Q: Do I have to let the lawn clippings dry out before I spread them around as a mulch?
A: Generally that is a good idea. Pieces of green grass can dry to a solid sheet which sheds water. Grass mulch has a high nutrient value, whether green or dry, but in our climate it does not break down as quickly as it would where summer afternoon showers are a regular occurrence.
It is safe to scatter fresh grass clippings in a vegetable garden, between plants and between rows, as long as irrigating water can reach the ground between handfuls of clippings. The grass will become green manure, feeding nitrogen to the soil. Nitrogen from grass helps vegetables grow in the same way as weeds which are cut and left between vegetable plants. Personally, I feel even better about the weeds, since a green manure from weeds turns an enemy into an ally.
Q: What would be good groundcovers to plant?
A: First ask yourself whether you want an area that is solid groundcover, or whether you want only to cover bare patches of ground between other plants--in a perennial bed, for example. There are several excellent groundcovers which gallop over the ground at a great rate. Some of them have dense root systems which choke out the roots of neighboring plants. Some of them have such vigorous top growth that they smother anything smaller than a tree.
For covering ground in a flower bed, think about low-growing perennials like primroses, violas, the creeping forms of evening primrose and hardy geranium, as well as biennial forget-me-not. Although viola plants may die over winter, they seed so well that their return is dependable. If you decide to grow violas, choose your favorite color and plant only that one. Violas cross-pollinate with great ease, and the resulting mixtures are always muddy looking. My violas are an extremely dark purple with a small yellow eye, called 'Bowles' Black.' I need to pull out a few every year with larger yellow or white spots. (I also need to pull out a good many seedlings.) Being ruthless about color has paid off, though; I have kept the same deep purple for many years.
My absolute favorite groundcover in a flower bed is bugle (also called Ajuga and bugleweed). It blooms early, while taller perennials are just getting started, but its leaves are attractive all summer and fall. For a solid mat the varieties of bugle with green or burgundy leaves are the most successful. The forms with variegated green and white leaves are attractive plants but grow only slowly. They leave gaps between their stems big enough for weeds to start growing.
Because bugle is so vigorous, it needs to be thinned every year if it is not to take over a flower bed. Once a patch of bugle is well established, I do an annual pull when the flowers turn brown and before they make seeds. I pull all the flower stems and yank out piles of new growth. If I accidentally pull out some roots in the process, no matter. Thinning once a year is enough to keep the bugle well behaved, and it is not an onerous job because the roots are shallow. I can pull quantities of bugle for the compost pile with bare hands. I need no digging tool as long as the soil is damp.
Bugle grows in sun or shade, but other groundcovers have definite preferences. For shady areas sweet woodruff is an attractive choice. It blooms with tiny white flowers, but it will smother neighboring plants if they are delicate. Equally good are vinca and Waldsteinia, supposedly called 'barren strawberry,' although I have seen that name only in print. Waldsteinia has leaves like a strawberry plant and flowers that look like yellow strawberry blossoms. There is no fruit. In my garden it was slow to establish but finally reached some critical mass and now dominates its area. Vinca needs no description.
There are more choices for groundcovers which form a solid mass in sunny places. Thymes are among the best, and the best of the best, creeping thyme, will cover the ground at a pace much faster than creeping. One of its advantages is that it is so dense, both above the ground and underneath, that few weeds can penetrate an established planting.
Several ornamental strawberries also make impenetrable groundcovers within a few years, because their runners continually plug gaps between leaves. My favorite is 'Pink Panda,' which has bright pink flowers. The birds like it too, for its small berries.
Other possible groundcovers include creeping veronica, stachys (lamb's ears), low growing varieties of dianthus (pinks), and several saxifrages. Nothing is more useful than bugle, in my opinion. It will even stand some foot traffic.
Violets are a special case to consider. I love patches of them in my lawn, both when they are flowering and when they have only foliage. I have learned the hard way to keep violets out of my flower beds because their roots make a woody mass and they spread aggressively. I am still trying to eliminate from my landscape a large and lovely white violet. It makes more seeds than purslane and spreads faster than cheatgrass.
Q: What are the plants blooming now with big purple balls of flowers?
A: Flowering plants that look like chives on steroids belong to the same family as chives and onions. Usually they are called by the family name, allium, and they are increasingly popular. Most ornamental alliums have light purple flowers, but white and yellow are relatively common. Allium plants range from less than a foot tall to giants three feet or higher. The little ones tend to spread by seed, and they may seed new colonies wherever the wind blows. Some ornamental alliums, since they are bulbs, will multiply by splitting off "offsets," or miniature new bulbs. Some of the largest alliums are named hybrids--like 'Globemaster' and 'Purple Sensation'--which do not make seeds and thus multiply very slowly.
Ornamental alliums have several virtues: Because they take up little space, they can be planted in the middle of lower growing flowers. Even one makes a striking vertical accent in a flower bed. They also make excellent cut flowers, either fresh or dried. Since their leaves are onion-flavored, they are not high on the deer wish list. Ornamental alliums seem immune to diseases and insect pests, but bees and butterflies love them.
The disadvantages are two: many ornamental allium leaves begin to wither even while the plant is still in bloom. They must be planted where their ugly legs will be hidden. The second problem is that bulbs, which are sold only in the fall, can be hard to find. Look for them with tulip and daffodil bulbs.