What's the sheet foam board for?

I made a visit to one of our local plant growers who sells plants to both the public and to area retailers. He first starts his seeds in seed boxes. I recall seeing the boxes but don't remember the exact dimensions. I think they were about 1 foot by 2 feet and about 2 to 3 inches deep. He plants the seeds in a seed starting medium and then tranfers the small plants to individual peat cups when the plants begin to get their true leaves.

My process is to plant in rectangular seed boxes (plastic or wood) and let the plants grow to set-out size. Some thinning might be required in the seed boxes if the seeds are too close together. The seed boxes are placed under the overhand of the roof on a plant stand such that they receive afternoon sun. When it comes time to remove the plants I saturate the box with water. This minimizes root damage when the plants are extracted. Any plants which succumb to transplant stock can be replaced with a new plant. I plant somewhere around 120 to 150 total broccoli, cauliflower, and brussels sprout plants and moving to the cups adds a step that isn't needed....(i.e. unnecessary time and effort).

Plants are ready to set 4 to 5 weeks from seeding.

Greenhouser, I will drill 1 1/2" holes in the foam board sheet to set the 6oz cups in so they won't blow over in with our afternoon wind and rain showers, Thanks for asking Guilt Trip