A Guide to Starting Seeds Indoors
Most of us don’t have a long enough growing season that we can direct sow seeds outdoors. So we are left with a choice of either buying plants that we can put in our gardens after our last frost or starting our seeds indoors while our gardens are still in the grip of winter cold.
To start your seeds indoors, you must first create the proper environment. Choose a surface or table that is large enough to hold all of your seedlings and that you don’t care if it gets dirty (it will) or wet (it will).
Aha, you think, that sunny window is the perfect place to start my seeds. Sorry, but it’s not. What looks like a sunny window to us appears much darker to plants. Plants use parts of the light spectrum that we can’t see and glass blocks a lot of those parts of the light spectrum. Trying to start plants in front of a sunny window will result in weak, spindly plants.
For best results, you want to use lights. There’s no need to invest a lot of money in special “grow” lights. Plain old fluorescent shop lights work just fine. You want to hang them on chains above the surface where your plants will be growing. The lights should always be one inch above your seedlings. The chains make it easy for you to raise your lights as your seedlings grow.
Invest in a timer. Even though your lights are one inch from your seedlings, they are still not as bright as sunlight so they will need to be on for 15 to 16 hours a day. To prevent you from forgetting to turn your lights off for 8 hours, use a timer to do it automatically for you.
Plastic is your best bet. Clay pots dry out too quickly. Plastic containers retain moisture better. You can buy seed starting flats or you can make your own from any kind of plastic container. Just make sure that your containers have a hole in the bottom for drainage. Recently, I’ve seen people growing seeds in eggshells which are then planted in the garden while still in the eggshells. This would be great for tomatoes which require calcium to prevent blossom end rot. Again, be sure to have a hole for drainage.
Seeds germinate when the soil reaches a certain temperature. Heat mats can fool your seeds into thinking that the soil is warming because it is spring and time to grow. Heat mats are also a must if you are starting tropical plants such as peppers or impatiens. For tropical plants, you want to maintain a temperature between 70°F and 75°F. For all other seeds, a cooler temperature of 65°F to 70°F is fine.
Always, always use a sterile soilless seed starting mix. This is critical because you want to prevent disease and pests from destroying your seedlings. Soilless mixes, as their name implies, contain no soil. This allows proper drainage so that your seedlings don’t drown. You can use regular potting mix, but be aware that there is a strong possibility of fungus developing and the dense soil will make it more difficult for roots to develop and water to drain properly. Also, many potting mixes come with fertilizer already mixed in. This is too strong for your young plants. And if you are an organic gardener, you want to control the types of fertilizer that you use on your plants especially if you are growing vegetables.
Fresher is always better, especially if you are growing flowers. Vegetable seeds will stay viable for 3 to 5 years with decreasing germination rates. Flower seeds are rarely viable beyond one year. Check your seed packets. They will always tell you how old the seeds are. For instance, seed packets this year will say “packed for 2014”. You can also use seeds that you have saved from your garden last year. If you saved from open pollinated plants, you should get identical plants this year. If you saved seeds from hybrid plants, the resulting plants will not look like the parents. The parents were the result of crosses between two varieties so their offspring will have the characteristics of the original varieties.
Planting Your Seeds
Timing is critical. The seed packet will tell you how many weeks before your last frost date that you should plant your seeds. NOAA has a chart that will tell you when your last expected frost will be. Remember, this is an AVERAGE. You could get a frost after that date. In fact, last year (2013) New Jersey where I live which has an average last frost date of April 15, had a frost a month later on May 15. Once you know your average last frost date, you can count backwards from that date to arrive at the date on which you can begin sowing your seeds. This date will vary depending on what you are planting. Using a calendar to keep track of your sowing dates is recommended.
Also critical is planting depth. Again, your seed packet will tell you how deeply to sow your seeds. Some seeds require light to germinate, so you can sow them right on the surface of the soil and not cover them. I have seen a few seed packets that don’t tell indicate a planting depth. In that case, the rule of thumb is to plant your seeds 2 to 3 times as deep as the seed diameter. If the seeds are very tiny, almost dust, those need to be surface sown. Once you have planted your seeds, gently press down on the soil. You want to make sure that that the seeds have good contact with the soil. Remember, soil temperature tells them when to grow so you want them to not be stuck in an air pocket.
Put your watering can away. You’re going to be using a mister or sprayer. Before you even plant your seeds, you want to moisten your soilless mix using warm water. Moisten, not wet, not drenched. Just moistened enough so that your seeds will have good contact with the soil. Keep the soil moistened with a mister or sprayer, using warm water, as your seeds germinate. By the way, using a watering can which dumps water will cause your seeds to float to the sides and corners of the containers. Once your seeds have germinated, you can switch to room temperature water. Don’t use cold water that can chill them.
Even though the soilless mix contains no nutrients, you will not need to fertilize your seedlings until they develop their first set of true leaves. That’s because seeds contain all the nutrients your seedlings need to germinate and then develop those first two leaves. After that, you want to use a water-soluble fertilizer at half-strength. This is just like feeding a baby. You don’t give infants adult food and you don’t give seedlings full-strength (adult) fertilizer.
Have you seen those giant fans in commercial greenhouses? They make sense when it is warm outside, but why would they be using them when it’s cold outside? The fans are used for two reasons. The most important reason is to prevent the growth of algae and fungi which develop rapidly in a warm, moist environment. A light breeze will prevent them from getting taking over and destroying the plants.
The other reason why you would want to use a fan is to strengthen the stems of your seedlings. Think about it. Inside your house, the air is still. They don’t need thick stems to be able to stand up. When you put them outdoors where the air is constantly moving, they will just flop over. So it’s a good idea to have a small fan running on its lowest setting to “strengthen” the stems of your plants.
Congratulations! You have a whole, healthy crop of plants ready to go into your garden. But before you do that, you have to acclimate them to the outdoors. This is referred to as “hardening off”. Starting ten days before your planting date, bring your seedlings outdoors for an hour or so, increasing the length of time each day until they are able to be outside all day. Don’t start them out in direct sun. Like us, they can get sunburned. Put them in light shade at first, gradually increasing their exposure to the sun each day.
Starting seeds indoors has two advantages. It allows you to grow varieties that are not available at the Big Box stores or your local nursery and it’s much less expensive than buying plants. For a small initial investment, your garden can be the envy of the neighborhood.