When to Plant a Fall Vegetable Garden

The number one mistake in planting a fall vegetable garden is planting too late. So how do you make sure your plants are ready in time for a harvest? Here is when to plant a fall vegetable garden no matter what growing zone you are in.

A woman transplants cabbages into soil that is covered with straw.

As you enter fall the daylight hours get shorter and the temperatures are cooler. The combination of these means the plants take longer than the average “days to maturity” to mature!

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Planning becomes a little bit tricky to get right since its not as simple as counting out how long a vegetable takes to mature. there are several methods to get this calculation close but before we jump right in, it’s important to know a few key details about your area.

Figure out your average first frost date

If you’re new to gardening, the average first frost date is the average time you’ll get a frost in your area. Most average first frost dates are based on a 50% estimation. Meaning there is a 50% chance you’ll get a frost before that date and a 50% chance you’ll get one after.

The reason knowing this date is important is because you’ll want most vegetables to mature before frost or right after if they are frost tolerant

I like this simple average first and last frost date calculator. If you want to see more of the probabilities of when you’ll hit certain temperatures, here is an awesome frost probability calculator.

Find when your area drops below 10 hours of daylight

When your area drops below ten hours of daylight plant growth slows significantly. Many times growth will be so little that it isn’t even noticeable. 

The reason this is important is if you want your plants to be harvested through late fall and possibly into winter, the plants need to reach a minimum size prior to that time (more on this later).

An aerial view of a garden and landscape covered in the first fall frost.

In my location, we drop below 10 hours of daylight on Nov. 24th and don’t get back above that until January.

Here is where you can find when your area drops below 10 hours of daylight. It goes by latitude and longitude, so if you don’t have yours memorized (I don’t!), click the box that says “need USA location” if you are in the US. Type in your city and state. Then click the “Get Data” box.

Calculating When to Plant a Fall Vegetable Garden

Now that you have that important information, you can start to calculate when to plant a fall vegetable garden. There are several different methods to doing this.

 First is counting days to maturity and then adding a percentage of time based on days to average first frost. The second method is using a gardening app or program with a built in calculator that works for a fall garden. The third way and probably the best is to calculate with either method, take notes of results, and adjust for the next year.

A fall planted garden with claytonia growing in the foreground.

It’s also important to keep in mind that no two years are going to be alike. Sometimes it’s unseasonably hot, so crops grow faster than planned. Or it could be unseasonably cold and everything grows slower than planned or even gets frost damage.

But keeping notes of generally when to plant in order for the vegetable to mature is always a good idea. 

Method 1: Count days to maturity and add a percentage to calculate how long it will actually take the plant to mature.

Here is a basic guide of how to adjust days to maturity for a fall planting.

  • Count days to maturity and add 10% more time when planting a crop 11-13 weeks prior to first frost
  • Count days to maturity and add 20% more time if you are 8-10 weeks prior to the last frost
  • Count days to maturity and add 40% more time for 5-7 weeks prior to your first frost date
  • Count days to maturity and add 60% more time for 3-4 weeks prior to your first frost date.
  • Count days to maturity and add 100% more time for 0-2 weeks prior to your first frost date.

This method is not exact but it’s a good guesstimate for most areas.

I will explain how this works using radishes as an example. Specifically, the variety Cherry Belle Radish which takes about 25 days to mature.

A hand holds pink radishes that were just harvested from the garden.

Example of Calendaring Days for Fall

If planting 11-13 weeks prior to an average first frost date, I would take 25 days and 10% of that number (2.5 days) and rounding to the nearest day would have a total of 28 days to maturity for a radish harvest. 

If planting 8-10 weeks prior to an average first frost date, I would take 25 days and add 20% of that number (5 days) for a total of 30 days to maturity.

If planting 5-7 weeks days prior to an average first frost date, I would take 25 days and add 40% of that number (10 days) rounded to the nearest day, so a total of 35 days to maturity

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If planting 3-4 weeks prior to an average first frost date, I would take 25 days and add 70% of that number (17.5 days) rounded to the nearest day, so a total of 43 days to maturity for a fall radish harvest.

