Whenever I encounter myths about gardening, I realize that I may be guilty of believing in some of them. As a Napa County Master Gardener, I've been trained to research information and to offer only science-based advice to home gardeners. So when I read something about gardening that sounds questionable, I always ask myself: fact or fiction?
Gardening myths and old wives' tales come from many sources. Even researching this article, I found that experts have differing opinions about the validity of many firmly held beliefs.
Myth: When you can sit on the ground comfortably with a bare bottom, it's time to sow seeds.
Truth: Taking the temperature of the soil before planting seeds or seedlings is important. For most vegetables, the soil should be between 55°F and 60°F when measured three inches deep. This warm soil helps roots to grow. But before the invention of soil thermometers, how was a gardener to know? According to folklore, farmers used their bare posteriors or their elbows to test soil warmth.
Myth: Placing gravel or pot shards in the bottom of a container improves drainage.
Truth: For many years, I planted pots this way. But during my Master Gardener training, I saw an experiment that demonstrated that soils had to be saturated before moisture would go to the next level. Putting some plain newsprint or a fine weed block in the bottom of your pot will keep soil from falling out or slugs from moving in, but gravel or shards won't affect drainage.
Myth: For a plant to bear fruit, you must have both male and female types.
Truth: While that statement is true for some species, many plants and trees are self- pollinating. Tomatoes are a good example. The flowers contain both male and female parts and just need to be jostled a bit or buzzed by bees to move the pollen around. I usually shake the plants daily as I pass by.
Pomegranates and most varieties of Asian persimmons are also self-pollinating. For small gardens, that's an advantage because you need only one tree to get fruit. In contrast, sweet cherries and kiwis will not produce fruit unless you have both a male and a female plant. Some apple varieties may be listed as self-fruitful, but you'll get more fruit if you have a second variety to cross pollinate.
Most garden vegetables, including summer squash and pumpkins, produce both male and female flowers. Bees make sure the pollen gets spread around. If the spirit moves you, you can help the process along manually.
Myth: Clay pots are better for container plants than plastic pots.
Truth: It depends what's in the pot and whether you are conscientious about watering. Clay pots do not retain moisture as well as plastic pots, and they tend to wick moisture away from the roots. Clay also is heavier than plastic and more breakable. If you tend to forget to water, then plastic may be the better choice for you.
Myth: After pruning a tree, treat open wounds with a wound dressing.
Truth: University research shows that is it not necessary to put tar or other wound dressing on a pruned or injured tree. In fact, it may be counterproductive. The tree had the ability to heal itself. Using a dressing can delay the healing or even cover up plant diseases and make them worse. Do proper pruning cuts with clean sharp tools at the correct time of year for the tree and let them air dry and heal on their own.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners (http://napamg.ucanr.edu) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Garden Questions?