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Starting Seeds Indoors

By: Eric Vinje Published: 14 Jan, 13 Updated: 3 Aug, 19

Growing plants from seed just might be the second most enjoyable act of procreation you'll ever experience.

By Bill Kohlhaase, Planet Natural

In addition to the fun — starting seed is the perfect cure for those late-season winter blahs — raising your own plants offers practical and aesthetic benefits. You’ll get an earlier start to your garden and you’ll be able to raise vegetable and flower varieties not offered as starts by your local garden store or nursery. You’ll have plants that are healthier, vigorous, more disease resistant and ideally chosen for your personal growing conditions. And you’ll be able to choose vegetables that taste better, produce earlier and store longer. You might even save some money.

Often a single start from your local garden supplier costs as much as a whole packet of seed. Plus, the satisfaction you’ll receive watching plants that you started yourself go into the garden is priceless. Your kids will love watching the miracle of growth from seeds they started themselves… and they’ll learn something as well.

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What’s a Seed?

A seed is a potential plant, an embryo surrounded by nutrients and food to get the seedling started. When the seed encounters the right combination of moisture, light, air and temperature germination begins.

Seeds can be hybrids or heirlooms. Heirloom seeds have been handed down from generation to generation and are naturally pollinated. Hybrids are plants that are artificially cross-pollinated in an effort to combine the best qualities (taste, vigor, disease resistance) into a single plant. The seeds produced by hybrid plants are usually not true in the genetic sense; in other words the plants grown from them usually revert back to one or the other of the hybridized plants. Heirloom plants produce true seed that produces the exact plant from which it was harvested.

Both types of seeds have their supporters. Heirloom seed supporters say they are more natural and produce a better tasting product. Hybrid seed champions say their plants are more vigorous and disease resistant. Many gardeners combine both types of seeds in their gardens. For a good discussion of the pros and cons of hybrids and heirlooms see Heirlooms vs Hybrids.

Choosing Seeds

When selecting seeds to grow inside, look for varieties that are adapted to your region and buy seeds packaged for the current growing season (seed germination percentages decrease over time). If you have last season’s seeds or seeds you’ve gathered yourself, check their ability to germinate by rolling several – say ten for statistical purposes – in a moist cloth or paper towel, inserting the towel in a sealed baggie (to prevent evaporation) then checking for germination some 36-72 hours later. Don’t waste your time on seed with poor germination rates. Start fresh.

Look for heirloom garden seeds best suited to your growing zone and the conditions in your garden space. Do you need greens that are slow to bolt or resistant to mosaic or other viruses? Consider the variety, yield and plant size you prefer. Do you favor pole beans or bush? Is your garden space more suitable for regular squash and cucumber plants or smaller, compact varieties? Consider which vegetables you prefer and which you will use most of. Do you want to experiment with a variety of different plants or focus on just a few? Remember, when those once tiny seedlings are transplanted into your garden they will take up more and more space. Whether you’re doing rows or square foot gardening, in large plots or small, it helps to have a garden plan. Consider sun exposure for heat-loving plants, shade for those plants with a tendency to bolt. Design your space to give yourself easy access to your crops. A little planning before seed starting will save you trouble and wasted seedlings down the road.

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Author

Eric Vinje

Eric Vinje founded Planet Natural with his father Wayne in 1991, originally running it as a grasshopper bait mail-order business out of a garage.

Eric is now retired, but is still a renowned gardener known for his expertise in composting, organic gardening and pest control, utilizing pesticide-free options, such as beneficial insects.

Eric believes when you do something good for the environment, the effects will benefit generations to come.

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All the heirloom garden seed offered by Planet Natural is non-treated, non-GMO and NOT purchased from Monsanto-owned Seminis. Planting instructions are included with each packet and shipping is FREE. Let’s grow together!

If you buy seeds well ahead of when you plan to sow them, it is best to keep them in a sealed plastic bag or glass jar in the refrigerator. This will help ensure their integrity and keep them from germinating too soon.

Starting Times

To figure out when to start a seeds indoors, think backwards. First, find out when the last frost occurs in your area. You may need to call your local Cooperative Extension Service. Local garden clubs and nurseries can also offer advice. Then, check the seed package to see how long before the last frost a particular seed should be planted. A North Carolina Cooperative Extension Service article titled “Starting Plants from Seeds” has a helpful calendar of start dates for most common vegetable and flowering plants.

Many seeds should be started 6-8 weeks before the last frost, others 12-14 weeks. Be cautious about starting them too soon. Seedlings that spend too much time indoors may end up weak and spindly. Not all seeds should be started indoors. Check for the recommendation “sow directly into the garden” on the seed package. Flowers such as clarkia, columbine, California poppies, sunflowers, nasturtiums and others will do better if they are sowed directly in the ground. The same holds true for lettuces and spinach, which grows quickly and can handle some cold weather.

How to Sow

Starting seeds indoors isn’t all that different than outdoors. But maintaining your indoor starts requires a certain amount of care and discipline. Using appropriate containers and proper growing mediums as well as keeping a careful eye on growing conditions will reward you with healthy vigorous plants for your garden.

Start with clean containers that have good drainage. Almost anything can be used as a container: egg cartons, yogurt containers with holes drilled in the bottom, commercial seed starting trays, milk cartons, or whatever else you find lying around the house. Used pots or anything that might carry fungus or disease can be washed with a solution of 1 part bleach to 10 parts water.

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Once your containers are clean and holes are drilled or poked for drainage, it is time to choose an organic growing medium. Don’t use garden soil. Even if it doesn’t contain weed seeds, insects or disease, it compacts too easily and won’t allow tender root systems to develop fully. You can use a mix of garden soil and loam, peat or other growing mediums if you first sterilize the mixture by baking it in the oven for two hours at 170-180 degrees. There are many good commercial mediums you can purchase or you can make your own. Since the seeds already have enough nutrients packed into their endosperm to get started, any soilless mixture you choose need only to be sterile, not nutrient-rich.

