Garden of Eatin' / Seeds & Seedlings

What Days to Maturity REALLY Means On Your Seed Packets

How to use days to maturity on a seed packet to help you be a better gardener

I remember the first time I bought seeds for my garden. They were tomatoes, and the packet read “75 days to maturity.”

Great! I thought. If I start my tomato seeds in March, I’ll be picking tomatoes by May.

So imagine my confusion when the first tomatoes weren’t ready for harvest until the end of June—and this was in a Southern California garden that received ample warmth and sunshine.

It had me looking more closely at other dates of maturity on my seed packets: 80 days for melons, 65 days for cucumbers, 90 days for sweet peppers, 100 days for winter squash.

Sometimes the numbers were off by several weeks, and sometimes they were right on point (give or take a few days).

Why the discrepancies? And why did it seem like most major seed companies printed the “wrong” figures on their packets?

There is no simple answer to the mystery that is “days to maturity” or “days to harvest,” common terms that are used interchangeably in the gardening world.

If you’ve been puzzled by this very thing, here’s what you need to know about those numbers.

Golden Sweet snow peas on the vine

First, what does maturity mean?

Plant maturity is a term used with annual flowers and vegetables to indicate when the plants flower or set fruit. When it comes to vegetables, however, maturity is not so well defined.

It is generally accepted that maturity is the point in which you can start picking vegetables, whether they’re ripened fruits (like tomatoes and eggplants), fully-formed but still tightly-closed flower buds (like broccoli and artichokes), or full-sized roots (like beets and radishes).

It’s when beans and peas are at their optimal size, flavor, and texture for eating.

It’s also the point in which leafy greens (like bok choy and cabbage) are full grown and have formed a head or rosette.

However, keep in mind that many vegetables can be picked at various stages, so maturity, in these cases, can span a range of up to three months depending on when you consider the crop to be ready for harvest.

Related: 10 Fast-Growing Vegetables You Can Harvest in 40 Days or Less

You can harvest tender baby carrots at 3 inches long, or wait until they’re 8 inches long.

Palm-sized zucchini can be harvested with their blossoms still attached, or anywhere from 6 inches to 12 inches long (or even larger).

Some people like to pick baby leaves off lettuce as they grow, while others wait for the lettuce to form heads before picking the whole plant.

Understanding what days to maturity means on a seed packet

When do you start counting the days?

This is where things start getting tricky.

Some seed catalogs and seed packets are self-explanatory and will list days to maturity from seed, or days to maturity from transplant.

Many others, however, list only the days—which leaves you to wonder whether you start counting from the date you sowed the seed, the date the seed sprouted, or the date you set the transplant in the garden.

With little other information, one can assume that days to maturity refers to how the seed is started.

For seeds that are usually sowed directly in the soil, like corn and radishes, time to maturity is measured from the day the seed germinates to the day the plant is harvested.

For seeds that are usually started indoors first and then planted in the garden, like tomatoes and peppers, time to maturity is measured from the day you transplant the seedlings in the soil to the day you pick the first ripe fruit.

Even then, the timing can vary widely because one person might sow their seeds earlier, when the soil is cooler and day length is shorter, while another person might start their seeds later under more favorable conditions.

Related: Find First and Last Frost Dates Accurately with This Custom Planting Calendar

And that leads to another important factor that affects days to maturity…

Plant growth is partially dependent on Growing Degree Days

Day length can throw those numbers off.

Certain cool-weather crops, like radishes, carrots, cabbage, and peas, can be sown in spring or fall.

But while these plants grow quickly in spring, they tend to take their sweet time in fall as the amount of sunlight each day starts to shrink. (Not to mention the sun being lower on the horizon and possibly hitting less of your garden.)

If you’re hoping to harvest them before freezing weather arrives, be sure to add at least a week or two to their suggested “days to maturity” to account for less available light.

Temperature matters.

The time it takes from seed (or transplant) to harvest will differ between different growing regions.

Seed packets list only one “days to maturity,” whether they’re sold in zone 6 or zone 9. But the warmer spring weather and longer growing season of zone 9 means that tomatoes will ripen sooner there than they will in zone 6.

Some years, a warm-weather crop may take longer to reach maturity because of unusually cool weather, and a cool-weather crop may stall and bolt before reaching maturity because of unusually warm weather.

