How do I calculate greenhouse space for seedling trays?

Heirloom works it out from your plan: week by week, you see how much of your tables your seedlings need, and you spot the week your nursery overflows before spring, not in the middle of it.

Enter your usable table space once, shelf levels included, and give each tray its size in Farm data > Nursery containers. The Nursery then shows a bar for each week, as a share of your tables; hover a week to read the Area needed in square metres. The figure turns orange from 95% and red from 100%.

When a week goes over, move a succession a week earlier or later, sow in trays with more cells, or plan a temporary table or a cold frame. The graph follows as soon as the plan changes.

The steps are in Set your nursery space and containers and Forecast your nursery space and trays.