Starting Seeds
Rebecca Magron, Horticultural Consultant & Research Associate
Dated -
March 13, 2007

The Rutgers Master Gardener Helpline of Hunterdon County is open for the spring and summer gardening season beginning March 10 th. Spring and summer hours are Monday through Friday 9am to 12pm and Mondays and Wednesdays from 12:30 to 3:30. Stop by the office, located in the Rutgers Cooperative Extension office off Rte. 31, just north of the Hunterdon Medical Center, call the helpline at 908-788-1735 or email with your gardening questions.

As seed orders are coming in, gardeners everywhere are warming up their engines for the new gardening season by starting seeds indoors. There is a great sense of accomplishment that gardeners often get when they look at their gardens just before harvest and know that they did it all “from scratch”. That’s not the only reason to grow your own transplants: there is often a large selection in plants and cultivars when buying seed.

There are a few critical keys to success to growing your own transplants, including timing. Read seed packets carefully for the number of weeks to start indoors before setting out in the garden, then time your planting based on the type of seed and the average frost-free date (May 15th for Hunterdon County). For example, tomatoes and peppers like warm soil, so they are best planted outdoors no sooner than the end of May. You’re better off waiting another couple of weeks to start your seed if your tomato or pepper seed packet indicates only 8 weeks to grow a transplant. Overall, it’s better to be a little late than a little early. If the ground and weather are not ready when your transplant is, the wait may weaken your transplants.

There are different kinds of containers to choose from for starting seeds, including pots made of peat or plastic and flats. The most important consideration with containers is that there is adequate drainage and that they are clean. Using a well-drained, sterile moisture holding medium in your chosen container will help to avoid many problems. Soilless mixes based on peat moss are often ideal and easy to find.

Light, water and temperature are other critical factors for success. Seedlings need a lot of light to grow into sturdy transplants. Place the newly seeded containers or flats in a south-facing window that receives bright sunlight or use fluorescent lights. Lights should be 4 to 6 inches above the tops of the plants. Therefore, make sure the height of the lights can be adjusted easily. Most seedlings will grow well indoors at temperatures between 65 F and 70 F during the day, and slightly lower at night. After seeds are sown, the media should be kept moist, but not soggy. Water by using either a fine mist (to avoid displacing the small seeds), or by placing the containers in a shallow tray filled with water until the water moves up through the top of the media.

When seedlings are sturdy enough to handle (usually with 2 to 4 leaves), they should be transplanted into individual pots or thinned out by removing every other seedling if they were started in flats. Skipping this step may lead to weak, spindly seedlings due to overcrowding.

There are some common stumbling blocks to be on the lookout for: poor germination rates, spindly and pale seedlings, and seedling collapse. Poor germination can be caused by a number of factors, including either too much or too little water or using old seed. Also, some plants have special requirements for germination that need to be met, such as cold temperatures, so be sure to read the package for any special requirements. Spindly plants that are pale in color are usually either not receiving enough light, or temperatures are too warm. When seedlings collapse, over-watering and/or poor drainage is likely the cause.