Carol Stocker - Globe Correspondent
What to do this week Shear, pinch, or cut spent individual flowers or entire stalks that have finished blooming to conserve plants energy. Many annuals will bloom again if prevented from going to seed in this way. If you find you hate deadheading, grow self-cleaning annuals such as impatiens, cleome (spider flower), narrowleaf zinnias, ageratum, and wax begonia next year. However, let traditional “cottage garden’’ biennials (which live only two years) go to seed so they are able to replace themselves with their offspring next year, especially if you don’t mulch. These include hollyhocks, foxgloves, columbines, sweet Williams, Canterbury bells, feverfews, and forget-me-nots.
The garden needs an inch of water a week. Planters need more because of evaporation from the sides. The smaller the pot, the more often you have to water it, so use large containers when possible, preferably with saucers underneath. Containers with built-in water reservoirs minimize watering chores. Before leaving town for a week or more, group plantings in containers in light shade and water deeply. New trees planted along the street or in other paved areas benefit from plastic 15-gallon watering bags zipped up around the trunk or an adjacent stake. Fill them with a hose twice a week and they will slowly release moisture without run-off. Water new municipal street trees within reach of your hose to help them survive, and your town will be grateful.
Q. I have a question about a rhododendron that got out of control. Late last fall, we did a deep prune on it. This spring/summer, some new leaves have sprouted, but only near the base. At some point, should we trim down the branches to the point at which leaves appear?
A. Yes. Rhododendrons really hate to be pruned. If one grows too big for the space, it is better to dig up the whole shrub and move it, roots and all, instead of pruning it. When pruning any tree or shrub, try to cut branches back to a place where there are leaves emerging or at least another branch forking off that has its own leaves. If you chop the branch off in the middle, leaving a woody, leafless stub, the branch will often just die back to where there is green growth lower down, or it will start sprouting new growth from the roots, which is what your rhody is doing.
Q. Is there any way to get rid of mugwort?
A. Common mugwort (Artemisia vulgaris) has sprawling and pungently scented leaves with many herbal uses, including flavoring beer! But it can take over a garden or field in no time, and it is very hard to get rid of once established. It is one of those plants whose roots break off when you try to pull them out, especially if the soil is dry. So hand weeding is a long-term process because you can’t eliminate the roots, just deprive them of nutrients, and you may have to control rather than eliminate it. Other choices are applying herbicides or covering the area with plastic, a tarp, or cardboard until the mugwort has been smothered. Identifying new infestations early is your best defense. Mugwort resembles chrysanthemum leaves but has silvery hairs on the underside. For more tips on getting rid of mugwort, visit: gardeningknowhow.com.
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