Gardening 101: When To Start Your Seeds Indoors

Gardening 101: When To Start Your Seeds Indoors

4 Simple Steps for Planning When to Start Your Seeds Indoors

With the start of a new year is a fresh opportunity to grow—a vegetable garden! Growing plants from seed takes surprisingly more than just dirt, seeds, and water. It takes intense planning. If you’ve been looking for an excuse to utilize your calendar or planner and hope to grow a garden from scratch, then now is the perfect opportunity.

You should begin to plan starting your seeds indoors now, while there’s still time to prep the garden, select the crops for the year, and allow the seeds to germinate and grow before they are transplanted outside. Depending on which plants you choose, the amount of time they need to become strong enough to survive the outdoors will vary by a few days or weeks, and their ability to make it through the last frost will also vary.

In the following guide, we’ve attempted to account for these variables as much as possible. But if you have any questions about specific plants, share them in the comments section below!

Step 1: Determine Your Frost Date

The first step to figuring out when you should plant your seeds is finding out the last frost date for your area. A couple of different sites offer easy-to-use maps and frost date lookups by zip code:

  • Dave’s Garden will tell you when to expect the last frost of the spring and the first frost of the fall, along with the length of your frost-free growing season.
  • The Old Farmer’s Almanac will also provide this information in terms of 50% probability: as in, there’s a 50% probability that the last frost date for your area will be X.
  • PlantMaps displays a visual heat map of the last frost date ranges for each state, so you can see how that range changes from one zip code to the next within the same state.

However, the last frost date range is only a historical average and not a definitive last frost date for your area. Some places have longer and colder winters, and are more likely to experience an extra cold spell in the spring. Planning for the last frost to come too soon can be disastrous, as plants transplanted outside too early will die off. To be safe, go with the latest given last frost date.

For example: The last frost date in Pittsburgh, PA and Cleveland, OH generally ranges from May 1 to May 10. To be safe and protect our plants from an untimely demise, we’ll go with May 10 as the last frost date.

Remember that the last frost date for one city is not the last frost date for the entire state! Other parts of Ohio can have a last frost date as late as May 20, and in Pennsylvania it can be even as late as June 20. Keep in mind what your zip code is; a few miles can be a world of difference.

Step 2: Decide What To Grow

What do you like to eat? What vegetables or fruit do you find yourself buying most frequently at the store? These are some of the best plants to attempt to grow, as you’ll enjoy the fruition of your labor again and again throughout the harvesting season.

Fun fact: tomatoes are one of the most popular vegetables to grow in the garden, according to the National Gardening Association. For demonstrative purposes, we’ll use tomatoes as an example.

Unless you’ve gotten your seeds directly from the plant, they will come in a package or envelope with a chart on the back detailing how long the plant takes to germinate, the zones where it can be grown, etc.

According to the packaging of our cherry tomato seeds, they should be planted 6 to 8 weeks in advance to allow proper growth time and take 5 to 10 days to germinate. Since the last frost date in our area is May 10, we should plant our tomatoes indoors between March 15 and March 29.

Pro-tip: according to the experts, seeds take longer to germinate and grow when the ground and air temperature is colder; i.e. below 70° Fahrenheit (21° Celsius). If you don’t keep your house that temperature, or plan to grow the seeds in the garage or basement (where it is generally colder and closer to the outside temperature), then consider investing in a warming mat. Placing the seedling tray on the warming mat will help keep the soil warm and promote steadier plant growth. Otherwise, add a week or two to how long it will take the plants to grow. For us, that would mean planting the tomatoes indoors between March 1 and March 8.

Pro-tip: Consider Companion Plants

To help prevent various pests from devouring your precious vegetables, consider which companion plants would benefit your selected vegetables and of those, which ones you would actually like to grow. Certain vegetable and floral plants can repel or deter various insects and pests, so if you know that the vegetable you want to grow is prone to being attacked by a particular insect in your area, growing a plant that will repel it alongside your vegetable is a great idea.

For example: Tomatoes are frequently attacked by tomato hornworms, aphids, whiteflies, and spider mites, and can also be targeted by flea beetles and susceptible to root-knot nematodes in the soil.

Onions deter most pests including ants, carrot flies, and the aphids and flea beetles that target tomatoes. Similarly, thyme can repel the whiteflies and tomato hornworms, while dill can repel the aphids, tomato hornworms, and spider mites. Marigolds, particularly French marigolds, have been proven to help reduce root-knot nematodes in the soil by producing alpha-terthienyl. However, marigolds also attract spider mites. If you’re not careful, the spider mites can take out your marigolds and then move onto your tomatoes. It’s recommended to plant the marigolds as a cover crop in places where nematode is a particular issue after the tomatoes have had their last run. (Alternatively, using fresh soil each year can help with the nematode problem.)

If you like cabbage, then planting it near tomatoes is a smart move: tomatoes are said to repel the caterpillars that chew on cabbage leaves.

As you get more advanced with your garden, you can diversify the ecosystem in your background (or home!) to your particular preferences by keeping a plant’s strengths and vulnerabilities in mind. For more tips on how to protect your plants from wild animals and pets, check out our blog post, Gardening 101: Beginner’s Guide to Protecting Your Garden from Critters.

Step 3: Pick a Day of the Week to Plant Your Vegetables

Even though Wednesday, March 15 is exactly 8 weeks away from the last frost date of Wednesday, May 10, it may not be the best day of the week for you to plant your vegetables. If you work Monday through Friday and find yourself too preoccupied during the workweek to dedicate time to carefully planting the seeds, then consider picking a weekend day to do it instead. Planting your seeds a few days earlier on Sunday, March 12 or a few days later on Saturday, March 18 won’t hurt the vegetables, but it will help give you a relaxing moment to really enjoy sowing the seeds.

Remember, gardening is supposed to be enjoyable! If you would rather not start your garden from seed, consider buying established seedlings from a garden center or nursery. And if you don’t like to garden at all, then don’t sweat it. Not every home needs a garden. Do something else that you enjoy instead.

Step 4: Plant Your Seeds!

Now that you’ve got the day to plant your seeds indoors figured out, it’s time to do it. Be sure to have all the necessary supplies ready to go: containers for the seeds (seed starting trays, or any other container that is 2” to 3” deep with drainage holes), potting soil ideal for seedlings (such as seed starter mix), water, gardening gloves if you don’t want to get your hands dirty, labels to help you identify what seeds you planted in which containers, and the seeds.

If you’ve already gardened before and are looking to up your game, consider getting an indoor growing rack. The evenly distributed light from a growing rack ensures your seedlings get the right amount of light so that they grow into strong plants, instead of spindly seedlings leaning precariously towards the only light source.

Check on your seeds daily and watch nature’s magic at work! The best part of gardening is actually seeing the progress of your projects each and every day. When they’re seedlings, it’s also especially important to check on them daily to be sure the soil is moist enough and that the plants are getting proper lighting.

Let us know about your gardening experience in the comments below!

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