Friday, May 25, 2007

Frost and Drought

I may have lost some tomato plants last night, even though I had them covered. No big problem - I knew it was a gamble, and I went ahead and set some out because I had lots of extra transplants to keep as replacements. But it got me thinking about last frost dates.

We had some very early warmth this spring. Farmers were out seeding in late April, and I would say that's about a month ahead of the traditional seeding time for this area. The ground dried out, and I got worried about drought. Then it started to rain, and I don't trust my cracked gauge, but Mom says they have had 5 inches in the hills since May 9th, while the average for the whole month is only 2. But before all that happened, at the end of April, I was gardening with drought in mind. I refused Garth's offer of rototilling and in fact refrained from digging the beds at all, to conserve moisture. As I started planting early vegetables, I went to fetch water from the ditch near our yard and found that it was already dry. I took my bike and trailer and hauled a tub of water from a vernal pool over on the east side of the 604. I was worried, but full of hopes that my earliest-ever garden planting might help get plants well established before a summer drought hit hard.

Last year I talked to many people in this area who said the crops turned out better than they expected, considering how dry it was in the latter part of the summer. One farmer friend agreed with my speculation that the early spring and early planting had allowed the crops to get a better root system established, so they weathered the drought better than in former years.

But as my tomatoes show, early planting is a gamble. I don't know much about frost tolerance of the common field crops in this area, but I know there are times when fields have to be reseeded because an early crop was killed by frost. As our springs get warmer, and droughts become more frequent (as predicted due to climate change), farmers may try to adapt by planting earlier. But what about frost? How are the last frost dates changing?

I pulled out my CD of climate data for Western Canada and checked what was available for our area. Carlyle had max/min temperature data from 1922 to 1996 (with one year missing, 1962). I plotted last spring dates with temperatures less than or equal to 0ÂșC.

Now, where is my old statistics text book? I vaguely remember a lot of cautions about interpretation and testing where time series are concerned, but to me this graph seems to confirm my suspicion that last spring frost dates have not simply moved earlier. They have become more variable, with earlier dates contributing almost all the new variation, but late dates still occurring frequently.

What does that mean for adaptation? In my garden, I can plant things in succession, I can hold back extra transplants as replacements, and so on. But in a farm operation with thousands of acres under cultivation, what is to be done? Can farmers absorb the costs of having to reseed fields one year in six, say, or one year in four? Can they choose their planting dates strategically and be prepared for reseeding operations, or do they have to get it all in as quickly as possible and get back to their off-farm jobs? I wonder.

I also wonder about spring weather patterns in terms of soil temperatures and growing degree days and the overall shape of the warming. My second planting of peas has not appeared yet, and I think it's been ten days. Did the recent cold and cloudy spell chill the soil and rot the seed? How does this spring compare to the springs we used to get? Was a steady warming more the norm? I will have to ponder how to analyse my climate data for that.

UPDATE: Oh, yeah, and speaking of adaptation, I forgot to mention that whole area of adaptation that most people never think about, where there will definitely be problems: adaptation by every other species except human beings and their little collection of manipulated plants and animals. Are we already seeing the effects? What about that die-off of poplar in the hills in the '80s? The experts blame insects, but the locals say it was a combination of drought stress and a late frost. What about the decline in bees across North America? Insects can adapt fairly quickly because of their short generation time, but pollinators are closely co-evolved with plants, and some plants take a long time to reproduce. These changes are happening incredibly rapidly when compared to previous evolutionary history. Can genetic adaptation keep up?


Tim Hodgens said...

Hi Laura,

I like your curiosity and ability to look at data and trends. I especially liked your phrase: "the overall shape of the warming."

There is a reference to an animation on climate changes by growing zones in the U.S. from 1990 to 1996. The graphic shows the pattern of increased warmth migrating to the north...(a chilling graphic...hee, hee) You can find the reference on Emme's old blog:

Your investigation is looking at it's twin factor, last frost date. It's one thing for your tomato plants. And totally another thing for farmers. Daunting.

A few other things:

1. Monica at talks about the powerful dry spring they are having in Tennessee. She has several posts about it.

2. On my long list of things to do, I plan (eventually) to rig up some water barrels to capture water from roof run off for my garden, etc. That will also not have chlorine and fluoride in it which my tap water does. I guess that would be better for my vegetables and it should help a tad with my water bill.


Anonymous said...


I too keep track of weather trends in our area. Luckily, we do have online access to weather data for Athens, GA going back to 1898. That's not true for most places in the US - you have to pay for it. Canada has a much more complete and accessible set of records.

We also had a late frost that had severe repercussions for plants that were either flowering or just putting out leaves. The problem wasn't so much that it was a late frost - those aren't uncommon. The problem was that there had been three weeks of extraordinarily warm weather in March prior to the freeze, and that fooled a lot of native species.

