Three horticultural myths exposed
Some sage old sayings are based on facts – others are not worth the bother
Water works: no need to worry about ‘burning’ the leaves.
Sunday 23 July 2017 06.00 BST
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
Old school horts, look away now…
Not bothering with three conventional pieces of gardening ‘wisdom’ could save you time and effort
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
Can you dig it?
Don’t use sand if you have clay soil, just apply compost.
Have clay soil?
Then dig in loads of sand to open up the structure and improve drainage – so goes the old-
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.