If planting 0-2 weeks prior to an average first frost date, I would take 25 days and add 100% of that number (25 days) rounded to the nearest day, so a total of 50 days to maturity for a winter radish harvest.

Other considerations when calculating when to plant for a fall vegetable garden

Even though radishes are a cool season crop, they don’t like frost. Since they would take so long to mature, you wouldn’t want to plant them anytime past 5 weeks prior to the average first frost date. Of course there are exceptions, like if you have a high tunnel or a greenhouse to protect the radishes this would be a possibility.

Eliot Coleman in his book the Winter Garden Harvest says in his area, once you move below 10 hours of daylight, days to maturity triples for plants in an unheated tunnel. So a 40 days to harvest spinach would take 120 days! 

If that all sounds a little too complicated to figure out, you can try method two below.

Method Two: Use a garden planning program

There are several garden programs and apps available. My favorite gardening app is called Seedtime. Prior to using it, I was very much a paper planner kind of girl. I love the tangible, visible notes and writing it with my hands.

However, a friend convinced me to try Seedtime, and I have to admit, it’s ability to calculate harvest dates automatically based on seeding dates is a huge time saver. Especially if you have many, many successions of plantings and different vegetables to plant.

A screenshot of seedtime garden planner with cherry belle radish seeding and harvest dates.
This is a good visual representation of how harvest dates extend the closer it gets to your first average frost date. On this chart the light blue is when I’ll likely get the first frost, dark blue is when I’ll likely get a hard frost.

It’s free to sign up and use some of the features, while others are paid. I think you can calculate your dates into a calendar for free as far as I know.

I have a lifetime membership because I also like to use the interactive garden planner. And yet, I still prefer to use a paper planner for everyday notes so I can get my tangible gardening calendar fix, haha.

Method Three: Estimate, Take Notes, Learn

Method three is to estimate, take notes, and learn. I don’t recommend completely guessing, rather, using one of the methods above for estimates of when to plant. Then take notes of when you planted and the first day of harvest, how long you harvested, and when a frost came.

Also realize that using a row cover or sowing in an unheated tunnel will affect harvest dates and when plants freeze. 

A high tunnel is filled with vegetables that are planted for a fall and winter garden.

To me, this is all part of the fun to learn what works and what doesn’t. It’s not fun to plant an entire fall garden, only to have it all freeze. 

So you’ll definitely want to make sure you plan and plant on time. This is critical to a fall garden. As you record dates each year, you’ll be able to dial in exactly when to plant. That way you can make sure the harvest is fully mature.

Late Fall and Winter Gardening | Why Planting Dates Matter

If you’d like to plant for a late fall or winter harvest daylight hours are critical to know. If you aren’t in the very southern US, you’ll likely go under 10 hours of daylight during the winter.

As mentioned previously, when you hit the below 10 hours of daylight mark, plants grow almost imperceptibly. As a result, none or very little of that time will count towards your days to maturity of a vegetable.

So the plant needs to be mature before that point. A winter garden generally isn’t growing, it’s just maintaining what you planted earlier in the year.

Large purple cabbage is harvested in January and being held by a woman.
January 9th Harvest of Cabbage

You can also have plants that aren’t quite mature yet. In that case, let them mature after daylight hours increase above 10 hours again. However, there are several potential pitfalls like plants freezing or bolting as weather warms again. 

Bolting happens very often when a plant goes through a cold and dark time and then comes closer to spring. It’s a natural part of the plant’s cycle to set seed after this winter pause time has elapsed.

When I plant for a winter harvest, I harvest from December to February and try and pick everything by then. The reason is vegetables start to bolt, root vegetable quality decreases, and daylight hours are extending.

Conclusion

The number one problem with planting a fall vegetable garden is making sure the plants mature in time. Once you know your average first frost date, you can calculate when to plant using various methods like the following:

  1. Count days to maturity and add a percentage to calculate how long it will actually take the plant to mature.
  2. Use a garden planning program
  3. Estimate, Take Notes, Learn

Now that you know WHEN here is WHAT to plant for a fall vegetable garden.

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