Garden Detective: Prickly mystery plant

DEAR JESSICA: I hope you can help me identify this plant growing in my garden for the past two years. The first year, I thought it was poison ivy and tried pulling it out and destroying it. Then, I learned that poison ivy would not have prickly points on the stem, which this has. Now, I wonder if it is a blackberry plant, which would be wonderful. I am attaching three stages of growth for the plant in question. They are growing in a bed of pachysandra. -- Marie Siegel, Seaford

DEAR MARIE: At first glance, I was certain your plant was either a wild blackberry or raspberry, but not wanting to risk allowing you to poison yourself, I reached out to weed scientist Andy Senesac of the Suffolk County Cornell Cooperative Extension. In turn, he forwarded your photos to a taxonomist friend, who said your plant is "definitely a Rubus sp., but hard to put a species name on it with just these photos. Could be a raspberry." (Rubus is the genus of brambles that includes thorny fruit-bearing perennials like blackberries and black raspberries.)

If it's important to you to know exactly which species you're growing, Senesac invited you to bring or send a piece of the plant to him at 423 Griffing Ave., Riverhead, for more specific identification. (For more information you can call 631-727-4126.) But is it edible? "I would think so," Senesac said. "I don't know of any common Rubus sp. that are unsafe to eat."

DEAR JESSICA:I have friends who use their fresh grass clippings around their plants during gardening season. They swear by it, but I am not convinced. Do you have any thoughts on this? -- John Farrell, St. James

DEAR JOHN: Most mowers used today have built-in mulching mechanisms that chop up grass clippings into tiny pieces. These are best left on the lawn, where they will contribute a natural source of nitrogen to the soil as they break down. Just remove the grass-catching bag and allow the mulched clippings to land where they may. Using fresh grass as mulch, however, is not a good idea.

Let's look at the reasons we mulch in the first place to put this into perspective: Mulch keeps the soil temperature from fluctuating wildly, retains soil moisture and discourages weeds from germinating. In order to perform its function properly, mulch should be applied 2 to 3 inches deep.

Fresh grass, if applied thickly enough to serve as a proper mulch, will turn into a slimy, smelly barrier on the soil surface as it decomposes. It also will increase the soil's temperature as it breaks down, possibly so high that it may endanger plants. However, you can use fresh grass clippings as an ingredient in compost, where, when combined with dry items like shredded paper and crunchy leaves, will "cook" into a wonderfully beneficial mulch for your plants.

DEAR JESSICA: I always keep a few impatiens flowering plants in my partially sunny windows. These plants give a constant supply of flowers for daily worshipping (Pooja), especially in winter. I generally place the seeds in pots containing potting soil at the end of summer. Last season, I was not successful in maintaining the plants because they became infested with tiny insects and spider web strings were visible. After a few weeks, the plants stopped thriving. I have used household insecticides without any success. Please help. -- C.V.A., Hicksville

DEAR C.V.A.: It appears your plants succumbed to spider mites, which often target impatiens. The tiny, dotlike arachnids live in colonies of as many as 100 on the undersides of leaves. Because they are hidden from view, they often aren't noticed until they've injured the plant with their piercing-sucking mouthparts. Chlorophyll is drained from leaves, turning them yellow and sometimes causing them to drop entirely. The web you saw was the telltale sign of their presence.

The best preventive measure would be to inspect plants carefully before bringing them into your home; one infested plant can infect others. Ladybugs are natural predators of spider mites, so purchasing a box of the beneficial beetles and setting them loose around the infested garden plant should eliminate the problem. This isn't practical for houseplants, however. Chemical miticides can be effective, but must come into direct contact with the mites. If the infestation on your impatiens is widespread, you might consider disposing of them and starting over with new plants.