What to do this week: The two secrets of garden success are water and sun. This is a good time to move plants that are not thriving to a sunnier location. Nine times out of 10, that’s their problem. (Unless they need more water.) But full sun is scarce in New England gardens because of our heavy tree canopy, closely built houses, and devotion to sun-hogging lawns. If you don’t have a bed in full sun, consider cutting down a tree or cutting out an island bed in that sunny lawn. If your garden is in part shade, please don’t even try to grow peonies, sunflowers, and roses. Instead plant shade-tolerant perennial geranium, lady’s mantle, hellebore, bleeding heart, coral bell, hydrangea, begonia, annual lobelia, astilbe, and Japanese anemone. Or try native woodland wildflowers such as perennial lobelia, mayapple, columbine, thalictrum, amsonia, blood root, Solomon seal, and phlox. In full shade, please plant: lily-of-the-valley, ferns, wild tawny orange daylilies (but not the colorful hybrids), annual impatien, and, best of all, hosta. If all you really have is shade, buy the biggest planter you can lift and set it in a sunny spot on the deck or patio. I promise it will beat trying to garden in the shade.
Q. Creeping Charlie has completely invaded my lawn this year. No matter what I use, I can’t get rid of it. What should I do?
A. Creeping Charlie (Glechoma hederacea), which is also called ground ivy, is a vine that has round leaves with scalloped edges and small purple flowers. It forms a mat-like ground cover, using leaf nodes that form roots if they come in contact with the soil. Since every broken piece of rooted node can turn into a new plant, it is very difficult to weed out completely by hand. The only weed killers that work on it contain dicamba. Apply only in the early fall when the creeping Charlie plant is growing most actively; this ensures that winter temperatures will finish off the weakened plant. Also, apply dicamba only three days after mowing. Do not mow again for three days. This will allow time for the herbicide to work through the plant’s system. You can get rid of creeping Charlie in flower beds by either hand pulling (after rain or watering works best) or by smothering it with mulch or newspapers. Quickly remove any small creeping Charlie plants that reappear. An organic solution suggested by The Native Plant Trust in Framingham (www.nativeplanttrust.org) is to smother it with rolls of cardboard that painters buy at hardware stores. As substitutes, try Pennsylvania sedge or wild strawberry. Pennsylvania sedge (Carex pensylvanica) is a native plant that looks like lawn but requires mowing only once a year. It will grow in thinner soils and more shade than grass will. Wild strawberry (Fragaria virginiana) needs more sun but supports numerous pollinators. It also provides tasty berries in the summer.
Q. I definitely want to try one of the phloxes you mentioned (“Garden phlox is a pain, so what changed my mind?’’ Ask the Gardener, July 28). When is the best time to plant it?
J.C., Dover, N.H.
A. September is the best month to plant almost anything that’s winter hardy, from phlox to grass seed to trees to spring-blooming bulbs. It is often better than spring planting because the ground is warmed up, allowing roots to grow and prepare for boffo top growth next spring. In the fall, you also don’t have to worry as much about heat waves or water as frequently. For more information on phlox, visit perennialpleasures.net, a detailed website for a specialty nursery in Vermont’s Northeast Kingdom.