight hours and then use a shovel, soil probe or metal rod to determine how far the water has penetrated. Moisture should reach a depth of 18 to 24 inches. Run the water until you have wet the soil to this depth.

As for the white branch, take a sample – about 12 inches long, including the white portion – along with a healthy green segment of the tree to the UC cooperative extension office in Yuba City.

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

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• 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

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