Photoperiodism in veggies

From another recent thread

GWN wrote:I have read on spinach lately and apparently it is not the heat so much as the length of the days that makes spinach bolt....

Thanks for that! Photoperiodism is a topic that gets little attention by gardeners beyond onions (long day and short day varieties). I've wondered about it, but haven't looked into it.

A general description:

Long-Day Plants - plants that flower only when the daylengths are longer than 12 hours. Among the plants that fall under this classification are radishes, lettuce, spinach, potatoes, sedum, and beets.

From this site

Spinach, a long-day plant, cannot flower in the tropics because the days never get long enough (14 hours)

From this site

In lettuce and raddish, short days promote higher top:root ratio. This is desirable in lettuce because it is the top that is harvested but not in raddish in which the economic organ is the taproot.

I've noticed that pattern in lettuce, and now I know why. A couple years ago, I made the decision to pull lettuce plants as soon as they passed their prime, and not let them sit there just growing roots.

AHAH! thanks for this......

So this explains June bearing strawberries vs everbearing.

I did read that different strawberry varieties respond differently to day lengths, but I glossed over it

I was just admiring my blooming strawberries and wondering when the raspberries will start to bloom so they were on my mind.

I wonder if the shade people try to provide for lettuce in the summer to keep it from bolting is less about heat and more about less light.

Turan wrote:...I wonder if the shade people try to provide for lettuce in the summer to keep it from bolting is less about heat and more about less light.

Here's another fact to keep you thinking!

In a controlled environment, researchers have found that the absence of light during the 'night' is critical for the plant to do what it does at night, while a period of darkness during the 'day' doesn't affect the plant.

In other words:

At night, plants don't react to the ambient environmental light from the moon and stars. But all it takes is 5 minutes of light from a flood light to make them think it's daytime and start doing their daytime thing.

During the day, the lights can be shut off for well more than 5+ minutes, and the plants don't even begin to think it's nighttime.

So...my SWAG is that heavy shade on lettuce doesn't trick it into thinking 'short day'.

What's your guess?

ERm..... Photo what?????? I have never heard of it

boffer wrote:
So...my SWAG is that heavy shade on lettuce doesn't trick it into thinking 'short day'.

What's your guess?

I was guessing a long evening in lettuce terms..... with no idea how that works physiologically.
What puzzles me is that growing lettuce in the summer seems to work in the north where the days are very long in summer. In the South where there is not as much difference in day length lettuce becomes very hard to grow. We have all assumed that this is temperature related, not day length related. My guess is that it some of each and maybe other variables we have not brought up (water, nutrients probably).

Hmmmm... so you've noticed it to be true with your lettuce, but what about your radishes? Do they do better during the longer days? Hope so, since I just planted some.

I keep reading about lettuce being a year-round crop here. happycamper from our region posted in this thread that lettuce only needs 3-4 hours of sun per day and she grows it all summer behind her tomatoes. I kind of want to try growing it on the east side of the house where it only will get morning sun, but I know I'll forget about it and not water it consistently.

I remembered this thread while at the grocery store last night . I had certainly noticed that the radishes for sale are HUGE these past few weeks. Mine just sprouted - can't wait to see how they do with all this daylight.

OK then, I was hoping you'd forget about your radish question!

My radish harvests have always been a crap shoot. Sometimes it's a fast crop (3 weeks or so) with big bulbs, and sometimes they don't bulb after 2 months. No rhyme nor reason. I can't find a pattern: different weather, growing medium, etc.

I've gone searching for explanations, and have found that many others have experienced the same results. Interestingly, I found few anecdotal remedies for the problem. Usually, gardeners are sure they have a trick up their sleeve to solve garden problems, but solutions are far and few between for radishes.

For the time being, my practice is to pull squares of radishes that aren't bulbing after 3 weeks, and plant again. I plant rads from Feb. to Aug., and I just can't say that temps or direct sunshine make a difference one way or the other.

I've been growing French Breakfast for the first time this year, and so far, I'm having better luck with them than my usual varieties. I just bought a package of Cherry Belles after seeing the picture of the huge Cherry Belles that someone posted. (Sorry, I don't recall who it was.) I'm about ready to do a side-by-side planting of Champion, Early Globe, French Breakfast, and Cherry Belles, just to see what happens.

I've got Champion and French Breakfast and they all sprouted today. We'll see what happens.