Guide to creating a sowing schedule

Creating a planting schedule

Once you've decided what type of greenhouse you're going to choose or you already have an existing greenhouse and the new growing season is starting, it's time to make your planting schedule. You can start with the dates when you need to start sowing the greenhouse. Plan backward, starting from the harvest date, the sowing date can be calculated based on the plant's days to maturity (DIS). Days to maturity metrics are referenced in seed catalogs. DIS indicates the time the plant has to grow after it is transplanted; DIS does not take into account how long it takes for a seed to germinate and grow in a greenhouse or nursery.

Cold season plants • Plant in fall and harvest in winter • Plant in early spring and harvest in early summer		Warm season plants • Plant in late spring and harvest in fall
Spinach	50-60 days	Tomatoes	80 days
Broccoli	60-70 days	Melons	80-90 days
Onions/scallions	60 days	Summer squash	70-80 days
Carrots	60-70 days	Eggplants	80-90 days
Radishes	40-50 days	Peppers	80-90 days
Salad	40-50 days	Cucumbers	75-80 days
Parsley	60-70 days	Basil	60-80 days

To show you how you can create a growing plan, here is an example with tomatoes, where you want to get a 45kg tomato harvest from August 15th to October 19th.

An example calendar for tomato sowing planning.

First harvest date: August 15.
DIS (72 days after transplant): June 4.
Time in the greenhouse (6 weeks or 42 days): April 23
Harvest time per plant (3 weeks)
Harvest until October 19. = 9 weeks in total
Number of planting dates (9 weeks ÷ 3 weeks of harvest period) = 3 planting dates

Dates circled in red: sowing date
• April 23 - August 15 for harvest.
• May 14 - September 6 for harvest.
• June 4 - September 28 for harvest.

Dates marked in orange: transplanting to the greenhouse
• April 23 sowing date - transplanting on June 4.
• May 14 sowing date - transplant on June 25.
• June 4 sowing date - transplanting on July 16.

Blue marked dates: harvest
• April 23 sowing date - harvest from August 15 until September 5.
• May 14 sowing date - harvesting from September 6. until September 27.
• June 4 sowing date - harvesting from September 28. until October 19.

No matter how many varieties of seedlings you plan to start each season, it's always a good idea to have a planting schedule. The schedule can be both simple and complex, it all depends on your wants and needs. It helps you keep track of seedling varieties, ensures that you make the most efficient use of the space in your greenhouse, and acts as a reference over several years. This can help you gauge which breeds are most successful for you. This chart is for those who are starting seedlings in seed trays and transplanting them into pots that will later be sold or moved to the garden. Note: When choosing seeds that are started in trays and will be transplanted later, be sure to choose varieties that tolerate transplanting well.

The seed	Seed planting date	Days to germination	Number of pallets	Date of transplant	Number of seedlings transplanted into pots	Date of transfer to the greenhouse	Comments

Sample table for sowing planning and analysis.