The commercial guys pick 'em green (like yours) and spray them with ethylene, which turns them red, but they are still not ripe.

To ripen, to the best of my knowledge, you just have to leave them on the vine and let them do their thing. My "guess" is that they need magnesium, but it's just an educated guess.

Tomato,
Require 55-60 degree F temps for color change and temps above 85 degree F color change stops till cooler temps return. Do a search on temps vs color change its pretty interesting.

Tomatoes mature based largely on heat, so I've heard.

You can also try hanging red ribbons or something similar around them, that's supposed to help too. Strange, and I have no idea why or how it's supposed to work, but supposedly it does.

Another possible cause would be the nutrition. What are you feeding them?

I placed a red plastic tarp under several of my cherry tomato plants this summer and it really did make the fruit set huge. Maybe it's magic, eh?

I think it is magic. Were you sure to do the tomato ripening dance with it? Seriously, though, I have read in many places the same thing but I don't think I have ever read a reason as to why. After reading that differences between night and day temps often are the key, I would initially suspect it has to do with the added daytime heat. I have read that some varieties perform best with a difference of 10 degrees F between night and day temps. It's something to do with the difference more than the actual temps (within reason, I'm sure). If I get a chance and remember, I might look that up and provide a resource.

AFAIK there's never been any explanation for why tomato plants will have their fruit develop/ripen better when in the presence of red objects, but there's been a lot of evidence to suggest that it does work in spite of the missing explanation as to why it does.

To me it's just too simple a thing to do to leave undone. If it works, great. If not, you're out nothing but the time it takes to put some red ribbons around or whatever. No biggie.

My suspicion is that the plants respond to the increased red light. See, we forget that just because something has no eyes doesn't mean it lacks a response to color. Plants respond very strongly to specific wavelengths of light. A nearby red object could easily have an effect.

After all, an object is red because it absorbs light that isn't red and reflects light that is. So a red object near a plant guarantees that more red light strikes the plant.

Is that why it works? No clue. But it's possible.

hooked,

That's what the companies use to sell the red plastic. It is supposed to reflect red light back (to the bottom of the plants and leaves). Red mulch is supposed to also help.

Mike

I know another "trick":

When the plants set fruit, back off on the nitrogen and up your EC using premixed Epsom Salt (MgSo4) instead of nutrient concentrate. Tomatoes like the extra magnesium and need the nitrogen only for "vegetative" growth.

Also, back off on the moisture in general. Low water signals the plant to hurry up and set fruit; it's a "survival" thing, I think.

"the companies use to sell the red plastic"?

You almost make it sound like there's some Red Plastic Consortium out there trying to convince people they need more red plastic than they really do.

Also, I'd be cautious about lowering overall moisture during fruiting. It's not likely to cause a problem unless it fluctuates, which can cause splitting. It depends on what method you're using to grow. If it's DWC you can't really cut back on water.

>> "the companies use to sell the red plastic"?

You almost make it sound like there's some Red Plastic Consortium out there trying to convince people they need more red plastic than they really do. Have you read the brochures? They ARE trying to convince people they need it!

Whether it works or not aside - it does help control weeds and retain moisture not that this is really a concern with hydro!

Mike

Brochures?

The idea of red stuff making tomatoes ripen faster goes back way beyond any commercial product for that purpose. People used to tie red ribbons to their tomato vines before my grandma's day.

No one's sitting around trying to think up new ways to market red plastic specifically. People are simply trying to figure out how they can make money. Gardeners will buy red things if they believe that doing so will help their tomatoes. It seems to work so it's not a hard sell.

I know the product you're thinking of and it seems to me that it could go either way as far as being helpful. But it's not some vast conspiracy or con. It's just trying to meet a demand with a supply.

Oh, and I thought of something else that can be done for plants that stubbornly don't want to ripen. I do it at the end of the year when I start to worry that frost will kill the few green ones left. Simply cut off as much vine as you can that has tomatoes still on it and then hang it upside down outside out of direct sunlight. The plant will make a last-ditch effort to ripen the fruit with the reserves it has left. You can even pull the whole thing up by the roots and hang it like that (more root, more energy, more ripening power) if you have the room to do it.

Well, the general rule for lighting is that blue encourages vegetative growth and short, stocky, leafy plants while red encourages flowering/fruiting and a longer internode length. The peer-reviewed research seems to back this up. It's interesting how much the frequency of light seems to affect how plants respond. For example, I've read several papers on plants grown with low-pressure sodium lights. Low pressure sodium is nearly monochromatic yellowish orange -- a frequency that's generally considered suboptimal for photosynthesis. But plants grown under LPS still grow; they just end up starkly chlorotic. Yields are generally somewhat reduced (although it depends on the plant; some are unaffected), and the leaves generally have a higher starch content.

Red objects very well could help encourage tomato plants to fruit. But red lights would be even better. To plants, red light says "go all out on fruit/seed production", because they get more of it in the fall -- right before winter arrives to kill them.

Gee, this "red" topic kinda got out of hand. :O)

So, while we're all in the mood, I found an LED bicycle tail light at Harbor Freight and Tool (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=98417) for about $5. I got one and am leaving it on all day, pointing at several "test" tomato plants. I think the battery should last the entire growing season.

I'll just hide and watch to see if it makes any difference and report the findings here (if I remember that long.)

That's not much light, as far as plants are concerned; I'm not even sure they'd notice... but hey, can't hurt. :)