Some garden myths to lose

In this new age of ‘Fake News’ when facts are branded as fake and lies are freely airborne, it might be appropriate for gardeners to sort myths from garden facts.

Planting by the moon. I had a gardening friend who swore that you should plant root crops by the dark of the moon. I don’t automatically discount such advice, but finding credible evidence that this is true is non-existent.  True, the moon does affect ocean tides, but its effect on smaller bodies of water is nil and the likelihood that it can affect water movement in plants or germination has never been demonstrated. For more information on this myth see: .

Sunshine focused through raindrops will burn plants. Watering plants in the sun should not be done because droplets of water act like magnifying glasses and will burn holes in the plant’s leaves. If this is so, farmers would encounter huge losses after each daytime rainstorm. Sorry, but there is no way that a drop of water can raise the leaf temperature to a burn.

It is advisable to water gardens in the early morning hours to conserve water and to avoid nurturing moisture-fostering diseases. Plants so watered will dry as the sun shines; unlike plants watered in the evening or at night which will dry off much more slowly thus enhancing disease possibilities.

Copper strips keep slugs and snails away. This is a touted way (though not inexpensive) of keeping these pests from the vegetables in your raised beds. Allegedly, the copper induces an electric charge that deters the pests. Several tests of this shown on YouTube tend to disprove this method. A couple of tests used pre-1981 actual copper pennies and other copper materials in an experiment with snails and slugs. They observed the pests sliding across the copper undeterred. I am not sure that this is a definitive disproof of copper’s deterrence, but it does strongly suggests it doesn’t work. See:

There are ways to curtail snails and slugs and handpicking with a flashlight in the evening, early morning or during or after irrigation/rain will reduce their numbers. Diatomaceous earth and wood ashes piled in rings around plants will protect them as long as the materials are not wet and dry egg shells may work too. Baits using iron phosphate which are harmless to pets and children also can be used. Upturned citrus, shingles or boards with space beneath will provide hiding places that can be checked in the morning for pest disposal.

Use coffee grounds to acidify soil. While coffee grounds are acidic, mixing them into the soil would affect pH very slowly. Fresh coffee grounds tie up nitrogen as they decompose and this can adversely affect plant growth. It is best to use coffee grounds in your compost bin to facilitate the breakdown of leaves or high carbon materials. To acidify soil for acidophilic plants such as azaleas, rhododendrons or blueberries it is best to use soil sulfur as directed on the package.

Newly planted trees should always be staked. Unless the tree is top heavy or in an especially windy location, it does not require staking. Movement is good for young trees as the trunk will grow thicker and stronger when not immobilized by staking. Last winter, I pruned in a small local orchard where young fruit trees had been properly staked as if they were landscape trees. It should never have been done since fruit trees, when properly pruned at planting, need no staking. Unfortunately, they were not properly pruned at planting either. If properly staked, movement should be allowed to help strengthen trunks. Most trees should have stakes removed after 6 months to assure development of strong trunks.

Gravel in the bottom of containers improves drainage. A myth slow to die and one that actually is counterproductive with an increase in the possibility of root rot, not less, with the use of gravel. The water saturates the soil above the gravel as gravity moves it downward, so basically it makes the effective size of your container smaller by moving the saturation pool of water higher in the pot. It is better to use a potting soil that is porous and well drained. Adding perlite or organic matter will increase drainage and soil can be prevented from leaving though the bottom hole by covering it with a piece of screen or landscape cloth.

Adding sugar to the soil will yield sweeter tomatoes. Sugar in tomatoes is the result of photosynthesis. Adding sugar to the soil might feed some soil bacteria, but if you want sweeter tomatoes add sugar after slicing. Some tomatoes are genetically programmed to be sweeter than others and I vote for Early Girl as a sweet one. Happier gardening if you lose the myths.

If you have a gardening related question, you can contact the UC Master Gardeners at 209-953-6112. More information can be found at:

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