It may not look like much but this tray of potting mix has been seeded with oil pumpkins that will be transplanted in a few weeks. Canada has a short growing season and farmers often start plants indoors where they can control temperature, water and light while waiting for the soil to warm up. It’s a way of extending the season and gives plants a head-start while waiting for the days to lengthen and the risk of frost to pass.
Some considerations when planting for an indoor greenhouse:
- Tray size – How many plants per tray? The more plants per tray the smaller the available space for each plant to grow before it becomes root bound and larger seeds, such as squash, need more space; the oil pumpkins above are in a tray with 24 pots.
- Seed depth – As with all planting it’s important to know at what seed depth is needed.
- Labelling – It’s a good idea to label trays with planting date and variety name in particular.
- Germination – What germination rate is expected (if it’s low planting more than one seed per pot may be planted) and how many days for germination to occur?
- Lighting – Fluorescent lighting is fine but it needs to be close to the plants; about 5-10cm (2-4 inches). If the light is too far plants will end up lanky as they stretch towards the light.
- Number of seeds to plant – How many plants are planned for harvest? To account for losses calculate 20% loss in the greenhouse and a 20% loss at transplanting. For example, if 100 plants are started in the greenhouse then 80 plants would be transplanted in the field of which 64 would make it to harvest.
Even better than an indoor greenhouse is an outdoor heated greenhouse where plants get sunlight rather than artificial light. Unfortunately, there is some infrastructure yet to be built at Chelsea Gardens so for now the greenhouse is a basement room at the farmhouse.