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Oak trees growing in reader Diane Kerley's Holbrook

Oak trees growing in reader Diane Kerley's Holbrook yard have not yet dropped their leaves. This, it turns out, isn't unusual. Photo Credit: Diane Kerley

DEAR JESSICA: I have several large white oak trees on my property that have not yet dropped their leaves. For as long as I can remember, the majority of leaves fall by Thanksgiving. However, the trees seem to be holding tightly onto their brown foliage. Should I expect them to drop as the winter progresses or will there be a surge of leaves falling come spring 2018?

— Diane Kerley,

Holbrook

DEAR DIANE: All leaves — even needles on evergreens — have a life span, and when they reach the end of the line, they lose chlorophyll, change color (sometimes they simply turn brown) and drop. But oaks (and beech) trees sometimes are late to the party. What you’re seeing is something called marcescence, which is the retention of dead plant matter. The trees’ leaves have died, but they’re holding on to the tree.

There isn’t one definitive reason why this happens, but it’s believed to be a protective mechanism of the tree: very young trees, as well as those growing in dry, infertile soil, are prone to hold on to dead leaves until spring, when they drop, decompose and enrich the soil just as the tree comes out of dormancy and needs the nutrients most.

It’s nothing to worry about; just a marvelous example of nature taking care of itself.

DEAR JESSICA: I read your article about indoor lemon trees last month and have a tip for you. Since the trees are in the house when they start flowering, and there are no bees in one’s home, you need mention to all who want to grow a lemon tree to buy spray pollen, as I have had years with 15-20 full-size lemons, and they taste amazing.

— Andrew Hager,

Bellmore

DEAR ANDREW: So-called “spray pollen” products don’t actually contain pollen, but rather a synthetic hormone called kinetin, which forces fruit production despite a lack of pollination. These blossom-setting sprays aren’t appropriate for all plants, and are more often applied to tomatoes, peppers, eggplants, cucumbers, melons and strawberries in the garden than to indoor citrus fruit. Fruit from treated plants tends to grow misshapen, and oftentimes without seeds, but the flavor remains the same. This is the first time I’ve heard of the product being used on indoor fruit trees, so I consulted with an expert.

Horticulturist Vinnie Drzewucki, resource educator with the Cornell Cooperative Extension of Nassau County in East Meadow, tells me he believes Bonide Blossom Set spray, the only such product registered for sale in New York State, does work, but warns that its label “does not list it for use on lemons or citrus . . . so legally it can’t be used.” He went on to speculate that the reason could be simply that there’s “little to no scientifically valid research or documented evidence existing for the use of this substance on citrus or other plants for listing them on the label of a product. Funding such research to create this documentation is very costly, and a manufacturer might not find it cost effective to do it just to add another plant to the label.” Commercial citrus growers, Drzewucki points out, “don’t seem to use it, so there’s probably not enough estimated use by home gardeners to make it worthwhile for a consumer product label.”

His recommendation? “I think when it comes to growing lemons or any citrus fruit plant indoors, knowing and providing proper environmental conditions and cultural practices, with a little help from hand pollination of flowers, are what’s most important.”

DEAR JESSICA: My dad, Raymond Amendola of Shirley, is an avid reader of your column and thinks the information you share is excellent. He is having a problem with his brassicas and hopes you’ll be able to help. He describes seeing 1/8-inch to 1/4-inch shot holes in the leaves. He does not see any evidence of slugs but does see tiny whiteflies. Dad has tried using hot sauce as well as a general insecticide — to no avail. Do you have any other remedies to suggest?

— Kate Amendola,

Hell’s Kitchen

DEAR KATE: My guess is your father’s plants have been under attack by cabbage worms, which would create the holes you describe, as well as whiteflies.

The best defense against cabbage worms is a good offense, which in this case means covering new plants with floating row covers in spring. In addition, disrupting the life cycle of overwintering pupae in the soil can go a long way toward reducing or eliminating their emergence in spring, so give the soil a good tilling now.

After evidence of damage is seen, the best control is the bacteria Bt (Bacillus thuringiensis). Apply according to package directions.

The whiteflies look more harmful than they are, and they usually can be controlled with a simple rinse from a hose, directing water to the undersides of leaves.

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