Pouring cold water on some gardening myths

What is the cause of scorching on leaves? Photo: PA Photo/thinkstockphotos
What is the cause of scorching on leaves? Photo: PA Photo/thinkstockphotos

If you think ivy kills trees, watering scorches leaves and digging is always needed to control weeds, think again.

The Royal Horticultural Society is putting the record straight on a number of old wives’ tales which have worked their way into the gardening psyche.

Here, Guy Barter, RHS chief horticultural adviser, busts open some of the most famous myths.

Myth - Ivy kills trees

Guy says: “ Ivy is thought to seldom kill trees of itself, but the presence of ivy indicates the very strong suspicion of root disease especially honey fungus doing serious harm to the host and allowing the ivy to flourish under the diminished canopy.”

Myth - W ild flowers are easy.

Guy says: “Gardens are often just too rich and fertile for wild flowers so that the desirable flowers fade away and rampant grasses take over. Mixes of annual flowers that resemble wild flowers on the other hand are easy and highly beneficial to many insects and a wiser choice for fertile gardens

Myth - Water drops on leaves cause burning from the sun’s rays.

Guy says: “To focus sunlight, a water droplet needs to be above the leaf, and this can very occasionally happen with hairy-leaved plants (French beans for example) but in almost all cases scorching is not caused by wet leaves. Spraying leaves with pesticides or liquid fertiliser in sunny conditions can cause harm, however, as the water evaporates and the chemicals become concentrated, so can harm foliage.”

Myth - Ground cover plants save work.

Guy says: “Depending on the type of plant you use, ground cover plants can soon become so thick that laborious pruning and thinning is required. Sooner or later perennial weeds set up camp in ground cover and have to be winkled-out by hand as weedkillers and hoes cannot be used. Around trees and shrubs ground cover acts as a particularly pernicious ‘weed’ unless carefully controlled.”

Myth - Digging is required to control weeds.

Guy says: “The main reason for digging weeds is control, as burial of weeds is highly effective. But if weeds are controlled by other means such as mulches, herbicides or shallow hoeing, digging can be dispensed with. The only fly in this ointment is that sometimes weed control by other means can take longer and be harder work than digging, so it is not necessarily true for every site.”

Myth - Raised beds are best for growing crops.

Guy says: “R aised beds are a great idea for ill-drained clay soils in wet regions where they enhance drainage and make avoidance of compacting wet soil by trampling easier. But on other soils they enhance drainage to the point of drought (greatly increasing drought susceptibility) and impede flexibility in cropping as sprawling plants are hard to include in a strict defined bed. Therefore gardeners may do a lot of hard work at considerable expense for fewer crops.”

Myth - Moss is always a nuisance in gardens.

Guy says: “Moss is a sign that the soil is moist for prolonged periods. This happens when the soil is compacted, acidic or shaded. Moss has no roots and therefore cannot compete significantly with plant roots. In beds and borders it is a useful cover suppressing weed germination and limiting water loss. In lawns moss can indicate areas where perhaps grass should not be grown, under shade for example, where alternative plantings might be required. As moss cannot withstand treading, the presence of moss in lawns can indicate a lack of traffic and suggest that as access is not required then alternatives to lawns can be sought.”

Myth - Plants like being spoken to.

Guy says: “With neither ears nor language it seems improbable that the spoken word has much effect on plants, although it may be therapeutic to the chatting gardeners themselves!”