"Days to Maturity" Isn't What You Think It Means—Here's Why

Days to maturity... This cryptic term can be confusing and inaccurate, making you wonder where the seed companies pulled their figures from.

But there's a trick to using these numbers to your advantage so you can plan a more productive garden.

Here's the lowdown on what "days to maturity" and "days to harvest" mean for your seeds, transplants, and nursery plants. (It's not what you think!)

When do you start counting the days?

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

Temperature matters.

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).

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