Preamble: As global temperatures increase, the conditions common vegetable plants grow in will deviate from what these crops were bred to experience, as well as the genetic experience of their ancestors. Farmers and gardeners will have to start adapting by growing varieties that are more heat tolerant; and plant breeders will have to start developing varieties by crossing heat tolerant strains with each other.
In previous seasons, I have grown Moskvich tomatoes, a Siberian variety that tolerates the cool temperatures of September quite well. In 2023, the season was so hot that the Moskvich varieties did poorly from August onward. However, the cherry tomatoes did exceptionally well. This gave me the idea to test a number of varieties that are considered heat tolerant for 2024.
As for beans, I typically have grown a fairly dependable and good tasting variety called Maxibel. Most season's, the beans go dormant from the heat for a period of time, making timing of the pod picking difficult to predict. This season, I wanted to try some other varieties and compare them to the Maxibel to see if they perform better by tolerating the heat and thus avoiding dormancy.
Question 1: Do different varieties of beans tolerate heat better than others, and if so, which types?
Though generally regarded as a sun loving plant that requires warm temperatures, beans will start to suffer heat stress when temperatures go beyond 29 degrees Celsius. Typically, the plants drop their blooms and cease growing until the temperatures moderate.
Prediction: Some bean types are quite heat tolerant; typically romano and dry beans. Green beans tend to do less well. There are hundreds of green bean varieties, all derived from the original dry beans of South America. Some of these varieties have retained some of the heat tolerance genes of the dry beans. I suspect that the romano beans will do better than both of my green bean varieties. I have included yellow wax beans with my green bean varieties to see if there is a difference as well.
In previous seasons, I have generally grown Maxibel. As they are a familiar variety, I will use these as my control. I have also grown Dragon Tongue romano beans, and will try another romano (Forrester) to compare their performance.
First succession Green and Yellow Beans
Method: Grow the Maxibel beans (what I typically grow) as a control. I have used these for many years and thus familiar with how they respond to a range of seasonal variations.
Grow the other types of bean as close to the Maxibel's as possible, and plant them in beds that have the same regimen of amendments and preparation. Water and tend equally.
Data Gathering and Observations:
The first two beans planted were Maxibel and Goldrush, on the same day, on May 20. Both were expected to mature in 55 days. During their growth period, the weather was moderate to hot, with lots of rain and clouds throughout June.
These two bean beds were located fairly close together - the south end of the green beans were within fifteen feet of the wax beans. Both beds received an equal amount of sunlight. The wax beans were in a slightly lower elevation and may have had more access to subsurface water. Both beds were prepared for planting in the same manner - same inputs, aerating and weed control.
On their first harvest day, both bean types were ready.
Over 12 feet, Maxibel yielded 11 Lbs. 4 Oz.
Over 12 feet, Goldrush succession 1 yielded 12 Lbs. 8 Oz.
The quality of both bean types was good - tender, straight and of good length.
It was expected that that the Maxibel would produce a second flush over a two week period. Instead, the plants failed to produce any blossoms; two weeks later the plants started to show signs of being finished (yellow and rusty leaves ).The Gold Rush beans produced one flush and immediately developed rust very quickly without any sign of a second flush.
Photos: Top, the first succession of Goldrush yellow wax beans; two weeks after their one and only flush. Below the second succession of Goldrush as the flowers are blooming.
Note how the first succession is more vigorous; the plants are larger and leafier.
Romano Beans
As of this writing, I am unable to locate the documentation that records the exact quantities of the romano beans. It's here (I had it in November) but the page has been misplaced. I'll update this report when that documentation is available; until then, I will use the general observations that I kept in my field binder.
Dragon Tongue romano bean: I've been growing this bean since the early years at the previous farm - about 2014 or so. It has been dependable, and has turned out to be one of my favourite tasting beans.
Forrester romano bean: For the purposes of heat stress trials, I opted to try a different romano, despite the Dragon Tongue being adequate. This is a new variety for us, so I have no information with which to make any predictions.
Method:
Both of these bean varieties mature in 55 days. They were planted in late June, to be ready for mid August production. Both varieties were planted in the same bed, one type for the two parallel rows. Thus, both varieties had access to the same amendments, sunlight, water, and care.
Data Gathering and Observations:
Seed germination was even for both types, despite warming temperatures. During their growth period, the plants did not appear to have any challenges due to high temperatures. On their first harvest day, both bean types were ready.
My recollection is that the Forrester yielded about twenty per cent more than the Dragon Tongue. Both bean varieties were healthy and vigorous.
