On to the germination station! Preparation is the key!
Plan on starting your seeds 5-8 weeks before you can plant them outside. Count back from your average last frost date to figure the date to start your seeds (For central Connecticut – May 20th or the last full moon in May, whichever is later) . Tomato seeds need the “right” conditions to germinate and grow inside so preparation is the key.
A Place to Call Their Own. Depending on the number of seedlings you want to start, the area can be small, but the seedlings will likely need to be transplanted at least once into larger pots before it is warm enough to plant them outside. The plants from that one 12×18 seed starting tray could end up taking up 5 times the space by the beginning of May. The space will need to have good air circulation, easy access to water, room for lights, possibly a heat mat and be able to stand up to a little “mud”. A bright sunny window may seem a good choice at first glance, but will your nice white window sills need painting come June?
Containers. You can be creative by using something as simple as an old egg carton, or as involved as an APS (accelerated propagation system) or soil blocks. If it’s your first time starting seeds inside and you’re only planning on starting a few plants, I recommend using one of the seedling starting systems that are completely contained. Most are plastic or styrofoam which contain a water holding tray, a cell tray and many have a “water wicking” mat that reduces the number of times you need to remember to water. It’s a small investment for the best possible results. Some even come with a heat mat, a light and high dome cover if you want that “all in one” system. For many years, I’ve also used a “soil blocking system” (http://thesoilblocker.blogspot.com) which involves no containers at all. You can see pictures of both of these systems at Hart’s on our website and Facebook page.
A Happy Medium for the Roots to Grow In. It may be called dirt by some (my UCONN soils professor would not be happy if I did), but when growing inside, more often it’s a “soil-less” mix made up of milled sphagnum or peat moss, vermiculite, with maybe some compost or worm castings. These mixes are free of weeds, diseases, and fungus while holding moisture and are porous enough to allow air pockets too. Do not use garden soil! Most garden soil cannot meet this criteria when grown in a contained space and can lead to poor results. You can mix your own or purchase a seed-starting mix.
Here’s the mix I blend for starting seeds in containers. It’s finer than most bagged soils and it contains some nutrients to get the young plants started. Since I may make up a garbage can full of this mix or just a few cups, I’ve put the recipe in units rather than a volume measure. A “unit” can be anything from a coffee scoop to a 5 gallon pail. This is not precise, just a guide:
30 units of fine milled Coir (coconut fiber), sphagnum moss, or brown peat moss.
20 units well aged Compost
10 units Worm Castings
5 units “Turface” (or perlite)
1 unit Green Sand
1 unit Rock Phosphate
½ unit Kelp Meal
All ingredients should be sifted through a ¼ inch screen to remove sticks or clumps before combining. If you don’t have kelp meal available, use liquid kelp (seaweed) at the recommended dilution to wet the mixture before you plant. As the plants grow, you will need to add fertilizer to this mix. Use any organic liquid fertilizer at ½ the recommended dilution when you water.
A tip: moisten your mixture BEFORE you put it into the containers or cells. It might seem a little messier, but you won’t have the dry mix push out of the cells when you first water the seeds.
Heat For Their Feet. Tomato seeds germinate best at an 80° soil temperature. They will germinate at lower temperatures, but it can take weeks instead of days if the soil is too cool. There are seedling heat mats you can purchase or plan on placing the newly seeded tray on top of something warm. Tomato seeds do not need light to germinate; so many people use the top of their hot water heater (with the insulation pulled away) or the top of a radiator covered with a towel. An old heating pad set on a timer will also work. Even an incandescent light bulb can produce enough warmth to stimulate faster germination. After the seeds germinate, heat is no longer necessary but will encourage continued faster growth.
Let There Be Light; (and lots of it!) Tomato seeds don’t need light to germinate, but once those green sprouts appear, the young plants need 12-16 hours of direct sun every day. You could use a sunny window, but soon you’ll see your plants stretching toward the sun. Plan on supplementing sunlight with grow lights or use just grow lights on a timer. Full spectrum light bulbs in a standard shop-light fixture will do, or you can go with one of the many new bulbs available now. Read the recommendations for the distance these bulbs should be from the top of your plants as they grow. Traditional grow lights are set 4″-6″ above the plants. Last year I switched to T4 bulbs but didn’t realize the intensity of the light that these bulbs produced until one entire tray of seedlings was sun burned beyond saving. A tip: Static electricity will cause dry soil-less mix to cling to the light bulbs; therefore, dust the light bulbs regularly.
Facing Into the Wind. Plants started inside are still prone to some disease problems. Damping Off disease is the most common of them. This presents itself as a perfectly healthy little plant one day and the next day the little stem is bent over at the soil line. If this occurs, unfortunately, there is no saving that little plant, but measures are necessary to prevent the spread to still healthy seedlings. Remove the diseased plant as soon as you find it. One way to help control this disease is to make sure there is good air circulation around the seedlings at all times A small oscillating fan works well. This fan also will help prepare your seedlings for their eventual exposure to wind when you move them to the garden.