rot in potted plants
of my containerised shrubs and palms aren't doing well and I think
they might have root rot. What should I do?
rot in potted plants is generally caused by a fungus disease with
the formidable name of Phytophthora. The first sign a plant may
be infected is usually poor growth followed by leaf drop and dieback
of some shoots. Sometimes only part of a plant will die off while
the rest remains apparently healthy. With potted plants a sure sign
is wilting, even when the mix is moist.
The only way to tell
for sure is take the plant out of its pot and check the roots. Healthy
roots are usually firm and brown with whitish or yellow tips. Diseased
roots break away easily in your hand and are mushy or dark brown
Root rot in containerised
plants is almost always caused by the mix being too wet, either
from overwatering or lack of good drainage. Many plants can recover
from root rot, so unless yours are too far gone, don't despair.
Make sure the containers
have plenty of large drainage holes and when the pot is sitting
on the ground the holes aren't blocked - you may have to raise them
up a little so they drain freely. Saucers can contribute to this
problem. If you leave them full of water they can encourage root
rot, especially in winter.
Before repotting your
plants cut away all dead and dying roots - with luck there will
be some relatively healthy ones left. You could soak the roots in
a solution of Kiwicare No Root Rot, available from garden centres.
Repot using a good quality potting mix. Given the choice, I'd buy
one with the beneficial fungus Trichoderma in it which can provide
protection from soil-borne diseases, or you can buy the same fungus
as Trichopel, which you water into the mix to help prevent root
rot. Prune off any dead above-ground shoots. Then it's just a case
of careful watering, though if you've used a good mix and got the
drainage right, excess water should simply run right through with
no adverse effect.
Gardener, Issue 153, 2004, Page 26
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.