Let's breed a heat tolerant mashua!

General Discussions
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So, I have tried mashua three times here in Provo, Utah, and I’ve discovered that the leaves are delicious . . . and the plants cannot handle my very hot summers. Even well watered and kept in full shade, they just keel over and die once the temperatures are well above 90 degrees (which they are for about four months straight).

Meanwhile, common garden nasturtiums, which are in the same genus, are supposed to be quite heat tolerant and do fine here. Unfortunately, the leaves are incredibly peppery, whereas mashua leaves seem to be sweet and pleasant and not at all spicy. I want to eat mashua leaves!

So.

Let’s throw around some ideas to breed a heat tolerant mashua! :smiley:

Here’s what I want:

Priority #1: Something in the Tropaeolum genus that will produce lots of tasty sweet leaves and doesn’t mind hot temperatures.

Priority #2: Ability to make fertile seeds. I am willing to consider this the second priority because if something like this already exists can be cloned, I’d be willing to settle for that. :wink:

Priority #3: Tasty edible roots.

Priority #4: Productive at making tasty edible roots. (I’d rather have more than a tiny taste of sustenance every once in a blue moon. :wink:)

Priority #5: More cold tolerance would be nice. In fact, something that can’t handle my summers at all, but is willing to grow through my zone 7b winters and produce food during that half of the year, would be an acceptable Plan B.

Here are my thoughts so far about how to get there.

Cultivariable lists some close relatives that make tuberous roots. Does anyone know if any of those species are more heat-tolerant? (Or cold tolerant, for that matter?)

Pacific Bulb Society has some interesting descriptions of species in the genus. Since that website specializes in describing flowering bulbs, I suspect any species they list here would have reasonably-sized roots, and fertility may also be high because they’ve been selected for flowering.

Does anyone know more about any of those species than I can find on those two pages?

Does anyone know of any leads on where I might find seeds or plants of those species?

I’m also wondering about approaching the question from the other direction. Are there are any really heat-tolerant nasturtium species that produce tubers, or even thickened stolons? If so, perhaps it would be possible to start from there and select for thicker and less fibrous roots. It’s possible that might be an easier way to approach the question.

It looks like Tropaeolum majus and Tropaeolum peregrinum aren’t known to produce thickened stolons or tubers, but Tropaeolum majus does have a taproot. Perhaps that’s something to work with?

If you have ever grown a Tropaeolum species (including Tropaeolum majus, the common garden nasturtium), have you ever noticed anything along the lines of thicker roots, greater heat tolerance, and/or less spicy leaves in your population? Maybe that could be a starting place!

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I have grown Mashua from cultivariable before. You’re right that it sulks in the heat, but I’ve kept it alive in moist shade through 110F summers. But, being difficult to summer and difficult to overwinter, I gave up on it. Unlike you, I do have trouble with common nasturtium over the summer–it does great in the spring, wants to die in the summer, and if it survives, recovers in the fall for a new wave. It does better with shade, but at the expense of blooming. And that’s a problem I had with Mashua–it didn’t produce much root. I suspected it had to do with all the shade.

Anyway, I’m in if you want to propose a strategy, because I do love these plants. I have protocols for keeping cold weather plant alive through the summer when I have to, and greenhouses for winter management. But I have a lot of projects going, so I doubt I have room at the moment to start another large breeding project myself at the moment.

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Awesome! I’m very heartened to hear that you’ve managed to keep mashua alive through 110 degree summers! How often did you water the plants?

I’d love to hear about your protocols for keeping cold weather plants alive in the summer (and the reverse, with your greenhouse). I’ve wondered whether it may work to plant mashua in the ground in my greenhouse in full sun in, say, December, and see if maybe I can get good roots out of it before the midsummer heat really kicks in in June? I’d rather be able to grow it outside of the greenhouse, but if it may be easiest to nudge it towards behaving like a winter-growing, summer-dormant perennial in my greenhouse, I’d be amenable to that. :wink:

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Shaded, moist environments can be a lot cooler than ambient. In our desert it really cools off at night, so average ground temperature, and also water temperature, can be a lot more reasonable.

I have one greenhouse that has deciduous trees on the north side. During the winter it is minimally heated to overwinter marginal plants. In the early spring, I start new plants in it, and in the summer I open the end to let the air in, and it becomes a cool refuge in dappled light behind the trees. I used to put shade cloth on it before the trees grew up, but haven’t needed to of late.

Fabric pot bags in large trays work well to keep things cool. I water when the tray goes dry, and it doesn’t stay wet more than a day or two, so no mosquitoes, but lots of evaporative cooling. I raise fish in shaded stock ponds sunk in the ground with falling water for oxygenation, and anything planted around them stays cool, as well. Here’s Mashua just waking up in the spring in a fabric pot.

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And here it is in July, getting moved from the shady greenhouse to go live by the fishponds.

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I don’t seem to have any end of summer pictures of it, but this is the wasabi, which is much more heat-sensitive, just waking up at the end of September to start growing again.

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I recently had to disassemble all of my indoor systems after a major plumbing failure required the entire lower half of my house to be rebuilt. But I used to have an aquaponic system that included a shelf where the water ran very shallow across the tray so I could put potted plants in it for wicking and nutrition. It included a chiller to keep the water cold so I could grow wasabi and trout. I never put mashua on it, but it was part of my overall program of growing cold weather plants. I’m getting off-topic, but here’s a soil vs. shale test I did with wasabi in it (water adjusted to be a bit deeper for the water-loving wasabi).

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Yes, shaded, moist environments are definitely better for plants that don’t like hot desert heat. I’ve discovered that bananas (which are supposedly full sun plants) most decidedly want full shade in my climate. I’m glad to hear that strategy helps with mashua, too!

I have recently put two 250-gallon rain tanks on the south side of my greenhouse, in order to provide shade (and thermal mass that will cool down air temperature) for my zone-pushing plants that want a cooler, moister climate in summer. My last attempt at mashua died on me when I put it in a cool, moist summer environment that was suitable for non-zone-pushing plants (such as kale), but I’m thinking it may do better in the similar area I’m setting up in my greenhouse, since there’ll be a lot more thermal mass there. I could even let them trellis up the back of those full rain tanks, thereby having lots of that cooling effect on their stems and leaves in the summer. Do you think that would help?

Are there any particular mashua cultivars you have found easier to grow in your hot desert sun? Any that you find least promising? Or are they all basically the same difficulty?

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I suspect that keeping the roots cool is the most important part for temperature.

I grew a commercially-sourced mashua that didn’t do so well, and the Hoh from Cultivariable which did much better. If I were to try again, I’d probably reach out to Bill at Cultivariable to ask his recommendation for hot climate. I know one of the goals of Hoh was short season production so that you could get a crop before it got too cold. I think he’s transitioning back to just providing seeds, though, and maybe of fewer varieties. He’s had a lot of challenges, and I’ve had my own, and it’s been a long time since I’ve talked to him.

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I keep wanting to order things from him, but he hasn’t had any mashua available for at least the past two years, when I’ve been checking regularly. :frowning: I’ve ordered several mashua varieties that he bred from Planting Justice before, but I . . . really would like to be able to source things from Cultivariable directly!

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He really hasn’t been selling much for the last couple of years. This is the last communication I’ve seen from him, which made me hope he was doing better, but he hasn’t reactivated his community sites or added any inventory to his shop, so I hope he’s okay.

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I hadn’t seen that post, so thank you for linking me to it. He seems to have no mashua seeds for sale yet (sniff), but I did find he had restocked the Jancko Ajawiri potato, which I’ve been waiting for, so I nabbed some of those seeds. :grin:

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