Talking Green: When do I transplant?

Hi again,
Transplanting. I consider this different from pricking out because this is something you do either when the plant has gotten too big for the cell or it is time to put the plant into pots or the ground. You don't need to transplant really until the plants have outgrown their current home but you can transplant sooner than that. I like to wait until the plants have grown at least a few inches tall or they need more room for their roots because each time I transplant, it seems to shock the plant a little and they have to get used to their new home so I try to avoid it if I don't need to. I need to mention here that it is incredibly important to give a plant sufficient room for their roots to grow. Otherwise a plant will become stunted when it runs out of room for it's roots. When this happens it is generally called root bound and you can tell by looking at the roots and they are running in circles around the edge of the pot. With young plants though, it can be difficult and sometimes next to impossible to pull them out of the cell to check the root system. So the best way to know is to watch for roots poking through the bottom of the cells or if it seems that the plant has sort of stopped growing. These are both indications the plant is starting to run out of room. A plant can have roots poking through the bottom of the cell and not be root bound because they send roots straight down first but if roots have reached the bottom, chances are the roots will start to circle around the pot soon. It is best to transplant before a plant gets root bound. Giving a plant sufficient room for roots can really affect the size of the plant. I did a little experiment last year to see how much it would affect the plants and I left some marigolds a little longer in the cells and transplanted others and within a couple of weeks, the plants that were transplanted were nearly double the size. This is in no way a scientific experiment and just something for fun but it shows that giving a plant enough room is very important.
Also depending on where you are planning to transplant to can make a difference when to transplant. If you are planning to transplant in to your flower bed then the bigger the plant, the better I think. The more mature an annual is, the tougher it is. Also it is important to wait until it is warm enough that it isn't freezing over night any longer and the plants have been hardened off. I will talk about hardening off in the next post. Have fun!