3 Seed-Starting Methods Compared: Which Technique is Best for You?
Starting seeds allows you to experiment with the thousands of varieties of plants available and get a jump on the growing season. But it can be difficult to know which seed-starting method to use! Join Briana Yablonski to learn whether you should choose winter sowing, soil blocking, or seed trays.
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Any gardener knows the joy of browsing seed catalogs. Striped tomatoes, ruffled cosmos, and supersweet melons practically jump off the page and beg us to plant them. While choosing which seeds to grow is a challenge, so is determining which seed-starting method to use.
Since there’s not one best method for everyone, it’s hard to know which one is right for you! Here, I’ll explain three popular seed-starting methods and the pros and cons of each. Let’s look at winter sowing, soil blocking, and seed trays, explore each method’s pros and cons, and highlight the best method for certain types of growers and seeds.
The Three Methods: Winter Sowing, Soil Blocking, and Seed Trays
Before I discuss the best seed-starting method for you, I’ll cover the three methods we’ll explore. Knowing how these techniques work and the materials they require helps you determine whether or not they’re a good method for you.
Winter Sowing
First up is winter sowing. This is an easy and low-maintenance way to start seeds at home. Plus, since the whole process occurs outdoors, you don’t have to worry about setting your seeds on indoor heat mats or placing your seedlings under grow lights.
So, what does winter sowing involve? It’s easy to assume this method means you just plant seeds in winter, but it entails more than just planting seeds during the cold months.
In short, winter sowing is the process of planting seeds in outdoor containers in the winter and waiting until the proper conditions cause them to germinate. People often use milk jugs to create mini-greenhouses that trap heat and moisture and protect seedlings from the wind. These containers allow seeds to germinate even when outdoor temperatures fall below freezing.
Winter Sowing Pros
Winter sowing removes much of the work and time involved in seed starting.
- Low cost. This method requires only potting soil and seeds, making it a great option for starting seeds on a budget.
- Low maintenance. Once you plant your seeds, all you have to do is place them outside and walk away! While checking the moisture level every few days isn’t a bad idea, you can also rely on natural rain and snow to keep the soil moist.
- Quick. Filling a milk jug with soil takes less than a minute, and sprinkling the seeds across the soil surface takes just a few more seconds. There’s no filling seed trays or making soil blocks, and you don’t have to spend time carefully placing one or two seeds in each cell or block.
- Easy. Winter sowing is so easy that even young kids can do it! The trickiest part of the process is making sure you plant the seeds at the right depth—remember that most seeds prefer to be planted at one and a half times their width.
- Provides natural cold stratification. Some seeds, especially native flowers, require cold exposure before they will germinate. In other words, they require cold stratification or vernalization. As long as you set your seeds outside during the winter, this method naturally helps seeds break their dormancy.
- No need to harden off. Since your seedlings have spent their lives outdoors, you don’t need to harden off winter-sown seedlings before planting them outdoors. However, I recommend popping off the top of the milk jug for at least a few days.
Winter Sowing Cons
Although winter sowing is a pretty easy method, it’s not the best choice for all situations.
- Reliant on outdoor temperatures. Since you’ll place your mini greenhouses outdoors, the soil temperature and seed germination are at the mercy of the outdoor environment. If you experience a prolonged winter, seeds may not germinate and grow up by the time you hope to plant them. Planting tomatoes a month after your first frost isn’t a big deal if you live in an area with a long growing season. However, if you reside in an area with a short growing season, starting tomato and pepper seeds indoors is often essential if you want to harvest before the first fall frost zaps the plant.
- Potentially unreliable germination. All seeds germinate best in a certain temperature range. That’s why growers use heat mats to help germinate crops like peppers, cucumbers, and pumpkins and germinate lettuce seeds indoors during hot summers. Since nighttime and daytime temperatures often differ by 30 degrees or more, winter sowing exposes seeds to wide temperature swings. In some cases, this can inhibit successful germination.
- Fungal diseases. Milk jug greenhouses often develop high humidity levels. This moisture, coupled with a lack of airflow, encourages fungal diseases to develop.
- Easy to forget. While the low-maintenance aspect of winter sowing is often a pro, it can also turn into a con. If you forget to crack the lid of your milk jug on a sunny day, your seedlings may die.
Soil Blocking
Next up is soil blocking. This method involves using a metal soil blocker to create dense cubes of potting mix. These blocks serve as the perfect place for seeds to germinate and grow. Since the sides of the cubes aren’t contained in plastic trays and have direct access to the air, the roots are air-pruned. When it’s time to place the seedlings in the ground, they’ll face less transplant shock.
However, this lack of seed trays also makes the delicate soil blocks susceptible to damage. If you choose to use soil blocks to start seeds, remember to always bottom water to preserve the block’s structure.
Creating and caring for soil blocks can take some practice and skill to master, so don’t expect to be a pro on your first try. Rather than giving up, focus on using the proper type of soil mix and practicing your technique.
Soil Blocking Pros
Soil blocking is one of the best seed-starting methods for excellent plant health.
- No rootbound seedlings. Since soil blocking exposes seedling roots to the air, the roots are naturally air-pruned. Therefore, the seedlings won’t become rootbound. This provides a little extra wiggle room for planting dates, so seed blocks are a great option if you don’t know exactly when you’ll be able to get your seedlings in the ground. However, once the seedling’s roots take up the entire soil block, you should move your seedlings to a larger soil block or container.
- Limited root disturbance. If you’ve ever tried to remove small seedlings from a seed tray, you know how difficult it can be to do so without damaging the plant’s root system or crumbling the soil. Soil blocks are easy to pick up, so you can remove them from their trays even if the roots are small. That means soil blocks are the best option for root crops as well as those with tender root systems.
