You can pot-up at any time. I often do them at the cotyledon stage, others wait for the first set of true leaves to develop. Into what - any of the good soil-less growing mixes available. Some contain a small amount of fertilizer, some don't. Some swear by Miracle Grow Potting Mix, some hate it.

A popular one mentioned here often is ProMix BX, Sta-Green is another, Fos Farms is another brand. It all depends on what is available to you locally.

Dave

Here is a link that might be useful: brands of soilless potting mixes

Hmm...I suppose I need clarification. Is there a real difference between my seed starting mix and the different potting up mixes? I mean, one is coco-fiber (seed starter) but then you refer to "soil-less growing mix." Is that not the same as my seed starting mix?

No very different components. The soil-less potting mixes are made with peat, vermiculite, perlite, a low-dose nutrient charge of some type, and a wetting agent. Many also add bark fines to improve drainage and some include worm castings for further nutrients. Some also add beneficial bacteria to stimulate root development. All depends on the brand.

Coco coir is just that - shredded coconut fibers. No nutrient value and poorly draining. Ok for germination but provide nothing for growing on.

Dave

Looks like tomorrow or Thursday holds a trip to the hardware store then. I appreciate the input.

Brett - If they are already in 6" styrofoam cups, leave them alone until you're ready to put them in the garden.
John A

Yeah, what John A said. If the normal size drinking cup is full close to the top there is no reason to transplant. I have been using this method for several yrs with MG Seed starter with great results. Six to eight weeks after germination they are good to go...hardened off of course. I have 45 of them sitting on a chest of drawers under saran wrap as we type.

Unless you see roots growing out of the holes, leave them in the cups. They should be sufficient.

Brett what is 10-5-5 potting soil ?

Tomato seedlings do benefit from being transplanted (potted up) at least once before planting out. This stimulates roots, especially if you plant them more deeply (up to the first set of true leaves). If you don't want to buy larger pots, you can use 16 ounce cups like they sell at fast food places or even cut off half gallon milk/juice cartoons, with drainage of course. At the rate they are growing, they could be 18 inches tall in another three weeks. Generally you want the soil to be made of larger particles than seedling mix, so it drains very well. I prefer a mix that doesn't have fertilizer or moisture control in it. You want to let it dry out more between waterings and you want to be able to feed it with a balanced fertilizer at half strength or less.

Right on Ohiofem. Also, Brett, don't worry about higher nitrogen on younger plants. 3-1-2 is best for vegetative growth, the time nitrogen is used the most. Once fruiting starts, reducing nitrogen input causes energy generated by existing leaves to support the fruit rather then more leaves.