Hai Nexians,
I've got a Trichocereus Pachanoi cactus growing in a small room
with a window facing the South. It's grown fairly tall and is in need of
being re-potted in a deeper soil.

Now allthough the winters are too cold & harsh for my San Pedro, the summers
here aren't bad and I want to put my San Pedro on the balcony in the summer
to maximalise the amount of sunlight it gets. The main problem with this climate,
also in summer, is that the air is way too moist and it rains far too often.


This is why I've been planning to build a small Cactus greenhouse. In this
greenhouse the air must be fairly dry. Air should be refreshed regulairly,
and fresh air ought to be filtered to eliminate fungal spores &
other pests, before being pumped into the greenhouse.


Just an idea:
I've had the simple plan of closing off the bottom of a discarded car-tire,
poking some drainage-holes into that bottom and then building a cylindrical
"tower" of transparent, airtight plastic on top of that tire.
The tire would be filled up with layers of Gravel, Pebbles and Sand with
some soil/sand/gravel mixture ontop. The Cactus is then placed into the
soil and the top of the transparent cylinder can then be closed off with a lid.

A little airpump-system could be fixed into that lid, sucking up fresh air,
dehumidifying & decontaminating it* & blowing it into the greenhouse & blowing
out the old, stale air by displacement/pressure difference. Hooked up to a
timer socket this system could refresh the air every couple of hours.

*This Decontamimation could be done by bubbling fresh air up, through a
reservoir of diluted Hydrogen Peroxide for instance. Dehumidifying can
be done low tech by blowing the decontaminated fresh air through a pipe
stuffed with sponge-material.


This idea is simple as pie and is a great way to let your San Pedro, Peyote
or other magical cacti enjoy as much sunlight as possible without over-
exposure to moist, fungal spores & other threats.

When the winter strikes again I'll have to bring this greenhouse indoors again,
because temperatures may suddenly drop significantly below zero degrees Celcius.
Last winter we had temperatures of -18 degrees Celcius; Sure to mash up your
precious cacti overnight.

But this is off course a simple plan. I'd love to hear more creative ways to
build cacti-greenhouses. If I were to compose the transparant cylinder out of
3 cylinders, each a bit bigger diameter than the last, placed inside eachother,
would that isolate enough to keep temperatures inside survivable when outside
the greenhouse it is, let's say, -20 degrees Celcius?

Any knowledge & information that can help improve the efficiency of this greenhouse is welcome.

I also live in a quite moist climate. I live in NW Washington. I've always just put mine outside in the summer. Never seen any issues aside from sunburn if I don't transition them properly. I do know some people who like to apply a fungicidal dust whenever cutting them to avoid rot from getting into the cut. The person I knew who did this used the "Rootone" powder. Not only is it a rooting compound, but it has a fungicide in it as well.

Mine that I cut recently, I've just been making sure plenty of sun hits the cuts, and to keep them under cover until the cuts are well calloused. Seems to be working out so far.

there is no need for a dry climate grow house for your cacti.

i grow cacti down here in florida and trust me its plenty humid here and rains pretty much every day durring summer. you just have to plan accordingly. pot your girls up in the most well draining thing you can think of. I use cacti soil, perlite, and coarse sand as my mix. i go really heavy on the perlite and sand too.

if you get the proper drainage daily rain wont hurt your cacti. as a trade off the faster drying/more airy growing medium has to be watered more often durring non rain months to maintain max growth.

youre wanting to spend too much money when you could just change their growing medium and keep them outside until you get near your first freeze, if it freezes there. if youre up north stop watering around the end of october, and bring inside in november for the winter.

as my buddy ringworm would say, "these are not desert cacti, give them water and theyll flourish."

youre just gonna have to do a little hit and miss experiments.

goodluck.

also good:
I know a horticulturist who adds steer manure mixed into the blend. Really boosts growth. Personally I prefer to use (more expensive but more nutritious) worm castings. And a little agricultural lime keeps pH in the happy-cactus region, as well as providing essential minerals.

Thanks folks.

@ Dan; I assume the cacti you're growing outdoors are San Pedros? I know they naturally
grow on the slopes of the Andes, where it rains often. However Peyote IS a desert cactus.
Growing Peyote outdoors in humid, rainy climates might not work so well, right?
Well good to know my San Pedro is safe outdoors in the summer with well draining soil.

@ Pau; I have easy access to plentyfull horse manure. Would that work well too?
And worm castings need not cost a thing. Just dig up some worms, build a big,
wooden box, fill up with soil and put the worms in there. Cover with lid to
provide shade and wait. Will have to try that soil too on my cacti.

@ Nicechrisman; That's good to know too; the fungicide-trick, as I plan to harvest
only the middle-section of my San Pedro, so the bottom and top stumps can regrow
into 2 separate cacti again. I'd probably do good visiting my local gardening store
for some fungicides & rooting mediums.


For now I'll just repot my San Pedro in deep, well-draining soil so it can enjoy
the outdoors during the summer.

What about Peyote cacti though? Could I do them the same favor? Or is it safer to keep
Peyotes well protected from excessive humidity and rain?