From Les Lutz, Director of Horticulture:
Spring has arrived on the Cape! Now is the time to tend to your Cape Cod gardens.
Annuals & Perennials:
Seasonal flowering annuals, vines, herbs, and vegetables can be planted after the area’s average last frost date of May 15. Wait until Memorial Day before setting out cold-sensitive plants such as tomatoes, peppers, eggplants, and squash. When planting annuals, it’s always a good idea to pinch new growth to encourage stocky habit. Be sure annuals have been hardened off properly before planting them outside. Avoid fertilizing newly planted annuals for two weeks.
Continue to plant new perennials, ornamental grasses, and roses in containers. If plant roots are encircling the pot, make multiple cuts into the root ball with a sharp tool, and flare the sections outward when planting.
Trees & Shrubs:
This is a great time to be planting trees and shrubs. Water thoroughly and gently at planting time and continue for the first year. Plants need one inch of water a week, spread throughout the root zone. Mulch root zones to conserve moisture and to keep roots zones cool.
If pruning spring-flowering shrubs and ornamental trees is needed, do so immediately after they bloom. These include forsythia, viburnum, lilac, small magnolias, rhododendrons, and azaleas. Prune to the ground old canes of forsythia and lilac. An alternative time to do renovation pruning is in late winter when plants are dormant. Deadhead (or lightly prune) spent lilac blossoms to increase flower production. Avoid fertilizer with excessive nitrogen; it can encourage foliage at the expense of flower production.
Though not necessary, you can remove spent flowers of azaleas and rhododendrons. Take care not to break the new shoots at the base of these flower trusses when removing old flowers. To increase flower production for the following year, pinch off one-half of this new green growth when it is at least one inch in length.
Mow lawns at 2 to 2½ inches, removing one-third or less of the leaf blade. Leave grass clippings on the lawn to return nutrients to the soil, or add them to compost heap. Rake clippings slightly if they are heavy and wet. If you are applying grass seed, do not use a pre-emergent weed killer in the same area.
Fertilize lawns in mid-May if necessary. Late fall is a preferable time to fertilize. Monitor for weeds and hand pull or spot treat accordingly.
Tall perennials may require staking. If so, do this before they reach 6 inches. Fall flowering plants such as chrysanthemums, asters and tall sedums can be pinched regularly to promote stocky growth. Pinch once a week until the middle of July.
Continue to direct the growth of perennial vines on their supports. Check peonies for botrytis blight or other foliar fungal problems. Peonies that suffered from botrytis or bud blast last year should be sprayed regularly, starting when the plants are between 2 to 4 inches tall. Cage or provide support for peony blossoms when the plants are 10 inches tall.
Spring bulb foliage should be allowed to yellow and wither before removing it. The leaves manufacture food that is stored in the bulb for next year’s growth.
Now is the time to plant summer- and fall-flowering bulbs such as Asiatic and Oriental lilies, dahlias, cannas, tuberous begonias, caladium, crocosmia, freesia, and gladioli.
Fertilize roses with a liquid 20-20-20 solution when flower buds are set. Climbing roses should be encouraged to develop lateral, flower-bearing canes.
Monitor roses for insects and diseases. Check daily for black spot, especially in wet weather. Do not handle rosebushes if foliage is wet and infected. Wait until leaves have dried before removing them and spraying.