Wait Until Summer to Prune "Bleeders"
Some deciduous trees, such as maple, elm, birch, dogwood, and yellowwood (Cladrastis), are "bleeders." If you prune them in the spring when their sap is running, they will leak large quantities of sap. It's not harmful to the tree, but it can be messy and unsightly. To avoid this problem, prune these trees in midsummer or in late fall when the trees are dormant.
Feed Flowering Perennials
Most perennial flowers don't need heavy doses of fertilizer. An annual application of compost or an annual light sprinkling with a complete organic or slow-release fertilizer will keep them thriving. A few do appreciate a richer diet, including astilble, garden phlox, mums, Shasta daisies, delphinium, and lilies. Give these a supplemental feeding with a soluble fertilizer such as fish emulsion in midsummer.
Sow Seeds (Already!) for Fall Harvests
For a fall harvest of cabbage, kale, and Brussels sprouts, sow seeds in pots indoors or in a cold frame around the time of your last frost and transplant to the garden about 4-6 weeks later. Row cover fabric over plants is a great way to keep them free of flea beetles and cabbage worms.
Put Plant Supports Up Early
Get your supports for flowering perennials like peonies, delphiniums, and tall bellflowers (Campanula) in place before the plants get too tall. Hoops work well to support bushy plants like peonies, whereas tall, single-stemmed plants like delphiniums need individual stakes, ideally about three-fourths the final height of the stem. Twiggy branches, sometimes referred to as pea brush, work well to support lower spreading perennials like baby's breath and catmint.
Let Soil Warm Up Before Mulching
An organic mulch such as straw is a great way to keep down weeds and conserve soil moisture in the vegetable garden. But it also keeps soil cooler, so hold off spreading it until the the soil has warmed up, a week or so after your last frost date.