Frost Tolerance in Melons

[Joseph Lofthouse]

I inspected every diploid watermelon today. That pale green one might yet turn into a golden midget, but it is still quite immature.

I harvested 3 watermelons today which seemed mature, and one only because the vine was damaged.

Brix = 7. Over-ripe. Sister to the melon harvested a week ago.


Brix = 6. Vine damaged. Flesh didn't sweeten up. Seeds mature.


Brix = 8.5. A great tasting melon. Slightly over-ripe.


I love watermelon! I ate all three melons. I left the largest (over 8 pounds) to eat tomorrow. There was a melon in the tetraploid patch that I could have harvested, but I think I'll wait a few days until I can recruit family to help eat it.

[Joseph Lofthouse]

The watermelons were not visibly damaged by this morning's frost.

I ate the highest brix melon of the year today. A diploid. It came out of my landrace from last year.

Brix 10, though it didn't taste as sweet as the yellow melons. 8.3 pounds.

[terracotta]

Your top watermelon on page 4 looks dark red to me. Compatible to the highest red heirloom variety.

sustainableseedco.com/Allsweet-Watermelon-Seeds.html

[YoungAllotmenteer]

Sept 11, 2012 9:28:33 GMT -5 Joseph Lofthouse said:

London had a good soaking rain on 14 days. I had good rains on 3 days and that's during my rainy season!!!!

While you may carry a slicker or an umbrella, I carry a parka in my vehicle all year long, because I know that I am going to want it at night, even during the hottest days of August.

Watermelon requires about 900 GDD:13C in my garden to produce the first ripe fruit. [Growing degree days in which the average daily temperature is higher than 13 C.) There is not that much heat available in London during a growing season. That's not saying that watermelon couldn't be grown in London, just that they would need a warmer micro-climate, or genetics that allowed it to thrive in cooler average temperatures. I am selecting for desert conditions with extreme temperature differences and exceedingly low humidity. Perhaps there are other growers that are selecting for maritime conditions.

Its certainly a fascinating comparison. Even within the UK there are stark differences. Where I grow in the South-East versus my parents 100 miles away north, there is on average year round a 5C degree difference in temperature. I grow on 'the fens' at below sea level, on extremely free draining silt/peat soil. This has its rewards (few if any real pests bar rabbits, high levels of OM, high nutritional availability) and its downsides (The soil is bone dry, even this year when everyone has been complaining about the miserable wet summer).

I do just wish it was 10 degrees warmer during the summer, so I could successfully grow melons and things of the like.

[Joseph Lofthouse]

Yesterday I picked the first ripe watermelon of the season... This is a month earlier than my first diploid melon harvested last year!!! I wonder where that yellow skin on a round fruit come from? Sure seems like a nifty feature, to turn yellow when ripe. I might have picked it somewhat prematurely: Brix was only 5%. As of this week, it's looking like my watermelon landrace is going to stabilize on round fruits weighing about 4 pounds.



And then I ate the melon with those dirty hands. Good thing I'm immune to our local soil.

[steev]

You're not immune, just immunized, thanks to exposure.

Each of us is an ecosystem, walking around, of myriad bacteria, viruses, and fungi.

We tend to think of ourselves as individuals, separate from the world in which we exist, but that isn't so; we are members of a community, which we deny to our peril.

[Joseph Lofthouse]

I picked watermelons this week. A few watermelons have been ripening for the last month that I didn't get photos of.

Here's what they are looking like. Taste is mostly excellent. I can finally ripen a melon!!!! I am finally willing to call these a landrace. I have previously been calling them a proto-landrace. I'm really liking the orange and yellow melons. They taste best to me. I have been eating about 10 pounds of watermelon per day. I decided that I am not going to let them spoil this fall like I did last fall, so I've been sending them out to friends, family, and collaborators with a piece of tape attached with an ID and instructions to eat the melon and return the seeds in a paper bag labeled with the tape.



There are some red melons with yellow swirls. Mmm. Mmm. Mmm.

[steev]

Nothing is quite so successful as success. Bon appetit!

[hortusbrambonii]

Wow, those watermelons and their cold-tolerance are impressive, Joseph!
I like the yellow-red coloring a well!
Your landraces should be in every book of agricultural history...

[mayz]

Sept 11, 2012 9:28:33 GMT -5 Joseph Lofthouse said:

Sept 11, 2012 1:16:26 GMT -5 YoungAllotmenteer said:

I would be curious to get some more detail about your climate (given the 100 frost free days). I have tried, and failed to grow Watermelon previously with 365 frost free days, and now in the UK we probably have something like 210 frost free days, but given the low average temperatures (~18C / 65F) I still couldn't grow Watermelon.

I assume your climate is hot from the word go when the frosts stop, and is hot until the frosts start again?

This year, my watermelon growing season was pretty much 85 to 90 F during the day, and 55 to 60 F at night during July, and August. No rain or dew. Once a week sprinkle irrigation for 12 hours. The watermelons received frost approximately 10 times during June after they germinated and before it got warm enough for them to grow. Our last frost was on June 20th, the summer solstice.

Here are some graphs on the same scale [Courtesy of wunderground.com] for the weather this past June in London and in my garden.

