Fantastic thread! I love seeing all the tips and pictures.
Beth, I'm constantly blown away at what you manage with just rainwater collection (am I remembering this right?). It's so impressive either way, because you clearly are working with the land in a very sustainable manner.
My husband and I have irrigation from both our laundry greywater and a well. Plus roof and driveway runoff to our garden. For some reason, this monsoon season has been decent here in our section of the SE Arizona high desert. Last year was a "non-soon" which was pretty miserable, but this year there was enough rainfall for the toads to spawn and multiply.
Our desert gardening conditions - our garden is on the east side of the house. My husband made us a bunch of sunken beds and he lined the paths with rocks. We've found rocks to be really useful in gardening, as they trap water underneath. The sunken beds seemed to do double duty - besides trapping water, in the early spring they trapped heat like a little nest on the ground. This allowed a bunch of frost-sensitive plants to survive late freezes. I was very surprised by this, as my guess would have been that the sunken beds could make frost pockets. They did the opposite, as proven by the butternut squashes that came up extremely early from compost buried in the beds. The squash plants that were about 3-4 inches tall, but were totally below the level of the ground around them survived late freezes. The ones that poked up above the main ground level got frozen! This was an awesome accidental experiment.
We also have a couple wicking beds. And also, we have no fencing up and the garden has been frequented by jackrabbits. Greywater comes from washing clothes. Rainwater off half the house floods the garden. I also water by hand.
So with these conditions in mind: a high desert location with late freezes, 100+ temps through much of this summer; some monsoons coming through, but supplemental water; sunken beds or wicking beds; very sandy clay soil - here are the perennials that are doing well so far for us:
Sylvetta/Perennial Arugula - I second Beth's promotion of this plant. It's incredible! This is the first time I've grown it. My husband loves it (though it's a tad spicy for me). It was slow to sprout and I thought I'd killed it all. But then tiny little plant-lings came up, and they were so resilient. Some of the toughest seedlings I've ever observed. It produced a lot of tasty leaves in the spring and then bloomed. As summer approached, it sort of died back and I stopped watering it entirely because I thought it wasn't going to make it. Instead, it seemed to go dormant for a month then popped back to life after the first small monsoon! It quadrupled in size at that point and pumped out a ton more leaves. I call it "Cousin It" now. Jackrabbits don't seem to like it.
Sunroot/Sunchoke - Also seconding Beth's mention of this plant. (I also count this as a perennial vegetable since it's really hard to get rid of once you plant it. That meets the definition for my purposes.) Ours is going gangbusters. It does really really like the deep soaks from that greywater, though. It just started blooming. It's about 7 feet tall and 5 feet wide, and that row was created by 5 "crowns" we bought from Azurestandard.com's grocery section, so I don't know the variety. The jackrabbits trimmed the bottom branches in the early summer, but it didn't slow the plant down. Instead I noticed it made it easier to see if a rattlesnake is hanging out underneath, so that was nice. Obviously we haven't harvested it yet, but I've dug at the base a little to see what was going on, and the plants are sending tubers out much further than I thought they would. There will likely be some under the pathways, I think. Also, this plant attracted a ton of beneficial insects early in the spring - lacewings and all sorts of wasps combed it's leaves. Very interesting to watch, as there were very few pests on it. Just one wooly aphid-type insect.
Green Onions - These little store-bought freebies have done really well. Those in the pictures below are just the free starts from the ends of green onions I bought in store to eat. They haven't divided yet and I've seen someone else talk about that. This is different than my results in Oregon, where a few of the little onion ends created a seemingly endlessly multiplying patch of green onions in every type of weather. These have proven quite drought and rabbit resistant. Though they haven't multiplied, they really flush out a lot of leaves. We eat them almost everyday. In Oregon, you could brush snow off these and eat them all winter. I am looking forward to seeing if they are that hardy in the desert.
Shallots - not a perennial, but self-propagating so I'll include it for honorary mention. Shallots did very well for us this year, while our garlic and leeks bolted and died. Interestingly, jackrabbits ate the top half of the leaves. Shallots provided our first green onions of this year, before our standard green onion patch went full tilt. I like shallot greens a bit better than green onions, as they are sweeter. I was very impressed with how heat tolerant these were.
