How to Start Seeds Indoors: The Complete Guide

Gardening can be an expensive hobby if you purchase all your plants as potted nursery specimens. Fortunately, most vegetables and ornamental plants can be started from seeds, which offers a much less expensive way to populate your garden. Each type of plant has its own particular needs for starting seeds indoors. Seed depth, type of growing medium, and water and light exposure needs will all vary depending on the species. But the general process is the same for growing seedlings you can transplant into the outdoor garden.

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There are a few basic steps to starting most types of seeds indoors before they turn into seedlings that are ready to be planted outdoors:

1. Choose the right container to start off the seeds.
2. Select the right spot with enough light for seeds to germinate and augment the space with grow lights and a heat mat if necessary.
3. Keep seeds moist, but not too wet.
4. Gently prepare seedlings for the outdoors by hardening them off if you plan to move them into your garden.

Now that you know the road ahead, here's exactly how to start seeds indoors, with pro tips every step of the way to ensure success. You'll be eating fruits and vegetables and enjoying flowers in no time!

The Spruce / Heidi Kolsky

When to Start Seeds Indoors

A package of seeds will usually announce if the plant should be started indoors, with instructions that include phrases such as "start indoors eight weeks before last expected frost date in your area." A simple internet search will tell you the date of the expected last frost in your area. Count backward to, for example, eight weeks before that, and that's the date you should start your seeds.

Not all plants should be started by seed indoors because they are better grown by sowing seeds directly in the garden. Root vegetables, like radishes and beets, and row crops, like beans and corn, simply don&#;t transplant well. Other crops&#;like cucumbers and zucchini or flowers like zinnias and sunflowers&#;germinate so quickly that starting by seed early has no real advantage. To direct sow seeds, follow the seed packet&#;s instructions, which provide a planting date range based on the last frost dates in each USDA hardiness zone and recommended soil temperatures.

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Everything You Need to Know About Starting an Edible Seed Garden

Reading a Seed Packet

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The printed instructions on the back of a seed package will give you a lot of information on how (and if) you should start the seeds indoors. These elements are among the most important information to look for:

• Planting time: Most seed packets will tell you quite clearly if the seeds can or should be started indoors. For some species (tomatoes, for example), it is virtually mandatory to start seeds indoors in cold-weather climates. For other species it may be optional, and for other fast-growing species, there may be no indoor starting information at all&#;these plants are best planted directly in the outdoor garden.
• Days to maturity: This will tell you how long the plants take to produce edible fruit or ornamental flowers. Some tomato plants take as much as 100 days to reach fruit-producing maturity. If you want tomatoes in July, this means the seeds need to be started in early April.
• Light and water needs: The seed package will tell you if the seeds need lots of light. If so, starting them indoors may require a fluorescent grow light&#;or you may need to reserve your sunniest window for seed-starting.
• Soil needs: Some seeds can be started in ordinary potting soil, while others require a porous, fine-grained seed-starting mix. The package may also suggest an optimal soil temperature for seeds to germinate. Seeds that require 70-degree soil to germinate will clearly need to be started indoors in cold-weather climates since the soil does not get adequately warm until late into May.

The seed package will also give a wealth of other information, such as days to germination, fertilizing needs, planting depth, and transplanting techniques.

Before Getting Started

There are many good commercial potting mixes available that are suitable for starting seeds. Although they may be called "potting soil," they actually contain no garden soil at all. Instead, they are soilless mixes containing materials such as peat moss, perlite, vermiculite, compost, and more. This ordinary potting mix is fine for starting many seeds.

Some seeds&#;especially those that are small&#;may do better in what is known as a seed-starting mix. Seed-starting mix is a special form of soilless potting mix that is especially porous and fine-grained. It omits the organic materials found in standard potting soil. This is because seeds do not require the nutrients provided by organic material to germinate and sprout.

For many plants, a seed-starting mix is the best choice, because the organic material in a standard potting mix can lead to fungal problems. Avoid starting your seeds in outdoor garden soil, which can become compacted. And outdoor soil often contains weed seeds and disease pathogens that interfere with seeds germinating and sprouting.

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