After using this spring indoor seed-starting schedule for annual vegetable seeds for several years now, do we still recommend it, or is it time for a new plan?
The schedule comes from the All New Square Foot Gardening book. Mel Bartholomew, the author, is known for simplifying things. That attracted me to his work in the first place. The schedule is very simple, and it is still all we use. But I have made some adjustments to our particular situation, more about that below.
In this article, we want to take a look at when and why we start seeds following this schedule. Plus you can print yourself a schedule to follow with your exact dates and also adjust as needed.
Note: The free printable indoor seed starting schedule is at the end of this blog article.
Last frost date
That’s the date that all counting is made from. We start seeds indoors before the last frost date and plant them out before, at, or after the last frost date.
The last frost date is so important because some varieties grow well in cooler conditions, and can be planted early, and some do not tolerate any frost, and should be planted after all danger of frost is gone.
To extend the growing season, we start tender seeds indoors before the conditions outdoors are right for them.
The indoor seed starting schedule tells us how long in advance should seeds be started.
Facts vs experience
Every seed has a specific germination and growth rate. On average 2-10 weeks, depending on the variety, is enough to grow a healthy vegetable seedling. Some seed companies write these instructions on a seed package telling us when to start the seeds indoors (if applicable), when to plant them out, and how many days are expected to maturity (the number in parenthesis). These dates are facts, and they usually do not change from company to company, even though there are exceptions. We will look at one below.
The dates for a seed to germinate, and grow into a healthy seedling, and also the days to maturity are perfect growing condition dates.
Many gardeners though still like to start seeds indoors very early, they have made the experience that shows better results when starting seeds up to 5 months prior to planting. And the starting times differ greatly.
We on the other hand have had years of good experience starting seeds at a later date, never longer than 10 weeks prior to planting.
Experience matters, it does not help if you follow a schedule with very poor results. However, if you understand the “why” behind an experience, it can be changed into a different one. That is my goal in sharing this information.
It is a lot less work, caring for a seedling for 5 weeks vs 5 months. Personally, we would recommend growing an indoor garden, or at least some microgreens instead of starting seeds for the summer garden so early.
Understanding the growing conditions
Here we have a pepper seed package from West Coast Seeds. It reads: “Start indoors 5-8 weeks before the last frost”. We just covered that. If you know your last frost day, count back 5-8 weeks and there you have your seed starting date.
But that’s not all the seed package says. Being local to the west coast, and wanting to be especially helpful to the local growers, the seed company adds: “Start early March on the coast for transplanting in June into warm soil”. Now the time period between early March and June is 13-14 weeks!
So, what now, is it 5-8 or 14 weeks? That’s a huge difference.
Here is where understanding the growing conditions and times to maturity comes in.
A pepper seed needs 5-8 weeks of perfect growing condition to become a healthy seedling. Since peppers are a heat-loving summer crop, those days are preferably to be warm and sunny, with soil temperature for germination above 20C (68F).
The west coast is known for its overcast, cool weather. An average gardener, who would start pepper seeds there, would on average have just enough sunny days between early March and the beginning of June to grow seedlings. All other days are basically lost days for that seedling, they do not count.
Here is an example of peppers that were started in March (8 weeks prior to being planted out in a greenhouse) and harvested in August. How was that possible? We created the growing and maturing conditions that a heat-loving plant wants.
The times on the seed package for seed starting and days to maturity (the time from transplanting a seedling to harvest) are perfect growing condition times.
If you know that your growing conditions are not ideal for any given plant variety, you have two options: You can add more time, or you can create better conditions. We aim for the latter.
The spring indoor seed starting schedule also aims for perfect growing conditions and planting out dates.
What is special about this schedule?
The indoor seed-starting schedule from the All New Square Foot Gardening book does not just show the seed starting date, but even more important the planting out date. Those are really important dates to consider. The starting times are just simple math counting back from the planting out time.
You can add any variety from your seed collection that might not be on the schedule. For example: if the seed package says that the plant needs 10 weeks from seed to plant out, and can only be planted after all danger of frost is gone, you place your plant out date a week after the last frost day, so it sure will have no frost. Now you count 10 weeks back, and there you have your starting seeds date.
If the planting out date on the schedule does not work for you, move the seed starting accordingly.
