Learn to use your first and last frost dates (not your hardiness zone) to know when it’s safe to plant.
Every spring, I see new gardeners asking the same question: When can I plant my garden?
And just as often, I see them get overwhelmed by charts, zones, and conflicting advice.
Forget all that.
For vegetable gardens, timing matters more than growing zones.
Most vegetables and many cut flowers are grown as annuals, which means they live for one season and then they’re done.
Because of that, your success depends far more on frost dates than on your growing zone or hardiness zone.
In this post, I want to help you understand
- what first and last frost dates actually mean
- why they matter more than zones for annual vegetable and flower gardens
- how zones do fit in and when they don’t
- and how to use this info to know when it’s safe to plant for your garden
This information is so important to understand for gardeners of any skill level, and once you have it figured out, you’ll always have it in your toolbox.
Let’s plan your best garden season yet!
What Are First and Last Frost Dates?
Have you ever read the back of a seed packet and saw “Start seeds 6-8 weeks before your last frost date” and wondered what that meant?
Here’s what that means.
- The last frost date is the final expected frost in the spring
- The first frost date is the first expected frost in the fall (or, as I think of it, the death day for all my tomatoes and zinnias)
These two dates signal the beginning and the end of your growing season.
Everything in between is when most annual vegetables and flowers grow best.
Why Frost Dates Matter So Much
Our frost dates tell us when it is relatively safe to plant things that are frost-tender, or warm-season crops.
“Relatively safe” because there is still a chance of getting frost after your last frost date has passed. Remember, these dates are estimates, not exact.
We had snow once very close to our last frost date of April 25. Predicting the weather is not an exact science. Anything can happen!
Still, knowing your frost dates helps you:
- Avoid planting warm-season crops too early
- Plan seed starting and “last call” plantings
- Understand when your garden’s main growing window opens and closes
To find your frost dates, search your zip code or city and country in the box below from FrostDates.com.
Or google your zip code or city and “first and last frost date.”
Record these dates in your garden planner or keep it on a page with your seeds for future reference.
Don’t have a garden planner? You can grab mine for free right here.
For me, in central Indiana Zone 6a, my last frost date is April 25, and my first frost date is October 10.
The Exception to Planting After Your Last Frost Date
In general, it’s safest to plant your warm-season vegetables after your last frost date, when you’re unlikely to get a killing frost.
But not everything has to wait.
This is where a lot of the conflicting advice comes from.
Some crops actually prefer cooler weather (40-60°F or 4-15°C) and can be planted before your frost date.
These are known as cool-season crops and include plants like onions, peas, and cabbage.
So, warm-season crops like tomatoes and cucumbers grow best in the main growing season a.k.a. after last frost, while cool-season crops grow best in the cooler weeks leading up to your last frost.
If this is all confusing, just put a pin in it and we’ll circle back later!
So Where Do Gardening Zones Fit In?
Now, let’s switch over to gardening zones (or growing zones, or hardiness zones) for a minute.
The USDA has divided the US into 13 different hardiness zones based on minimum winter temperatures.
Each numbered zone stands for 10 degrees of temperature difference. Each letter within the zone stands for 5 degrees of temperature difference.
Zones tell us which plants survive winter and return year after year.
In other words, zones are about perennials, not annual vegetables and flowers.
When Zones Do Matter
Zones are helpful for knowing if you can plant:
- Perennial herbs and flowers
- Fruit trees and bushes
- Ornamental plants meant to overwinter
For example, oregano is hardy in zones 4-10, so I know it’ll come back year after year for me in zone 6. However rosemary is listed as hardy to zone 7 and above, and it has (correctly for my zone) not once made it to spring for me yet.
That’s why hardiness zones do make a difference in perennial gardening.
So, tl;dr, frost dates tell you when it’s safe to plant, and your hardiness zone tells you what’ll make it through the winter.
Any plants that can survive in your hardiness zone will be perennial, meaning the plant will come back year after year.
These can be planted whenever the ground is soft enough to dig into.
So both early spring and fall are still good times to plant perennials like these herbs.
To Find Your Growing Zone or Hardiness Zone
If you’re curious about your zone, the easiest way to find it is to Google it.
You can also check the USDA Plant Hardiness Zone map and find where you live.
Canadian friends can check their zone on this map.
Side note: My zone actually changed in 2023 from 5b to 6a. If you think you know your zone, it might be worth re-checking to see if it’s the same!
If You Don’t Live in the US or Canada
If hardiness zones aren’t used where you live, don’t worry about it.
Most vegetables are grown as annuals, so we can expect to plant them fresh each year anyway.
Instead, focus on your average monthly temperatures and when freezing temperatures begin and end.
For growing annual vegetables and flowers, that’s all you really need anyway.
Your Growing Season (The Part That Matters Most)
The chunk of time between your last frost and first frost is your main growing season, which is what really matters most for annual gardening.
This is when warm-season vegetables and flowers thrive and most planting happens.
It’s also the warmest time of the year for you. This is when it is safe to plant your annual vegetables.
Once you have passed your last frost date, you can plant any vegetable or flower you want.
If you live somewhere that doesn’t freeze, use your average monthly temps to divide the year into cooler and warmer seasons.
Many vegetables and annual flowers thrive between 55°F and 85°F.
Cool-Season vs. Warm-Season Vegetables and Flowers
Some vegetables thrive in warmer temperatures, but others like cooler temperatures. Let’s break it down.
Cool-Season Crops
These plants prefer growing in cooler temperatures, generally between 35°F (1°C) and 65°F (18°C).
Cool-season crops can be planted up to 4 weeks before your last frost date or later on in your main growing season to mature in the cool of fall.
Examples include:
- onions
- snap peas
- spinach
- calendula
- carrots
- cilantro
- arugula
- cabbage
- kale
- sweet pea flowers
Warm-Season Crops
These plants need warmth and are damaged by frost. Plant these after your last frost date or once temperatures are reliably above 55°F (13°C).
Common heat-loving plants include:
- cucumbers
- squash
- green beans
- basil
- tomatoes
- peppers
- tomatillos
- eggplants
- sweet potatoes
Find a full list of cool-season and warm-season garden plants in this post if you need help deciding what to plant.
So, When Is It Safe to Plant?
Here’s the simplest way to think about it:
- Annual vegetables and flowers = plant based on frost dates
- Perennials = choose based on your hardiness zone
If you know your first and last frost dates, you’ve got what you need to start your garden.
Make a seed starting schedule and plan a time to put your garden in. Use this post on planning your garden from start to finish.
Don’t stress too much about your growing zone. Just plant when the weather is warm and grow from there.
I hope this information gives you the confidence to plant out your garden this season. Happy gardening!