What to do this week: Move your houseplants outdoors to a shady spot for summer vacation, but don’t forget to soak them weekly. Plant container gardens in a soil-less growing mix (not garden soil) inside large, attractive containers with drainage holes. Cut asters and phlox back by half to keep them short enough to avoid staking. Thin phlox to five stems per plant.
Q. I would like to plant a clematis, but I’ve heard they can be fussy. Are there some varieties that are easy to grow and good for a beginner? Can I grow clematis to hide a long, ugly fence?
A. Clematis, known as the “Queen of Vines,’’ can be both rewarding and frustrating. One reason you don’t see them more often is that they generally require two to five years’ growth to put on a good show, if they ever do. After all your patience, they can die from clematis wilt, or for no apparent reason at all, just as they are getting good. Believing “a watched pot never boils,’’ I plant them in far corners of my garden where there is a shrub or fence they can climb, and then I forget about them. Years later, I will come across one of these clematis in full flower. What a lovely surprise! No waiting. No frustration. Fortunately, they seem to transplant easily, so I dig up the mature vine and move it to a more prominent location.
Of the more than a dozen kinds of clematis I have grown, I’ve had greater success with the smaller-flowered varieties, which seem longer lived than their more spectacular large-flowered cousins. My best performer has been the variety “Betty Corning,’’ with its hundreds of long-lasting lavender bells in late summer dangling from a pergola. “Madame Julie Correvon’’ is another tough small-flowered viticella clematis. It covers itself with 3-inch red flowers all summer, clambering over my Japanese spirea, which is the same color. Clematis needs something to climb and usually wants to grow straight up about 8 feet. Even if you plant the roots in the shade, it can reach the sun. For a horizontal chain-link fence, a friend swears by clematis Summer Snow a.k.a. “Paul Farges.’’ It looks like sweet autumn clematis on steroids, she said, with bigger wild-looking flowers through much of the summer, and it got huge in just two years. Sweet autumn clematis is another quick and robust grower with small white flowers in fall, but it can become a pest in the sandy soil of Cape Cod.
Q. What’s a fast-growing native evergreen for screening?
A. The evergreen narrow arborvitae hybrid called Thuja x “Green Giant’’ is being mass-produced for almost instant screening. It is replacing Eastern arborvitae because it is much less attractive to deer and faster growing. It can reach 60 feet tall and 12 to 18 feet wide, so plant yours at least 5 feet apart for a hedge in full sun or part shade. Although the “Green Giant’’ arborvitae has excellent pest resistance, it is sometimes susceptible to bagworms and scale.