DATE:   10/17/96
WRITER: Bob Polomski, (864) 656-2604

Getting to the Root of Cacti Problems

     Q.  My large Christmas cactus isn't doing well. Healthy
branches turn yellow and eventually brown and die. Meanwhile,
smaller, younger Christmas cacti in my collection look fine. What
can I do to correct this problem?  
     A.  Let's get to the root of the problem before making any
recommendations. Gently slip your cactus out of the pot and
examine its roots. If they are dark brown or black and their skin
slips off easily, suspect root rot. Overwatering or poor drainage
can cause this condition to occur. Trim off the diseased roots.
     If the plant is simply potbound, the container will be
filled with roots. Some may even be spiraling around the outside
of the rootball. Cut them with a sharp knife to prevent them from
girdling the plant. Also, make shallow cuts on opposite sides of
the rootball and along the bottom to free-up the congested roots.
     In either case, repot the cactus into a clean pot with
well-drained media, such as two parts of a standard potting mix
and one part each of peat moss and perlite or coarse, sharp sand.
If you had to root-prune, monitor the plant closely over the next
several weeks to help it produce new roots quickly and overcome
transplant shock. Water thoroughly, but do not fertilize for at
least a month. Thereafter, feed monthly with a balanced liquid
houseplant fertilizer from early spring through early fall.
     If after dislodging your cactus from the pot you find white,
healthy roots dotting the walls of the root ball, I would suspect
that the leaf-yellowing was caused by a lack of fertility. If
your cactus was growing in the same pot for several years without
being fertilized or receiving an annual topdressing of compost or
fresh media, the soil could have been exhausted of nutrients.
Repotting the cactus and following the fertilization program as
described above should improve the health and appearance of your
plant.
     Mist the plant often during its active growth period and
water it regularly to keep the mix moist, but not soggy. Avoid
the temptation to irrigate your entire collection at each
watering. I expect that the smaller cacti growing in smaller pots
would require more frequent watering, and, hence, have benefitted
from the attention; however, the larger cacti, like the one in
question, would prefer to be watered less often and only when the
soil indicates a need.
     In the fall when shoot growth slows down, allow the soil
surface to dry between waterings to reduce the chances for root
rot to occur.
     When your cactus stops flowering, allow the top half-inch of
soil to dry out before watering. Resume regular watering and
fertilizing when new stem growth begins in the spring.
     For best growth, your cactus should receive bright, but not
direct, sunlight. A location within three feet of a large window
facing south, east or west would be ideal.
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     If you have gardening questions or comments, write to 
Agricultural News & Publications, A-101 Poole Agricultural
Center, Box 340311, Clemson University, Clemson, S.C. 29634-0311.
                               END