Simple Mix: Add 1 part loam and 1 part perlite or clean sand to 1 part moist peat or leaf mold.

Cornell Mix: Mix together 4 quarts of shredded sphagnum or peat moss, 2 teaspoons of ground limestone and 4 tablespoons of an organic 5-10-10 fertilizer.

Loosen and dampen the soil before putting it into the containers to ensure moisture uniformity. Water the soil a bit more once it is in the containers until it is about as wet as a damp sponge.

Many gardeners prefer using pure vermiculite as a growing medium. It is sterile when first purchased and offers good drainage. Milled sphagnum moss or peat moss is also used because it inhibits the damping off of young seedlings. It should be well soaked before use as it will not retain the moisture from simple watering. Plants started in either of these mediums will need to be transplanted to containers with soil mixture or into the ground shortly after the first true leaves — not the cotyledons — have been established.

Fill the containers about 1/4 inch from the top with the growing medium, but do not pack it down. Tap the containers on a table or hard surface to help the medium settle. Use your fingertips to gently firm the soil.

Next read the directions on the seed package to determine how deep to sow the seeds. Generally seeds should be sown four times as deep as they are wide. Some seeds require soaking or chilling before sowing. Larger seeds, such as squash, beans and peas will germinate more quickly if soaked overnight. Don’t soak seeds for more than 8 hours as they may rot or become prone to fungus.

Smaller seeds can usually be broadcast on the top of the soil and covered with a thin layer of growing medium. Larger seeds can be separated and planted individually. Use the end of a pencil to create a small hole, drop in the seed and cover. Not all seeds will germinate and not all germinated seeds will survive so plant at least three seeds in each container.

Moisten the soil with a mister to make sure the medium is moist, and to help make contact between the mix and seed.

Be sure to label each container. Strips cut from a yogurt cup make sturdy and waterproof labels; use an indelible marker to write plant names and stick them in the soil. It’s amazing how quickly you can forget which seeds are where, even when you are sure you won’t. Plus, many seedlings look alike despite the fact that the mature plants are quite different.

Slide your containers or flats into plastic bags to keep the moisture level high and even. The outer coating of the seed must get wet to break down and start germination. However, too much moisture can lead to the growth of molds and fungi, so allow airflow under the plastic bag. Keep the mix the consistency of a wrung out sponge. Rather than use plastic bags, you can make individual greenhouse tops for your containers using plastic bottles or from clear, take-out container lids.

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Keep the containers in a warm (65-70 degrees), draft-free location. The top of the refrigerator can work well, or purchase a heat mat specially designed for starting seeds. Check the containers daily because as soon as you see the start of a seedling, they will need to be moved to a well-lit area.

As soon as the seedling emerges, remove the plastic bag or covers and place the containers in a spot with good air circulation. The seeds will also need an adequate amount of light (12-16 hours a day) to finish germination so choose a location with bright light. In many homes, there just isn’t enough sunshine and a plant light is needed. A windowsill with southern exposure may work well, but be sure the plants are getting bright light all day.

Continue watering the seedlings; keep the mix moist, but not dripping wet. Little containers dry out quickly so check your plants at least once a day, if not more. The first leaves to appear aren’t leaves at all, but cotyledons — food storage cells. Once the first true leaves have appeared (what looks like the second set of leaves), water with a weak organic fertilizer once a week. Don’t use too much fertilizer. Seedlings are particularly susceptible to burn. (No fertilizer should be added to your planting medium before seeds are inserted. Too much nitrogen discourages the germination of some seeds.)

When the seedlings are an inch or two high it is time to transplant them to individual containers, or to thin out the existing containers. To thin seedlings, cut the weakest ones rather than try to pull them out. Pulling unwanted seedling from the mix can damage the roots of the ones you are trying to keep.

After the last frost has passed, it is time to move the seedlings outside, but first they must be hardened off. About a week before the planned transplant date, start setting the containers outside in the shade for a few hours before bringing them back inside. Each day let them spend more time outside and more time in direct sunlight. Be sure to keep them well watered and check them daily for insects or disease. (See “Hardening Off Isn’t Hard” for more details.)

Transplanting

After the plants are hardened off and ready to be transplanted be sure to water them well. Water the ground where they will be planted, too. This helps avoid transplant shock. If possible, wait for a cloudy or overcast day to transplant and dig a hole about twice the size of the transplant’s rootball. Put the seedling in the hole and fill in with soil.

Leave a small depression around the plant’s stem to help trap moisture. Check the plants for moisture daily for the first week or so. Don’t let the soil dry completely. Deep, infrequent waterings will help the plant develop long roots. Shallow watering leads to shallow roots.

Troubleshooting

Plants are fairly resilient, but from time to time things can go wrong. Here are a few problems to look for.

Leggy Plants: Often due to overly warm conditions, too little light or overcrowding.

Curled Leaves: Probably the result of too much fertilizer. There is no need to fertilize seeds or seedlings until the first true leaves appear. Then use a weak solution (1/2 strength) of organic fertilizer.

Damping Off: When seedlings suddenly wilt and die for no apparent reason it’s likely due to fungi. To prevent fungus from attacking your delicate plants, space seeds evenly, thin seedlings as soon as they get crowded and avoid overwatering. A sterile growth medium will also help discourage fungal growth. If they’ve already wilted, it’s too late — compost them.

Discolored Leaves: This can be caused by a nutrient deficiency. Add a weekly dose of diluted organic fertilizer with trace minerals or make a weak tea by soaking compost in water, one cup compost to a gallon of water. Be careful not to over-fertilize.