Good Afternoon
Good Afternoon

Garden Detective: Powdery mildew, overgrown grasses, dangerous porcelain berry

Overgrown ornamental grasses, like this one in a

Overgrown ornamental grasses, like this one in a Levittown yard, can be divided and transplanted. Credit: Bob Lindsay

DEAR JESSICA: Our cucumber plants grew beautifully this summer, but then started to die suddenly. Anything on the ground looked brown and dried out within two weeks, while the vines died more slowly. There almost seemed to be a while mold on the plants. Any idea what this could have been from? — Andrea Lewkowicz, South Hempstead

DEAR ANDREA: It sounds like your plants succumbed to powdery mildew, a fungal disease that coats infected plants with white, powdery spores. When that coating spreads over leaves, it blocks their ability to absorb sunlight. When the infection is severe, it can prove fatal to the plant.

Weather often plays a role, as the pathogen favors hot and humid spells, but such cultural factors as crowding plants, allowing weeds to grow and overhead watering, encourage the disease.

I have found that drenching affected plant parts, including the undersides of leaves, with neem oil, which is derived from the seed of the tropical neem tree, is effective against powdery mildew when caught early. But affected plants must be monitored daily, with applications repeated when symptoms return. Horticultural oils are effective, as well.

If plants are too far gone, however, they should be removed to avoid spreading the disease.

DEAR JESSICA: Thanks for all the great advice you provide. I learn something new every week.

My parents have an ornamental grass growing at their home in Levittown. It appears to be doing well and has gotten much larger in the few years since it was been planted. My parents are concerned about the increasing diameter of the plant. It is now brushing up against the house and is blocking access to an outdoor hose spigot. They love the plant, but just need to thin it out a bit. Can the plant be "split" down the center from top to bottom or would this kill it? Can it be quartered? If so, when is the best time to do it? — Bob Lindsay, Levittown

DEAR BOB: Yes, warm-season ornamental grasses like the one your parents have can be divided. The best time to do this is on a cloudy day in spring or early summer.

You’ll need a long-handled, pointed shovel and a saw. A long-handled garden fork and flat-edged shovel are optional, but will make easier work of lifting and dividing roots, and you can switch between them and your pointed shovel as needed, depending on soil conditions.

If you didn’t cut down last year’s growth in autumn, do it before dividing the plant. Water the ground to soften soil before beginning.

There are two methods. Let the size of your plant, the quality of your soil and the strength of your muscles guide you:

1. Dig up the entire plant and cut or otherwise split the root ball into two or more sections, each with leafy growth attached, then replant each clump and water.

2. Use your shovel to cut a deep half-circle around one side of the grass, then plunge a shovel down through the center of the plant, into the soil beneath it and under half the roots. Using your garden fork or shovel, work your way around the cut portion to sever it completely. Be sure to dig deeply enough to lift all the roots under the section you are lifting. Remove it from the ground and fill the remaining hole with soil, tamping firmly. Plant the removed half of the grass elsewhere, and water both plants well.

DEAR JESSICA: A few years ago, I found this weedlike vine growing behind the shed. It looked kind of like a grapevine in terms of the leaves, but all it grows are pastel-colored berries. I have never seen any berries that color before. They look like Easter egg colors! Do you know what they are? — Tony Correnti, West Islip

DEAR TONY: I agree your plant is beautiful, but it’s also an extremely invasive weed called porcelain berry. And I hate to tell you this: You really need to remove it.

Porcelain berry (Ampelopsis glandulosa var. brevipedunculata) produces showy, pastel-colored berries that resemble robin's eggs or, as you noted, Easter eggs.

It’s so detrimental, the U.S. National Park Service has called it “a vigorous invader of open and wooded habitats, where it shades out native shrubs and young trees. As it spreads, it climbs over and blankets existing plants and weakens and kills them by blocking sunlight.”

Vines can reach 25 feet long and are tough as nails, thriving equally well in sun and shade, dry and wet conditions, and in any kind of soil. It hogs water and soil nutrients, and can choke out every plant in its path. If you don’t think it’s a problem because it hasn’t yet overtaken your garden, consider that birds and other wildlife that eat the berries can spread their seeds far and wide, setting up the ecosystem for big trouble.

The best way to eradicate porcelain berry and prevent it from wreaking havoc is to pull it out by its roots. This is best done when vines are young, as established roots are stronger and can be difficult to remove. If you find that's the case, cut the vines down to about a foot off the ground and spray the openings of cut stems with a systemic herbicide containing glyphosate or triclopyr — but protect nearby plants so the chemical doesn’t kill them as well.

More Lifestyle