IN THE GARDEN SUMMER ALWAYS BRINGS PATCHES OF BLUE.

Byline: JOSHUA SISKIN

It often seems that a selection of flowers of a certain color burst into bloom all at once.

A few weeks ago, I was noticing everything orange -- including lantana, marigolds, `Stella d'Oro' daylilies, marmalade bush (Streptosolen jamesonii), wallflower (Erysimum cheiri), `Judy Garland' roses, `New Guinea' impatiens, and `Profusion' zinnias. The latter, by the way, also available in rose and white, is an incredibly durable, mounding, hot weather ground cover.

Now, it seems, I am seeing nothing but blue and its variations.

Predictable, yet always breathtaking, is the sight of Jacaranda trees in full flower. It's a sure sign that summer is here, as are those perennially exuberant lilies of the Nile, also known as Agapanthus, which appear in June and July. Before Agapanthus blooms, the color of its flower buds is almost identical to that of jacaranda flowers. As Agapanthus flowers open up, they assume an increasingly paler shade of lavender blue.

Blue is the most elusive landscape color and seems to quickly fade in our hot climate. Agapanthus breeders must be aware of this since they have recently developed several varieties - `Elaine,' `Ellamae,' and `Storm Cloud' 7/8 whose inflorescences appear in royal blue.

Agapanthus normally grows to 4 feet or more, but there are two smaller Agapanthus selections commonly seen: the highly satisfying, mid-sized `Queen Anne' and the diminutive and disappointing, weak-flowering `Peter Pan.'

The truest blue flowers may be found on certain hydrangeas, which when fertilized with aluminum sulfate, turn a vivid cerulean. After experimenting for years with growing hydrangeas in the Valley, pruning them at all times and in all ways, I have finally reached the conclusion that if you want to grow glorious hydrangeas, just leave them alone.

You can cut off the spent flowers if you wish, but otherwise the plants should not be pruned in any way, shape or form until they reach their mature height of 5 or 6 feet. Only after they have grown to this size should you consider slightly reducing their height -- that is, if you want them to continue flowering to the maximum extent.

Other blue flowers sighted at this time of year include bog sage (Salvia uglinosa), a tall, spreading perennial that grows well near water or in filtered sun; chaste tree (Vitex agnus- castus), with stunning blue spires and compound, five-leaflet palmate leaves; and the plumbagos, whether the dark blue dwarf plumbago ground cover (Ceratostigma plumbaginoides), or the sky blue cape plumbago (Plumbago auriculata), an amorphous, billowy Cal-Trans standard that serves well as a screen or property barrier where water saving is important.

Although normally seen in light blue, cape plumbago also comes in bluish purple varieties.

No discussion of blue flowering summer plants would be complete without lavender. The English lavenders are the bluest types, while Spanish and French varieties have stronger violet tones. There are more than a dozen varieties of lavender (Lavandula spp.) available in the nursery trade, from large bushes to compact mounds, and foliage can be smooth, toothed, lacy, green, gray or silver. Due to their drought tolerance, they make stalwart container plants.

The hotter it gets, the more I notice how plants benefit from a minimum of water. In my back yard, in the shade of a massive elm tree, I have a seven-foot tall Fuchsia magellanica thicket, with red orange tubular flowers. It has developed over the past decade or so with a bare minimum of irrigation. In the last several years, it has never seen water more than once a week, even in the hottest weather.

This woody fuchsia has propagated itself through self-sowing, which has allowed a cluster of stout seedling specimens to grow up around the original plant. If this fuchsia had been getting water several times a week, it never would have survived this long, succumbing to the gall mites that spin their webs across its newly emerged leaves from time to time. Gall mites, in case you did not know, are the implacable foe of Valley-grown fuchsias and thrive where fuchsia leaves are overly succulent due to excessive watering.

TIP OF THE WEEK: Hot summer weather is the most favorable time for planting tropical fruit trees such as citrus, mango, and papaya.

Cactuses also appreciate summer planting.