Massonia outside

[Acid John]

Was surprised to see this in the Kew rock garden Saturday.

[Clarke Brunt]

I'm a bit surprised to see that too! I grow Massonia pustulata in pots, and I have them outside whenever I can in the growing season (i.e. winter in the UK) - they easily get etiolated (leggy) inside where it might be too warm or have insufficient light. But I find that the leaves aren't frost hardy beyond a degree or two. I once lost the entire lot outside when I was away for a few weeks, and there was evidently hard frost (luckily I had some seeds or seedlings to grow more). This winter (2019/20) I persisted with them outside until January (there had only been light frost), but with incessant rain (and maybe some frost damage to the leaves), some were rotting, so I've brought them inside. I'd still like to put them outside when possible e.g. today looks a nice sunny day, but several degrees below freezing is forecast for tonight, so they'll be coming in again. During their dormant season (summer in UK) I keep them dry in the greenhouse.

So why aren't Kew's plants being killed by frost - unless this is the first winter they've been outside, and there hasn't been serious frost yet?

Talking of unexpected outdoor 'succulents': I've got at least two self-sown Boweia volubilis growing in gaps between the patio slabs - the bulb is probably under the slabs so no chance of getting them out.

[Acid John]

I'm wondering if the large rocks are acting as heat sinks?

[Paul in Essex]

That is very interesting - thank you for posting this!

[Aiko]

This M. pustulata in the first two pictures looks more like a M. longipes (the fourth one looks more like a M. pustulata, but could also be a M. pustulata). I have read / heard earlier that M. longipes is quite a bit hardy.

Because of what I have read / heard, this year I have left two mature M. longipes plants unprotected in the greenhouse for the winter to see what is true about this. Luckily or unluckily there has been not frost greater than -3C up here so far. They still look fine. But mine are in the greenhouse only get moist when I give it to them, so no winter rains regime from nature.

[ralphrmartin]

Mine have been unheated in the greenhouse for the last 2 winters, OK so far. Not too much frost here, although there was one this morning.

[Aiko]

I am sure almost every winteractive succulent can take a temperature up to -5C, even when the soil is soggy. The main question for me would be, can they (in this case my Massonia longipes) also take -10C.

We don't have those temperatures every winter up here, but we do have some nights between -5C and -10C in the height of winter on a few nights with a clear sky.

[Terry S.]

Don't forget that Kew is actually a rather warm garden. The altitude is close to sea level, there is some amelioration of the climate from the river Thames flowing next to it and it is close enough to London to have some benefit from the enormous amount of heat released from buildings in our capital. Kit Strange who looks after the bulbs at RBG Kew, does raise a lot of material from seed and I suspect that she and colleagues are experimenting to see what they can get away with. Massonia saniensis survived outside at the much colder RHS Wisley for many years, but that species is summer-growing, from high in the Drakensberg and it did have overhead protection in the winter.

[Aiko]

I am sure almost every winteractive succulent can take a temperature up to -5C, even when the soil is soggy. The main question for me would be, can they (in this case my Massonia longipes) also take -10C.

Well, they can't take temperatures between -10C and -15C, I can at least say. Still feel confident of anything below -10C. I will try that next winter, if the winter cooperates.

[Ernie]

Massonia bilfolia
Lives in the greenhouse. Down to 6c in winter. In the summer I keep it dry and it often gets baked. Comes back every year.