Linder's Garden Center

Starting Seeds Indoors & Outdoors

Starting Seeds Indoors

The first step to starting seeds indoors is to determine when to plant the seeds. There are two major factors to consider:

the average last frost date for your area, and
time needed to grow seedlings (ie. time needed to germinate seeds until seedlings are ready to transplant outside)

First determine the average last frost date at your garden site. This can range from May 2 in the southeastern Metro area to June 11 in the Arrowhead region, and can further vary a week or more earlier or later depending on local weather, moisture and topography. You may also consider getting a jump on the season by using season-extending devices such as cloches, water tubes or pre-warming the soil by temporarily laying a sheet of black plastic.

Next, check the back of the seed package for suggestions as to time needed to grow seedlings to transplant stage.
Note the time needed to grow your seedlings to transplantable size and start them at the appropriate time. Seeds started too soon produce thin, weak plants that often do not recover or produce well. It’s better to start a bit late, rather than too early, since plants should go outside as soon as they are big enough.

For example, tomatoes need about 6 to 8 weeks for this. If the average last frost date in your garden is May 7, you will need to start seed about the middle of March. If in doubt, wait a few days. Tomatoes and other seedlings planted too early and held too long often do not produce as well as those planted later or even those directly seeded into the ground.

The following few simple guidelines will help you grow healthy, sturdy plants that can reward your efforts with tasty vegetables or vibrant color.

First, and most important, read the seed package! There will be specific information about germination needs for each plant type. For example: some seeds need darkness to germinate; some will not sprout without light. Some seeds need their hard seed coats nicked or filed to speed germination; some may need to be chilled or soaked in water to start the growth process. Some seeds do not transplant well and are best planted directly outdoors a little later in the season.
Start with new or sterilized containers and a high-quality, sterile seed-starting media.
Plant seeds according to package recommendations and at the proper depth. Keep pots evenly moist but not soaking wet.
Soil temperature is important whether you are starting seeds indoors or directly into the ground. Optimum germination temperature should be listed on the back of the seed packet. A heat mat is a great tool if you are starting seed indoors; a soil thermometer is very helpful in determining when to plant seeds or transplant started plants outdoors. Soil that is too cool may seriously delay growth or cause the seeds and roots to rot and fail entirely.
Cover to maintain high humidity and place in a warm location. (70 to 75 degrees for most plants)
Remember to check seedlings daily for moisture, humidity and light.
As soon as 70% of the seedlings have emerged, remove the cover and move to a slightly cooler location.
Good air circulation is very important. This reduces the risk of diseases, particularly ‘damping off’. Running a small fan periodically near your small plants is helpful.
Be sure to provide plenty of light as soon as the first tiny leaves appear. A florescent light 3 inches above the seedling tips is ideal. Leave it on for 12 to 16 hours each day. Otherwise set them in your brightest windowsill. Provide at least 6 hours of darkness as well.
Begin fertilizing seedlings weekly with quarter-strength balanced fertilizer when they have their first ‘true’ leaves.
When the seedlings are about 2 inches tall and have at least one pair of true leaves, they can be moved into individual pots. Handle them carefully, lifting with a small fork or pencil tip. Try to not touch the fragile stem with your fingers; any bruise invites disease. Adding a bit of timed-release fertilizer to the potting mix is a good idea too.

Be sure to ‘harden off’ your little plants gradually.

Begin setting them outside for an hour or two any time the air temperature is above 55 degrees. Start in a sheltered mostly shady spot or on a cloudy day, gradually increasing the sun exposure and duration over the next week or two.
Soil temperature should be in the optimum range for your plants and night air temperature should suit as well before you transplant seedlings outside. Cool-season plants such as broccoli, onions and pansies can be set out when soil temperatures reach 55 degrees and air temperatures at night stay above 40 degrees. Warm-season plants such as tomatoes, peppers and impatiens need soil temperatures above 65 degrees and night air temperatures consistently above 55 degrees. Planting these out in cooler conditions can stunt the plants, sometimes beyond recovery.
Transplant into your garden in the evening or on a cloudy day when there is little wind. Water the young plants well using a ‘starter fertilizer’ according to package directions. Protect them from mid-day sun and windy conditions the first couple of days by shading with a light-weight ‘row cover’ fabric. A small wooden board planted on end on the south side of your seedlings will work too.

Directly Planting Seeds Outside

Determining when to plant seeds outdoors depends more on the actual soil (not AIR) temperature at the planting site than the calendar. Test this with an inexpensive soil thermometer, available at your favorite Garden Center (Linder’s!). The back of the seed package should list an ‘optimum’ germination temperature. Soil too cold will delay or even prevent seed germination, especially if the soil is also too wet. Cucumbers, for instance, will refuse to start at soil temperatures below 50 degrees F. and will be very slow to sprout in soil up to 60 degrees. Optimum germination temperature for cucumber ranges between 70 and 85 degrees; at that temperature, they should come up in 7 to 10 days.

With a little care, you can grow sturdy little seedlings on your own. Happy gardening!