IN THE GARDEN PROSPEROUS CLEMATIS VINES HAVE SHADY ROOTS.

Byline: JOSHUA SISKIN

This month's correspondence concerns clematis vines, scorched oleanders, dwarf orange trees and 30-foot-tall hedges in the Santa Clarita Valley.

Q: I live in Northridge and would like to plant a clematis vine. I get about three hours of high noon sun and the rest of the time it is shady. Can you recommend a suitable clematis?

- L.M., Northridge

A: Regarding clematis (CLEM-uh-tis), the number of sunlight hours the stems, leaves and flowers receive is not critical; more important is making sure that the roots of your clematis grow in the shade and that the soil they grow in is well-drained and compost-rich.

Clematis is a rapidly growing vine that will grow skyward when it can twine itself around a vertical support, whether trellis, patio post or tree trunk. A popular species for the Valley is evergreen clematis (Clematis armandii), with both pink and white varieties available. To make sure roots are shaded, plant clematis between low-growing shrubs such as Wheeler's dwarf pittosporum or in a bed of shallow-rooted ground cover such as Serbian bellflower (Campanula). For everything you wanted to know about this magnificent flowering vine, access the excellent Web site, which originates in Southern California, at clematis.org.

Q: I am writing to inquire about a possible bacteria or fungus that seems to be affecting a large hedge of oleanders on my property. They seem to be drying out and dying slowly, despite watering. I see this happening to oleanders on other properties around my house. Is there some sort of bacteria, fungus or insect that is affecting them, and if so, is there a fungicide or other treatment you would advise?

- Dan Price, Northridge

A: It sounds like your oleanders are infected with a bacterial disease that is spread by an insect known as the glassy-winged sharpshooter. This 1/2-inch-long insect with folded wings perched pyramidally on its back is usually found clinging to a plant's stems. When you attempt to grab it with your fingers, it surreptitiously darts away.

The bacteria that cause oleander leaf scorch live both in the plant and in the mouth parts of the sharpshooter. Infected plants thus serve as source material for dissemination of the bacteria. There is no cure for this disease. Control of the insect is being attempted through release of miniature wasps, which parasitize and cannibalize the sharpshooters.

Meanwhile, the best control is to prune out scorched oleander shoots, sterilizing your pruning shears after each cut. Once a sharpshooter has sucked sap from an infected plant, the bacteria will remain in the insect's mouth for the rest of its life, which can last up to six months.

Q: I have two dwarf orange trees. One was full of blossoms and lots of little oranges and they all fell off. The other is very thick with leaves and lots of big oranges. How do you explain this?

- A Valley orange grower

A: As a rule, when any plant or tree fails to grow and develop properly, it is because of a mistake made at planting. Perhaps your problematic orange tree was in a root-bound condition when planted; that is, its roots had encircled their container and were not pulled apart or sliced through prior to planting. It could also be that this tree was planted in hard soil or in too much shade. Also, if your oranges are different varieties, it could be that the healthy tree is suited to our Valley climate while the other is not.

Q: I need to plant trees or tall shrubs that will act as a barrier between my yard and a neighbor's yard. We previously had Leyland cypress trees between our yard and theirs, but they died from some kind of blight. They were about 30 feet tall and very thick, so we couldn't even see the two-story house next door. I live in Santa Clarita, where it gets very hot in the summer and occasionally freezes in the winter. Can you think of something that can survive the temperature ranges, grow tall (fast), and not break up walls or concrete? We have a concrete deck and pool running the whole length of the planter. One friend recommended Ficus nitida, but a nursery told me it couldn't take the cold winters. Someone also recommended a Podocarpus, but I don't think they grow tall enough.

- Sandy Gohlich, Santa Clarita

A: Due to your cold winters, any Ficus tree species, with the exception of the edible fig (Ficus carica), is a risky proposition in the Santa Clarita Valley. Podocarpus (yew pine) trees would grow tall enough, but often become chlorotic or yellow-leafed in the alkaline soil of Santa Clarita. Podocarpus also have roots that will break concrete but, then again, almost any tree has the capacity to break concrete unless it is planted with a root barrier.

You might consider the willow-leafed peppermint eucalyptus (Eucalyptus nicholii), a slender tree with a weeping growth habit. Alternative hedge trees would include the Italian cypress (Cupressus sempervirens) and the California incense cedar (Calocedrus decurrens).

TIP OF THE WEEK: Speaking of Ficus trees, indoor-plant enthusiasts may wish to investigate Ficus triangulata. This is a slender, durable tree whose highly exotic, velvety, deep green triangular foliage holds up well in both low- and high-light situations.