Planter can calculate planting dates in two ways:

• Frost-date planting is the default and counts weeks from your frost dates.
• Climate-based planting dates (in beta) personalize your planting windows using your local climate and what each plant can handle.

Frost-date planting

Your frost dates are the average last frost in spring and first frost in fall at the weather station nearest you. Each plant in Planter has a set of offsets from those dates, like:

• Start tomatoes indoors 6–8 weeks before your last spring frost
• Transplant them 1–2 weeks after it
• Sow kale for a fall crop 6–10 weeks before your first fall frost

Frost dates matter because frost can kill a tender plant overnight. But they only tell part of the story. "Two weeks after your last frost" means something very different in Chicago than it does in coastal Los Angeles or Phoenix. In one place, that's when nights are finally warm enough for tomatoes. In another, it's a few weeks before the summer heat shuts them down. And where frost is rare or non-existent, counting weeks from a frost date doesn't tell you much.

Climate-based planting dates (beta)

Climate-based planting dates start with two things instead of one.

Your local climate, day by day. For your weather station, Planter uses the normal high and low temperatures for every day of the year, along with rainfall, soil temperature, and the odds of a frost on any given date.

What each plant can handle:

• Heat: how hot it can get before the plant struggles. For example, tomato are happy up to about 90°F and start to stall beyond that.
• Cold: how cool the nights can be before growth stalls, and how cold it can get before the plant is damaged. For example, tomato growth can stall when temps are lower than 50°F.
• Soil temperature: how warm the soil needs to be for seeds to sprout when you sow them directly in the garden.
• Time to harvest: how long the plant needs in the ground to mature.

Planter looks at every possible planting day and asks: if I plant today, will the weeks ahead suit this plant all the way to harvest? A day where a hard frost or a stretch of extreme heat would hit before harvest is ruled out. The days where conditions look good the whole way through become your planting window.

How climate-based dates can differ

Depending on where you garden, climate-based dates can look quite different from frost-date ones:

• Hot summers: A crop that can't take the heat gets a window that has it ripening before the worst of summer, or a second window once it cools down. In South Florida, for example, tomatoes are planted in late summer so they ripen in the mild fall weather.

• Frost-free climates: These climates were previously unsupported but are now supported with climate-based planting dates!

• Fall and cool-season crops: Hardy crops like kale keep their fall windows, timed so they have enough time to mature before the cold sets in.

• Crops that need a cold spell: Some crops, like garlic, need weeks of cold before they'll form bulbs (this is called vernalization). Planter makes sure a planting date leaves enough cold time in the ground, so your garlic gets the winter chill it needs.

• Clearer reasons: The plant timeline shows why a window opens or closes, like when it's too hot for lettuce in midsummer.

What stays the same

• Plants without enough data keep their frost-based dates. Climate-based dates only apply to plants whose temperature limits we've reviewed. Everything else uses frost-date planting, and we're adding more plants over time.
• Your own edits win. If you've changed a plant's planting dates yourself, Planter keeps your dates. To go back, open the plant's edit page and check Reset to climate-based dates.
• Your tasks are up to you. When you switch planting methods, Planter asks whether to update your current-year scheduled tasks to match.

Turn on climate-based planting dates

1. Open Settings.
2. Under Location and frost dates, turn on Climate-based planting dates.
3. Choose whether to update your existing tasks to the new dates.

To go back to frost-date planting, turn the switch off.