Growing Your Own Seedlings

Q.  I replanted 3 week old seedlings last weekend and had a really hard time doing it.  The biggest problem was the roots of the seedlings growing close together were all intertwined and I had to pull some of them apart, no doubt damaging them.  What am I doing wrong – and how should I do it right??

A.  Growing seedlings is very important to those who are serious about gardening in any volume, and essential for those doing it commercially.

Using the same planting mix we recommend for Grow-Boxes (25%-35% sand by volume, mixed with your choice of sawdust, peatmoss, perlite, etc), to plant seeds you should add 1 1/2 ounces of Pre-Plant mix (3 level tablespoons) to each 18″ X 18″ tray, or 1 ounce to a 10 X 20 tray, and mix it in.  Use only trays with adequate holes for proper drainage. 

Smooth the soil mix with a straight board.  Make 1/4 to 1/2″ (1/2 to 1 cm) indentations the length of the tray about 2″ apart with the edge of a board.  Plant no more than 100 seeds per row.  This will give you 4-500 seedlings in the narrow trays and 7-800 in the large square ones.  Gently cover seeds with 1/4″ of soil mix, smooth soil surface, cover with burlap, and water with plain water.

Maintain soil temperatures between 70-80 degrees fahrenheit (20-28 C) and water with plain water gently through the burlap until seeds germinate and the first seedlings emerge, then water with Constant Feed solution made from Weekly Feed (1 ounce in 3 gallons of water – or 30 grams in 12 liters) and remove burlap.  No light is needed during seed germination, but give maximum light to the plants immediately upon emergence.  Grow-lights are needed for 14-16 hours each day because they are not as bright as sunlight.

Maintain temperatures above 65 degrees fahrenheit for best growing
conditions.  Never let the soil in the flats dry out, but maintain moist – not wet – conditions at all times.  Flooding your plants with water –
especially if your flats do not have adequate drainage – will subject them to drowning for lack of oxygen, and to the Damping-Off fungus disease.

When the seedlings have at least one set of true leaves (after the seed
leaves that are the first to come out of the ground), transplant into other flats at 2″ intervals, about 36 per narrow flat or 64 in the 18″ X 18″ flats, or into plastic 6-paks or small pots.  Transplant only
strong, healthy seedlings.  Flats should have both Pre-Plant mix added to the soil, as described above and 1/2 that much Weekly Feed before transplanting.  And all watering should be with Constant Feed solution.

Continue with even temperatures, strong light, and regular watering with Constant Feed, until plants’ leaves overlap and they are ready for transplanting again – in the garden or into larger pots.  Tomatoes will need pruning – probably twice – because they take almost 8 weeks before being ready for transplanting into the garden.

For much more detail, with graphic and pictorial illustrations, see Let’s Grow Tomatoes, the Mittleider Gardening Course, and most other Mittleider gardening books.