Bolting

[ElizabethB]

Food for thought. Research that shows that bolting is related more to hours of daylight rather than heat.

https://www.finegardening.com/plants/art ... bolts.aspx

Even my warm weather herbs like dill and basil bolt very quickly. Planting in deep shade sounds like a plan. Dill, basil, parsley, cilantro, lettuce, spinach and other greens.

I would love the L for a BLT fresh from the garden when the T is ripening.

Have any of you heard of these studies? What is your opinion?

Information courtesy of Lafayette Parish Master Gardener Association.

[rainbowgardener]

I just noticed you didn't get a response to this. I think it is a very complex interaction of triggering factors. I found and article awhile back, which I can't find now that says it is not only related to heat AND day length, but increasing day length. When the days are getting longer, it will trigger bolting, even if not hot (but hot can also trigger bolting in stable light conditions). So spinach is better grown in fall when day light hours are decreasing (and temps are cool and what not- it's a lot of confounded variables since they all work together) I'm not sure how you would sort out increasing day length from cumulative sun exposure, which some people say is the trigger. I guess you could measure cumulative sun hours and see if the same amount of cumulative hours trigger bolting if spread over more days (day length stable) or less days (day length increasing). Anyway it is complicated, soil heat factors in there. I don't know if people have checked on how age of plant figures in (days since germination). We know that different varieties have different days to maturity programmed in and maturity in something like spinach would probably be when it starts bolting?

I think the plant just knows when it feels right

[digitS']

But, wouldn't this mean that lettuce would bolt almost upon emergence in Alaska and grow for months without bolting in Sub-Sahara Africa?

The onion farmers will advise you that if their onion plants bolted before forming bulbs in your garden, it may well have been a result of setting them out in weather that was too cold. Bok choy also behaves this way in my garden.

I remember happening on a lightening-struck evergreen tree on a mountain top. It was almost covered with more cones than needles! I don't see the issue of stress mentioned in these reports.

Steve

[rainbowgardener]

I don't know that we would talk about a pine tree "bolting," but you are right that stress figures in there also. Like I said a complex interaction of triggering factors and which one is dominant, I'm sure would depend on conditions also.

Trying to think through the Alaska e.g.:

Here's climate data for Fairbanks, Alaska, which is pretty central:

https://www.climate-zone.com/climate/uni ... fairbanks/

So a gardener in Fairbanks would likely be planting lettuce in April when lows are averaging 20 and highs are averaging 40. To the extent that heat triggers bolting, it would never bolt, because their hottest month is July when highs average 72.

But in April

https://www.gaisma.com/en/location/fairbanks-alaska.html

dawn would be at 7AM and sunset at 9 for 14 hrs of sun with days getting longer quickly. So to the extent that long and increasing sun hours triggers bolting, it would tend to bolt quickly.

So the interaction of low temperatures and long days would be something in the middle...

Of course they could re plant for a "fall" crop in mid July and at that point, temperatures would be cooling off and days would be shortening and it would last until October when it gets too cold.

[digitS']

My opinion:

The "Finegardening" article puts too much emphasis on day length. The plants are genetically geared to reproduce and there are a number of factors as Rainbowgardener notes.

Trees react to day length more strongly than garden annuals. But, we aren't talking about trees.

Steve

[rainbowgardener]

Well, it is complicated. Certainly if the plant doesn't die, it will bolt/ reproduce at some point and some days to maturity factor is genetically programmed. But I have planted the same variety of spinach seed in Oct to overwinter and grow in late winter/ early spring and in mid-March to 1 April to grow in spring. The overwintered spinach that takes off growing again around the beginning of February grows much bigger and lusher and lasts way longer than the spring planted stuff, which bolts very quickly when days get longer/ temps warm up (which happen together). In fact the fall planted and spring planted stuff end up bolting about the same time, which suggests that the sunlight/heat factors are definitely important.

That's not research its my anecdotal experience, but it is what I have seen. I am now a big fan of fall planted spinach!

[lily51]

It seems to me heat increase, especially sudden and of a good amount, has quite an effect. In the greenhouse bolting is not a problem even with lots of light unless the heat goes high. Just a casual observation.