The Laptop Gardener

Garden Myths Not Worth Repeating

Myths, old wives tales, and folklores abound even in the world of gardening. Gardening lore often gets passed from neighbour to neighbour as homegrown tips based on little or no scientific research. The myths start out as common sense conclusions and keep getting perpetuated time after time. Pretty soon they are part of the global gardening consciousness and they are believed to be true. Once this happens it is almost impossible to undo the belief. The poinsettia poison myth is still being trounced after eighty years. Well, here’s my attempt to dispel some popular garden myths.

Myth: Botanical “natural” pesticides are toxic to pests and harmless to other living things (including gardeners). Not true, in fact some botanical pesticides that are derived from poisonous plants are even more toxic than commercially prepared ones. Both pyrethrum (made from Chrysanthemum cinerariaefolium) and rotenone (made from two tropical legume family plants, the South American Lacepod or Lonchocarpus and the Asia’s jewel vine or flame tree which is known botanically as Derris) are popular botanical pesticides. Pyrethrum and rotenone are moderately toxic to humans (particularly children) when inhaled or ingested. Interestingly both are extremely toxic to aquatic life, and are used as fish poisons.

The flowers of the chrysanthemum used to make pyrethrum are harvested shortly after they open and are either dried and pulverized or the oils from the flower are extracted using solvents. The active ingredient works on the nervous system to cause paralysis and death (if in sufficient quantities). Cats are particularly susceptible to poisoning from pyrethrums.

Rotenone is a contact and stomach poison that is made by grinding up roots and varies in its human toxicity from very high to low depending on how much of the pure derris root is used in the pesticide. Treat natural pesticides with the same caution that synthetic ones deserve (or give them even more). One of the most toxic pesticides is nicotine, which is derived from the tobacco plant.

Myth: The soil under oaks, cedars and pines is acidic. The top inch or so might be acidic, but if the bedrock underneath is limestone then the soil above that rock will be on the alkaline side. Oak leaves, cedar leaflets and pine needles have to build up for centuries to make a significant amount that will have any impact on alkaline soil.

Myth: Moss grows in lawns that need lime. Lots of conditions favour the growth of moss in lawns. Having an acid soil is not the most significant one of them. The most important reason that moss is found in the lawn is that conditions are not favourable for a lush, healthy lawn. Moss is an opportunity seeking plant and will settle almost anyplace that there’s an open spot. Too much shade, poor drainage (moist conditions), poor fertility or compacted soils are all conditions where lawns do not grow well. When this happens moss is almost certain to arrive. Don’t add lime to correct a moss problem unless a soil analysis indicates an excessively acidic result.

Myth: Mushrooms and toadstools sprouting in the lawn mean that the soil is deficient. On the contrary, fungi such as mushrooms and toadstools are living off nourishing decaying material. A rotting tree root or other decaying organic matter is likely the cause of the fungi. This is a good sign that there’s nourishment being added to the soil. The visible structures are the flowering and fruiting portion of an extensive underground plant.

Myth: Ants are needed to make peony flowers open. Many people believe that ants are actually eating the waxy coating from the peony so that the flower can open. Others believe that the peony is secreting a sugary substance that attracts ants to feed. In any case, the ant is enjoying a symbiotic relationship with the peony and is not doing any harm by being on the flower bud. Once the bloom starts to open the ants vanish. Peony flowers can open just fine without any ants – just ask a florist.

Myth: Poinsettias are poisonous. This hugely popular garden myth is not true. There have been no cases of plant poisoning from poinsettias. This poison myth started in 1919 when a two-year-old child of an army officer stationed in Hawaii died of poisoning. The cause was incorrectly attributed to a poinsettia leaf. To persuade the public of this myth, members of the Society of American Florists frequently eat poinsettias for the press in December. The leaves taste like a bitter radicchio and won’t kill you, just make you sick. The plant though should not be eaten and is hazardous because of the milky sap. The sap can cause an allergic reaction for some people.

Myth: Some plants can repel mosquitoes. Amazing but not true, there are no plants that repel mosquitoes. If you rub the leaves of certain plants onto your skin, the oils and aromas can help discourage mosquitoes from biting. It is asking a lot of a plant to release essential oils into the air in quantities that can keep mosquitoes away for distances like 6 feet though.

Myth: Clay pots are better for houseplants than plastic pots. Clay pots cause the moisture in the soil to evaporate faster than plastic pots. This can be helpful for houseplants if the waterer is heavy handed – then clay is better. If houseplants are watered only when they need water instead of on a regular schedule then plastic pots should be adequate.

Myth: It doesn’t pay to use leftover seeds from flowers and vegetables. Most open packets of seed start to loose their viability as soon as they are exposed to heat and extreme humidity levels. If seeds are stored under ideal conditions in a tightly sealed jar in a dark, cool, dry location then they should store well for several years. The length of time varies according to the seed. To extend the viability even further, place some powdered milk in the bottom of the glass jar to soak up humidity.

Myth: Hostas are shade plants and don’t tolerate the sun. There are many hostas that perform very well in the sun if they are given adequate moisture. In fact, the native habitat for many hostas is in a sunny location at the edge of the woods. Some hostas that tolerate more sun are: Francee, Patriot, Sum and Substance, Gold Standard and Royal Standard.

Taking a moment to look at these myths with a bit of scepticism will hopefully lead gardeners, after some critical thinking, to come to the conclusion that not all gardening lore is valid.