I also have to start my early beans inside so there is no problem with transplanting them. But yours look ready for outside now. And from what you say outside isn't ready for them. I don't know your climate at all but I think you may have started them too early. Have you got anywhere very light and fairly cool where you could try to keep them ticking over until the ground is ready? Or maybe you'll have to start again.

This post was edited by floral_uk on Thu, Apr 24, 14 at 11:30

As someone else who gardens in a cold climate with a short growing season, I tend to agree with Flora - you started your beans too early. Your bean transplants are nearly ready to go into the ground, with warm weather still weeks away.

While I can direct seed most common beans here with a good chance of success, I use a lot of bean transplants. For heat-loving beans such as limas & yardlongs, transplants are virtually necessary in my area to ensure a good harvest. It is also good practice to use bean transplants if you have limited seed or temperamental Spring weather, since it overcomes cool-soil germination issues & means that nearly every seed which germinates will survive. And if growing a bean for seed, it increases the chance of getting dry seed before wet Fall weather arrives.

I would never use flats filled with soil though, for the reasons given in the OP. My preferred method is to use peat strips, with sterile soil less mix. Planted pot & all, this avoids root damage during transplanting. 32's work well for larger beans, and 50's for smaller beans & Vignas (cowpeas, yardlongs, adzuki).

To further lessen transplant shock, place a little sand in the bottom of the tray & nestle the peat strips into it after planting. Provided the sand is kept moist (but not overly wet) those long bean roots will not be air pruned, but will grow into the sand. At the time of transplanting, those roots can be gently pulled from the sand. Working quickly to keep the roots from drying out, gently coil them into the hole beneath the plant, then water immediately. I have had virtually no transplant shock using this method.

As a rule, I consider beans to be ready for transplanting when they have their first true leaf. This generally takes about 2 weeks, so I start bean transplants that much earlier than the recommended date for direct seeding. If transplanting is delayed by bad weather, I've held bean transplants up to a month before planting. Much beyond that, though, and they will become stunted.

For squash & cucumbers, I use the same procedures as above, except I omit the sand. It is worth noting that it takes an intense light source to grow beans, cukes, and squash indoors, or they quickly become leggy... shop lights are not up to the task (spoken from experience). If at all possible, those transplants should be placed in direct sunlight as soon as possible after germination.

I learned about using peat pots from Zeedman. I start them indoors about May 15 and as soon as they emerge, they go into the greenhouse where they get more light. Then at the age of about two weeks they go outdoors about June 1.

Some years our soil might not get up to 65 F until July so I also start some in potting mix but only 48 hours before they go outside. If the single roots are still short they transplant fine.

My daughter brought over some small sunflowers in pots about April 1st. She wanted them to stay in my grow light until they could go outside.....