Second succession of green and yellow beans
At the same time I planted the Romano beans (late June), I sowed the second succession of green and yellow beans for the August harvests.
As the Romano Beans were expected to provide the bulk of the second round of bean deliveries, I planted far fewer green beans (24 foot row as opposed to 100 foot row). Owing to the number of CSA customers who had expressed an interest in the yellow beans, I planted 24 foot row of these as well.
Method:
I planted the second succession of green and yellow beans close to the first round of Maxibel's, in a pair of twelve foot beds that were next to each other and the bed that grew the first round of yellow beans. the first round of . The beds were prepared and amended in the same manner, and had equal sunlight, water and care. Half of the green beans were maxibel, the other half were a variety I was sampling a called Speedy. Speedy matures about a week sooner, so I assumed it would wind up being sold in the store, and would only be distributed to CSA customers if it produced a vigorous second flush.
Data Gathering and Observations:
The weather was somewhat warmer, though steady rainfall and some cloudy days helped mitigate the high temperatures.
Speedy failed to germinate - no plants emerged. I suspect that a surge in temperature right at planting time may have contributed to this.
The maxibels germinated somewhat late but did ok after that, producing a somewhat weak flush in time for the second delivery in August.
The yellow beans germinated but failed to thrive. The plants were about one third the size and yielded small, curled pods that quickly became infected with a rust, sign of stress.
The data from the Romano beans are on the same document as the second succession of green and yellow beans. The data here will be updated as soon as the document is located.
Conclusions: As predicted there APPEARS to be some impact of heat upon the bean varieties I grow. (Eg, results from the two yellow bean successions may have reflected the difference in temperatures. The first grew through late May into mid July; the second from late June into mid August).
However, I made further observations of other crops at the same time; and I was able to find another piece of information about the soil type and some of it's challenging characteristics on the web. The peppers (stunted fruits on some varieties), tomatoes (succumbing to blight during weather conditions not conducive to blight), and carrots (failing to germinate evenly or on time or at all) were telling me that some other factor was effecting the productivity of some crops.
The one new piece of information was a single page document published by a soil researcher and professor in the US. (source now forgotten). This apparently otherwise unpublished page (it appeared to be an exam study page) pointed to the unique characteristics of muck soil's chemical properties, which in turn, opened up a whole new line of questioning....
Armed with new knowledge, I halted the heat stress trials for the tomatoes and "did a little digging" around these plants to see if there was something different I could do.
I'll go into detail on this new chapter in the coming weeks, including what I learned, how I tested it in the field, and the surprising conclusions I arrived at that would completely change some of the growing methods that I had been trained to use.
Question 2: Do different varieties of tomatoes tolerate heat better than others, and if so, which types?
Though generally regarded as a sun and heat loving plant from the Mediterranean, tomatoes will start to suffer heat stress when temperatures go beyond certain ranges. Tomatoes grow best between 20 and 30 degrees Celsius. They become heat stressed between 30 and 40 Celsius, and cease growth altogether around 40 degrees. These temperature ranges are a generalization - some varieties will tolerate slightly higher temperatures, while others bred for northern climates may have lower tolerances.
Symptoms of heat stressed stressed tomatoes curled leaves, dropped blossoms (leading to lower yields) and generally slower growth. At higher temperatures, growth stops altogether and the plant ceases producing lycopene, the pigment that produces the color in tomatoes. The fruits may turn color on the outside, but remain undeveloped (green, poor flavor) on the inside.
Prediction: Some varieties may have a higher heat tolerance than the others, possibly due to the climate that they were bred in. Cherokee Purple and Prudens Purple (Tennessee) Cherokee Carbon (Northern California) will likely perform better than Moskvich (Siberia). Cherry tomatoes have consistently grown well during hot seasons.
In previous seasons, I have generally grown Moskvich and several cherry tomato varieties. 2023 was an exceptionally hot season and the Moskvich tomatoes did very poorly. I will use the Moskvich as a control to measure the performance of the other tomatoes against.
Method:
Data Gathering: Number of plants, variety, average Lbs. per plant
14 Sweetie Cherry tomato:
8 Moskvich tomato:
12 Prudens Purple tomato:
6 Cherokee Purple tomato:
6 Cherokee Carbon hybrid tomato:
Note: Due to uneven seed germination, I was unable to do an equal quantity (8 plants) of the non cherry types.
Other observations:
Signs of heat stress, heat induced dormancy periods, comments about season weather, etc.
Data Analysis: