IN THE GARDEN HOW TO ELIMINATE FUNGUS ON SUMMER FLOWERS.

Byline: JOSHUA SISKIN

By now, after so much scorching sun, the color may be all but bleached out of our gardens. But this does not mean we cannot still plant colorful flowers which, with some luck, may even withstand the dog days of summer that lie ahead, and carry us through to the cooler days of mid- October, when our half-year season of heat usually comes to an end.

Ironically, summer-flowering annuals are highly sensitive to fungus pests. The plants obviously need water to survive but any excess in the soil or on leaf or stem surfaces will lead to their quick demise.

The trickiest summer annuals to grow are vinca or periwinkle. Unfortunately, there is no way any nurseryman would guarantee the health of these beauties, especially when they are planted in hot weather. A type of Phytophthora is the fungus that usually kills annual vinca, and it strikes at stems and leaves, causing them to wilt. A drip irrigation system, where water cannot splash onto shoots, would be the best guarantee against fungal attack.

Petunias are also sensitive to summer fungus. Water them too much and their foliage will quickly wither and die. It would be better to plant them in half-day sun so that their watering could be kept to a minimum.

Marigolds are also susceptible to fungus. In their case, dense pom-pom flowers with many crevices are susceptible to disease. Water that gets into these crevices cannot always dry out. Aging marigold flowers are more susceptible to this malaise than fresh ones, so remove the blooms as soon as they begin to fade.

Zinnias are another summer flower with fungus susceptibility. In their case, powdery mildew affects their leaves, turning them white. This problem increases as the days get shorter and the nights get cooler. Reduce nitrogen application and accentuate the potassium when fertilizing.

Cosmos - which produce large daisylike flowers in white, lavender, pink and red - are one summer flower that, as long as they get full sun, should stay fungus-free.

Speaking of fungus, two e-mails came in on the subject:

Q: I am having problems with my bell peppers, tomatoes and pumpkins. The plants grow very well but the fruit develops white spots, which later cause the fruit to rot. Is this caused by a disease in the soil? I know the soil here is not the best

- George Keene, Newhall

A: Your instincts are correct about your soil carrying a disease, especially if you have been planting those crops in the same area for a number of years. The kind of fungus you describe is known to occur in the absence of crop rotation from one year to the next, especially where conditions for growth are inadequate - as in the case of your poorly drained Newhall soil. Improve your soil with compost, and plant corn or carrots the next time around.

Q: My Buddleia, which had gone absolutely wild, was trimmed, only to reveal a white substance underneath and around the bush that looks like something between cauliflower and vomit (pardon the description). It doesn't look like anything I have ever seen before. I am assuming that, with the horrible heat wave and all the watering and overgrowth of the bush, it is some kind of fungus. So my question is, what is it? And what do I do about it?

- Judith Yaniv, West Hills

A: What you have is a slime mold, which is similar to a fungus but is actually its own category of organism. It even moves, ever so slowly, in amoebalike fashion. Slime molds grow on rotting organic matter, especially bark, and are not at all harmful. In some countries, they are eaten, believe it or not.

TIP OF THE WEEK: Buddleia, or butterfly bush, is water-thrifty and produces gigantic wands of minute flowers that attract butterflies. Buddleia may be cut back radically just before it begins new spring growth, shaped into a shrub or hedge, or allowed to develop into a somewhat weeping tree. Flowers are every shade of blue, pink and lavender, or just plain white.