Growing and Transplanting Seedlings

Growing and Transplanting Seedlings

Unless you live in a climate with enough of a growing season for many vegetables, growing and transplanting seedlings is a must. These seedlings take 6 to 7 weeks to be ready for transplanting outdoors. At this point of development they have  4 or 5 sets of permanent leaves. They are also sturdy enough to handle the harsher climate.

Transplanting seedlings of cabbage family

Seasons and Temperatures

Some examples of cool weather crops that we start in the Northeast are: the cabbage family (broccoli, cabbage, cauliflower, Brussels sprouts) and celery. These vegetables take 90 days on average to fully develop. Some of the warm weather crops that need to be started indoors, are the nightshade family (tomatoes, peppers, and eggplant). Also some of the squashes. Booth families are intolerant to cold weather below 50°F. These and various other vegetables have a long season and would need transplants.  See video on What kind of seeds should I buy?

Sunshine and Placement For Seedlings

A nice sunny windowsill is needed where the seedlings can be kept moist and get enough sun for 6 hours a day. This will allow you to grow the seedlings indoors. If you put them outside on a warm spring day they have to come in during the evening. If not, I recommend using a full spectrum grow light as an ideal alternative. Seedlings can be started in flats, small pots, or peat plugs. Read more about season extender’s.

Sterilizing the soil

The medium or potting mix is loose, t should also be sterile. There are many on the market that can be used. If you decide to make your own soil or compost mixture, you can bake it in the oven on trays covered with aluminum foil for about 45 minutes in order to sterilize it. You would place moist soil, (not overly wet), on the trays and stick an oven thermometer through the aluminum foil. Once the thermometer in the soil reaches 180°F then you would bake it for an additional 30 minutes. Keep below 200°F, as the soil can emit toxic substances that are not beneficial to the plants.

The same can be done in the microwave oven. Place 2 lbs. in containers or plastic bags and microwave for 2 ½ minutes.

Allow soil to cool off and then mix in peat moss or perlite to make sure you have enough drainage and looseness in the soil. To read greater detail starting your own seedlings


One advantage of transplanting seedlings is you have full control of the spacing. Also, there is no thinning to do as the thinning took place when you were starting the seedlings. You will have better control over pests like slugs, and cutworms, which will show up when they are placed outdoors. Summer seedlings can be kept in a cool shaded area in the middle of the day to avoid scorching by extreme UV rays. Water on a regular basis and move them around, if need be, to the proper light, unless you are using grow lights.

When do you place them outdoors?

Transplanting seedlings must first be hardened off. What this means is you have to get them used to being outdoors. Place them outside for longer periods of time and bring them in only if the temperatures are going to drop. The seedlings get used to having more sun, wind and a harsher climate than what they have been used to indoors. You need to toughen them up.

If they are spring crops and the leaves are formed, plant them once the temperatures in the soil are above 50°F. All dangers of frost are gone. If they are the summer vegetables; then I would wait until the soil temperatures are above 55°F and the evenings are above 50°F. See video on How to take care of seedlings

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