Starting your own seeds is one of the most rewarding things a gardener can do. When everything outside looks cold, dead, and dreary, we can have some bit of life right inside our homes. Although it sounds easy, starting seeds inside can be challenging for a number of reasons. Our winter homes are not really ideal for plants that have certain environmental requirements not easily met.
The first mistake many of us make is not giving our plants enough light. It is tempting to think that a table set by a window should be more than enough, but it won’t be! Seeds need a lot of light to get going. Remember the new plant only has a small amount of energy stored in the seed to get started. It needs to photosynthesize to make more food for itself. This can only be done when there is adequate light for leaf growth and development. Too little light will force the plant to stretch in an attempt to reach a brighter location. This is called etiolation. As a plant stretches toward the light, the elongated stems are weaker and often your seedlings will end up flopping over. When transplanted outdoors as weather permits later in the season, the plants will be half laying on the ground and looking sad. This may also lead to disease problems. Fortunately, there are many light fixtures readily available to help seedlings grow. You can easily find one that will fit a plant stand or shelf in your house. There are even free-standing units available. Growing seedlings (or plants) near windows can set us up for a second problem – cold drafts. There is nothing worse for a plant than a cold drafty environment, which can lead to diseases or cold injury. Plant growth may be stunted. Seeds also need proper temperatures to germinate, and the microclimate near the window may be 10 degrees F cooler than the rest of your house (more on this in a minute).

Seeds need two basic things to sprout – water and temperature. If the temperature in the house is too low, the seeds might take much longer than anticipated to sprout, or they may not sprout at all. Many times when this happens, the gardener thinks there must have been something wrong with the seeds, when in fact it was the environment. So this leaves the gardener with three options, each of which has costs and benefits. Pick the one that is most favorable to your situation.
The first and easiest is to turn up your thermostat. This will make the overall house temperature warmer with the obvious disadvantage that heating the entire house could substantially increase your utility costs. Another disadvantage is that the heat may not be where you need it, heating the upstairs more than you would like, when you are starting seeds downstairs, for example. A better approach is to use a heat mat under the seed starting trays. These can be a bit expensive as you need both a mat and controller, but once you buy them, they should last many years. A single controller can sometimes operate multiple heat mats, so this may save you money in the future if your hobby expands. The disadvantage to heat mats is that they can only raise the temperature to about 10 degrees above ambient. So, if you start seeds in a 50 degrees F basement, the seed starting medium could only be heated to about 60 degrees F.

The best option in this case, would be to heat an individual room or space. If your home heating system does not allow you to do this, you could purchase an oil-filled electric radiator to bring up the temperature in your seed starting room.

The biggest mistake people make with any type of plant (houseplants, outdoor garden, seeds, etc.) is overwatering. People generally do not intend to overwater, but worry the plants will dry out. Wet, soggy soil, however, makes conditions ripe for disease. With seed starting, our biggest enemies are the fungal diseases known as damping off and botrytis. Both can wipe out a whole tray of seedlings in a few days. By the time you see it, it is usually too late to do anything. Letting the soil dry out between waterings is the best way to prevent these diseases. On the flip side, avoid placing plants right above a radiator or near a wood/pellet stove as these dry the air and may dry the medium too quickly. Humidity domes are useful when getting seeds to sprout as they keep hold the moisture in, but should be removed a few days after the plants are up to increase air circulation and avoid diseases.

The last problem has to do with timing. If plants are started too late, one could end up with tiny plants that will not fare well when placed in the ground. Plants should be tall enough to allow for planting and mulching, with a well-developed root system. Too little of a root system may cause the plant to wilt quicker and potentially become stunted or die if the gardener is not monitoring soil moisture. Also, the plant should be tall enough to have a thick layer of mulch placed around them. If the plants are too short, you may not be able to mulch properly and the plant could suffer from excessive weed pressure in the long-term, and drying out in the short-term.
If you start your plants too early, they will be gigantic and falling over by the time they are ready to be transplanted into the garden. Many times, there is mechanical damage to the plant from the resulting flopping over in their plant trays. Although this is less of a problem with tomatoes that can be planted deep, other plants do not benefit from that and will look unsightly. Overgrown plants not only out grow their pots and flop over, but they may run out of nutrients too. This results in the yellowing and possible loss of the lower leaves (in favor of the new growth at the tip). The solution is to fertilize your plants to correct the nutritional deficiencies, but then this exacerbates the over-growth problem.
The final mistake is not fertilizing. Our little seedlings are growing in very small amounts of soil. Although our “soilless mixes” often have some nutrients added in, they are only meant to help the plants get started. Once you have two sets of true leaves, it is a good idea to start fertilizing. Follow package directions as too much is just as harmful as not enough. There are some mixes that have fertilizer built in for feeding the plants a longer period of time, so know your medium and adjust accordingly. You really want to avoid getting to the point of a nutritional deficiency. This can stunt growth, affect the quality of plants, and alter the timing of moving outside due to inadequate height.
So, if you plan on starting some seeds (and I hope you will), there are a number of things to keep in mind. You want bright light hung near the seedlings, proper room and soil temperatures, and watering only after the soil dries out. Figure out when you plan to put your plants in the ground and count back the number of days needed to germinate your seeds (this is temperature dependent).

Also, do not forget the time it will take to move your seeds outside and gradually get them used to the sun and wind. This hardening off period takes about a week or two. A general rule is to start thinking about starting seeds around Saint Patrick’s Day, but this varies by plant species. The seed packets will tell you how early to start your seeds from your planned plant-out date. Fertilize your plants according to package directions when the second set of true leaves appear. And remember, no matter what methods you use to start seeds, keep a record of what worked and didn’t and adjust accordingly the following year.
Happy planting!
Matt Lisy