FRESNO DESK - The American Nature lover looks forward to this time of year in California. Cars are pulling off the freeways. Drivers step out, and stare unblinkingly at the billions of flowers and blooming shrubs along the Pacific Coast and the Sierra uplands.

The California Poppy is breaking into a chorus of red and orange praise to the warming sun. Wild Mustard, Indian Pink, Thistle Sage, Pale Sweet Pea, Verbena, Meadow Lotus abound and the Monkshood are enough to startle any California highway traveler.

No special training is necessary to appreciate the beauty of this nation's natural wildflower heritage. If you are interested in getting closer to Nature this week, try guided wildflower walks, nature talks, or other outdoot activities that are schedule during the next few weeks. Some of these are listed below.

Wildflower slide show: For wildflower enthusiasts who'd like to preview the view before taking off in search of spring color, the California Native Plant Society on Wednesday will present a dual-projector slide show depicting the advance of spring from California's low desert northward and upward through the valleys and foothills to the subalpine high country of the Sierra. The free presentation by plant enthusiasts Wilma and Bill Folette, who have spent years photographing wildflower displays throughout the West, starts at 7:30 p.m. in the Garden and Arts Center of McKinley Park, 3330 McKinley Boulevard in Sacramento.

Wildflower Express: The Western Railroad Museum at Rio Vista Junction, 12 miles southeast of Fairfield on Highway 12 in Solano County, is conducting Wildflower Express train rides through the Jepson Prairie on weekends through May 11. Trains pulling historic equipment depart at 1 p.m. on Saturdays and Sundays, with additional departures scheduled at 3:45 p.m. on April 5, 12, 19 and 26. Tickets for adults range from $12 to $35, depending on which of three classes of service is selected. Children ages 4-12 ride for $8 in coach class. Admission to the museum is included. For reservations, call (800) 900-7245.

Learning Exchange: The Learning Exchange is sponsoring several wildflower field trips this month. The first, exploring the Buttermilk Bend Trail along the Yuba River, takes off at 10 a.m. Saturday, with a pre trip classroom session scheduled for Tuesday evening. A June 7 Tahoe Basin trip will be preceded by a June 3 class. Both trips will be led by naturalist Karen Weise.

A third trip, this one conducted by Bob Tribe, visits the Tomales Point area of Point Reyes National Seashore on April 19, with a pre trip class scheduled for April 17.

The fee for any of the trips is $29; call 929-9200 to register.

Yosemite National Park: Several field seminars focused on wildflowers have been scheduled by the Yosemite Association, a nonprofit educational group. They include three days of strenuous hiking in the lower mountains (April 18-20), "botany basics" (May 30-June 1 and July 18-20); Wawona wildflowers, waterfalls and giant sequoias (May 30-June 1); mountain wildflowers for the relaxed botanist (July 14-18); and a pair of photo workshops (May 9-11 and July 25-27). Course fees averaging $50 a day include room reservations or free shared camping space, plus free entry into the park. For a catalog, call (209) 379-2321 or write Yosemite Field Seminars, P.O. Box 230-S, El Portal, CA 95318.

Julie Stauffer Carville: The author of "Lingering in Tahoe's Wild Gardens," Carville leads spring and summer wildflower hikes in the Sierra. Next up: Codfish Falls near Colfax, April 20; Spenceville Wildlife Preserve, April 26; and Sagehen Creek at North lake Tahoe, June 7. There is a $35 fee for each outing. For information: 274-3827.

California Native Plant Society: Dedicated to the study and preservation of California's native plants, the CNPS can provide information and brochures at its office, at 1722 J Street, Suite 17, Sacramento 95814; phone 447-2677.

Most CNPS field trips are limited to members only, but an April 19 outing to Jepson Prairie, led by docents, is open to the public. To get to the Jepson Prairie Preserve, approximately 12 miles south of Dixon on Cook Road, take Highway 113 south from Dixon until it turns east at an overhead warning light. Continue straight ahead on Cook Road (gravel) over the railroad tracks to the parking lot.

For information on other CNPS wildflower outings, contact: Eva Butler, Sacramento Chapter, 443-6282; Dawn Aulenbrock, Tahoe Chapter, (310) 327-9915; Chet Blackburn, Redbud Chapter, 885-0201; Sue Britting, El Dorado County Chapter, 626-8366; or Jennie Haas, Sierra Foothills Chapter (209) 586-5704.

California Poppy Festival: If your travel plans take you south next weekend, check out the 6th Annual California Poppy Festival in the Antelope Valley town of Lancaster, not far from the California State Poppy Reserve, where more than 1,700 acres of the golden flowers are in bloom. For information: (805) 723-6085.

Southern California Wildflower Hotlines: For information on wildflower sites in Southern California, the Theodore Payne Foundation maintains a hotline at (818) 768-3533. A hotline for Northern California may be established soon.