You've come up with your own phrasing to describe this - mine is "more erratic weather". I think it's a little more encompassing than "hotter days, more frequent and severe storms, etc.," that the media has used.

There are general trends too, and lately I've been looking at the trends between 1920-2006, 1970-2006, and 1994-2006. In view of a NASA report a few weeks ago, and two others in the last month, I would say that I can see a much faster increase in average temperatures, especially in the autumn here. And we follow the predicted pattern of a consistent decline in precipitation in all seasons, but especially in summer or autumn.

The NASA report projected a 10 degF rise by 2080, in much of the North American continent. Most alarmingly it also predicted drastic declines in precipitation in those areas where temperature increases. Whether it's part of a cycle or not, we've seen that for the last ten years here.

Granny said...

I live in one of the "breadbasket" areas of the USA and the climate is always a major issue around here.

The lack of bees is alarming, at least to me.

arcolaura said...

Hi Tim,
I've heard reference to that hardiness zones animation - it sounds compelling. I haven't found anything similar for our area, but the National Land and Water Information Service has zone maps from 1967 and from 2000. They differ in resolution, though, so it's difficult to compare them.

The dry spring in Tennessee - I notice that I have been hearing a lot more about regional droughts and wet spells and warm winters and such, but I have to wonder if this is partly a phenomenon of blogging. Before the blog, I didn't hear what people were seeing on the ground in different regions, unless it was catastrophic weather with property damage and loss of life.

I love my rain barrels! I was hauling from a pond earlier because the barrels were still upside down to protect them from freezing and cracking, but they're set up now, and all three are full, and the tub half full besides! I dithered for a long time about lids and screens and spouts and so on. Finally I did one, with a piece of window screen wired over the top and a tap installed through a hole near the bottom. Then I got two more, and just cut the tops open and let them fill. I dip the water out with a watering can, and if I notice mosquito larvae in there, I use up the water, rinse the barrel and let it dry in the sun, and start over. Last year I got worried about lead from the paint that's flaking off our house shingles, so this year we have been collecting only from one downspout off the garage roof, and using a hose from the fancy barrel (raised up on concrete blocks) to siphon off water into the other two barrels before the first one overflows. My advice: if you have a barrel, go ahead and use it, and refine your system later if you need to.

arcolaura said...

Wayne - you are seeing big changes in autumn? In our area, as I understand it, most of the change has been in spring, particularly with overnight lows getting warmer. As you say, that early warmth is a big problem for species that are fooled into active growth or flowering while the frost risk is still high.

Decline in precipitation scares me. Our area has been desert in the not-so-distant past, so I see that as an inherent tendency of the area, and then you add these predictions, and I start wondering about migrating. This spring as I was scouting for a pond to haul from, I was thinking, what would I do if the town no longer supplied water? Could I haul my own? How reliable is the Kisbey aquifer (about 8 miles west)? Should I add a cistern to our renovation plan? Could we rely on snow and rain to fill it?

arcolaura said...

Granny - I hope the lack of bees is alarming to many. I just can't picture a successful adaptation to a drastic reduction in pollinators. School kids walking through fields, like they used to do to hand-pull weeds, only now hand-pollinating the crop? No, I suppose it will be some kind of microbot proposal. But every adaptation adds a burden to the system. It's not that any one problem is insurmountable; it's the rate at which we're piling up new problems. And meanwhile the unmanaged parts of the biosphere are struggling along, without a say in the whole thing, and without the advantage of our much-touted adaptability to carry them through.

Hmmm. I'm getting agitated again. Time to go take the frost covers off, do some weeding and enjoy the morning.

Anonymous said...


Our autumns seem to be the biggest changes. I don't want to rationalize but I would guess that increasing temperatures during the summer extend well into later months. And the lack of precipitation accompanies it, not only in autumn, but now in summer and spring.

And that's all the more worrisome since while a lack of precipitation during the autumn months (SON) has usually been the case it's even more so now. Added atop the summer deficits it's a real problem.

I've also been worried about water sources. Right now we have a well, and it's a *deep* well - 500 feet. But we still collect water from the roof into a large pond, and I dip into it and do any watering I must from that.

Still - that well we have requires electricity to persuade water from it. I know you're wanting to get into weeding and planting so I won't continue with that!

arcolaura said...

Hehe - Wayne - did you catch me commenting busily over at your place after I said I was going gardening? I did get out a little later, and found that several tomatoes are definitely dead. But lots of things are growing, and the birds are singing, and the forecast looks good.

Is your well too deep for any sort of mechanical (manual) pump as a backup? I read about pumps a while ago, but I've forgotten the limitations of the different kinds.

Madcap said...

Hi! I'm still tongue-tied, but kicking around, reading. Finally spring on the prairies, I think - and only May 29th!

arcolaura said...

I hope you're right, Madcap, because I set out all my transplants and gave the extras away, and I'm entrusting my garden to the care of hubby and daughter for the next four days. Oh, it looks good to see all those arcs of tender green plants, though!