Weed, Weed, Weed
Summer weeds are in full swing now, so try to stay ahead of them. Spend just 15 minutes per day weeding, and you'll be surprised at how much you can get done. Don't wait, or you may end up needing to take a week's vacation from work just to catch up.
Use Fabric to Tie Plants
Tear up an old T-shirt or other soft fabric into strips (or use purchased plant ties) to bind climbing roses, tomatoes, and vines to their supports. Twine or wire will almost certainly damage plant stems, inviting disease.
Remove Spent Rose Blooms
Deadhead roses (prune off spent blooms) to encourage plants to produce more flowers. Some types of roses have a relatively limited flowering period, while others will continue to bloom all summer long. In either case, it's best to deadhead to keep plants looking healthy.
Water New Plants
The most common cause of failure in new plants is lack of water. Be sure to water new transplants and newly planted trees and shrubs frequently until they get established. During hot, sunny weather, this might mean a deep, thorough watering every few days, especially if your soil drains freely. Check soil moisture levels by digging down a few inches.
Watch for Cabbage Loopers
If the leaves of your cabbage-family plants, including broccoli, cauliflower, and kale, have lots of holes, they're probably infested with cabbage loopers or cabbageworms. Inspect plants carefully for the light green caterpillars, and/or their dark-colored droppings. Use Bt -- a biological control that affects only caterpillars -- to control them. (Note that this insecticide also kills other caterpillars, some of which may be the larvae of butterflies you enjoy, so use it sparingly.)