Young tomato seedlings growin in tray with plant markers

How to Grow Seeds Indoors – Tips for Success

It can be so rewarding to grow seeds indoors and then to transplant into the garden. Following our guidelines below will provide you with healthier plants and an increases harvest.

There are several reasons that you might want to grow your own vegetables or flowers from seeds:

  • You can start them off early, when it’s still too cold outside, then transplant into the garden when the weather warms up.
  • The harvest season can be extended. Many vegetables will produce a crop weeks earlier if started indoors
  • You can grow from seeds new or unusual specimens that are not available in most stores
  • Planting seeds in the home garden can give you an endless choice, you get to choose what variety you eat, and when you eat it,
  • Plants can be expensive so you can lower the cost per plant if you grow them from seeds; this is particularly useful if you have a large area to fill.
  • A controlled indoor environment will produce healthy plants, and you will reap the benefit from these all season long
  • You can grow seeds purely for pleasure and experience the complete life cycle of a plant

Annuals and vegetables are easy to grow and germinate quickly so you can start with these if you are a beginner. Most seed packets have a lot of information on the back which can help you, for example before you can grow certain seeds they need to be soaked. Make sure you read and follow these instructions.

Seed Starting Containers

Any shallow container which is about 3” deep can be used to grow seeds. Egg cartons, yogurt pots, Jiffy Pots or custom-made Seed Flats are all suitable as long as they are clean; wash used containers with a mild bleach solution to disinfect them. Any pots you choose should have holes in the bottom for drainage. Sit the containers in a tray to catch any overflow during watering.

Seeds being planted in a plastic flat
An easy way to start a lot of seeds is to plant a row of seeds in a plastic flat

Potting Mix for Planting Seeds Indoors

Use a soilless potting mix which will be predominantly sphagnum moss. Also called peat moss, this growing medium is light, drains well and is water retentive. Never use garden soil which could be infected with weed seeds, diseases or insects. It also tends to be heavy, and you will find that it will compact after several waterings. Fertilizer is not required at the germination stage. Mother Nature has provided its own fertilizer inside the seeds shells.

Planting Your Seeds

  1. Fill the containers with potting mix, tap down and dampen.
  2. Plant the seeds that you wish to grow in the mix check the instructions for the depth or any special preparation, for example soaking.
  3. Cover with plastic to retain heat and moisture as 60-75 degrees F is the optimum temperature for germination. A Heat Mat can be used to provide bottom warmth to enable you to grow seeds successfully. Some people just put them by a fireplace or an oven or indeed any other warm position.

You should start to grow the seeds about 6-8 weeks before the last frost in your area. Try experimenting with dates as some plants require more time while others like lettuce and cabbage require less. Is also a good idea to stagger plantings to extend the harvest and avoid having too much at the same time, though your friends and family may be the winners here!

Germination: When Will Your Seeds Sprout?

Germination times varies depending on the type of seed grown. This information will almost always be found on the packet. The first leaves that appear on your baby plants are called cotyledons and are not true leaves but food storage cells. At this stage remove the plastic, give them light and keep them moist. When the true leaves appear, it is time to add a bit of fertilizer to encourage good roots and healthy growth.

2 young tomatoes growing in a tray
On this young plant, you can see both the first leaves (the oblong ones) and the “true” leaves which resemble the leaves of a mature tomato plant

How Much Light Do Seedling Need?

As the seedlings grow bigger, they will need 12-18 hours light. The best way to achieve this is to use a fluorescent or high-density light as there may not be enough sunlight, especially in spring.

Th plants can be ‘potted up’ when a couple of inches tall into 3-4 inch pots to allow the roots more room to develop. If they are getting tall and lanky, it probably means they are not getting enough light, and they may also need thinning out. A useful tip to encourage strong plants is to lightly ruffle them with the palm of your hand once or twice a day.

group of young seedlings growing in small pots sitting in a tray
When not given enough light, young plants may grow too tall too fast, as they stretch to find the light.

Damping Off: A Common Problem

One fungal disease that you may face when you grow seeds is called damping off and is usually caused by excessive moisture or poor air circulation. To avoid this use a sterile soil mix and don’t grow too many seeds in a small area. If you encounter the dreaded damping off, scrape the mold off the surface. Then cover the soil with finely crushed sphagnum moss or using a small fan to increase air circulation.

When you grow seeds indoors, you need to harden them off, that is acclimatized them gradually to outdoor conditions before you plant them outside in a prepared garden bed.

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