When to Start Seeds Indoors 

Every gardener knows the familiar itch to start seeds indoors that happens in late winter. While you may have enjoyed your downtime, the desire to get growing is strong and can’t be denied. 

Luckily, starting seeds indoors is relatively easy and pretty cheap, too. It’s also an excellent way for beginners to test out seed planting skills. If you get to the point where you’re starting enough seeds for a market garden, you’ll probably need to upgrade to a greenhouse. But starting seeds indoors is a wonderful option for urban gardeners or anyone growing at a smaller scale. 

So let’s jump in. Personally I have started hundreds of seeds indoors over the years and have learned a lot along the way. By the end of this guide I hope you feel confident enough to know how and when to start seeds indoors. 

Why Start Seeds Indoors for Your Homestead Garden?

These are a few of my favorite reasons to start seeds indoors:

1. Jump-start on the Season: Indoor seed starting allows you to get a head start on the growing season. This is particularly beneficial for plants that have a longer growing cycle especially if you live in a zone with fewer frost free days.
2. Bring a little green inside: Nothing helps break up the doldrums of winter like a tray of green little plants sprouting strong.
3. Cost-Effective: Starting seeds indoors is a cost-effective method of gardening. Seeds are generally less expensive than mature plants sold at nurseries.
4. Wider variety of options: When you start you own seeds you have a world of varieties to choose from. Heirloom types for unique flavors and greenhouse breeds that self pollinate.

Selecting the Right Seeds and Pots for Starting Indoors

Before we dive into the process of starting seeds indoors, it's important to understand that not all seeds are suitable for indoor starting. Some seeds are best sown directly in the garden, as they do not transplant well. 

Having the right pots and seed trays for indoor starts can make or break your success. Small seeded crops do great in small cells originally but often need to be potted up before being transplanted out. Larger seeds like pumpkins prefer a small pot to be started in. Our homesteader seed starting bundle provides you with both. 

Typically, seeds of warm-season vegetables like tomatoes, peppers, and eggplants are ideal candidates for indoor starting. With proper care they transplant well and benefit from being started in a controlled environment.

Brassica family crops do very well from transplants. This makes them great for succession planting. You can have new bok choy and cabbage ready to go in as you harvest from your beds through the season. 

Salad greens and herbs can be started indoors to good success. They will do well indoors for a while as long as they are transplanted out before they get root-bound. 

On the other hand, root vegetables like carrots and beets prefer to be directly sown into the garden or under tunnels as they can be disturbed by the process of transplanting. If you need to start them indoors, be very careful of the tap roots while planting. 

Pole beans and peas sprout and grow quickly when planted out. There is little advantage to starting them indoors since they will grow bigger and faster outdoors. 

Cucurbits like winter squash and cucumbers are not big fans of having their roots disturbed. If you do need to start them indoors it is recommended that you transplant at the 2-4 leaf stage and be very careful to not distress the roots as you do. 

Finding the Ideal Indoor Planting Dates

Knowing when to start your seeds indoors is crucial. The ideal time to plant seeds indoors depends on the type of plant and its specific growing needs. Most seed packets will provide information on the best time to start seeds indoors, usually indicated as a certain number of weeks before the last expected frost date in your area.

For example, if a seed packet recommends starting seeds indoors 6-8 weeks before the last frost date, and your average last frost date is May 15th, you would count backwards 6-8 weeks, which would give you a range from March 20th - April 3rd. 

You may already know your frost dates, but if not it can be helpful to understand your growing zone. The USDA Planting Zone Map is a useful resource for understanding which crops are hardy in your area.

Average Last Frost Date by Zone

Now that you know your zone, you can get an estimate on your last frost date. Here is the general breakdown, but do note that nature is unpredictable. These dates are based on a 30% probability, meaning that you have a chance of frost outside these dates. 

You could certainly get a cold snap after this date, or have warm weather for weeks preceding. So be sure to watch your weather when it comes time to plant outside and have plans in place to mitigate frost danger with frost blankets. If you need to know more about How Frost Blankets Work this article can help.  

When to Start Seeds Indoors for Spring

To make it even simpler, I’m going to work 6 weeks back from each of the above last frost dates, to give you an estimated idea of when to start seeds indoors. 

An important caveat is that not all seeds take 6 weeks to start. Some are slower (I’m looking at you Lisianthus) and some are much faster (like bok choy). But 6 weeks will work for a general estimate.

When to Start Seeds Indoors for Fall

In the fall, you will want to give your overwintering crops the best chance of survival by ensuring healthy transplants go in the ground at least 6 weeks before the first chance of frost. This means you will want to start your seeds indoors 8 weeks before. If you are planting root crops in ground, these are also good dates to work from. 