London, June 2012:


Joseph's Garden, June 2012:


I would describe my climate as extreme... Daily temperature swings of 40 F are typical, with swings of 50 F fairly common. (Due to the high altitude and dry climate, I have intense sunlight during the day, and dramatic radiant cooling at night.) So I might have a high of 85 in the day and frost at night. In London temperature swings of 20 F between night and day are typical, and it is fairly common for the high and low temperature for the day to be within a couple degrees of each other.

My dew point can be as much as 70 F below the current temperature, and even at night it is often 10 to 20 F below. In June 2012, London had dew about 24 days. I had dew/frost about 8 days.

London had a good soaking rain on 14 days. I had good rains on 3 days and that's during my rainy season!!!!

While you may carry a slicker or an umbrella, I carry a parka in my vehicle all year long, because I know that I am going to want it at night, even during the hottest days of August.

Watermelon requires about 900 GDD:13C in my garden to produce the first ripe fruit. [Growing degree days in which the average daily temperature is higher than 13 C.) There is not that much heat available in London during a growing season. That's not saying that watermelon couldn't be grown in London, just that they would need a warmer micro-climate, or genetics that allowed it to thrive in cooler average temperatures. I am selecting for desert conditions with extreme temperature differences and exceedingly low humidity. Perhaps there are other growers that are selecting for maritime conditions.

Comparison is not complete as hours of sunshine is the most important parameter after temperature. And sunshine modifies the REAL temperature to which the plants are exposed. GDD calculated from meteorological data (temperature under shelter) doesn't represent the real temperature of the garden.

Thus 900 GDD in sunny Utah doesn't correspond to 900GDD in cloudy UK.

[Joseph Lofthouse]

While my garden gets brilliant sunlight during the daytime, it also gets intense radiant cooling at night... So the effect of warmer than air leaf temperatures during the day might be somewhat counteracted by much cooler leaf temperatures at night due to radiant cooling. I estimate the nighttime radiant cooling on surfaces at about 10 F. And there seems to be a high temperature cutoff (at least in corn) in which metabolic pathways shut down due to temperatures being too high. My brilliant sunlight may trigger metabolic shutdown. But in any case I can barely pull off 900 GDD:13C with sunlight in my garden, so being able to grow watermelon in England with only 600 GDD:13C and cloudy weather seems unlikely. Watermelon originated in a desert, so at least I have that going for me.

[canadamike]

Coming back on frost resistance, but this time in cucumis melo, true melons, Tom ( daewinslair) informed me today that the VOATANGO X GNADENFELD F-2 cross of 2010, an F-3 now, just gave him many melons, but he just picked a huge 10 pound melon, he says it is the best of his life, and it was picked in his Minnessota garden a few days ago...we are in October for crying out loud....other melons have long long died from cold nights....this is a true cold weather warrior. And it is incredibly sweet Tom Says..

Given the fact that this is a second planting done July 10 ( first ones were eaten by bugs)and that Minnessota has cool night starting in September, were other melons usually die of the ''sudden death syndrome'' in September, usually early in the month, it is quite an achievement and a testimony of the quality of the genetics.

I would like to point out that both Gnadenfeld F-2 and Voatango produced despite being severely attacked by powdery mildew. Leaves were white, but they pumped out melons, especially Voatango.

The Voatango were tasteless, but it is normal for such a strong plant that gave 40 pounds of melons for a single vine in a super rainy end of summer and fall, where we had something like 380% of the usual amount of rain...

I want to REPEAT what I said earlier in this thread, VOATANGO gave me a flower after a frost (that even killed lots of tomato plants by the way).

I think we have a real winner here...next year seeds will be F-4

By the way, Voatango had a reputation to resist heat and drought going for him before I tried it...

[raymondo]

Certainly seems to be a winner Michel. I wonder what other wonders Madagascar holds. I'd love to go there one day.

[DarJones]

Joseph, that high temperature shutdown is not what you think. You can graph this in your head. Corn photo-saturates at about 1/3 of full sunlight, somewhere around 500 to 600 mols. When sun intensity increases beyond that level, the plant enters moisture stress where it has to pump increasing amounts of water to the leaves where evaporation cools the leaves back down to survivable temps. What you are seeing is the point at which energy expenditure to counter leaf temperature extremes exceeds energy being produced by photosynthesis. The same thing happens with all plants, just at lower levels of sunlight around 400 mols.

Palms are tropical adapted plants that can take much higher levels of solar intensity. They produce a waxy coating on each leaf that absorbs some of the excess UV. en.wikipedia.org/wiki/Carnauba_wax

[Joseph Lofthouse]

I'm not doing much with attempting to develop frost tolerance in watermelons... I have ended up focusing more on quick germination and robust early growth so that the plants can produce a crop in spite of the short season. This has meant smaller fruit sizes. Perhaps some day I will revisit selection for frost/cold tolerance. I have taken to germinating in pots because it makes it easier to screen for quick germination. Then I transplant bare-root into other pots, then into the field.

It's nice once in a while to plant seeds from other growers to give me a comparison, and show me how far I have come... These two pots were planted on the same day and treated as near to the same as possible. One pot contains my landrace seeds, the other pot the same number of seeds of mixed varieties that people sent me as gifts.



p.s. note to USDA bureaucrats: "Foreign" in any of my writings or photographs indicates that the seeds haven't grown in my garden before, not that they crossed capriciously defined borders.