GARDENING : SOME INGREDIENTS FOR THE ULTIMATE GARDEN SALAD.

Byline: Joshua Siskin

A tangy radish, a broccoflower and a brussels sprout. These cruciferous edibles would quite a salad make, but when it comes to pretty garden plants, I would choose to grow a cousin of theirs, the sweet alyssum.

Sweet alyssum (Lobularia maritima) is a plant that you love, then hate, then love again. You love it for its excellence as a border plant in white, wine red or purple, but especially in white. You love it for the way it offsets a scarlet salvia, a yellow marigold or a purple petunia. You love it for its ability to grow in and spill out of containers, for its adaptability to almost any exposure and for its fragrance.

Then, one day, you hate it because it turns brown as it ages and looks raggedy and then self-sows, as though it were a weed, in places where it shouldn't be. But this dislike is overcome through recognition of its sublime tenacity - its insistence on freshening up your garden with brand new volunteer plants throughout the year.

Sweet alyssum belongs to the Brassicaceae or mustard family. The old name for this family - plant names never stop changing - was Cruciferae, which was and forever would have been an entirely proper and logical name because the flower petals of each cruciferous plant are in the shape of a cross. Perhaps the name was changed in honor of Brassica oleracea, the most protean of plant species. Among the various subspecies and cultivars of Brassica oleracea are the following: cabbage, broccoli, cauliflower, brussels sprout, kale, kohlrabi, and collard green. Not to forget broccoflower, a hybrid of broccoli and cauliflower, which you may have seen in the market (looking like a pale green cauliflower), and ornamental kale - that ruffled white or purple, lettucelike ornamental that is used in winter as a bedding plant.

Sweet alyssum, also known as sweet Alice, is native to southern Europe, where it grows on cliffs dangling over the sea. Salt and wind do not upset its equilibrium.

Although sweet alyssum is an annual, it has perennial cousins that are equally tough. Basket-of-gold (Aurinia saxatilis) is a ground-hugging plant I have observed growing in a Woodland Hills garden for several years. It receives little, if any, summer irrigation. Each spring, it produces clusters of lemon-yellow flowers, which are shown off brilliantly against a background of gray flannel leaves. It is growing near an area that receives considerable foot traffic; even though it is trod upon every now and then, it springs back after each shoe pounding and continues to glow with life.

Another group of alyssum relatives with special merit are the wallflowers (Erysimum spp.). Wallflowers are grown as annuals, biennials and perennials, with flowers in yellow, orange, red, mauve or brown. Like alyssum, they grow in full or part sun. Sunset Western Garden Book contains a heart-stopping description of Erysimum ``Bowles Mauve,'' one of the most popular wallflowers: ``Bloom is practically continuous; the plants, though perennial, may bloom themselves to death after several years.''

Wallflowers get their name from an imprisoned 14-century maiden who fell to her death while trying to escape over a wall to meet her lover.

Perennial candytuft (Iberis sempervirens) is a ground cover relation that produces wedding gown white flowers upon a background of deep green leaves. There also is annual candytuft (Iberis umbellata), which blooms in shades of pink and mauve and then self-sows.

There are many mustards (Brassica spp.) in this world, some good, some not so good. Mustard greens grow as reliable as lettuce and make a tangy addition to your salad. Mustard weeds can be an enormous headache; their seeds were brought to California in the sacks of wheat carried by Russian settlers in the 1800s. Brassica nigra, whose seeds are used for making table mustard, also can become a weedy invader.

Mustard can be a nuisance. At the Theodore Payne Foundation, Kevin Connelly killed a slope of it through solarization: The weeds were watered heavily before being covered with clear plastic; the intense heat created beneath the plastic steamed the mustard to death. But even this weed has its moment, as in early spring, in a wide open waste area - such as south of the Ventura Freeway (101) just west of the San Diego Freeway (405) - where its masses of clear, butter-yellow flowers blind the eye.

Tip of the week: Before planting annual vinca (Catharanthus roseus), amend the soil with plenty of compost and, to ensure good drainage, some pea gravel. Vinca is susceptible to phytophthora fungus that attacks leaves, so avoid overhead watering if possible.

MEMO: Joshua Siskin's column appears every Saturday. He welcomes questions from readers. Write to him in care of the Daily News Features Department, P.O. Box 4200, Woodland Hills, Calif. 91365-4200. You can also reach him through this on-line mailbox: JoshSiskinaol.com. Topics of general interest will be discussed in the column.