What to do in your garden in April
Agastache. Deep rose pink 'Ava' agastache received the 2005 Green Thumb Award from the Mailorder Gardening Association for good reasons ― its extended bloom season and long-lasting flower color. Introduced by High Country Gardens ( www.highcountrygardens.com or 800/925-9387), the 4- to 5-foot-tall by 2-foot-wide perennial begins blooming in midsummer and continues well into fall. The flower spikes elongate up to a foot or more over a period of weeks. They can be cut to use fresh or dried as an everlasting flower.
Bare-root plants. Sunset climate zones 1, 2: Bare-root plants are less expensive than container-grown plants. In cold-winter climates, now is a good time to set out cane berries, fruit and nut trees, grapes, rhubarb, roses, and strawberries. If you can't find them bare-root, look for plants in containers.
Flowers. Zones 7-9, 14-17: All warm-season annuals can be planted now. Plants in sixpacks are best buys; they'll catch up quickly to those growing in 4-inch pots and jumbo packs. (To produce instant color for a special event, use 4-inch plants.) Try ageratum, bedding dahlias, globe amaranth, impatiens, lobelia, Madagascar periwinkle (Catharanthus roseus), marigold, petunia, phlox, portulaca, salvia, Sanvitalia, statice, sunflower, sweet alyssum, and zinnia. Zones 1, 2: Wait until the soil warms and any chance of frost has passed.
Herbs. Plant a specialty herb garden from Mountain Valley Growers (www.mountainvalleygrowers.com or 559/338-2775), such as biblical and butterfly-attracting herbs and those with edible flowers. Each selection comes with six plants ($25), and some can be paired with a book on the subject (prices vary).
Dig or hoe weeds. Zones 7-9, 14-17: As soon as weeds appear, remove them by cutting them off just below the soil surface with a draw hoe, loop hoe, or shuffle hoe (available from Lee Valley Tools, www.leevalley.com or 800/871-8158). To prevent weed seedlings from surviving on surface moisture, hoe in the morning so the sun bakes them during the day. Uncoil roots. Before setting out plants from containers, gently knock them from pots, then use your fingers to uncoil any bunched-up roots. If the rootball is solid, use a knife to score four 1/2-inch-deep cuts around the sides and one on the bottom (don't do this on bougainvillea).
Destroy dodder. This parasitic weed usually infests agricultural crops, but it can become a pest in home gardens. When dodder seeds germinate in spring, thin, yellowish stems twine around whatever plants they touch, extracting water and nutrients from them through rootlike haustoria (food-absorbing growths). Eventually a mat of stems forms around the host plant and the dodder loses contact with the soil. Remove and destroy infested plants, especially before seeds form. In late winter or early spring following an infestation, treat the soil with a preemergence herbicide to kill seedlings when they first appear.