Want Big Beautiful Vegetables? Start With Seedling Trays

A modern farmer puts emphasis on efficiency in any energy exerted in vegetable production. Efficiency is not just about doing less or working smarter, it also means concentrating on activities that have the greatest potential for succeeding.

Big yields depend on environmental factors as well as nutrient composition and application – but also on giving the seedlings the best possible start to life.

In this article, we’ll show our method of how we grow lettuce from seed for our hydroponics system.

Carlo Rossa Leafy Lettuce in DWC Hydroponics

50 Holes Seedling Tray (Square)

Tray Measurements:

21″ x 11″ x 2″ (L x W x H)

Hole Cell Measurements:

46 x 46 x 50mm (L x W x H)


128 Hole Seedling Tray (Square)

Tray Measurements:

21″ x 11″ x 2″ (L x W x H)

Hole Cell Measurements:

29 x 29 x 46mm (L x W x H)

Seed Germination

To germinate seeds properly, it’s important to understand that seeds need moisture, warmth, and oxygen. As long as these conditions are met, there’s a higher probability of successful germination rates. There are many different ways people can germinate seeds. Some use a tissue-culture method, or germinate in soil-less media, while others use conventional soil-based methods. A common technique is to soak seeds a night beforehand to soften the outer shell.

In our greenhouse, we rely on the characteristics of cocopeat to consistently give us high germination rates. Cocopeat is airy, fluffy, and retains a great amount of moisture before drying out. Roots grow fast through the cocopeat fibers due to the availability of oxygen and moisture while getting the warmth and humidity on the topside. We use 1020 Trays with drainage holes and humidity dome to “wake up” the seeds, then remove the humidity dome after the seeds have sprouted.

Seedling Trays

In about 5 to 7 days from emergence, we carefully pluck a young sprout and transfer them into seedling trays. For lettuce, we like to use either 50 holes or 128 holes seedling trays. Prior to transfer, fill the seedling tray with cocopeat and make a little hole in the middle of the hole to easily insert the sprout. By giving each sprout its own space to grow in, the roots won’t have to compete with other seedlings for nutrients. 

Romaine Lettuce seedlings in 50 hole square trays

50 Holes Seedling Tray (Round)

Tray Measurements:

20-3/4″ x 11″ x 1.75″ (L x W x H)

Hole Cell Measurements:

Top dia: 4.5cm / 1.75inch

Bottom dia: 3.5cm


128 Holes Seedling Tray (Round)

Tray Measurements:

2ft x 1ft x 1.5″ (L x W x H)

Hole Cell Measurements:

1.5″ hole diameter


When the newly germinated seed sends out its sprout, it uses up the food inside the embryo and converts food into energy by way of enzymes. But once the seedling has settled into the seedling tray, the roots need to access a source of food for it to continue to grow. While cocopeat is rich in organic matter and carbon, it is still important to provide a light dose of macro and micronutrients. We mix a light dosage of Peters 20-20-20 with Ajent811 Potassium Humate and Energyc Amino Acids and apply via spray. 

Leafy lettuce in 128 hole seedling trays (round)

Automated Misting Irrigation System

Daily irrigation is necessary for the seedlings to have enough moisture to nourish the roots. But it can happen that you get too busy to remember to water your seedlings, and by missing a day it might potentially dry out your entire seedling stock. Therefore we recommend using an automated misting irrigation system that is activated automatically without having to ever worry about it. See video below:

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