Purple potatoes, red popcorn, and giant green caterpillars – horticulture will go Technicolor at Family Horticulture Day. A variety of indoor and outdoor exhibits, staffed by Dane County Master Gardeners and Dane County 4-H youth and adult volunteers, will give visitors hands-on experience with horticultural science (but nobody has to handle the giant caterpillars).

The caterpillars (technically, Manduca Tobacco Hornworms) eat tomato leaves and turn into hawkmoths – jumbo moths the size of hummingbirds. Scientists study Manduca as a model organism – a quick way to study the genes involved in how things grow. The purple potatoes, along with their red, pink, yellow, blue and white brethren, will be part of the Rainbow of Potatoes. Visitors can take home a seed potato to plant.

In addition to giant green worms and purple potatoes, the indoor stations will offer visitors a chance to extract DNA from wheat germ, manipulate a micropipette to move a millionth of a liter of water, and use hydrogen peroxide to investigate the Foam Factor in seeds.

At the outdoor exploration stations, horticultural adventurers can learn about biological control of purple loosestrife, rain gardens and native perennial gardens for home landscapes, and spring flowering bulbs. Meditative adventurers can walk the station”s labyrinth.

In tents outside, visitors will learn how to transplant tomato seedlings and successfully sow vegetable and flower seeds. The red popcorn (along with white, yellow, purple and black) is part of the Popcorn Challenge. Take the challenge to figure out which makes the best popcorn.

The Soil and Plant Analysis Lab will offer an open house, including demonstrations and Q and A on how to collect soil and plant samples for analyzing lawn and garden soil fertility.

Family Horticulture Day is the finale of Science Expeditions 2005, a month-long series of public science events at the UW-Madison. The event will run from 10 a.m. to 2 p.m. Saturday, April 30. The West Madison station is located at 8052 Mineral Point Road, about a mile west of the beltline. For more information, go here.