Garden Detective: Transplanting rhododendron

DEAR JESSICA: I have a very large, beautiful, blooming rhododendron about 10 feet high and 10 feet wide, but it is covering a front window. While the privacy is nice, it makes the room very dark and covers a good portion of the house. At a lecture at my local library, I was told rhododendrons can successfully be transplanted, as they have shallow roots. Do you agree? I read they should be transplanted in early spring before blooming time. Does that sound right?
-- Sue Ruben, Farmingdale

DEAR SUE: It's true; rhododendrons have shallow roots, so it's relatively easy to move even large, established plants. Still, you'll have to dig quite a bit because the root system of a 10-foot rhododendron likely is quite wide. The best time to transplant your shrub is, in fact, in early spring, so aim to do this in late March. Take care to dig up as much of the roots as possible and place the entire shrub onto a tarp to avoid losing soil and damaging roots when moving it to its new location. (Dragging it on a tarp also will be easier than trying to carry it.)

The new location should offer some shade, and the soil there should be on the acidic side, with a pH level around 5.5. To keep root exposure to a minimum, plant quickly into a hole that you've prepared in advance. Mix equal parts compost or well-rotted manure with the soil removed from the hole and fill halfway. Tamp down firmly to eliminate air pockets and water before filling the remainder of the hole. Tamp again and water well. Mulch with an acidic variety like shredded oak leaves or pine needles.

Monitor soil moisture all season and water regularly until frost, as you would a new plant. Once re-established, rhododendrons typically don't require much attention.

DEAR READERS: If you've been following along for the past few years, you're familiar with late blight. The disease, which was responsible for the Irish potato famine in the 1840s, periodically affects plants in commercial fields late in the season without much fanfare. But in 2009 it was found very early in the season on plants being sold directly to consumers at local big-box stores.

Every year since then, the pathogen has been present and weather conditions favorable for a re-emergence. Now, for the fourth consecutive year, it's back: Late blight was identified earlier this month on a farm in the Riverhead area.

The disease is caused by a pathogen that can release millions of spores per plant per day, especially during wet weather. Those spores are carried by wind "typically within 30 miles but potentially long distances until air currents or rain bring them back down," said Meg McGrath, a Cornell University plant pathologist stationed at the Riverhead office of the Cornell Cooperative Extension of Suffolk County. Theoretically, spores from one infected plant in Nassau County could destroy an entire crop on a farm in Riverhead, she added.

The disease results in elongated brown lesions on stems and large grayish-green to brown spots on leaves that cause the plant to blacken, wilt and die. White mold full of spores encircles spots visible on the undersides of leaves.

Start inspecting potato and tomato plants now, and continue to do so every week throughout the growing season. "Keeping an eye out for symptoms, reporting and managing late blight are the responsibility of anyone growing these crops," said McGrath.

If late blight is detected, plants should immediately be bagged tightly in plastic and set in the sun for a few days until they die, then disposed of only in the trash -- never composted or left on the ground in piles, as spores will continue to form until the plant dries up.