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Pruning Hydrangeas, Squash Problems and Other Questions

To Prune or Not to Prune

At this time of year, hydrangea blossoms are fading and the plants can look “leggy” and even spindly.  The UT Extension agents passed along an informative post written by Ken Tilt of Auburn University on pruning hydrangeas in mid-summer.  You can read the full post here.  The bottom line is, if you prune, you should have a reason beyond “because the neighbors are pruning their hydrangeas.”  Since there is no life-sustaining reason to prune hydrangeas, it boils down to if you prune to manage the plant’s size or you can’t stand looking at a straggly plant, the time to prune is now and not much past mid-August.  The reason to prune now and not later is to make sure the plant has time to put out new growth, including next year’s flower buds, before the first frost.

Also, for a complete review of pruning your trees, shrubs and plants, you can download the UT Extension publication on the topic here.  The pruning rule is generally spring blooming plants should be pruned immediately after flowering; prune summer flowering trees and shrubs in late winter or early spring before new growth appears.

Got Cukes?

Another question that pops up at the Chattanooga Market Master Gardener table is “why isn’t my cucumber/squash/pumpkin/watermelon vine producing anything?”  Hamilton County Extension Agent Tom Stebbins addressed this question in his July 3 column in the Chattanooga Times Free Press.  The gist of the article is that vegetables and fruit in the curcubit family – squash, gourds,  cucumbers, melons and pumpkins – have a timed pollination process in which the male flowers bloom first, with the female flowers blooming later.   Female flowers usually open for just one day, so timing is important.  Bees and other insects pollinate the female flowers with the pollen from the male flowers and “fruit set” is accomplished.

If the female flowers bloom first – you will not get fruit.  If wet weather or exceptionally hot weather interferes with bee activity, you will not get pollination and therefore no fruit.  If you don’t have pollinators like bees because you use pesticides or bees aren’t attracted to your garden area, you may not get pollination and therefore will not have successful fruit production.   Successful curcubit fruit set is yet another reason to have a “bee friendly” yard and neighborhood.

Vinegar – the Organic Weedkiller Fact or Fiction

A trickier subject concerns using vinegar as a weed killer.  There are a lot of stories about grandparents using vinegar this way, and gardeners who would like an organic solution to weed problems can find plenty of advice on the Internet along these lines.  Household vinegar is a diluted solution of acetic acid, usually around a 5% solution of the acid to water.  The acetic acid in vinegar burns foliage, which kills the exposed part of the plant but not necessarily the roots.  The USDA conducted studies on using vinegar for weed control and found that in fields and greenhouses, a 20% solution of acetic acid (4 times the strength of household vinegar) will control 80-100% of annual weeds like foxtail, pigweed and velvetleaf.  Perennial weeds treated with a 5% solution (household strength vinegar) showed 100% shoot burnout.  The roots, however, were not affected and shoots always regrew.  Therefore weeds with taproots like dandelions will need to be dug out to get effective control.  The Oregon State Extension Service’s summary of the research on vinegar for week control can be found here.

The bottom line: if you use vinegar for weed control, remember that the vinegar will damage all foliage that gets sprayed, including plants that you do not want to kill.  Also, while you may see the green part of the plant wither and die, this does not mean that the weed is dead and gone.  Maybe the best advice is to save the vinegar for your pickles.

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