HAVE a decent sized cycad that is in the ground and has done really
well for the last few years. All of a sudden the outer leaves are
turning brown and dying off at an alarming rate. I can't see any
pests on it and other cycads close by are not affected. Any ideas?
your cycad is Cycas revoluta, the most common one available
at present, there are a couple of points to consider. Shortly after
producing a flush of new leaves (which usually appear all together
from the of the top of the trunk) the old leaves start to deteriorate,
generally turn yellow and die off. To keep the plant looking good,
you eventually need to cut these old leaves off and in good conditions
with a healthy cycad this can become an annual event.
However, if your plant
has not produced any new leaves for some time and the old ones are
dying off, it's a signal all is not well and the most likely problem
is root rot or rot in the base of the trunk which, with palms and
cycads, is often referred to as the caudex. A good way to check
if there may be a root problem is to gently put pressure on the
caudex and try to rock it very gently to and fro - if the root system
is healthy it will resist the pressure, but if it moves easily then
there is very possibly a problem with the roots.
If this seems likely,
the next step is to dig the whole thing out of the ground, clean
off the soil from around the roots to check out what is going on
down there. If there is any black, dead-looking tissue, try to clean
it away until you find healthy reddish or pinkish tissue in the
caudex. You may have to use a knife or saw to cut away the dead
material. At the same time, cut off any yellow or brown leaves close
to the trunk. If you still have a significant piece of healthy caudex
left you could wash it down with a fungicide solution such as Thiram
or dust the cut surfaces with Flowers of Sulphur in an attempt to
prevent further rot. The next step is to place it in a warm, dry
spot so the wounds you've made can start to heal. Leave it to dry
off for quite some time - they can be left for weeks and still survive.
Check the caudex every now and then to see if the rot has stopped.
After a while, if it looks reasonably stable, you can try planting
it in a pot of free-draining mix, or even plain pumice sand, in
the hope that it will send out new roots - just like a giant cutting.
This process will take
several months, but if you're lucky the plant will survive and eventually
Gardener, Issue 201, 2006, Page 31
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.