GARDENING : HOT-WEATHER PLANTING SECRETS FOR A HEALTHY GARDEN.

Byline: Joshua Siskin

It is especially during hot, dry summers that people begin to understand why the healthiest gardens are densely and diversely planted. When plants are very close together, they protect each other in various ways.

Transpiration, the movement of water from soil to root to stem to leaf and finally into the atmosphere, is generally viewed as an entirely negative process of water loss. However, in dense plantings, water (or water vapor) that exits one plant is trapped in the garden by those adjacent to it, elevating the humidity to each plant's benefit.

For reasons not entirely understood, cool roots make for healthy plants, and dense plantings mean that the roots of each plant are shaded and cooled by the plants surrounding it. Also, the ground is shaded, resulting in minimal evaporative water loss from the soil, and irrigation frequency can be decreased.

As the amount of water applied in a garden is reduced, the amount of excess, standing water - and the disease problems that accompany it - is also reduced. By the way, the principles of dense planting apply not only to gardens in the back yard, but also to container gardens on the patio or on the balcony.

The downside of close planting is restricted air circulation that may lead to insect problems. This is where diversity, density's partner, comes into play. Each type of flower attracts a different group of insects, the greater the diversity of flowers, the greater the diversity of insects. In a community of many different kinds of flowers, beneficial insects - the ones that consume or parasitize insect pests - feel at home.

In ``Great Garden Formulas,'' a new book by Rodale Press, the publishers of Organic Gardening magazine, a total of 102 plants, representing 23 species, are recommended in a xeriscape or dry-climate planting scheme for a garden that is only 160 square feet in size. Six weeks after planting, this garden will only need to be watered every 10 to 14 days. Among the suggested plants are penstemons, sages, yarrows, coneflowers (Echinacea), African irises (Dietes), roses, daisies and society garlic.

The subtitle of this volume reads ``The Ultimate Book of Mix-It-Yourself Concoctions for Your Garden.'' A solution whose main ingredient is castor oil is promoted as a gopher repellent. A mixture of garlic, onion, Tabasco sauce and cayenne pepper will supposedly keep dogs from digging up your garden. Scented bars of soap, hung from trees, were effectively used in Maine as a deer deterrent.

``Great Garden Formulas'' is actually a compendium of potions and notions developed by gardeners across the country. Southern California is represented by Andy Lopez of Malibu, founder of the Invisible Gardens of America. Lopez has concocted a solution whose outstanding ingredient is alfalfa meal. Lopez sprays it on his plants early in the growing season to prevent fungal diseases. The alfalfa serves as a mineral tonic that strengthens plants so that they will resist the advances of fungi, which generally become more active as the growing season progresses and the weather warms.

Lopez has also devised a molasses foliar spray for fungus prevention. I know you're thinking the molasses will attract ants but, according to Lopez, ``The plants absorb the molasses instantly. There's nothing left for the bugs!'' As an oil spray to keep fungus off the wet surfaces of plants during winter and early spring, Lopez utilizes coconut, castor or a light salad oil. He mixes one teaspoon of oil with one teaspoon of dishwashing soap in a gallon of water. Use this spray only on shiny-leafed plants; it may burn leaves with fuzzy surfaces.

In this book, another local authority, Dr. Garn Wallace, who runs a soil-testing laboratory in El Segundo, contributes a soil mix recipe that is appropriate for planters or containers. Mix 2-1/2 gallons of loam soil with 2-1/2 gallons of compost together with -1/2 teaspoon of potassium sulfate, -3/4 tablespoon gypsum and 2 tablespoons of blood meal. Six weeks after planting, spread 2 more tablespoons of blood meal on the soil surface. To lengthen the life of this potting soil, add 1 or 2 gallons of composted bark chips when preparing it. The chips will decompose slowly, maintaining the structure (porosity) of the soil in the containers. Annual fertilization should be as follows: ``Each year, mix up the appropriate mineral powders (mentioned above) and blood meal with a little fresh compost and add them as a top dressing to the container.''

Tip of the week: Sharon Lovejoy from Cambria recommends this Band-Aid for a scratched finger: after washing the finger, squeeze sap from an aloe vera plant onto the scratch, wrap in a lamb's ear leaf and tie a blade of grass around the leaf. Presto, you have a garden-grown Band-Aid.