Temperatures really begin to heat up in June -- and that typically marks the end of the planting season. But continue to check out clearance sales for plants as there are often good deals to be had!
Be sure and add organic matter to your soil as you plant -- it will improve your ground over time and help get your new plants off to a great start.
Watch your lettuce and other cool-season vegetables; they tend to bolt, or send up a flowering stalk once it gets hot. Once they bolt, they're usually too bitter to eat. It's probably too hot to sow new lettuce seeds in the sunny garden, but you may be able to get a small crop if you plant in the shade.
Or, replace cool-season vegetables with warm-season crops such as beans, pumpkins, squash, and corn.
Spring-blooming bulbs' foliage should be yellowing. Add the leaves to your compost pile once they have turned yellow and pull out of the ground with no resistance. Don't remove the leaves before this, however -- otherwise your bulbs may not perform as well next year.
If you haven't already mapped out your garden's spring bulb display, do so now. That way you can know exactly what bulbs you'll want to purchase this fall and where to plant them so they'll look good next spring.
Heat-loving summer bulbs are coming into their own. If you haven't planted any yet, get them in the ground now.
Deadhead annuals, perennials, and summer-blooming shrubs to promote additional blooms. This will also prevent them from self-seeding.
Watch for signs of garden pests -- if you catch them early, you can usually keep them from becoming an epidemic that ruins your yard.
Lacebugs are a big problem on azaleas, though you don't usually notice the damage until August or September. But now's the time to attack them. Look at your azalea's leaves for black spots on the bottoms and the black-and-white insects on the leaf tops. Spray with neem oil, insecticidal soap, or a similar product to keep them in check.
Examine junipers, birches, cherry and arborvitae for bagworms and other leaf-eating caterpillars, then treat with Bacillus thuringiensis as needed. Keep an eye out also for aphids and other small sucking insects, as well as whitefly. Spider mites can be treated with pyrethrums, an extract from mums.
Keep an eye out for containers of standing water in your garden -- they may be breeding grounds for mosquitoes. Change the water in your birdbaths daily and use environmentally friendly mosquito-control products.
Finally, this is a good month to take cuttings from the fresh growth of many trees and shrubs, including serviceberry, lemon verbena, chokeberry, angel's trumpet, bougainvillea, butterfly bush, hydrangea, jasmine, dogwood, magnolia, and stewartia.