These common variations in days to maturity are directly affected by a heat accumulation index called Growing Degree Days (or GDD).

More heat accumulation days means more ripe tomatoes

What are Growing Degree Days?

Growing Degree Days are used in agriculture to determine when a crop will reach maturity. Each day’s GDD is calculated by subtracting a base temperature (which varies by plant species) from the daily mean temperature, with negative values recorded as zero.

For the math geeks out there:

GDD = (High Temperature + Low Temperature) / 2 – Base Temperature

The base temperature for a plant is the temperature at which any significant development slows or stops.

Tomatoes, for example, have a base temperature of 50°F. They do not grow at temperatures below 50°F, and they need 1,300 to 1,700 GDD to ripen (depending on cultivar).

Knowing this, you can effectively predict how many days it will take for a tomato plant to mature in your garden, in your climate, during the growing season.

While GDD is primarily used to predict plant development in commodity crops like corn, wheat, and soybeans, it can be computed for any crop using local weather information.

Temperature is just one part of the whole picture, however.

Pests can affect how long it takes for a plant to mature

Environmental stressors can also affect days to maturity.

Rain, drought, pests, over-fertilizing, and under-fertilizing all play a role in how quickly a plant reaches maturity.

Combined with the wide range of climate zones in the country, it makes you wonder how useful the “days to maturity” label actually is when there are so many variables involved.

But—and this might be surprising to you—knowing this number can help you select seeds, plan your garden, and be a better gardener.

Compare the days to maturity on different varieties of plants to plan your garden better

How to use “days to maturity” to help you be a better gardener.

By knowing how long it roughly takes for a plant to mature, you can use days to maturity on a seed packet as a guide to compare different varieties of the same vegetable you want to grow.

Disclosure: All products on this page are independently selected. If you buy from one of my links, I may earn a commission.

For example, if you’re trying to maximize your tomato crop yield, you may come across indeterminate varieties like Early Girl (50 days), Sun Gold (57 days), Green Zebra (75 days), and Beefsteak (96 days).

While these values will differ across climate zones, Green Zebras will always be ready for harvest before Beefsteak tomatoes, no matter where you live.

If you have a short growing season, it’s worth looking into early cultivars (Early Girl) or cherry varieties (Sun Gold), as they’ll ripen a full month before larger slicing tomatoes like Beefsteak, giving you a good harvest before frost sets in.

On the other hand, if you know that it takes 120 days for Pink Banana squash to mature, you can pass on that variety and choose a winter squash that’s more likely to succeed in your climate (like Table King acorn squash, an early maturing variety that takes 80 days).

But if you really wanted to try Pink Banana squash (or any long-season vegetable) in a northern climate, you’ll know that you need to start those seeds indoors to give them a jump on the growing season.

Days to maturity will help you determine how soon you need to start seeds, as well as how many succession plantings are possible in your climate before the weather turns too cold or too hot.

Go with varieties that work well in your garden, save those seeds, and grow them again year after year.

Future plants will acclimate to your local conditions over time, allowing you to calculate a more accurate days to maturity for each variety you grow.

Get More Help with Selecting Seeds

Read on for help on unraveling the other mysteries of seed selection for your garden.

Days to maturity for a vegetable start begins on the day you transplant it in the garden

A note on “days to maturity” for a vegetable start.

Days to maturity aren’t just listed on seed packets. They’re also found on plant markers that come with vegetable seedlings and starts at the nursery.

I admit, this is a weird one.

Do you start counting from the day you buy the plant or the day the seed was started by the grower?

It’s hard to get a consensus since nurseries themselves might not even know (unless they started the seeds in their greenhouse and know what stage the plants are at).

But, a generally accepted answer is that the countdown begins from the day you transplant the seedling in your garden (the same way it applies for transplants you started indoors yourself).

When you’re ready to start your seeds:

This post updated from an article that originally appeared on January 28, 2019.

View the Web Story on what days to maturity means on seed packets.

About Author

I'm a plant lover, passionate road-tripper, and cookbook author whose expert advice and bestselling books have been featured in TIME, Outside, HGTV, and Food & Wine. The No-Waste Vegetable Cookbook is my latest book. Garden Betty is where I write about modern homesteading, farm-to-table cooking, and outdoor adventuring—all that encompass a life well-lived outdoors. After all, the secret to a good life is... Read more »