Most of the heavy lifting in the garden is finished by now, so June is the time for tweaks & a little grooming.
When Nepeta finishes blooming this month, take a deep breath — and cut plants back hard, so they are only a few inches tall. It seems drastic, but this haircut will give you compact, non-floppy plants that will rebloom without taking over the entire neighborhood. Try it once, and it will become an annual habit for you, because the plants look so much better. This technique is also very effective for making thrifty specimens of mature Alchemilla (Lady’s Mantle), Cranesbill Geraniums, Aquilegia (Columbine) and Heucheras (Coral Bells).
If your Lilacs need pruning, go ahead and do that now, or remove the spent flower heads.
Fall-blooming Asters bring vivid color — and butterflies — to the garden when most other plants have faded. But some varieties can achieve heights that seem overwhelming. Enjoy the blossoms on more compact plants if you cut Asters back now by half. Just finish this pruning by the end of June.
Fertilize your Roses as soon as the first flush of bloom is finished, then at least one more time in early August. Plants will reward you with more flowers and more vigorous growth.
Although we fertilize most perennials just once, in early spring, Clematis is an exception. These heavy feeders benefit from a monthly application of 5-10-10 or 10-10-10 fertilizer, now through the end of August.
Daffodil leaves feed the bulb, providing the energy for next spring’s blooms. Depending on how far north you live, the foliage may be getting pretty tired by now. Be sure to allow foliage to remain for at least six weeks after bloom is finished, even if it’s floppy. When the leaves begin to turn brown, go ahead and cut them off at ground level.
Dahlias love warmth, so they should be growing nicely now. If you didn’t install stakes when you planted any of the tall varieties, it’s a good idea to add stakes now — before plants become top-heavy and threatened by every passing storm. Watch the video with details on growing and staking these exuberant growers, which bring so much color to the late summer garden and bouquets.
Source – White Flower Farm