If you grow a greenhouse garden, you can adjust the seed starting times accordingly. It will take some practice to see how your greenhouse performs. A simple plastic poly gives you only about 3 degrees of protection at night. If you don’t use any heat source, you might want to wait with heat-loving plants till the last frost day, just like whiteout a greenhouse.
In our Geodesic Dome greenhouse, we use a car radiator to heat and cool the space. This allows us to plant about two weeks earlier than the last frost day (still watching the weather though).
Again, using the same idea, counting the seed starting back from the plant out day, adjust the seed starting date for a greenhouse to your situation. I simply add a “G” – for the greenhouse, to my schedule. Or you can print out two chards, and make one for the greenhouse and one for the garden.
Starting time for cold weather crops
Following this schedule, you will be starting cold-weather crop plants like brassicas and onions first. The reason is that they also can be planted out first. Cold weather crops generally like it cool. As we have mentioned before, this schedule does not just give you a starting time, but also a plant-out time.
The advantage of planting cold-weather crops out earlier is to prolong your growing season, but also while cold-weather crops do like it cool and often will grow better in cooler conditions. Also, the cabbage butterflies tend to come out in late summer, so harvesting the broccoli before that is a win-win.
Since our weather is very unpredictable, and I never really know what our early spring will be like, I have moved the schedule for the cabbage family plants about 2-4 weeks later. This gives me a bit more time if our spring does not come at the usual time as expected, and I get better results.
Another good option is to start cold weather crops on schedule but in winter sowing instead of indoors. This way they are already out in the elements and will germinate according to the weather.
Not all plants we might grow are on the chart, only the main crops from a plant family. So if you also grow Brussels sprouts and shallots, start them with other brassicas or onions. Compare the seed starting and planting out dates on your seed package and add them where you see fit.
Starting time for nightshade family plants
Nightshade family plants like tomatoes, peppers, eggplants, etc. are summer crops and like it bright and warm. In our area, the daylight from October 28 to February 14 is below 10 hours.
If you start your seeds before or right at the edge of the 10-hour day, they will grow very slowly and there is a danger that they become spindly. Spindly and weak seedlings, for the most part, are no good. They do recover after being transplanted, but that takes time, precious time that a short-growing season gardener does not have.
To avoid having spindly seedlings you can use a grow light, but then your seedlings will grow fast and the result will be overgrown seedlings.
Some plants do need longer to germinate, so for example start ground cherries earlier.
Remember, the important date is the planting out day on the schedule, it is what we are aiming for. If you are not sure about the weather, start a week or two later; in this case, if you have to wait longer, the seedling will not overgrow.
Seedlings that are at a stage where they are almost putting forth buds are just right. The roots are still young and will adapt easily to the new location, and the plant is ready to grow and produce a lot of fruit. Read more about when to start tomatoes here.
By the way, if you can’t wait, start a plant or two early and give it the best conditions possible indoors. This way you can have really early tomatoes. Read more about growing tomatoes indoors.
Peppers and eggplants are particularly heat-loving, eggplants even more than peppers. Do not rush planting them out, making sure all danger of frost is over.
Starting time for cucurbits family plants
Cucurbits family plants are squash, zucchini, cucumber, pumpkin, etc. Most of them are very fast-growing plants, and they too like it summery bright, and warm. Most of them also don’t care much about being transplanted. If you want or need to start them indoors, give them a bigger pot (4-6 inches), and do not start too early.
Personally, we start spaghetti squash and winter squash indoors and wait to plant them out a week or two after the first frost. Zucchini we mostly just start in the garden directly, even though during cool springs (and we never know ahead of time what spring will be like) starting indoors is a better idea.
Cucumbers can be sprouted to give them a head start and planted directly into the garden or greenhouse.
Print your own seed starting schedule
Here you can print out your very own indoor seed starting schedule. We have two pictures for you to choose from.
To print out the schedule, click on one of the pictures below to open it in full size. Now you can print or save it on your device. It is free printable for you :).
This is the picture without dates, it is for you to make your own if your last frost date is different from ours. Write your dates into the schedule counting back from your last frost day.
If your last frost dates are the same as ours, choose the second picture with the dates on it.
Happy spring seed starting!