Texas weather, freeze susceptibility, sand plunge

Monica Swartz eciton@alumni.utexas.net
Sun, 26 Jan 2014 21:28:13 PST
Cynthia asked about how winter-growing bulbs respond to the 
temperature turmoil in Texas. I live in Austin (zone 8b) though the 
microclimate at my house on the edge of the escarpment is 
significantly more extreme than in the city. I grow hundreds of 
winter-growing species from S. Africa, California, and the 
Mediterranean, most with little to no weather protection and I've 
been planting loads of winter-growing bulbs into the ground to see 
what works.
This winter has provided several events with 80 degree F temperature 
swings in 24-48 hours and one rainfall event of over 15 inches in a 
few hours. The plants grow when the weather is good, and pause when 
it is not. The wild swings in temperature make no difference in when 
they flower or go dormant. In my experience, most winter-growers are 
far more freeze-hardy than you might expect.
The real killer this year was the first freeze in mid November. I 
lost several species and had lots of damage even though it was barely 
below freezing. It simply hadn't been cold up to that day and I 
believe that the plants need the trigger of some cool nights to make 
the heat-shock proteins that protect them. A mild freeze out of the 
blue was far more deadly than the recent 15 degree ice storm.
I have only been growing in Texas for a few years and I still have a 
lot to learn. This November's lesson was a hard one. On a brighter 
note, I've also learned how fantastic a sand plunge is!!! I built a 
small plunge in full sun for winter-growing Brunsvigia, Haemanthus, 
Boophane, and Gethyllis and all are growing and flowering happily 
without the freeze damage shown by the same species on shelves just a 
foot away. I think they could go below 10 degrees F before the first 
leaf burn on the edges. Even more surprising is that I left the pots 
in the plunge all year and let them get summer rain without cover. 
They loved it, lots of flowers (the Brunsvigia seed I sent to the BX 
came from this plunge) and one Gethyllis split into three. Our rain 
is infrequent but heavy (35 inches a year on average). Those of you 
in drier climates should have little to fear. I have read about sand 
plunges on this forum for years and now I'm more than convinced, I've 
started building my second one.
monica expecting more snow tomorrow after 75 F today

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