- Less transplant shock. Another benefit of air-pruned roots is decreased transplant shock. While factors like temperature, soil moisture, and sun exposure all play a role in transplant shock, plants grown in soil blocks typically experience less than those grown in seed trays.
Soil Blocking Cons
While soil blocks are great for plant health, this technique isn’t the best choice for all skill levels.
- Requires skill and practice. When you watch an experienced person create soil blocks, it looks as easy as making a basic sandcastle. But, forming stable soil blocks requires a fair amount of practice and skill. Playing around with the type of potting mix, soil moisture, and the amount of soil you place in your blocker can help you get things just right.
- Upfront cost. The easiest and most common way to create soil blocks is with a specially designed tool called a soil blocker. These tools come in different sizes; some of them make three-quarter-inch blocks, and others churn out two-inch blocks. While you only need one size blocker to start out, having more than one size allows you to up pot blocks as the plants grow. Each blocker costs around $50.
- Requires indoor space. Unless you have access to a greenhouse, you’ll need to place your soil blocks indoors. Overhead watering can crumble the blocks, so bottom watering is a must. Depending on the size of soil blocks you use and the number of seeds you start, you’ll need anywhere from a few square feet to multiple square yards of space.
Seed Trays
Finally, there are seed trays! These tried and true, beloved objects make it easy for gardeners of all skill levels to start seeds. All you have to do is fill the cells in a seed tray with a suitable potting mix, plant your seeds, and water. As long as you keep the soil moist and place the trays in an area with a temperature that encourages germination, the seeds should sprout in a few days to a few weeks.
As the plants grow, their roots will fill up the cells they’re growing in. When the roots reach the edges of the cell, you can either transplant them into your garden or up pot them to a larger seedling tray.
Seed Tray Pros
There’s a reason gardeners of all ages turn to seed trays each year! Here are a few advantages of using seed trays.
- Easy to use. Compared to soil blocks, seed trays are easy to use. All you have to do is fill them up, plant your seeds, and watch them grow. Of course, the proper soil mix, temperature, and soil moisture are all essential parts of growing healthy seedlings, but the process of filling the trays is simple.
- Allows you to start seeds at any time. Since you can place seed trays on heat mats, in coolers, and under lights, you can use seed trays to start seeds at any time. Planting tomatoes in seed trays in the winter or late spring allows you to plant them outdoors as soon as the first frost arrives.
- Flexible upfront cost. Starting seeds in trays can be as simple as planting seeds in an old yogurt container or pudding cup. However, if you want to invest in high-quality seed trays, you can do so. You can also determine whether or not you want to spend money on items like heating mats, fans, and grow lights.
Seed Tray Cons
While seed trays are the preferred method of many gardeners, his method isn’t perfect for everyone. Consider these cons before planting your seeds in trays.
- Requires indoor space. While there’s no rule saying you can’t keep your seed trays outside, most growers opt to keep their trays indoors, especially during the winter and early spring. Indoor growing protects the trays from heavy rainfall, wind, and cold temperatures, allowing for strong germination rates. So, if you want to use seed trays, ensure you have a safe indoor area that can accommodate them.
- Plants may become rootbound. If plants remain in their containers longer than they’d like, they will eventually become rootbound. Not only does this decrease plant health, but it also increases the amount of transplant shock the plants face.
The Best Seed-Starting Method for Small and Crowded Spaces: Winter Sowing
If you live in a small studio or one-bedroom apartment, you might not have room to set out seedling trays or soil blocks. And if you share your home with children and pets, you may find that curious hands and paws disturb any indoor seedlings. If either of these is the case, winter sowing is your best option for seed-starting.
Since winter sowing involves placing seeds outdoors, you don’t have to sacrifice precious indoor space for seed starting. Just fill your milk jugs or other plastic containers with soil mix and seeds, and then set them outdoors.
If you have some indoor space to set up a grow light and seed trays or soil blocks, prioritize starting long-season and warm-weather crops like tomatoes and peppers indoors. While these seeds will germinate if you plant them using the winter sowing method, starting them indoors ensures you can transplant mature seedlings as soon as your last frost date arrives.
The Best Seed-Starting Method for a Plastic-Free Life: Soil Blocking
If you aren’t a big fan of using plastic, soil blocking is the best seed-starting method for you. This method doesn’t rely on plastic seed trays or milk jugs—all you need is a flat tray to hold the soil blocks.
With that said, some gardeners aren’t opposed to using plastic but hate throwing out flimsy seed trays after a few uses. And I get it—tossing out the trays makes me feel like I’m wasting money and precious resources. If you like starting seeds in trays but are looking for a longer-lasting option, look for rigid plastic seed trays that last for years.
The Best Seed-Starting Method for Seeds that Require Cold Stratification: Winter Sowing
Winter sowing is the best option if you’re planting seeds that require exposure to cold before they can germinate. This method naturally exposes seeds to cold, so there’s no need to pop seeds in the freezer before planting. Once the proper outdoor conditions appear, the seeds will germinate.
The Best Seed-Starting Method for Beginners: Seed Trays
Even if you’ve been gardening for years, starting your own seeds can be intimidating. However, starting with seed trays makes the process easier. While winter sowing involves the least work, it’s not suitable for all seeds. Seed trays are suitable for starting crops ranging from tomatoes to zinnias to cilantro, so you can use this method for all the plants you’re starting from seed.
While filling the seed trays and planting your seeds is easy, brush up on a few common mistakes and tips before planting. Providing enough light, proper airflow, and correct temperature are all key parts of growing healthy seedlings in trays.
Final Thoughts
The best seed-starting method for you depends on your experience, space, budget, location, and goals. If you’re not sure which method to choose, don’t be afraid to experiment with more than one!
