IN THE GARDEN COLORFUL PERENNIALS DEFY COLD WEATHER.

Byline: JOSHUA SISKIN

As we settle into cooler weather, it is interesting to note that certain eye-catching perennials, not famous for cold tolerance, are blooming magnificently. Just the other day I spotted a Mandevilla vine so dense with pink flowers that you could not see the leaves. This subtropical plant gains in popularity from year to year even though its durability is open to question.

It has large dark-pink pinwheel flowers and tendrils and is a favorite subject for climbing up an arbor or wooden, white lattice fence. It is subject to iron-deficiency chlorosis and aphid attack, but when it is well- fertilized and situated out in the open where air can circulate freely around it, Mandevilla can stay healthy for years.

The combination of purple and orange flowers never ceases to delight, as when purple Mexican sage combines with orange lantana and orange bird-of-paradise. There is also the unforgettable tapestry hedge of orange 'Livin' Easy' roses intertwined with 'Purple Robe' potato bush.

And then hydrangeas have suddenly re-bloomed as if there were no tomorrow. The recently introduced red hydrangeas, an intriguing alternative to the traditional pink and blue, have proven to be a durable addition to the partial sun garden.

Not to be distracted by the flowers of fall, there are several important garden tasks that need to be done during this season.

Division of most herbaceous perennials is one of them. If you have large clumps of lily-of-the-Nile (Agapanthus) whose rhizomes have risen to the soil surface, they should be broken apart. Plant individual rhizomes wherever you wish, whether in the ground or in pots. Deal with clumps of tuberous daylilies (Hemerocallis) and Shasta daisies in a similar fashion. A spading fork is the tool of choice for this chore. In order for clumping perennials to flower at full capacity, they must be divided every several years.

Overseeding dormant Bermuda lawns is also a job for this season. Winter or annual rye is the least expensive grass for overseeding. The problem with winter rye is that it does not hold its color well, grows extremely rapidly, and may die out in patches during rainy periods when it cannot be mowed on a weekly basis. Perennial rye, although more expensive, may also be used for overseeding. It grows slower and is sturdier than annual rye, surviving much longer into the warm weather of spring.

Tree trimming is definitely a task with some urgency attached to it at this time of year. Top-heavy trees, as we have already seen with our first rain, can fall over in a storm. Sometimes the wind cannot blow through thick foliage so it will simply break the tree's canopy where it puts up wind resistance. Other times, the ground will become so saturated from a downpour that the roots will lose their hold and the entire tree will come crashing down. In any case, taking weight off a tree and allowing wind to blow through it as a result of pruning will save you from arboreal disasters in the stormy months ahead. <

The credo of tree trimmers should be ``less is more.'' A good tree trimming is like a good haircut; it is clear that something has been removed, but the new look is only marginally different from the old. The reason for conservative tree trimming is that radical trimming results in rampant, succulent new growth that is highly susceptible to breakage, in addition to distorting the basic shape of the tree. Fall (or winter) pruning is also recommended because disease organisms and insect pests that enter trees through pruning cuts are less active during our colder months.

TIP OF THE WEEK: If you have balcony planters or flower pots and would like an exotic specimen spilling out of them, choose Dichondra 'Silver Falls.' This plant has small, heart-shaped, silvery-white foliage that hangs in chains. Give it the same exposure you would to ivy geraniums, meaning a good half day of sun at the least.