Homegrown: Transplanting seedlings

Linn County Extension Master Gardener Intern, Jane Schildroth, provided the following on transplanting seedlings:

It's almost spring and that means seedlings to many gardeners.  Starting your seeds is the first step; the second step is to transplant.  Not sure when to transplant?  The time to do this is when your little seedlings get their second set of “true leaves.”  Your plants will become stronger if you transplant them into a slightly larger cell or pot for continued growth until it's time to plant them in your garden or into outdoor containers.  Be sure to handle the seedlings by their leaves – not their stems, which are easily damaged.  Use a knife, small spatula or plastic fork to dig up the seedlings.

First, fill the new container (this might be a peat pot or even an empty, clean plastic yogurt cup with holes in the bottom) with transplanting mix and use your finger to poke a hole in the center.  Carefully place the seedling as far down into the hole as possible and gently move the potting mix firmly around the stem.  New seedlings can be transplanted a bit deeper than they were originally growing.  Water the new seedling very gently with a mister.

If you have planted many seeds in one larger container, you'll need to thin them out to one seedling per pot.  To do this, Iowa State University recommends using a razor blade to cut all but the most vigorous plant off at the soil line. They don't recommend pulling excess seedlings because you could damage the root system of the plants you want to save.  As the plants flourish, you may remove the growing tip by pinching off the top to encourage branching.  Pinching is only recommended for flowers, and not recommended for vegetable seedlings.

It's best to grow your transplants under artificial lights placed 6-8 inches above the plant.  Try to maintain a 12-hour cycle of light and darkness and when watering, keep the soil moist but not saturated.  Also be careful you aren't too vigorous with watering or you'll wash out the seedlings.  Using a soluble fertilizer in the water will encourage growth.  Be sure to follow the instructions with the fertilizer to avoid any problems. 

At this point, you're off to a great start for a great garden.  Once your transplants get a bit bigger and the temperatures outside begin to feel more like spring, it'll be time to move your tiny plants into the garden or other containers outdoors.  Look for tips to harden off your transplants in the next few weeks.  For more detailed information on seedlings, visit the ISU Extension website and check out

http://www.extension.iastate.edu/Publications/PM874.pdf.