Common Mistakes Made While Growing Seeds Indoors

illustration of common mistakes growing seeds indoors

Kelly Miller/The Spruce

You can save a lot of money by starting seeds indoors, especially if they live and turn into robust plants. But, growing seeds indoors and keeping them alive can be challenging. Avoid these 11 common mistakes, and you can greatly increase your odds of success.

Not Supplying Enough Light

Seedlings need a lot of light. No matter what anyone tells you, chances are that you do not have enough natural light in your house to grow robust seedlings. Even a south-facing window usually will not do. You can, however, use artificial light. Get some grow lights developed specifically for plants. Or, for a more economical solution, purchase some large fluorescent shop lights and put in one warm bulb and one cool.

Hang the lights from chains so that you can raise them as your seedlings grow. Keep the lights as close to the seedlings as possible without touching (2 to 3 inches). After your seedlings appear, keep the lights on for 12 to 16 hours a day. To make this easier, hook up a timer to turn your lights on and off automatically.

Woman potting plants in greenhouse
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Giving Too Much or Too Little Water

The amount of water you give your plants can make or break seedling growth. This is one of the most challenging parts of growing plants from seeds. Because seedlings are so delicate, there is very little room for error when it comes to watering. Keep your sterile, seed-starting medium damp but not wet.

There are a few things you can do to maximize the chances of getting it right:

  • Cover your container with plastic until the seeds germinate.
  • Water from the bottom. By letting the plants soak up water through the bottom holes in their pots, there is less chance of overwatering. Do this for 10 to 30 minutes, checking for moist soil every 10 minutes with a finger or knuckle at the top of the plant.
  • Check the wetness of your plant's soil at least once a day.
  • Buy a self-watering, seed starting system.
  • Make a free, self-watering seed starter.

Starting Too Soon

Chas Gill, who runs the Kennebec Flower Farm, says that one of the biggest mistakes people make when starting seeds is they start their seeds too early. Lots of plants do not like the cold and exposing them to chilly air and soil will stress them out. Stressed out plants are more susceptible to pests and disease. Most plants are ready to go outside four to six weeks after you start the seeds.

Planting Too Deep

Seeds are finicky when it comes to how deep they like to be planted. Some seeds need complete darkness to germinate, and others need some light. This information is usually on the seed packet. If there is no information, the rule of thumb is to plant seeds twice or three times as deep as they are wide. This can be a challenge to figure out, but if you are not sure, err on the shallow side.

For seeds that need light to germinate, make sure that they are in contact with your seed starting medium but not covered. To do this, first press the medium gently down to make a firm surface. Then place your seed on top of your medium and gently push down, making sure the seed is still exposed.

Womans hands planting
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Taking Plants Outdoors Too Early

There is no benefit in a tough-love approach to seedlings when they are young. They will either instantly die or become weak and then fail to thrive. Even the most stalwart plants, when young, need a huge amount of coddling and attention.

When your seedlings are about ready to go outside, you need to prepare them for the transition. The process is simple, though it can be time-consuming. The process of hardening off exposes your plants to the elements gradually. Put your seedlings outside for more time every day over 6 to 10 days, depending on your patience, the outside temperature, and the fragility of your seedlings. This gradually prepares them for the wind and sun.

Starting Too Many Seeds

Starting modestly is the way to go. If you buy many more seeds than you can start, it will become much more difficult to nurture them into adulthood. Work on self-restraint in this area, particularly if you are a beginner. You can always do more direct planting in your outdoor containers when it gets warmer.

Keeping It Too Cool

For seeds to germinate, most must be kept warm from 65 to 75 F. A favorite place to do this is on top of the refrigerator. There are special, warming ​seedling mats that you can buy to put under your seeds. You can also use a small heater set on a timer placed next to your seedlings. You will only need to worry about this until the seeds sprout. After that, most can tolerate fluctuating temperatures (within reason). Whatever type of light you use, natural or artificial should produce enough heat to keep them happy.

Poor Labeling

Use popsicle sticks and write the name of the seeds and the day you planted them in permanent ink. Stick them into the soil next to the seeds you’ve planted or label by row. When it comes to plant labeling, use permanent ink Sharpies. Also, take photos to help you keep track of your plants.

Close-up plant nursery with label in house
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Giving Up

Starting seeds can be a laborious process. It takes dedication, attention, and time. That said, one of the most satisfying benefits of this labor of love is eating a tomato that you nurtured from day one. The biggest mistake in starting seeds is giving up, even if you have made a few mistakes.