Some plants need to be started indoors, while others need to spend their whole life outdoors. Some are resistant to frost, and others need cozy soil temperatures in the 70s or higher. This tool from the Old Farmer’s Almanac provides a general planting calendar and information on which plants should be started indoors vs outdoors based on your zip code. Write the details directly on your seed packets or on a list for your future reference.
It’s important to know your local freeze dates too. This help you determine when to plant in the spring. The back of your seed packet will have language like “plant outside two weeks after last frost” or “start indoors three weeks before last frost.” If you live in an area with a short growing season (i.e. a short summer), avoid plants that may not mature before the first freeze in the fall.
Maturity dates are found on the back of seed packets. Subtract the number of days to maturity from your fall’s first frost date to determine when to plant that specific variety.
As the climate crisis increasingly affects local weather patterns, expect for these average frost dates to vary and plan for possible losses by planting more than you think you might need.
Starting seeds indoors
Depending on what you’re growing and where you live, some seeds will have to be started indoors and eventually transplanted outdoors, especially those that have long maturation periods and need an extended season. If you live in an area with a long winter, you will need to start most of your seeds inside so that they have the ability to mature and grow strong before planting them outside to face the elements.
If your soil quality isn’t that great, seedlings nurtured indoors the first few weeks of their life will have a better chance of survival once planted outdoors. Critters also have a tendency to pull out and snack on seeds, so seedlings may fare better in this situation too.
Starting your seeds inside is also a great option if you live in a region where you have multiple planting seasons. You can get a head start by planting your seeds indoors so that the seedlings are ready to be planted outside as soon as it’s time to transition your garden to the next season.
Growing from seed requires soil, containers, warmth, light, and very regular watering. Choose organic soils and containers that can be recycled—or consider repurposing supplies from your recycling bin like old yogurt containers and egg cartons. Buy or repurpose a spray bottle for watering, so as not to damage the delicate seedling stems. Water at least twice a day during germination; the soil should never feel dry to the touch. Place containers on a sunny windowsill where they’ll stay warm and get 4+ house of sunlight each day. Look into inexpensive indoor growing lights if your home lacks natural light.
Always plant more than you think you’ll need and expect some losses during this fragile phase. Share any extras you have in seedling swaps and with neighbors and friends.
Transplant your seedlings according to seed packet information or planting calendar.
If you grew your seedlings from seed at home, they’re well accustomed to the relatively consistent temperature, light, humidity levels, and lack of wind and pests indoors. That’s also the case if you’re transplanting seedlings purchased at a nursery or garden store, where your seedlings likely grew up in a climate-controlled, protected greenhouse.
Before you transplant outside, you’ll need to do what’s called “hardening off” or slowly acclimatizing your seedlings to the elements and their new outdoor home. Start with just an hour or two a day and work your way up to leaving them out overnight. When you finally plant in the soil outdoors, water thoroughly to help them settle in their new home.
Seedlings and seeds are extremely sensitive to new environments and can experience shock when planting; make sure to keep to a consistent watering schedule, feed your plants if needed, and cover them from sunlight if it’s particularly hot or sunny when you are planting.
Remember to minimize disturbance of seedling roots and garden soil during transplanting to give the plants a better chance for survival and to protect microbes so they retain carbon in your soil.
Planting seeds outdoors
Some crops—including root vegetables and fast growers like peas—must be grown from seed outdoors because their delicate roots won’t tolerate transplanting. Seed packets will advise whether it’s best to start the variety indoors or outdoors.
If you live somewhere warm, with a very long (or even constant) growing season, consider planting seeds directly outdoors to disturb plants less in the transplanting process.
Don’t forget to label!
Whether you’re starting indoors or planting outdoors, don’t forget to add labels to your newly planted seeds and seedlings! Weeks or months later, you won’t remember what you planted where. A tiny melon seedling looks a lot like a cucumber seedling, but one needs lots of room to spread out and the other needs to climb up a trellis.
Create labels from repurposed or compostable materials, like popsicle sticks, which can be moved from pot to plot and reused year to year.
Read the beginner gardener toolkit for more about when and how to plant your garden.