by Michael Smith (Veshengro)
If you are interested in growing a garden, there are lots of people offering advice from the internet, to books to even those you know very well. However, not all advice is good advice and some is just downright silly. Sorting out the good from the bad is sometimes difficult, especially if you are a novice gardener.
So, no matter where you get your gardening advice from, it is a good idea to be sure that your source is reputable and that there is truth behind the claim. Some gardening tips of old have now been proven wrong in light of new discoveries.
So let us now look into some of these myths that should be discarded in the light of new findings.
Paint pruning cuts
Pruning cuts painted over with tar or pruning paint may give the impression that the tree is well looked after. Latex, shellac, petroleum and asphalt compounds are some of the materials used for wound dressing. The idea is to seal off the cut surfaces to prevent rot and other diseases. However, new research finds that wound dressings of this sort do not benefit trees and that, in most cases, they may be quite harmful.
When any part of the stem is damaged or cut, trees use their self-healing mechanisms to form a scar tissue or callus at the site of the injury. This helps keep out pathogens that may otherwise infect the trees. Wound paints prevent the formation of calluses, thus interfering with this natural healing mechanism. They can actually seal in water along with spores and microorganisms that cause decay. Bleeding cuts, in particular, should never be dressed in any way.
It is better to make the cut as clean as possible using a sharp instrument. With a clean saw/pruning shears and make a slanting cut close to the collar of the branch, but not too close. Then, leave it to the tree to do the rest. Do heavy pruning towards the latter part of winter when the trees are at minimum risk of infections. Exception here being those of the prunus variety where science says to do any pruning and reduction just after the trees have flowered. It is reckoned that as the tree is then in heavy sap flow the flow of said sap will flush away any risk of pathogens entering the cuts.
Organic pesticides are safe
The truth is that they are not necessarily so.
We hear a lot about the detrimental effects of chemical pesticides; so by contrast, organic pesticides may appear to be safe. Organic compounds derived from plants and animals may be more biodegradable than man-made chemicals, but it is just so wrong to think that they are all harmless to people or the environment. Some of the most poisonous substances on earth are derived from plants and animals, typical examples being snake venom, ricin derived from castor plant and botulinum toxins produced by bacteria.
Several organic pesticides are used in agriculture; they have varying amounts of toxicity. For example, Rotenone extracted from the roots of certain tropical bean plants is a very potent pesticide, insecticide, and piscicide, all rolled into one. Despite being organic in origin, it has been found to be six times more toxic to humans and other animals than Sevin, a chemical pesticide of similar action. Rotenone is banned in some countries but continues to be used liberally in others.
Nicotine, pyrethrum, and neem are some of the other plant-derived pesticides used by gardeners. Nicotine has high toxicity for mammals, including humans, and is thought to be responsible to bee deaths; pyrethrum has immediate action on pests while being less toxic to mammals. Neem, which has a slow action and disrupts the metabolic pathways of insects, may be safe for other animals.
Bacterial toxins such as Bacillus thuringiensis (Bt) toxin and Alpha Beta Protein are used to trigger defense mechanisms in crops. They induce the crops to produce biochemicals that make them more resistant to potential pathogens. The safety of these toxins, as well as that of the additional substances that plants produce against them, is under the scanner.
So, organic pesticides should be chosen carefully for their merits rather than their “organic” label. And, they should be used with the same caution that you reserve for man-made chemical pesticides and fertilizers.
Amend clayey soil with sand
Clay holds on to water; sand quickly drains. So, when you’re told to add sand to clayey soil, it seems quite logical. But what actually happens is that you get more compacted soil that defies tilling, let alone better drainage.
Imagine what would happen if you poured sand into a tin of marbles. The sand will pack into the spaces between the marbles, making it difficult for both the sand and the marbles to move about. The same way, the fine clay particles fill the spaces between the larger sand particles, giving a thick, mortar-like consistency when mixed with water.
The best way to amend clayey soil is adding plenty of compost and leaf mold. These light materials get clay particles to stick all over them, but resist compaction. It gives the soil an airy structure that facilitates better drainage. Once amended with compost, adding sand may have some additional benefit.
Don't water the garden in the heat of the day
No gardener will have escaped this myth. Well-meaning fellow gardeners everywhere would warn you that you will end up killing your plants if you water them at noon. The explanation given is that the water droplets act as lenses concentrating rays of the sun onto the leaves.
The myth may have been handed down from the time the legendary Archimedes burned Roman ships with his parabolic mirror or came from school children who used to burn paper and ants with magnifying glasses.
However, if you have ever attempted it, you would know how long it takes to achieve the expected results, and that the magnifying glass has to be kept at a particular distance from the target throughout and not applied directly to the object. In the same was as the story that (broken) glass bottles in the wild will cause forest and bush fires. Again, the distance is wrong.
Having said this, however, it is possible that soluble salts in your water, as well as possible chlorine (which is added to tap water) can cause burning but not so much as that the droplets themselves act as a magnifying glass but that when the water droplets evaporate, the caustic salts deposited on the leaves may cause burn spots.
Plant trees in deep holes to give them stability
When tree saplings are transplanted, gardeners are often anxious that they should get a good foothold in the new location. After all, they are to face fierce windstorms and other vagaries of nature as they grow. Thus the advice to dig a deep hole, at least twice the height of the root ball, is often followed with religious fervor.
Now it turns out that deep holes are not what give stability to the trees, but wider ones. The planting hole should be ideally twice the diameter of the root ball, if not more. This provides a large area of loose soil for the roots to spread out. A wider base would obviously anchor a top heavy tree better than a narrow one.
Fill the planting hole with compost and fertilizers
This myth probably comes from the desire of every gardener to provide every help possible to help a new plant. Compost-rich soil is a great growing medium, and fertilizers can make plants flourish. But planting time is definitely not the best time to provide these.
When you fill a planting hole with compost, you are giving the plant a relatively loose medium rich in nutrients. It also absorbs moisture well. The plant will restrict its roots to this area since it has no need to spread them out to the harder and drier soil beyond the planting hole. For one thing, it affects the stability of the plant. Another problem crops up when the watering is eventually reduced. The fast-draining compost dries up quicker, leaving a dry zone around the plant. With not enough roots beyond this area, the plant suffers. That's why you often find, in such situations, that, if the plant was raised in a pot, it has not grown any further as far as roots are concerned than the size it was in the pot.
When it comes to fertilizers, high concentrations can burn the roots, especially the new roots the plants need to put out to establish itself. Root burn is a common reason for new plants not thriving despite all your attention.
After keeping the new plant in position, backfill the planting hole with the same soil you dug up. Water well. Allow the plants to spread out its roots in search of nutrients first, and then apply compost and fertilizers around the plant, but never too close to the stem. Some gardeners dig a shallow ditch around the plants for adding compost, but that is not necessary. Just cover the compost with a thick layer of mulch.
You must wash and sterilize your pots
That, alas, is a myth and one that was invented in the time of the big houses by head gardeners loath to lose their well performing staff at the end of the active season having to hire new at the next and then having to train most of them up again. So they claimed to their masters that all pots needed to be washed and sterilized and all that jazz during winter and thus he had to keep the staff on.
And, to all intents and purposes, the list of myths could go on for a great deal longer still. Charles Dowding has written and published a small little book on this subject entitled “Gardening Myths and Misconceptions” and I can very much recommend it.
© 2020
