"Ian Keeling" wrote in message
...
When my grandfather died aged 99 my parents salvaged one of his cacti. I
didn't want to see it go, as I'd known it all my life.

Now, it's rather large (I estimate about 4' in height), though probably
not as large as it ought to be given its age, considering the size of
the pot it's in, which I rather suspect is the original one...

Presumably it would benefit from repotting, but I wouldn't want to risk
damaging it in the process

....

Because cacti like other succulents store water in the plant body,
repotting isn't as much a priority as it is with other plants. In
addition cacti can absorb water faster than can other plants. So
that quite large plants can survive in quite small pots providing
they're in a well drained compost and are given a good regular
watering (maybe soaking from underneath) during the watering season -
say late March late September in the UK.

Authorities seem to differ as to whether stressing cacti by keeping them
in small pots promotes flowering.

You should be able to tell if the small pot is hampering the plant by the
extent of any new growth it makes in the spring after its first watering
and feeding. If bright green new growth appears at top centre of the plant-
the growing point - then it's still o.k. Possibly under optimum conditions
an experienced grower could double the size of the plant within the next
five years. You need to decide if that's what you want, or whether you're
happy to poodle along at a slower pace. As the plant will adapt to
the prevailing conditions more or less.


....

(I hope I can avoid serious injury to
myself). Any tips on procedure? Or should I just leave it be? (Not sure
of the species - I think it may be Cephalocereus senilis).

...

Cephalocereus senilis "the old man" cactus is covered in whispy hairs
and is incapable of hurting anyone.

For cactus with serious spines, the normal recommendation is to wrap the
body up in newspaper prior to handling. However IMO this can damage the
odd spine, and far better is to cut out pairs of "tongs" out of old bath
sponges or similar plastic foam. Although care is necessary when disengaging
the foam from the spines afterwards.

If the compost is at all dry, it should be possible to lift the plant and
rootball out of the pot as it stands. Otherwise, just upend it over a sheet
of newspaper cradling the top of the plant in the palm of your (foamed)
hand and lifting off the pot. The only problem with this approach is that
dry compost, sand and grit may falls over the plant, and get lodged in the
spines requiring a good brushing afterwards - hardly the end of the world.

The cacti to look out for are opuntia - the ones with the flat pads.
While most of these don't have prominent spines, they have small
pads (glochids) which are made up of tiny spines which can stick
in the skin, which you don't notice until afterwards when they start
to itch. They may require an eyeglass and tweezers to remove.

As with most plants, unless you're experienced and know what you're
looking for in terms of root diseases etc, it probably not advisable to
fiddle around with the roots. Just shake off any lose stuff and make
sure to bed the roots in well into the new pot. As the compost should
be fairly free running this shouldn't be too much of a problem.

....

And would
this be a good activity on 26th December (right time of year probably?)

....

Definitely not IMO. The best time for repotting is spring just before the
start of the growing season. Say March. If you're going to repot, use the
next size pot up, choose a pot with good drainage holes, fill the bottom
third of the pot with washed pea shingle - that's small round stones the
shape of peas, not broken shingle the "size" of peas as some suppliers seem
to think.

The compost you use needs to be free draining. Some people spend
fortunes on made up cactus compost, some people make their own secret
recipes using loam, or leafmould in combination with sand and grit. I myself
use around one half spent peat compost from almost anywhere, one quarter
sharp sand, and one quarter grit. Another maybe controversial addition is
adding a bit of charcoal.

During the growing season the plants are well soaked from underneath once
a month in a dilute liquid feed - just a standard powdered feed Phostrogen
or similar - low nitrogen plus trace elements.

For top dressing some aquarium suppliers in markets sell miniature
pea shingle for around £1.50 a bag. Preferable IMO to turquoise
crystals or whatever.

If you were seeking to grow prize specimens you might be repotting
annually, and inspecting the roots of plants, which were all being grown
under glass. Otherwise, most cacti respond well to any kindness they
receive.
Good drainage, a regular dilute liquid feed between March and September
and the best available light usually a south facing window both summer
and winter. The closer to the window the better. And kept dry and frost
free in the Winter.


michael adams