Question
I've had a cactus for 20 yrs now. I do not know the name/species.  It is now 6 feet high.  There are 3 main "trunks" and each has about 10 off-shoots from top to bottom and each of those off-shoots has more off-shoots, etc., etc.  It is EXTREMELY prickly - very short (about 1/4" long spikes) on each shoot.  When we've move houses twice, no one ever wants to be the one that has to move this sucker.  

Question: Obviously after 20 years I have never been able to clean it.  (Each arm / off-shoot is three sided) and the growth is fairly dense.  Traditional dusting doesn't work 'cause any sort of dusting cloth (or whatever) catches in the "needles".

I've thought of hosing it down but getting it from the livingroom to the backyard is basically impossible.  Also, even if I were to get it out and put a plastic bag around the base of the cactus, I would be afraid that enough water would get through the "cracks" of the plastic bag and into the soil and kill it with too much water.

Any ideas?  On one hand it still looks great, but on the other it really does need a clean.

Answer
Gabi,

I am sorry for the delay in answering you, have had some computer issues that are now resolved. You have a Euphorbia trigona (possibly, based on your description). What you can do, is let your plant dry out completely (might take close to a month in your area), then hose down down outside. You may end up with white spots however, so you may want to use distilled water rather than water right out of the hose. Waiting until it is completely dry with ensure you won't over water it. Hope this helps.

Sincerely,

Greg