I have an old Crassula ovata (C. argentea; Jade plant; Money plant),
which has sentimental value. It has lived for many years in a just
frost-free greenhouse in a 45cm pot, growing quite well. It's 150 cm
high, and hasn't been replanted in umpteen years.

One evening I decided to move it to a new conservatory, and at the same
time repot it in a 50cm square pot, topping up with decent 1:1
compost:sharp sand.

The next morning there were ants coming out the pot and exploring the
conservatory for new nest sites. SWMBO was not amused. We lifted the
heavy pot out onto the patio, and first dealt with the ants inside the
conservatory. I then puffed ant powder (bendiocarb) all over the
surface of the compost in the Crassula pot, and into the pot saucer, so
there was no escape. Two days later I soaked the compost with a hose.
After a couple of days in the hot sun, the ants reappeared crawling up
the plant! This time I used a pyrethrin-based ant powder. A couple of
days later, some ants again reappeared on the main trunk.

I got the plant out of the pot, and turned a hose on the rootball to get
off as much soil as possible. Then I got a container large enough to
hold the rootball, and put the plant in it. I added a detergent, and
filled the container with water until the rootball was almost completely
immersed. I then added a few litres of thiacloprid solution over the
rootball, until it was fully immersed. After 24 hours, I removed the
plant and let it drain. I left it in a large pot in a dry place. Two
days later, the ants reappeared!

No wonder they are such survivors - I have a sneaking admiration for
their persistence! I've given up on putting the plant in the
conservatory - it will go back to the greenhouse. I'll root a cutting,
and grow that on - in ant-free compost!

--

Jeff