seed germination

Patty Ferguson

New seedlings emerge from trays.

If you’ve ever planted seeds expecting to see them emerge in a few weeks, only to be disappointed with no sprouts or sprouts that die, then you know the difficulties of germinating seeds.

Seed germination is the process of a plant emerging from its seed or shell. For this to occur, certain conditions must be met. Gardeners have the option of direct-sowing seeds outdoors, but for some plants, indoor planting offers a safer environment where optimum growing conditions can be met.

Starting seeds indoors

While there are some exceptions, seeds generally need oxygen, water, suitable temperatures and light to sprout.

There are several methods for seed germination, including using a paper towel, rock wool, water or soil as a medium to sprout seeds. This article will cover the soil method, which is the most common.

Start with new seed-starting soil, a fine mix available at garden centers. You don’t want to use soil from your garden or reuse potting soil. It can contain diseases or toxins that can kill your seeds. Using a sterile, high-quality seed-starter mix is essential to avoid fungal and bacterial diseases.

You can use disposable containers made for sprouting seeds, but they must have adequate drainage. If you are reusing a container, it’s important to scrub and disinfect it with a minimum 10% bleach to water solution.

Pre-moisten the soil thoroughly before spreading it in the container, but do not over-saturate. Over-saturating can remove the oxygen from the soil.

Before planting, it’s imperative that you read the seed packet. If the packet isn’t specific with planting instructions, look it up online (how to germinate marigold seeds, for example). Different seeds have different needs. As an example, large seeds might need to be soaked in water for 24 hours.

Certain seeds are covered in a tough coating or shell that makes it harder for moisture to penetrate. A gentle nicking of that layer is key to enabling germination. The process is called scarification. Some of these plants are nasturtiums, morning glory, moon flowers, turnip and some peas.

Other seeds require exposure to freezing temperatures before germination can occur. This process, known as stratification, may require a visit to the fridge or freezer. Some of these are aster, sedge, black-eyed Susan and anemone.

There are plants that need to be kept humid with a change in temperature. For instance, some seeds need to be kept warm and moist during germination, followed by a period of being cool and moist, or the other way around. This imitates natural conditions and tricks the seeds into sprouting. Two examples are angelica and viburnum.

And some seeds require light to sprout, including begonia, columbine, geranium, petunia, impatiens, poppies and snapdragon.

Potential problems

Being aware of potential problems is a great way to avoid them. These are some of the most common problems people have with seed germination, and how to avoid them.

  • Incorrect moisture levels: Keep the seed moist but not boggy until your seedlings sprout. You can do this by misting your seeds after planting, then covering them with plastic wrap, or a clear lid. Never let the soil dry out.
  • Wrong temperature: Seeds don’t always require warmth. Different seeds germinate at different temperatures. Heat mats can help, but some seeds prefer much cooler soil. Read the seed packet or look for a chart online.
  • Old seeds: Using fresh seeds is critical to ensure good germination. Seed packets have expiration dates to let you know when they’re past their prime. And keeping seeds stored appropriately is the best way to keep them fresher for longer.
  • Finicky seeds: Most packets have information about the length of time a seed will take to germinate. The listed time frame is under ideal conditions. Be prepared to give germination a few extra weeks.
  • Special light requirements: Some seeds don’t require exposure to light to germinate. Heat lamps and grow lights are mainly meant for your seedlings. Once your seed has germinated, it will require light to grow.
  • Wrong depth: Seed pack should give a planting depth. Many seeds just sit on the surface and aren’t covered in soil at all. Vermiculite is excellent to lightly sprinkle on top of soil to help with moisture while allowing light to still get through.

Now that you have the basics, it’s time to get going with your own seedlings. Happy planting.

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