GARDENING VALLEY'S ROADS IN FULL BLOOM.

Byline: Joshua Siskin

One of the advantages of learning about and becoming a lover of plants is the alleviation of boredom when you're driving. For the botanically inspired, each turn in the road carries with it a certain excitement; you never know what might be growing around the bend. Even on a stretch of familiar highway, you can be pleasantly surprised. As the seasons change, so do the flowers by the side of the road.

As you drive north toward the Valley on the San Diego (405) Freeway, you might have noticed several plants that are presently blooming with insouciant glee. Yes, we have experienced a heat wave this past week, but you would never know it looking at these plants, which - growing on the long slope which rises up to the right from the northbound lanes - are never watered except by the rain.

The one plant you cannot possibly miss, even if you have the dullest horticultural eye, is Spanish broom (Spartium junceum), which has planted itself just past the Getty Center exit sign and here and there over the entire slope. Its bright yellow flowers are simply unavoidable. Native to the Mediterranean, Spanish broom has naturalized itself in California. It can be aggressive, even invasive, if left unchecked.

A relative of Spanish broom that also blooms in bright yellow this time of year, and is available in many local nurseries, is Sweet broom (Genista racemosa). Its flowers are fragrant and are used for bouquets and vase arrangements. It, too, can reseed itself and has the capacity to spread, although this tendency is seldom expressed in our area. All brooms are attractive to ravenous caterpillars, which can defoliate them by summer's end. Use Bacillus Thuringiensis, commonly known as BT, an organic pesticide, to curtail the growth of caterpillar pests on this or any other plant.

A little further on, you will begin to notice orange clumps dotting the freeway-adjacent slope. These orange clumps are known by the name of sticky monkey flower (Mimulusaurantiacus). This perennial California native can grow to 4 feet and is covered with flowers that will remind you of snapdragons and penstemons, both of which are monkey flower relatives. Its stems and leaves are covered with a sticky, volatile oil. Sherbet orange is the classic monkey flower color, but annual monkey flowers can also be found in various shades of red and maroon. Monkey flowers are usually happiest in full to partial sun, but may require some supplemental irrigation in very hot areas. One species, the bright yellow Mimulus guttatus, is tolerant of light shade.

Close by the monkey flowers, you might notice some plants from which long purple wands extrude, waving in the wind. These wands are the flower spikes of woolly blue curls (Trichostema lanatum). Woolly blue curls can be found throughout the hills and canyons in the San Fernando and Santa Clarita valleys, and in the Santa Monica Mountains as well. Once you see this plant up close, you will definitely want to plant it. Long stamens protrude from the flowers like so many serpent tongues. A word of caution: the woolly blue is easily killed by excessive summer irrigation.

Immediately after you pass the ``San Fernando Valley'' sign that stands above the shoulder on the northbound 405, you will notice half a dozen large shrubs blooming in yellow and orange. These flannel bushes (Fremontodendron californica), which will eventually reach a height of 20 feet, are the most drought tolerant of all California natives, requiring no water whatsoever during the summer. The downside of the flannel bush is its flannel, an eminently inhalable fluff that covers its leaves. Be sure to put on a dust mask and a hat before pruning a flannel bush. If you have never seen a flannel bush, you can find a fine picture of its flowers on the cover of the Sunset Western Garden Book.

Just beyond the flannel bushes, growing at the edge of the freeway shoulder, are some pink-flowering clarkias. Clarkias are wonderful native annuals that everyone should try because they come up so easily from seed. Flower colors are in the pink to lavender range. The growth habit of clarkias is erect and they may reach several feet in height. If you are looking for a native plant that gives you the feel of an English garden, this would have to be it.