Vegetables to start indoors 8 to 12 weeks before last frost date. Avid gardeners can’t wait to get their gardens started each spring. Because weather is still inconsistent in early spring, how do you what to plant before your last frost date and in what order?
Your last frost date is defined as the last date that you will “most likely” see a plant-killing frost in your area in the spring of each year. Because we live in different climates and elevations, this date can range widely from one state to another, and even from one township to another.
Once you live in an area for a while you’ll even find that your specific yard may have its own microclimate based on the amount of sunlight and wind it receives.
Have you ever bet on the weather, planted your garden – and lost? If you are growing crops for food there is serious concern about whether or not there will be an early frost. Taking the bet means that all your hard work can be foiled when immature crops freeze.
Fortunately, there is also an absolute last frost date – which is the date after which it has NEVER frozen in your part of the world.
Typically, frost can occur when the temperature falls below 36°F, especially in rural areas. It is a localized phenomenon and can be quite variable across a small area. The National Weather Service does not keep track of “frost” exactly, but they do keep track of when temperatures hit the freezing mark or fall below.
Some adventurous gardeners push the limits on their frost dates and plant their gardens as early as possible. USDA hardiness zones classify freeze temperatures based on their effect on plants:
- Light freeze: 29° to 32°F—tender plants are killed.
- Moderate freeze: 25° to 28°F—widely destructive to most vegetation.
- Severe freeze: 24°F and colder—heavy damage to most plants.
How adventurous are you?
Would you plant your garden (or cold weather crops) if there was only a 50% chance of a moderate freeze in your area? I’ve done that in the past and I can say that it does depend on the year and how the winter has gone.
Some winters are cooler than others, but I think overall, I’ve won the battle over half of the time and turned out having a successful garden with no plant loss.
What to plant indoors 10 to 12 weeks before your last frost date
These three vegetables are slow growers and need a bit of advance planning to be ready for planting out after the last frost date.
- Asparagus, while usually grown from one-year crowns, can also be started from seed. Once established they will take a light frost, but not as young seedlings.
- Celeriac is a type of celery grown for its baseball sized, nut-flavored roots. Start the seeds early and set them out after the temperature reaches 55F.
- Celery is one of the most challenging vegetables to grow because of its long growth cycle. Bolting is caused when it is exposed to temperatures under 55F.
What to plant indoors 8 to 10 weeks before your last frost date
If you missed planting asparagus, celeriac or celery, you can still catch up on them in these two weeks. In addition, these three vegetables are warm weather crops that can be planted indoors 8 to 10 weeks before your last frost date.
- Eggplant needs daytime temps of 65F to 95F and if the temp dips below that they will not produce fruit.
- Leek needs a long growing season. Plant early for summer harvest and again in the fall for overwintering.
- Sweet or Hot Peppers need heat to grow and set fruit and nighttime temps below 50F will stunt seedlings.
You may be tempted to start other warm weather crops very early, but that would be a mistake. Holding these seedlings indoors under low light would produce lanky plants that are stressed. Wait a few more weeks and read this article to see what seeds should be started 6 to 8 weeks before the last frost date.
Related articles: What to plant 6 to 8 weeks before your last frost date
What to plant 3 to 4 weeks before your last frost date
How do I know my last frost date?
I’ve created a handy worksheet to help you determine your last frost date and how to use this to know when you should start specific seeds indoors. This will also help you decide on the best time to plant them outside in the garden.
Here’s How to Use the Last Frost Date Planting Worksheet:
- Find your last frost date. This is the date that you are usually NOT going to see another freeze. Maybe you already know it – if not head on over to Morning Chores or the Farmers Almanac and use the handy freeze/frost date calculator. You can look it up by your zip code and get a range of dates when frost is and is not expected. They will also give you the average number of growing days per year. How handy is that!
- Make note of these dates and enter the average last freeze date you collected from the website, in the first column. (ex: To figure out when I should start my broccoli seeds I take my last frost date of March 5th)
- Get out a calendar that you can use for your seed starting and planting times. Some people in the South will begin seeds in December for setting out in late February.
- Add or subtract the number of “weeks to set out” (in this case subtract 3 weeks) to get the “set out date”. That means that in my area I can plant broccoli outside the week of Feb 12th.
- Count back from the “set out date” (Feb 12 – for my broccoli) by the number of weeks to grow indoors (-6) to get your “start indoor date”. My seed starting date for broccoli happens to be Jan 1st, which by now is long gone.
Don’t worry if you’ve missed the seed starting date, there is often still a window of time to get started. If it is not too far gone, start the seeds anyway. Most cool weather crops can be planted in succession until the days get very hot during the summer months.
If it is getting on in the season, purchasing starts from the local nursery may be your best option this year.
The Last Frost Date Planting Worksheet works to help you know when to plant certain vegetables and herbs in your garden without danger of frost damage. Enjoy!
Now that you’ve determined your last frost date, what should you be planting right now?