CactiGuide.com

Hi everyone,
I've got a south-southeast facing balcony that's screaming for some cacti to make it their home, but I could use some advice on how to grow them outdoors in containers. I'm in hardy zone 8b, and my balcony is extremely sunny and hot during the summer (nearly all my balcony plants that are appropriate for my hardiness zone died this summer. The only survivors were the tropical plants and the Opuntia Ficus-indica - on sunny days, it gets easily 10C hotter on my balcony compared to "normal" outside temperatures). It also gets next to no rain thanks to the overhanging balcony of my upstairs neighbor. So I was thinking about no water in winter, and watering them myself during the growing season. The only thing I'm worried about is the humidity in the air, which is pretty high around here.

Is there anything I need to be aware of when growing them in containers? Most information I find about growing cacti outside is on growing them in gardens not containers.

And how do I go about picking the right species for these conditions? Because it's not just cold and humid air in winter, but also summer heat and full days of direct sun that they'll have to take in.

I think you should install some shading screens to reduce sunlight intensity and heat during summer time. What kind of containers you use for cacti? Witch of them died last summer? It's a good idea to put small pots into wooden boxes to reduce heating of soil, roots and plants. Cacti with dense spines and wool are are more resistant to strong direct sun. Watering has to be controlled by the grower as well and maybe more frequent during summer months. If you have where to store some of the plants that will not stand winter cold growing of species like Ferocactus, Parodia, Mammillaria and many others would be possible. Many Echinocereus species could be grown just full-time on that balcony.

Building of a cacti collection takes some time. We try different species, lose some and replace them by others until things level up and got set up.

Thanks for the advice, George! I hadn't thought about the heat stress caused by warming pots. That might go a long way to explain why some of my non-cacti plants didn't make it... The only cactus I had on my balcony was the Opuntia and it's planted in a larger clay pot. The things that died weren't cacti, but other plants like sunflowers and hollyhocks (which do well on sunny spots around the neighborhood, but my balcony might be in a different category).

Because the opuntia was one of the two plants that didn't just survive but actually thrived in the summer months (it made some new pads, looks generally healthy), I'm looking to expand my outdoors cacti collection I'll probably take up your suggestion of starting with a plant stand that I can move indoors during the wintermonths and where I can put up a small shading screen. Unfortunately, I can't attach any larger shading screens over my balcony.

Well, maybe for different cacti species on your balcony just initial temporary shading (in spring, hot summer days or after bringing a plant from a store or nursery where it has been grown in different conditions) will be enough. For winter hardiness also is important to stop watering a month or two before real cold weather comes and exclude rain and snow influence despite of overhead balcony sheltering.

See also about possible species in these topics:
viewtopic.php?f=20&t=33059
viewtopic.php?f=20&t=16398

Winds might be a problem, as winds carry small droplets of rain.
The cactuses must be absolutely dry in the winter.

My cactuses live on my balcony every day that have temperaturen above freezing, but I had to take them indors the other day when hard winds brought small drops of water into my otherwise dry balcony.

My outdoor plants get whatever rain and snow comes along. Albeit it is desert, they do get a handful of heavy waterings.

I would select plants hardy to your winter, and if needed protect them in the summer. Easier to provide shade than heat. With the humidity I’d opt for free draining soil(I use it anyway with very arid conditions) and give plenty of time to dry between waterings.