FLOWER POWER - EVEN WHEN IT'S HOT.

Byline: Joshua Siskin

The flowers you planted in spring may have all but disappeared now. If so, you might be wondering if there is something you could plant that would flower despite summer's heat and bloom straight into fall.

There are a number of perennials with refreshing blue flowers that are blooming now. Blue is a cool antidote to the Valley's red-hot heat of July, August and September.

Bluebeard (Caryopteris species) has airy, long-lasting, scented, true blue flower clusters and aromatic foliage. Bluebeard is a full-sun plant and deciduous, so you need not worry when you see it drop its leaves in October or November. Pruning should be done in late winter, just prior to resumption of growth in the spring.

Iochroma is a fast-growing perennial, reaching 8 to 10 feet, covered with elongated tubular flowers all summer long. Iochroma might be classified as a shrub except for the remarkable amount of semi-succulent growth it puts out each year, prompting some gardeners to cut it back by half on an annual basis. The classic Iochroma has purple flowers, but blue-, red- and pink-blooming types are also available.

Several pages could be written on blue-flowered sages (Salvia species) that bloom this time of year. One of the most distinctive is Salvia uglinosa, a plant with baby-blue flowers that are guaranteed to lure hummingbirds into your garden. Unique among our garden sages, Salvia uglinosa propagates itself by means of rhizomes, fleshy underground bulblike structures. Just like agapanthus and irises, the most familiar rhizomatous plants, Salvia uglinosa will happily spread itself throughout a sunny - or even half-sunny - garden bed.

A favorite sage of mine is Salvia sinaloensis. Its leaves have a purplish-bronze cast and its flowers are marine blue. It grows in a perfect mound to little more than a foot tall and is best situated in half-day sun or partial shade.

A wonderful perennial for the container gardener is the so-called throatwort, Trachelium (tra-key-lee-um) caeruleum. Its genus name is derived from trachelos, the Greek word for neck, due to its efficacy in curing sore throats. The flowers of throatwort are produced in delicate sprays borne in profusion for months on end. This is a plant for close-up viewing since its flowers are not at all shrill; their beauty is whispered rather than shouted out loud.

Anise hyssop (Agastache foeniculum) is rewarding not only on account of its soft blue flowers, but also because of its licorice fragrance, which makes it an appropriate subject for an herb garden. Herb gardens seldom lack for mounding or matlike plants, but they are often bereft of taller-growing species.

Anise hyssop, which can reach 5 feet tall, would make an excellent background to the low-growing plants that take up most of the space in a typical herb garden. Speaking of tall herb garden subjects, make sure to include lemon verbena (Aloysia triphylla) in the mix. Lemon verbena, which also grows to around 5 feet, also happens to be blooming now, but keep in mind that its intensely fragrant leaves are present practically year around.

Tip of the week: Most of the blue-flowered perennials mentioned above, as well as many other not-so-common plants, may be found at the Garden of Eva, a plant vendor at the Studio City farmers market, which is held each Sunday. The market is located on Ventura Place, just north of Ventura Boulevard and immediately east of Laurel Canyon Boulevard.

GARDEN WONDER

Gardener: Warren and Gyneth Gleason

Residence: Woodland Hills

Plant of interest: The Gleasons removed an overgrown Persian lilac from their yard, thinking they would never see so much as a leaf from the plant again.

Instead, a seed from the lilac became lodged in - and subsequently grew out of - the trunk of their pine. The lilac sprouted five branches, about 18 inches long, ``almost like a fern,'' Warren says.

``A couple months ago, the gardener asked if we wanted the branches cut down, because they were interfering with our bird bath. He cut them off, and they regrew. He's cut them off several times, and they keep regrowing,'' he says.

What makes this plant amazing: ``I can't figure out how the branches were able to grow out of the trunk,'' he says.

Maintenance: ``When I water the pine tree, I water the (lilac) fern.''

What Joshua Siskin says: ``You see that occasionally, where trees root in other trees. It happens in the cracks of a trunk, especially in trees with rough surfaces, like palms.

``It's not like a graft; the seed just gets lodged in the trunk. Seeds are very opportunistic - they just need a foothold to grow.

``When seeds grow through the trunk, they're able to tap the water coming up through vessels in the tree. Eventually, the tree would be affected, but the seedling usually dies before growing too big.''

- Mike Chmielecki

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Photo: Warren Gleason shows the Persian lilac sprouting from the trunk of his pine tree. Andy Holzman/Staff Photographer