Wait for Warmth to Plant Heat Lovers
Don't be in a rush to set your heat-loving plants like tomatoes, peppers, eggplants, and melons out in the garden. Wait until the weather is settled, the soil is warm, and the danger of frost is past. Plants that are exposed to too much cold weather early in their lives will be set back and they will never fully recover. Black plastic mulch laid in the garden bed a couple of weeks before planting time will help to warm the soil. If you can't resist setting out plants on the early side, give them some protection with row covers or hot caps.
Sow Herb Seeds
Sow seeds of annuals herbs such as dill, chervil, fennel, and cilantro directly in the garden where they are to grow. For a continuous supply of young leaves, make repeat sowings every few weeks. Let some dill and cilantro plants flower if you want to harvest the seeds. (The seeds of cilantro are called coriander.)
Scatter some borage (Borago officinalis) seeds around the vegetable garden. The beautiful sky-blue flowers of this sprawling herb will attract pollinating bees, and you can even eat them yourself! Add the edible blossoms to salads for color and cucumber-like flavor, freeze them inside ice cubes to dress up summer drinks, or candy them for use as edible floral decorations. Sow seeds in spring where they are to grow. Let some of the flowers go to seed and you'll have volunteer plants every year after with no effort on your part.
Raise the Flower Garden to New Heights
Add a focal point to your flower garden by erecting a tuteur (a free-standing pyramidal or obelisk-shaped trellis) and planting an annual or tender perennial vine to adorn it. Morning glory and sweet pea are traditional favorites, but there are plenty of other choices. Consider moonflower (Ipomoea alba), black-eyed Susan vine (Thunbergia alata ), hyacinth bean (Dolichos labbab), cup-and-saucer vine (Cobaea scandens), and cardinal climber (Ipomoea x multifida).
Plant in Drifts
When adding new plants to your perennial flower garden, you'll get the most visual impact if you set out drifts of plants in odd-numbered groupings. Unless you're planting large perennials such as goatsbeard or baptisia, try to include at least three individual plants of any one kind. This keeps your garden from having a spotty, unfocused, "one of everything" look. If purchasing multiple plants at one time doesn't fit your budget, fill in with inexpensive annuals as you wait for your perennial "keepers" to get large enough to divide and spread out.