Preparing for Seed Starting

Before you start sowing, gather the necessary supplies:

• Seeds
• Seed starting mix
• Plant markers
• Seed tray with a humidity dome

If you are new to starting your own seeds or want a little refresher please head over to our Seed Starting 101 article. 

Soil Blocks vs. Plug Trays

There are many benefits to starting seeds in soil blocks, but our favorite is the space-saving. I can start enough seeds for a flower cutting garden with the small soil blocker in a single tray. We particularly like using the small soil blocks for tiny seeds like snapdragons or thyme. They are so slow to grow that they don’t need potting up. 

Cell plug trays are great for larger quantities of plants. Be sure to keep everything planted in one tray the same days to maturity. This allows you to harden off the transplants properly. 

There’s no definitive right answer between soil blocking or using trays. We have farmer friends on both sides of the argument. We also know many people who use a mix of both depending on the plant being grown. 

Sowing Your Seeds

Once you have your supplies ready, follow these steps to sow your seeds:

1. Prepare Your Seed Starting Mix: Pour your seed starting mix into a large bucket or tub and add water. Stir it with a trowel or your hands until the mix is uniformly damp. Fill your seedling pots with this pre-moistened seed starting mix. You can make up your own seed starting mix using our recipe for Microgreen Growing Media. 
2. Plant Your Seeds: Place 2 seeds on the surface of the seed starting mix and gently press them down. If your seeds are small or require light to germinate, you can leave them uncovered. For larger seeds or those that require darkness to germinate, cover them with a layer of seed starting mix.
3. Label Your Trays: Label each tray with the name of the plant and the sowing date. This will help you keep track of what's growing and when it was planted. 
4. Use a Heat Mat: Soil temperature is what tells most seeds to sprout. Using a heat mat is extremely helpful and will greatly increase our success rate.
5. Provide Adequate Light: A very bright south-facing window may work, but we really recommend lights. It’s hard for a seedling to get enough light with just a window. Every time I’ve gone that route, the plants tend to be a bit leggy and scraggly. 
6. Maintain Moisture and Warmth: Mist your seeds with water and place your pots in a seed tray. Cover the tray with a humidity dome or plastic wrap to create a greenhouse effect, keeping the seeds warm and moist.

Caring for Your Seeds and Seedlings

Within a few days to a few weeks, your seeds will start to germinate. As the seedlings emerge, they will need light. Remove the humidity dome or plastic wrap and move the seedlings to a sunny spot in your home or place under lights. 

Continue to keep the mix moist but not overly wet. Seedlings should be watered once a day or every other day, depending on the amount of sun and heat they receive.

If you’re using small soil blocks, note that they do tend to try out quickly. You’ll want to make sure you’re watering daily.

Common Mistakes When Starting Seeds Indoors

Avoiding common mistakes can set you up for indoor seed starting success. Here are a few to watch out for:

• Starting too early:  It's tempting to get a jump on the season, but starting seeds too early can lead to root bound or leggy and weak plants.
  
  
• Using poor-quality soil:  Using a sterile, lightweight seed starting mix can help avoid problems with disease and give your seedlings the best start.
  
  
• Over or under-watering:  Both can lead to problems with seed germination and seedling health. It's important to keep the soil consistently moist but never waterlogged.

Seed Starting FAQ

What’s the best way to start seeds?

Starting seeds indoors is one of the best options (in a greenhouse is also great!). Starting seeds indoors does not require a lot of equipment or skill, making it a great option for beginners.

Do you need grow lights to start seeds indoors?

You don’t need grow lights to start seeds indoors, but they certainly can help. A very bright, south-facing window can work, but you’ll want to make sure you regularly turn the plants to prevent them from getting too long reaching for the light.

How often should you water new seeds indoors?

Seedlings in trays can be bottom watered every couple of days. Small soil blocks will probably need watering every single day. Especially if you live in a dry climate or have the heat running. 

What month do you start seeds indoors?

What month you start seeds indoors depends on your location and growing zone. In general you want to start seeds indoors 6-8 weeks before your last frost date.

Can you start seeds too early indoors?

You can definitely start seeds too early indoors. This is one of the biggest mistakes gardeners make. Every time I’ve started seeds super early, they end up getting too leggy (long) and the later-started plants invariably perform better.

What is the ideal temperature for starting seeds indoors?

Seeds like to be at a temperature of about 70-85 degrees. When starting them indoors you can try to find an ideally warm spot, or use a heat mat to guarantee the proper temperature. If you aren’t familiar with heat mats check out this article. 

Written by: Mallory Paige, Emily Gaines

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