Dear Garden Problem Lady


Neighbors had their dogwood tree sprayed three times this spring for something called “Discula Anthracnose”. Would you please explain what that is. We wanted to get a Dogwood this fall.

In D.C. it has become a well-known fungal blight that can kill dogwoods. First diagnosed in 1978, it spread across the southern states, and into the north, quite concentrated in cities like DC. There is no cure for this Anthracnose. However, careful pruning, and then fungicidal spraying, can keep healthy dogwoods alive. Diagnosis must occur promptly after the first sight of browning of leaves, flowers, or whitening of trunk or branches. 

My neighbor says he is resorting to solarization. My high school Latin tells me it involves the sun.

Anyone with a bad sunburn knows the unexpected (because invisible) destructive power of the sun. Farmers use solarization to clear whole fields of grass and weeds. You can use it to clear even a small patch of grass, weeds, or a raised bed, where you want to plant something else. The only problem—it takes time—at least six weeks if you use sheets of clear plastic over the area, longer if you use just layers of newspaper. First cut whatever is growing down to the lowest height you can. Water the area deeply. Lay the plastic, weighing it down at the edges and all overlaps. Solarization is relatively cheap, chemical free, and purges the soil of weeds, grass, seeds, pests and pathogens. But you cannot do this in the shade.

We want to create a vegetable garden out of part of the back yard, and the soil is hard as a rock. Is rototilling a good idea?

The smallest rototillers cost over $150 (see photo), but you need something bigger to go deep enough. Best to rent a big one for a few hours. Mow or clear the space of shrubs or ivy and big weeds. Run the rototiller in rows, back and forth, several times. Plants can’t reach the rich nutrients in compacted clay soil, so you must break up the top layer enough to remove it, and go deeper. Electric rototillers do save labor. But after you go deeper you must break up the lower layer too, enough to mix it with compost and manure, even some sand, to lighten it more. Perhaps at this point “double-digging” with a long spade might be easier. You will have broken up much of the clay, mixed it with lighteners, and brought it back to its original level. Plenty of work. Another negative—rototillers do kill worms—if any. But other worms will return.

For information about the Capitol Hill Garden Club, visit the club’s website: The club is on summer break. Meetings will resume in September.

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