Lettuce Handbook

Germination Media
A formulation of Peat-Lite is the media in which the lettuce seeds are sown.  The ingredients are as follows:

• Sphagnum Peat Moss = 15.5 liter (1/2 bushel)

• Horticultural Vermiculite - fine grade = 15.5 liter (1/2 bushel)

• Dolomitic Limestone = 65 ml (5 Tablespoons)

No other ingredients are recommended.

The media can be prepared using a mixing device such as a clean cement mixer.  If the media is made manually, care should be taken to ensure thorough mixing.

This volume of media will fill the 12 plug trays (128 cells) produced each day.  Large batches should not be stored.  No more than one weeks supply of media should be prepared at a time.  Poor results have been obtained with 'old' germination media.

Plug Trays

Plug trays contain 128 (11 ml volume) plugs and are approximately 0.3 by 0.6 m. A 2.5 by 1.3 m Ebb and Flood bench will hold 16 plug trays.  Plug trays can be obtained from greenhouse suppliers.

Day 0 - Lighting
Light in the germination area on Day 0 is maintained at approximately 50 micromol m^-2s^-1 of its capacity.  Light is provided to ensure complete germination.  Humidity covers are in place during the critical germination period to maintain a high humidity around the germinating seeds.  Light level is raised to approximately 250 micromol m^-2s^-1 after 24 hours.

Day 0 - Temperature
The temperature within the germination area is maintained at 20^o C during the first 24 hours.  This is for two reasons:

1. It is imperative to keep the seed moist.  A lower temperature, in conjunction with lower light levels and a high humidity, will help prevent the seed from drying during the critical germination period.

2. The seed has a thermal dormancy; that is, the seed will not germinate if the temperature is high (above 25^o C).

After 24 hours the seedling has begun to germinate and the temperature is raised to 25^o C.  The rate of seedling growth at this temperature is optimum.

Day 11 - Seedling Roots

This photo shows the roots extending from the bottom of the seed plugs.  The roots are delicate and easily broken.  Care should be taken to protect these roots during transplanting.

Styrofoam Floats

This 10 cm x 10 cm Styrofoam block floats on the surface of the pond.  Each Styrofoam floater is cleaned between each growing cycle with a weak bleach solution.

Day 11 - Positioning Seedlings in Pond

This is an example of the spacing within the pond after transplanting the seedlings from the germination area to the pond area.  They are grown at this 10 cm x 10 cm spacing for 10 days.