Utah's nurseries, greenhouses and florists are expecting one of the biggest sales days of the year Saturday, the day before Mother's Day, as children prepare to honor Mom and homeowners throughout the state get ready to unleash their green thumbs for the biggest planting day of the year.

If only the weather will cooperate.Forecasters at the National Weather Service at Salt Lake International Airport say Saturday is expected to be partly cloudy, with temperatures in the mid-50s and a 40 percent chance of measurable rain. Sunday's forecast is for scattered showers with temperatures in the 50s.

A rainy weekend could dampen some enthusiasm for planting flowers, but it probably won't diminish the sales of cut flowers, potted house plants and mixed arrangements that will be given to Utah mothers on Sunday.

Seed companies, fertilizer manufacturers, greenhouses and gardening stores are making life easier for homeowners and offer a variety of new products this year for gardeners.

Seed companies are trying harder to develop just the right seeds for special climates and soils so gardeners can more easily find the varieties of flowers, fruits or vegetables most suited to their yards.

New fertilizers that are water soluble and in smaller grains promise to enrich soils faster and better, and there are new soil additives on the market that can make a new gardener look like a veteran farmer.

Applying fertilizers, soil additives and lawn food is easier, too, with watering devices that allow gardeners to use ordinary garden hoses to spray yards and gardens. And there are new insecticides that work better and are more specific.

Mike Bray of Bonneville Nursery in American Fork said he is looking forward to a huge weekend. "Something special we are offering this year is a terrarium or garden under glass for indoors."

David Whiting of Wuthrich's Center Street Greenhouses in Bountiful said he has a much better supply of Martha Washington geraniums and impatiens this year. "We weren't able to get as many of these plants last year as we wanted."

He said pansies will be a big seller this year. "It is one flower you can plant now and not worry about, even if we have a late frost. It can withstand cold better than most other flowers."

Kyle Timm of Wasatch Shadows Nursery said dwarf pine trees will be a big seller this year. "They are beautiful trees, but they don't get very big and they don't need pruning and are easy to care for. Japanese maples, for instance, grow from 5 feet to 15 feet tall."

He said the weather is probably good enough now to plant sensitive annuals, such as geraniums, begonias and impatiens, and many vegetables.

Ken Johnson of Pineae Greenhouse Inc., Centerville, said he doesn't expect to sell as many potted plants as he has in some past years, but he expects the sale of combination planters, hanging baskets of plants and more exotic inside flower decorations to be popular.

"There is a growing trend, too, to landscape, put up fences, build patios and install attractive, eye-catching flower and tree arrangements in yards. The greenhouse business continues to grow as people become more and more interested in making their homes and yards more attractive and interesting."

Merlyn Neff Olson of Neff Floral, Salt Lake City, said mixed arrangements of roses will probably be one of her best selling items this weekend, and Ruby Sant of King's Greenhouse, Lehi, said tropical indoor plants and tropical trees could be her big sellers. "Our 4-foot-tall rubber plants and 6- or 7-foot-tall palm trees look great inside a home."

Those who want to transplant bedding plants and vegetable starts into yards and gardens should observe a few basic principles, according to Bill Varga, Utah State University Extension horticulturist, and Shawn Olsen, USU Extension agricultural agent in Davis County.

When shopping, look for plants that are stocky and compact with a healthy green color. Tall, lanky specimens or those already blooming are undesirable choices, Varga and Olsen said.

Ask the nursery operator if plants have been hardened off, that is, gradually acclimated from the greenhouse to the outdoors. If not hardened off, the plants will sustain a severe shock when planted outside.

To harden off plants, set them outdoors in a protected place for a few hours the first day or two. Then gradually move them from the shade into the sun for an hour or two, leaving them out longer each day. The process will likely take several days.

When hardened off, plants should be set in a bed worked 12 inches deep. Fertilizer can be worked in just before planting. Dig a hole for the transplant, set the plant in it and press the soil down firmly.

The firming of the soil eliminates air pockets and makes a good bed for the plants to take hold in, Varga and Olsen said.

After transplanting, water annuals and vegetables immediately and keep them moist, but not waterlogged, until they are established, which will take about a week or two. Then water when the soil is barely damp at about the 2-inch-deep level.