Spring Indoor Seed-Starting Schedule – Free Printable

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?

This spring indoor seed-starting schedule with a Free Printable is much more than just another printable schedule. We explain the reasons behind the dates and how to customize it. The article has a lot of information; once you get it, you will never depend on anyone else’s opinion. That’s what we want for you! 

The schedule comes from the All New Square Foot Gardening book. The author, Mel Bartholomew, is known for simplifying things, which attracted me to his work. The schedule is very simple, and it is still all we use. We have adjusted it to our situation; more about that below. 

In this article, we will examine when and why we start seeds according to this schedule. You can also print yourself a schedule with your exact dates and adjust it as needed.

Note: The free printable indoor seed starting schedule is at the end of this blog article. 

How to find your Last frost date

You must know your last frost date for the spring indoor seed starting schedule. If you live in Canada or the USA, go to this link to find your last frost date.

All counting is based on that date. We start seeds indoors before the last frost date and plant them out before, at, or after that date. 

The last frost date is important because some varieties grow well in cooler conditions and can be planted early, while others do not tolerate 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 seeds should 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, as well as the days to maturity, are perfect growing conditions days. 

Many gardeners, though, still like to start seeds indoors very early. They have found that starting seeds up to five months before planting produces better results. The starting times differ greatly.

We, on the other hand, have years of good experience starting seeds later, never more than 10 weeks before planting.

Experience matters; following a schedule with very poor results does not help. However, if you understand the “why” behind an experience, you can change it. 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

The picture above shows 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 you have your seed starting date. 

But that’s not all the seed package says. The seed company, which is local to the West Coast and wants to be especially helpful to local growers, 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 should be preferably 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 starts pepper seeds there would 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 (eight weeks before being planted 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 the indoor seed-starting schedule?

The indoor seed-starting schedule from the All New Square Foot Gardening book shows not only the seed-starting date but, even more importantly, 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 is not on the schedule. For example, if the seed package says that the plant needs 10 weeks from seed to planting and can only be planted after all danger of frost is gone, you place your planting date a week after the last frost day, so it will surely not have frost. Now, you count 10 weeks back, and there you have your starting seed 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 charts, one for the greenhouse and one for the garden.

Seed starting time for cold weather crops

Following this schedule, you will start cold-weather crops like brassicas and onions first. They can also be planted out first, as cold-weather crops generally like cool weather. As we have mentioned before, this schedule gives you a starting time and a plant-out time.

Cold-weather crops can withstand some frost, but you must still monitor the weather and provide them with a frost blanket as needed. See also how different plants survive frost.

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.

Seed starting time for nightshade family plants

Nightshade family plants, such as tomatoes, peppers, and eggplants, are summer crops that like bright and warm weather. In our area, the daylight hours from October 28 to February 14 are below 10.

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.

You can use a grow light to avoid having spindly seedlings, but then your seedlings will grow fast and overgrown. Read more about starting seeds without grow lights here. 

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 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.

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, ensuring all danger of frost is over. 

Seed starting time for cucurbits family plants

Cucurbits are squash, zucchini, cucumber, pumpkin, and other members of the squash family. Most of them are very fast-growing plants, and they, too, like summery, bright, and warm conditions. They 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.

We start spaghetti squash and winter squash indoors and wait to plant them out a week or two after the first frost. We mostly just start zucchini in the garden directly, even though starting indoors is a better idea during cool springs (and we never know ahead of time what spring will be like).

Cucumbers can be sprouted to give them a head start and planted directly into the garden or greenhouse.

Free printable seed starting schedule

Here, you can print out your own indoor seed-starting schedule. We have two pictures to choose from.

To print out the schedule, click on one of the pictures below to open it in full size. Then, you can print or save it on your device. It is free to print.

This is the picture without dates. If your last frost date is different from ours, you can make your own. 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!

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