Three horticultural myths exposed
Some sage old sayings are based on facts – others are not worth the bother
WHILE many age-old gardening practices are now supported by scientific evidence, some of the most common ones have consistently been shown to be either unnecessary or downright counterproductive when put to the test. So simply not bothering with the following three conventional pieces of gardening “wisdom” could save you time and effort, and will almost certainly give you the same or even better results. Old school horts, look away now…
Crocks in pots While still a mainstay of the TV gardening show, the idea that putting a thick layer of broken terracotta pots over the drainage hole of a container will improve drainage was disproven over 100 years ago. As liquids move more slowly between different layers of substrates than a single substrate, this advice can in fact cause the pots to be slower to drain. This practice is usually advised for use in terracotta pots, as plastic and resin alternatives contain multiple drainage holes. Yet being porous, terracotta pots tend to be the least likely to suffer waterlogging: they are prone to drying out too fast. The only benefit of crocks in pots may be to stop potting mix from falling out of the drainage holes and making a mess when newly transplanted. If so, a piece of card, mesh or one shard of broken pot would be a better option. Watering on sunny days Traditionally we are told to avoid watering on hot, sunny days at all costs, as water droplets can apparently create tiny lenses to focus the sun’s rays and burn the leaves of plants. People who dutifully follow this horticultural gospel may avoid watering extremely thirsty, wilted plants in scorching weather due to fear of burning them. However, in reality water droplets evaporate off far too fast for this “lens effect” to ever actually happen. The benefits of giving severely dehydrated plants water when they need it most will outweigh any potential risk. The only caveat here is that precisely because water evaporates off quickly on hot, sunny days, watering in the cool of the evening or morning is generally more efficient.
Sand improves drainage Have clay soil? Then dig in loads of sand to open up the structure and improve drainage – so goes the oldschool advice. But studies actually show that you would have to add more than 50% sand to clay soil to achieve this. That’s an enormous cost financially, environmentally and, frankly, to your back and elbows. Swap sand for organic matter such as compost instead and you’ll only need 5-10% to get ideal soil consistency, plus the benefits of added nutrients and micro-organisms and for way less cost and effort.
Urban gardening in Berlin.