5
Weather
We all get a little haggard in a long winter; it’s no
coincidence that you’re more likely to fall sick in
chilly, damp conditions when you’re uncomfortable
and run down.
It’s much the same for plants, especially in these days
of increasingly dramatic changes in our climate. Extreme
weather conditions can happen any time of year and they’re
really tough for growing plants. Heavy rain can flood the soil,
drowning roots and washing out nitrogen completely. Long,
hot, dry spells lock up nutrients so roots can’t get at them. And
frosty days freeze and damage vulnerable plant cells.
All these conditions cause leaves to turn yellow, so some-
times when you’re faced with a sickly-looking plant, it’s a good
idea to look up at the sky.
Other symptoms to look out for:
• Standing water: Poorly drained soils waterlog easily,
filling soil air pockets with water and drowning roots.
Digging in organic matter helps open up heavy soils,
or you can install drainage pipes.
• Scorched leaves: Yellowing leaves with brown, scorched
tips in summer often mean your plant is gasping for
water. Water new plants particularly well in the year
after planting as they haven’t yet sent roots into the soil.
• Frost: Yellowing leaves in winter could be cold-induced
chlorosis, caused by soil microbes slowing down in cold
weather so they don’t deliver nutrients to plants. They
usually recover but covering plants with horticultural
fleece and cloches keeps them warmer longer.
6
Weedkiller
Sometimes, we are our plants’ own worst enemies.
A slip of a spray gun, the wind blowing in the wrong
direction, and a splash of herbicide lands in the
wrong place. Result: yellow leaves. Protecting nearby plants
with sheets of cardboard helps, but it’s better for them and the
environment not to spray at all.
Herbicide damage can happen indirectly. Aminopyralid is
a herbicide commonly used on grazing pasture and can end
up contaminating manure, causing serious damage when
used, unwittingly, by gardeners. Source manure carefully; if
you can’t be sure, a test sowing of susceptible plants like fava
beans will tell you if your batch of compost is clean or not.
Other symptoms to look out for:
• Stunted growth: Stalled growth and yellowing leaves are
classic signs of general broadleaf herbicide damage.
Prune off affected leaves as quickly as possible, and water
thoroughly to dilute chemicals.
• Curled leaves: When seedlings emerge with distorted,
fernlike leaves that curl in on themselves, it’s likely you’ve
been using manure contaminated with aminopyralid. Ditch
affected plants, as they won’t survive. The chemical breaks
down in soil, so after a year compost should be safe to use.
• Brown patches: When leaves yellow in patches which die
back leaving the rest of the leaf healthy, your plants may have
been exposed to a contact herbicide such as diquat, which
kills only where it touches. It’s sometimes used by farmers to
clear fields prior to sowing. Rinse thoroughly with water and
if the plant is only lightly damaged it should recover.
Maximum Yield
47