IN THE GARDEN NEW LAVENDER HARD TO RESIST.

Byline: JOSHUA SISKIN

Mona Lavender may sound like an ingenue in an F. Scott Fitzgerald novel or a singer in a punk-rock band. Actually, though, this is the name of a new ornamental plant variety brought out after many years of laborious breeding and cross-breeding at the Kirstenbosch National Botanical Garden in Capetown, South Africa. Plectranthus 'Mona Lavender' is a plant that, after you spot it at the nursery, will move immediately into your shopping cart. This plant has just about everything you could ask for in a garden ornamental: decorous foliage (bronze green on top, purple underneath), long blooming habit, plentiful sprays of violet flowers and a compact growth habit. Its semi-succulent shoots beg to be broken off and stuck in sand or a small cup of water in order to grow roots and give you new plants at no extra charge.

The only disadvantage of 'Mona Lavender' is its sensitivity to frost, so it would, ideally, be planted under the canopy of a large tree or kept in its container under a patio roof, locations where the temperature is always several degrees warmer than in the open air. 'Mona Lavender' does best in the shaded to partial-sun garden, a fitting companion to impatiens and coleus, though it requires somewhat less water than either of these two garden staples. Another garden-worthy plant on nursery shelves this time of year is the Caribbean or Peruvian lily (Scilla peruviana). This plant is misnamed because it is actually native to Spain. No winter bloomer has more vivid royal blue flowers than this. It does persist in the garden where soil drains well, but does not bloom every year, adding to the pleasure you will experience when it does flower.

Q: Our 30-year-old California pepper tree is dying of sudden oak death, Texas root rot or oak-root fungus - take your pick. A local nursery looked at the yellowed, dry leaves from a cutting and said it looked like sudden oak death syndrome - and there was no known cure. We have other pepper and ash trees in our yard. Is there anything we can do to save our sick tree? Is there any preventive treatment we can give the roots of the surviving trees so they do not follow suit and die, too?

- Herman Benson, Echo Park

A: As you were told, there is no cure for root rot. However, you can stop its spread, in some cases, by layering manure and compost over soil in the problem area. Acid soil pH - acidifying humic acid is a product of decomposition - discourages soil fungi that cause root rot. This is one of the reasons azaleas are planted in peat moss; the low pH of the moss discourages growth of the phytophthora fungi that regularly decimate azaleas wherever soil pH is high, as in most of southern California. You should also make sure that there is no standing water on the soil around neighboring trees. Verify that the soil drains well in the problem area, installing French or area drains if necessary. Finally, there is some evidence that phosphorus helps trees resist sudden oak death, a disease that strikes many tree species. As a precautionary measure, feed your problem trees with a fertilizer rich in phosphorus.

TIP OF THE WEEK: This is bare root season for roses and deciduous fruit trees. An important characteristic to note when selecting these dormant plants is the diameter of cane (in roses) or trunk (in fruit trees). The thicker the trunk, the stronger and more vigorous the plant is likely to be. Especially when it comes to trees, height alone is not a criterion for robustness.