No one knows where they’re from or how they begin. Like urban legends, gardening myths spread like wildfire from gardener to gardener until everyone knows them. Often, they seem logical. But in general, they have little or no scientific basis.
The sad thing is that they usually make gardening more time consuming or complicated. Or they detract from the appearance and productivity of the garden. And they are tenacious! Some date back to the 17th century, if not earlier… and as we keep repeating them, they continue to prosper and harm future generations of gardeners.
What’s worse is that I’m writing this column knowing full well that many readers won’t believe me. “Who does he think he is to contradict what my grandmother, who knew everything about gardening, taught me?” I therefore suggest that you do your own comparative study. Sometimes you need to see it to believe it.
EIGHT GARDENING MYTHS
1. After pruning, the wounds of trees and shrubs should be painted with pruning paint to protect them from diseases.
On the contrary, when a wound is covered with paint, tar or another product, this tends to trap the humidity present on the wound and thus it creates a microclimate conducive to the development of harmful fungi. It is better to clean a wound well, to remove irregularities and allow the surface to dry out. But don’t apply any coating.
2. Removing leaves from tomato plants so the sun can reach the fruit hastens the ripening of the fruit.
Tomato fruits don’t need to be exposed to the sun to ripen. The proof? An immature tomato ripens just as quickly in a paper bag, a dark pantry or on a window sill in bright sunlight. Likewise in the garden. The fruits do not ripen any faster if you remove the foliage. Moreover, doing so reduces the energy input to the plant, resulting in smaller, less tasty tomatoes. Thinning out tomato leaves can even cause sun scald (sunburn) to tomatoes when they’re suddenly exposed to strong sunlight!
3. Removing the suckers from tomato plants will increase the harvest
A sucker is, by definition, a stem that doesn’t produce fruits and steals energy from the parent plant. Some plants produce such suckers: apple trees, lilacs, etc. In tomatoes, the little growths you see at the leaf axil aren’t suckers, but rather secondary stems. Instead of stealing energy from the mother plant, they give it more by absorbing sunlight. In addition, these faux suckers will produce more tomatoes. Letting them grow can even nearly double the tomato crop if the conditions are right .
Also, recent studies show that eliminating suckers tends to cause foliar diseases, further reducing the quantity and quality of tomatoes produced on the plants. Removing secondary stems may, however, increase the size of the remaining tomatoes, but only a little. If you remove these stalks, the total weight of the crop will be significantly lower, often by a third. For more on the subject, read: FYO: No, You Don’t Need to Remove Suckers from Tomato Plants.
4. Don’t watering your plants in full sun. That can burn the foliage!
This myth is based on the principle that a drop of water found on a leaf can act as a prism, increasing the intensity of the sun and leading to it produce great heat. And that does seem logical.
However, it just doesn’t happen. Have you ever seen plants catch fire because there were drops of water on their leaves? I didn’t think so. No one has!
That said, there’s not much point in watering when the sun is beating down. However, that’s not because doing so will burn the foliage. Instead, it’s because almost all the water will evaporate and therefore won’t really benefit the plants. Water early in the morning if you can: it’s still cool (hence less evaporation) and your watering will be more effective. Avoid watering in the evening, however, because the foliage then stays moist longer. And that increase the risk of disease.
5. Always place a drainage layer of gravel at the bottom of flower pots.
On the contrary, a drainage layer of coarse material reduces drainage and takes up space that could have been used for roots. This is because there is too much of a contrast between the size of the soil particles and that of the drainage layer, and that disturbs capillary action. The gravel or shards, being much larger than the soil particles, cause the soil to retain more water and prevents surpluses from evacuating. Plants thus remain sitting in stagnant water and might rot.
If you want an effective drainage layer, place it on the surface of the soil and not at the bottom of the pot. Thus, the water will evacuate from the crown, the place of the plant most prone to rot, and will remain near the roots, which tolerate its presence better.
6. Pick up those grass clippings. If not, they’ll cause thatch buildup!
Contrary to popular belief, grass clippings do not contribute to thatch, that overly thick layer of dead plant debris that hinders the growth of healthy lawns. In fact, decomposing clippings help stimulate microbes that will reduce excess thatch. It’s best to leave your grass clippings in place rather than bag them, especially if you have a mulching mower. It saves time; plus the clippings are a free source of nitrogen for your lawn. And also help water it!
7. Removing faded flowers from lilacs increases their flowering the following year.
Studies show that this is not the case. In reality, most lilacs are essentially biennial in bloom: a heavy bloom year will be followed by a weaker bloom year and there is nothing you can do to avoid it. This does not mean you should never to prune a lilac, however. You can prune to reduce its height, to remove the suckers that hinder its growth, etc., but simply removing the flowers is a completely useless gesture. Harmless, but useless.
8. When a plant is in poor shape, always fertilize it.
In general, when a plant is in poor shape, it doesn’t have a very strong root system and can’t absorb the fertilizer that you pour on its soil. On the contrary, fertilizer can damage its weakened roots. Better to find the real cause of the problem (insects, diseases, bad location, etc.) and fix that. When the plant starts to grow again, then it will be the time to fertilize it.
However, there is an exception to this recommendation: if the plant suffers from a mineral deficiency, i.e. the lack of an element (in this case, its growth will normally be stunted and its foliage deformed, yellowed or reddish), you should fertilize it… but not by its roots, because they are too weak to absorb the fertilizer well. Instead, spray the fertilizer, diluted to a quarter of the regular dose, directly onto its foliage. Thus, it will be quickly absorbed by the foliage and will act without delay to correct the problem.
And that’s it for eight common gardening myths. There are many more! But before you look into old superstitions about gardening, think about it for a minute. Always ask yourself if there is concrete evidence that a technique is effective. Very often—in fact, almost always—the less we humans act on plants, the better they grow!