Anyone know much about cacti?

[Fishkeeper]

I got a greenhouse for Christmas, which I'm very excited about, but I don't think I can keep it healthy if I stock it with orchids. I have low blood pressure that causes frequent low-energy days, plus this needs to be low-
maintenance for when I eventually go off to college. To that end, I'm stocking it with cacti instead, plus a 110 gallon fish pond (stock tank) to help keep the temperature stable and let me grow some water plants.

Anyone know if there are barrel cacti that stay small, 1 foot across or smaller? I'm building wooden planters about a foot deep, with hardware mesh bottoms for drainage, elevated for easy reach. The greenhouse gets dappled sunlight most of the day, it's under trees to keep it from overheating in summer, so it should work for most cacti. Everything will be watered about once a week, and I can avoid watering things that need a winter rest for the winter.

And is there such a thing as a desert orchid? As in, something that I could happily grow alongside cacti? I'll also take suggestions for desert daisies and similar.

[Bulbopedilum]

Astrophytums are cute, small, round, spineless cacti, although spiny variants are available and I don't know how much maintenance they need. My guess is that the maintenance is just "sun and water".

Try Eulophia Petersii, I've heard it as the "desert orchid" or "succulent orchid".

What about tillandsias? Spray once a week and that's enough and you can grow them practically anywhere.

[estación seca]

It's going to depend on how much light you can provide. All cacti will survive in too-low light, but they won't look good. The classic barrel cacti are in genus Ferocactus. Most require very high light all year. F. glaucescens grows in dappled shade in oak forests, so it might be a good choice. F. virescens is a small barrel and one of only 2 non-Opuntia cacti endemic to a winter-rainfall area (though it does fine with summer water.) Ferocacti are susceptible to rot in acid soil. If you use a high-organic potting mix like typical "cactus mix", you must repot every 2 years.

A lot of S American cacti were lumped into Echinopsis, but hobbyists still call them by the old names. They all tolerate a little frost, some much more. Many Lobivias have largish solitary stems and have spectacular flowers. Soherensia bruchii grows as large as Ferocactus but is a high-elevation, cooler growing plant that does well in temperate greenhouses. Oroyas are also higher-elevation, solitary globular cacti with great flowers. Neochilenia nidus is another with great flowers. Globular Echinopsis have been hybridized to achieve amazing flowers in a huge range of colors.

[Paul]

As Bulbo mentioned Eulophia petersii (linked to an information page for you) is a desert orchid. Don't know how easy it is to find.

Typical store bought "cactus soil" is garbage in most respects, being far too peaty and thus water retentive. If you did decide to use store bought potting soil, plan on cutting it at least 50/50 if not more with perlite (preferably large or medium grade). A gritty mix would be a better choice.

By and large, most cacti, as Estacion said, require high light year round. Depending upon how brutal your midday sun is, some species may need shaded during that time.

Before going all out plant-wise, get a digital thermometer and find out just how hot and cold that greenhouse will get. Keep in mind, summer results will be markedly different than your winter readings. With this in mind, plan on provided LOTS of ventilation and air movement for when temps get too high. Even with dappled shade, in your neck of the woods, you may need to invest in some shade cloth for the summer months.

In addition to cacti, you might want to check out succulents like Echeveria and Euphorbia. But again, do your research to determine how much light they require.

[Fishkeeper]

I got soil sold for container gardens, and I'm going to mix plenty of sand and some pebbles into it. The mesh bottoms of the containers should help with drainage, as well.

That's a pretty neat orchid, thanks. I'll have to see if I can find one.

Anyone have any suggestions for container pond candidates, either submerged or emersed plants?

I have a high/low digital thermometer in there. It shows the highest temp in its memory, the lowest temp, and the current temp. Pretty neat, but I'm not paying much attention to the readings yet, I'm in the middle of insulating it with bubble wrap so everything inside doesn't freeze.

I'm definitely going for succulents. I have an echeveria that's been doing well in similar light, so it's going in, and I'm going to find some other echeveria. I also have some aloes, a pencil cactus, and some mixed succulents that I've been growing as houseplants but plan to move outside. I'm also going to get some succulents like people plant in hanging baskets, string of pearls and the like, and line the edges of the containers.

After some thought, I'm probably going to include a container garden with carnivorous plants, mostly sarracenia pitcher plants. That'll depend on if I can rig a successful rainwater catching system. I plan to set up a Christmas tree box (long, narrow plastic box) on a stand, just below the eve of the roof, to catch runoff. That'll run for awhile to see what I can get, then, if I get enough water for it to be successful, I'll put a bog garden under the outlet with drainage tubes leading into storage buckets so it can't flood. I have to test it, but I think it'll work, and it'll look really cool.

[Paul]

Originally Posted by Fishkeeper

I got soil sold for container gardens, and I'm going to mix plenty of sand and some pebbles into it. The mesh bottoms of the containers should help with drainage, as well.

Nix the sand. Often too small and so winds up resulting in compaction over time. Better would be to get some chick grit from a local feed store. Fine pine bark can also be added as an organic component. In an ideal media, the various particulate would all be roughly the same size.

Depends on the size of the mesh making up the bottom of the containers. It can indeed help but keep in mind that really fine particles (and organic components all break down to fine particles at some point) can clog up the holes in the mesh if those holes are small.

[Fishkeeper]

I'll scratch the sand and go with a grit of some sort, just use a quarter-inch of sand or so as a topdressing for appearances.

The mesh is 1/8", and I'll cover it over with a layer of pebbles to keep the dirt in. Shouldn't clog up enough to be anywhere near waterproof. Even if it does try to clog, the planters will be a foot deep, so water pooling at the bottom for a little while as it drains won't be an issue.

[estación seca]

A lot of people go to a livestock feed store and get chicken or turkey grit.

[LexyBoy]

The larger Echinopsis (including Lobivia and Soehrensia) make nice plants, as do Echinocereus, though most of these are a bit small to qualify as 'barrel cacti'. All have great shows of flowers and won't need any winter heating (except some Mexican Echinocereus perhaps, not sure how cold you would get).

But, and I say this without really knowing your climate, I think they'd do better outside with perhaps winter rain shelter. They'll do better with the brighter light and cooler nights.

[estación seca]

Central Texas is probably too cold to grow Ferocactus outdoors in the ground. They could be summered outdoors and brought in for the winter, maintained dry all winter. They do fine with warm, wet summers so long as the potting mix is maintained alkaline. This means no organic matter in the soil. Ferocactus are highly susceptible to fungus in acid soil mixes, which I think partly accounts for their reputation as difficult in cultivation.

Golden barrel (Echinocereus grusonii) would likewise do great outside for the summer, then brought in for the coldest weather. So long as days get above freezing it easily handles temperatures into the upper teens F / -8C. It isn't too picky about being cold and wet, and it does really well in hot and wet.

The Soherensia and probably most Echinopsis should tolerate the winters outdoors if well-drained. It doesn't rain much in the winter in central Texas. For some reason people in the US who could grow Soherensia outdoors just don't. It is hard to find here.

In habitat Soherensia gets enormous. It is a slow growing plant, however.