Hold Off On the Roundup

A Bay Weekly reader called complaining that the weed killer Roundup was not killing the weeds he was spraying. Matter of fact, he said, “ I might just as well have been spraying the weeds with water.”

If you read the Roundup label carefully, you’ll see that it “should be applied only on actively growing weeds.”

What the label doesn’t say is do not apply on weeds that are under drought stress.

Plants under drought stress are not actively growing but are in a kind of dormant condition. When a plant is in a drought stress condition, the chlorophyll is not functioning and cell sap is not flowing from the leaves to the stem and to the roots. As a result, weed killers like Roundup, 2,4-D and similar herbicides are unable to be transported throughout the plant tissues where they do their thing.

For Roundup to kill a plant, it must be transported from the foliage down to the roots, where it kills the root system. A dead root system means a dead plant. When Roundup is sprayed on a drought-stressed plant, the chemical simply stays on the surface of the leaves, where it deteriorates from heat and ultraviolet rays from the sun.

If and when we ever receive a good rain, you must wait at least a week before applying Roundup or any other weed killers. Just because the plants look like they are growing following a good rain, that doesn’t mean they’re functioning at capacity. They have some catching up to do and repairs to make.

If the drought were extensive, like it has been this summer, some of the thin leaves will never recover and thus will not be receptive to foliar-applied herbicides. Applying foliar-applied weed killers to such plants is a waste of time and money.

Pruning Blueberries for Bigger Fruit

Dear Bay Gardener:

I have a few blueberry bushes that are about seven years old that have produced nicely but are getting a little scraggly. I have been trimming runners and eliminating water shoots, but I’m not certain of the best time to prune the large bushes for renewal growth. Instinct tells me that pruning in late summer or early fall would give them a chance for growth once the weather cools, but I would love to have your expert advice. I always read your column in Bay Weekly.

–Kay L. Parris, [email protected]

A Stop pruning out the water shoots. They should be replacing the older stems. Prune blueberries in mid- to late-March. They should be pruned back severely. Depending on the cultivars you are growing, either yellow stem or reddish stems, remove all spindly and twiggy stems, leaving only three to five strong yellow or reddish stems per branch. Remove all branches below the belt line and those higher than you can reach standing on the ground. Renew the oldest stems with those strong water shoots.

The oldest stem on your blueberry plants should not be older than five or six years. Vigorous stems make for bigger berries and larger clusters of berries.

I am an old blueberry grower from New Hampshire, and I enjoy teaching people how to prune if you would like to come and watch me prune my blueberry plants in March.