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Problems with mandevillas and brown lawn patches

Mandevillas need to be fed with a water-soluble plant food that is high in phosphorus.


Mandevillas need to be fed with a water-soluble plant food that is high in phosphorus.

What to do in the garden this week: This has been a good summer for plants: not too hot and not too dry. But be vigilant about providing an inch of water once a week to garden flowers, vegetables, and any struggling or new plantings if it does not rain sufficiently. To reduce losses to evaporation, water early in the day or use a soaker hose or inground irrigation. Continue to fertilize vegetables, annuals, and potted plants, but stop feeding more permanent plantings so they can start to slow down and prepare for, yes, winter.

Q. Last year at this time I bought a medium-size mandevilla in a plastic or fiberglass container. When purchased, it had many buds and flowers. I overwintered it in its original container in my enclosed breezeway, where the winter temperature never dipped below 45 degrees. This summer, I placed it outside (still in its original container) in a sunny spot, but to date, no buds have appeared. What happened, and how can I induce the plant to flower?


Larry K., Acton

A. Mandevillas usually flower their heads off. When you bought yours, it had been force fed fertilizer by the growers and given optimal irrigation to create all those enticingly unfurled flowers which vaguely resemble half opened pink or red umbrellas. The sunny spot sounds good, but by now this tropical vine has used up all the fertilizer that came in the original container. It needs to be fed every couple of weeks with a water-soluble plant food that is high in phosphorus. (Follow the package instructions.) It also likes frequent watering so keep the soil moist, but not wet. It should winter over fine in your breezeway again as long as it gets sunlight and temperatures do not fall below 45 degrees. In the winter, water it only when it is dry. If it thrives and needs re-potting next year, select a container only a couple of inches larger than the current one or the mandevilla will expend its energy growing roots instead of flowers.

Q. I have been experiencing a continuing problem trying to establish a lawn in one section of my front yard. My yard is approximately 30-by-24 feet, and the problem area is a strip 3-by-15 feet. Each year, the lawn dies in that strip and I reseed the area each fall. The lawn is reestablished and grows beautifully through the fall and ensuing springtime. It then proceeds to die during July and August. Much of the rest of my lawn goes brown during the hot summer because I do not water it. It comes back in early fall, except for this strip which is reduced to a dirt patch. When I reseed this patch I detect a lot of “spaghetti” like roots just below the surface and I try to cut as many as possible. The area is bordered on one end by a large evergreen shrub and on the other end by a very large tree on the sidewalk. I have been told by garden nursery people that my problem is caused by those “spaghetti” roots which hungrily soak up any available moisture in the area and any additional watering will also be absorbed by the roots. I have no problem with removing the evergreen shrub if that is causing the problem, but I can’t do anything about the tree. I have examined the soil very carefully and I haven’t seen any indication of grubs or other root killers.

Dan Hines, West Roxbury

A. How frustrating! It sounds like you probably have a Norway maple planted on the sidewalk strip, as this is the most common street tree that municipalities used to plant. It is also the worst for gardens and lawns because its greedy roots extend far beyond the heavy shade of its canopy. In fact, it is so bad that it is now illegal for nurseries to sell them in Massachusetts because they have been formally classified as an invasive species. Their seedlings sprout everywhere, including hedges, and threaten to push out the native sugar maples in woodlands that provide fall color for our leaf-peeping tourist industry. You could kill most trees by hacking a large notch in the bark and immediately painting the wound with Round-Up. But that wouldn’t be legal for municipal trees. So you are stuck with it, which means no lawn for you! You could plant your problem strip with carefree evergreen vinca, which tolerates worse conditions than grass does. Vinca would also create a nice winter effect with your evergreen shrub, which you should spare because it is blameless.

Carol Stocker is an award-winning garden writer for the Boston Globe. Send your questions, along with your name and the name of your town, to
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