Deadhead Rhododendrons and Lilac
Snap or prune off the faded flowers from rhododendrons, azaleas, and mountain laurels. Be careful to avoid damaging the growth bud just below the flower cluster. This puts the plant's energy into new growth rather than seed production. Pinch off the step tips of azaleas to keep plants bushy. Remove faded lilac blooms to improve next year's bloom.
Remove the spent flowers from repeat-blooming roses to keep them blooming and apply a fertilizer high in potassium to stimulate more flower production. If not already applied, consider mulching rose beds to conserve soil moisture and to prevent fungal spores from splashing onto foliage from the ground. Use organic pest controls if pests appear.
It's Not Too Late
If you haven't completed planting annual and vegetable transplants don't hesitate to purchase new plants or even sow seed. Yes, you'll miss having the earliest blooms or harvest, but you'll still be rewarded with months of production up until frost. If transplanting, try to choose a gray day just before a rain.
A number of perennials rapidly send out new growth in all directions. Some of the culprits include obedient plant (Physostegia virginiana), bee balm (Monarda spp.), and gooseneck loosestrife (Lysimachia clethroides). Their exuberance is both a blessing and bane. Before they take over an area, decide on the space you want to allow them, then regularly pull up and discard the excess or share with friends.
Fall-blooming chrysanthemums, now given the botanical name Dendranthema grandiflora, grow best in full sun and well-drained soil. They are heavy feeders and should be fertiized three times during the growing season. With the exception of dwarf cultivars, mums should be cut back two or three times before August 1 to keep plants compact and to encourage the maximum number of flowers.