On April 9th, stuff in the cold frame looked like this. Two weeks later, growth has been pretty significant.
Now we are at the tricky part of the year where you have to decide what track to take. Once plants get this big, you have three choices, hold, pot up, or plant.
Holding: Holding means keeping them in the same pot for now. The benefits are that they are less likely to outgrow your cold-frame before you get them in the ground. The negatives are that plants outgrowing their pots are needy. Really needy. They need more water (often daily) and are more vulnerable to vitamin deficiencies. Notice how the plants in the lower right hand corner are very light green? They are hating on their cramped toes and want a bigger pot or a bit of nitrogen. The biggest negative to holding too long is that you can stunt the plants and sometimes they won't recover from it.
Potting Up: Potting up means transplanting to an bigger container. It need not be a pot. Big Gulps with holes cut in the bottom work great and are Earth Friendly! The benefits of potting up are that the plant continues its rapid growth and you get a bigger plant going in the garden. The negatives are that it's work to pot up, bigger pots take up way more space and each time you transplant a plant it may get shocky. Shocked plants stall their growth for a period of time. For tomatoes that period is short for me so I pot them up several times. For peppers, they will pout for a couple of weeks, so I only do it once to them.
Planting Out: Planting out refers to getting the plant into its final location in the elements. Whether it be a container or garden soil, a planted out plant is more vulnerable to the elements and hungry varmints. Planting out early means you may get an earlier and possibly more productive harvest or it may get you a cold shocked pouty plant that starts recovering in late June. Planting late delays the harvest and may decrease the overall amount your plant produces that season.
There are all kinds of rules that exist as to when you should do any of these things. You can follow moon phases, farmer's almanac's, relatives rules or Tommy Skilling the weatherman. Me? I never put all the eggs in one basket. Thus, this weekend will involve a bit of holding, a bit of potting up and if the rain allows, a bit of planting out too.