Three hor­ti­cul­tural myths ex­posed

Some sage old say­ings are based on facts – oth­ers are not worth the bother

The Myanmar Times - Weekend - - Weekend - BY JAMES WONG

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.

Photo: Felipe Trueba/epa

Ur­ban gar­den­ing in Ber­lin.

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