One of the rites of spring is the inflicting of some sort of torture on your lawn - not to mention the torture to your body as you wrestle a piece of heavy equipment to perform this ritual.

Why do so many of us undertake this activity? And which is more beneficial, power raking or aerating?Lawn-care experts have changed their tune to a certain extent in the past few years. Power raking generates tremendous heaps of brown organic material. When examined in cross section, the reduction in the depth of the thatch layer is minimal. If power raking removed enough thatch to allow air and water to penetrate the soil, most of the growing crowns would be eliminated. Recovery to a green lawn would be extremely slow.

Half an inch of thatch can help cushion grass roots and insulate against the heat of summer sun. This also can minimize compaction and conserve moisture. Lawn clippings don't influence thatch much. Sloughing grass crowns, stems and roots constitute that layer. The grass clippings are somewhat beneficial as fertilizer and don't add significantly to a thatch problem.

Power rake lightly if you need to remove some excessive accumulations of leaves and debris. The operation may help to scatter nightcrawler mounds and reduce bumps.

Aerating will do your lawn the most good. Aerating or coring a lawn is necessary to reduce soil compaction. Rent a machine that will make holes in lawn surfaces to allow better movement of water. You'll also let air into the soil, which is as necessary as water for root functioning. Getting air into the thatch layer will help its decomposition and reduction. Fertilizer movement to the root zone will make its use more efficient. In other words, an aerated lawn will require less water and will respond to fertilizer and soil-warming faster than a poorly aerated one.

Lawns that get heavy traffic may need aeration annually. Sandy soils won't require aeration as frequently as a lawn planted in heavy clay. South- or west-facing slopes will need frequent aerating because they dry out quickly and have little chance to absorb water, especially if it is applied at a rapid rate. That unperforated thatch layer sheds water very effectively.

If you are plagued with too many earthworms in the lawn, aerating will give the worms a place to deposit their castings without bringing them to the surface, which creates those objectionable bumps.

There are several ways to aerate. Coring removes cores or plugs of soil, leaving small holes about 1/2 inch wide and 4 inches deep. These plugs can be left on the soil surface or raked and removed. The lawn mower will break them up and they'll gradually disappear.

Just be sure to do a thorough job. There should be a hole every 4-5 inches over the lawn surface.

Gas-driven aerators or coring machines may be rented, or there are manual types that can be purchased at nurseries and garden centers. Some work with water pressure to dig the hole, leaving no cores or plugs on the lawn afterward.

Lawn-care specialists may be hired to perform the aerating job.

For a copy of the fact sheet "Lawn Aerating - Thatch Management" send 10 cents and a stamped, self-addressed envelope to 2001 South State Street, Room S1200, Salt Lake City, UT 84190.

Crabgrass and spurge control

It's time for the herbicide application that will prevent these weeds from invading lawns. Dacthal, betasan and pendimethalin are available at garden stores. Read the label for rates and weeds they'll control.

Apply them after any aerating and power raking operation.

Free workshops

April 4, 7 p.m., "More Vegetables from a Small Space." Granger Bishop's Storehouse, 3648 South 72nd West.

April 5, 2 or 7 p.m. Same topic. Extension Office Training Room S1010, South Building, County Government (CGC), 21st South and State. Enter by northeast double glass doors.

(Note new dates for "Gardening in a Drought.")

April 11, 3 p.m., "Gardening in a Drought." (CGC) 7 p.m. Same topic, Granger Bishop's Storehouse.

April 13, 3 or 7 p.m. Same topic, CGC.

April 22, 3 to 6 p.m. Drip systems on display. Hatch Patch 8236 Mulberry Way (1405 East) Sandy.

Red Butte Gardens in color

Flowering bulbs are spectacular now through June at Red Butte Gardens of the state arboretum, at the University of Utah east of Fort Douglas.

Visit Red Butte Gardens early in April to see the blues, lavenders and golds of crocus, miniature iris and striped squill.

A combination of gold and scarlet with accents of white and blue will put tulips, hyacinths, daffodils and narcissus at center stage by mid-April.

Visit Red Butte Gardens in May for the amazing array of hybrid tulips in yellows, oranges, reds and purples.

June will bring pink and purple giant Allium, the delicate hues of Siberian iris and the bold colors of a prize-winning hybrid iris collection.

Plants are clearly labeled and a printed checklist is available at the garden gate or from the arboretum office.

Red Butte Gardens is open daily from 9 a.m. to sunset.

For further information, call Pam or Mary Pat at 581-5322.

To find wildflowers

The arboretum after April will offer a wildflower hot line. Call 581-4969 to get locations and timing of wildflowers blooming in Utah.