Starting Seeds Indoors and in the Greenhouse

A presentation by Arthur Lerner of FRESH New London, with input from the New London County School Garden Network members.

The first question to ask is, “Are seeds alive?” – the answer… of course.  So, storing seeds is important. A cool dry place with low humidity is best. A good rule-of-thumb is to think of the number 100. Seeds should be kept at less than 100 degrees and less than 100% humidity. At FRESH New London, seeds are often stored in a portable cooler.  It keeps the seeds at a constant temperature - other thing to monitor, keeping the conditions from fluctuating too much.

Germination:  A quick overview of the parts of the seed:  The seed is like an egg with the shell on the outside (which is like the bran of the seed); the white of the egg gives the yoke nutrients to grow, (which is like the endosperm of the seed); and then in the middle is the yoke (which is like the germ of the seed). All three parts have an important job to do!

Before planting it is important to learn how to read the seed package. This gives you the class and variety, short summary of the plants characteristics and most important, the sowing instructions. This gives you the yield to expect or how many seeds should germinate or the germination rates,- these can be fun to calculate with the students as part of a math lesson. The packet usually tells you how long it will take to germinate, how closely to plant them and how long it will take to fruit or flower.

 Soil preparation: Preparing the soil is important. To germinate the seed has to Arthur recommends using a “soil-less” potting mix or seed starting mix that has the appropriate fertilize added. If you just pour water on top of the soil after the seed has been planted it won’t absorb, it might run off, taking the seed with it. So it is better to hydrate the soil first, getting to a light consistency where you really can’t squeeze more than a drop out of it. Too wet and it will harm your seeds and form clods.

If you choose to make your own seedling mix, you can use the following recipe:

•     4 parts sphagnum moss
•     4 parts perlite OR an equal mixture of perlite and vermiculite
•     1/4 Tablespoon dolomite lime per gallon of mix to adjust for pH and add calcium and lime

Creating healthy soil

You can also use coir. Some schools are even making their own soil blocks, like they do at the FRESH New London farm.

Containers: Using containers in the classroom or green house are great. Some schools use premade containers or planting trays, others use cardboard egg cartons and poke a hole in the bottom for drainage.  The cardboard container can be planted right into the ground, all the way up to the top of the container. There are also planting pods made out of manure, but they are expensive. Some suggested that Kurieg cups can be used to sprout then the plant can be transplanted. Whatever the container, it is important that they have good drainage and that they are kept where temperature are around 70 degrees or higher, in order for the seed to germinate. If the temp falls below 60 degrees, germination will slow or the seed with rot. 

Planting depth:  Of course following the sowing instructions is important, and a good rule of thumb is plant the seed three times the width of the seed. There is a temptation to plant the seed deep, but this causes the seed to not sprout.

Light: Ambient light is enough light for germination. After the seed sprouts the light must be about 6” above the plant and able to raise as they grow. Florescent lighting needs to have full spectrum to ensure that vegetative growth continues to include flowing and fruiting. This time of year, light coming through the window is not enough. Newer schools may have UV light protection on the windows, making more challenging to start plants in the classroom.

Hardening Off: This involved toughening up the small plant to withstand outdoor light, temperatures and wind. A cold frame can be used or Susan Munger, from UConn's Master Gardener Program suggests bringing plants outdoors, an hour at a time, then gradually increasing the amount of time, over a week or so. "If plants are put out in the hot sun they can get sunburned", says Munger.

Try various kinds of containers for starting seeds.

Watering: For seeds to germinate, it has to imbibe water. The seed expands and the food supply becomes active to nurture the germ. This can be a fun thing for kids to learn – to handle the seeds, soak them overnight or put in a wet paper-towel.  If the seed and the soil are well hydrated it is foreseeable that you won’t have to water until the seedling pokes up through the soil.  Over and under-watering can be an issue, especially when multiple people are overseeing it. Arthur suggests watering using a schedule or log, so proper watering can be monitored.  Using a watering tray that allows for watering from the bottom, which is one way to water without disturbing the seed. Food Corp Member Chelsea Hahn, shared that she tells the kids, “The seeds would rather be a little thirsty than swimming”.

Suggestions on What to Plant: You can start now planting some salad greens (mesclun and brassica, etc.). Wait for planting zinnias, tomatoes, and peppers until late March. Arthur recommend the book, “Seed to Seed”, by Suzanne Ashworth. What is your school garden program planting right now?

Composting: There are always questions about composting, what to put in the compost. There is interest in learning more about composting, worm composting, using compost tea, etc. Stay tuned for our upcoming Blog post about "all things compost."