Chufa/Tigernut/Earth Almond/Yellow Nutsedge/Nutgrass -
This is my first time growing these in a desert location, but since they are grown commercially in Spain it seemed worth a try. I have them where they get flooded by the laundry greywater, like the sunroots. I put them in raised rows like I read about in this guide to growing chufa: Detailed guide on how to grow Chufa (Cyperus Esculentus)
I'm growing this batch to expand my planting stock, as we are going to be in a new location next year. I sourced them organic by buying the Tigernut brand that is sold in many natural food stores. Though my main use for them is to grow them in a large greywater bed that I want to use for growing our own chicken feed, we also like chufa tubers made into the raw beverage Horchata de Chufa which is basically chufa "milk". There are lots of recipes, but the basic premise is like a nut milk - soak the tubers, blend, strain. People sweeten it, but we find it's sweet enough for us as it is! It's quite tasty and refreshing.
Prickly Pear - Just adding another supporting vote for that one! The fruit is divine. The variety that grows wild near us tastes just like loganberries. There are tons of varieties in cultivation and the fruit tastes wildly different. Some have almost no acidity, whereas others are quite tart. Some like this wild variety on the east side of the Chiricahuas tastes like raspberries mixed with blackberries, mixed with a little banana, whereas others have a totally different flavor.
We've picked about 10 pounds to freeze and processed at least as many into juice. We've found we don't need to remove all of the spines as long as we run them through our macerating juicer. The pulp that comes out of the juicer is spiny as can be, though. You end up with a ton of seeds that you can replant in the wild. The other neat thing I read about lately is that the fruit is high in magnesium and a little less so in potassium - making it a great electrolyte drink! It's also very high in mucilage, like the leaves. So it's a natural cure for the misery that comes with the heat and dryness of the midsummer desert weather. :-)
Here are two more possibilities for the desert, but they can't tolerate freeze and thus would need to be brought in for the winter and they would likely need greywater or supplemental water to thrive:
Lemongrass - These are in our wicking bed, as I read they need constant moisture to grow well. I started these from some bought at an Asian market. I can't believe how well they are doing - WAY better than the lemongrass I grew in Oregon. Apparently, lemongrass likes a lot more sun than it got in my Oregon yard. When I move them next, I'll put them in more sun. I don't think they needed the passionvine over the top for shade, though the galangal behind them might still. The location in the picture is on a north and east wall, and I'm going to attempt to overwinter some in that wicking bed. Another discovery, fresh lemongrass straight from your garden is so tender! The main stem is tender and totally edible, unlike the stuff I would buy in stores. The leaves are prolific and make awesome tea. I'm also saving leaves for trying some basketry later this year. Eight plants turns out to be way more than we can eat, but we're enjoying the tea and the other potential uses.
Galangal root - This is a big experiment. It's in the shade, hidden behind the lemongrass in the wicking bed. The house is cement block, and so the temperatures are very stable in that little corner. There is also ginger in there, but the galangal root is doing better. I believe this is lesser galangal. I bought it off Etsy from a person in Florida. It had a slow start and hated the direct sun and wind of the late spring when the lemongrass was still small. The leaves burned in the sun and wind. But when the lemongrass took off, so did the galangal. I'm not sure everyone would consider this a "vegetable", since it's very strong flavored and it more of a spice, but it's wonderful thing to have on hand if you like Thai food. These plants will likely have to come indoors for the winter. I'm not sure I want to risk any of them outside in our zone 8a..but I might experiment with one. The growing season for ginger and galangal root is VERY long, and I probably won't have a harvest until next summer, if what I read is correct. 9-12 months growing in the ground... Makes you appreciate buying it, right? It's the sort of thing that's worth it if you love Thai food and want it organic. And if you are in the low desert that rarely freezes, I imagine you wouldn't have to bring them in if you had them in a nice microclimate.
Thanks for starting this excellent list!