Start Seeds Indoors or Direct Sow (Plant) Seeds Outdoors?
Are you new to gardening from seed? Have you pondered which seeds should be started indoors and transplanted, or when it might be best to direct sow seeds outdoors? Then you’ve come to the right place! This article will explore the pros and cons of starting seeds indoors versus planting them directly outside. I’ll also share a list of vegetables (and situations) that are better suited for one or the other. Most veggie seeds can be started either indoors or outdoors, yet there are a select few that do not like to be transplanted at all!
What does it mean to “direct sow” seeds?
Direct sow is a gardening method where seeds are planted outside, directly in the soil in their final growing destination (e.g. in a garden plot, raised bed, or large container). There they will sprout, grow, and die. To direct sow seeds outdoors, follow the instructions on your seed package (when the time is right!). As a general rule of thumb, cover seeds with a light layer of soil that is about three times the thickness of the seed itself. Thus, very small seeds are buried far less deeply than larger seeds.
In contrast, seeds may be started indoors, where the young seedlings will eventually be transplanted outdoors to their forever home. By “indoors”, I mean any time or place that seeds are started in containers (seedling trays, small pots, peat moss pods, etc) in a protected location. So, this could mean literally inside a house, as well as in a garage, climate-controlled greenhouse, or similar.
Ideal conditions for seed germination
First, let’s start with a quick overview of the ideal conditions seeds need to sprout and grow, which is important to understand as you begin to navigate the seed-starting world.
- In general, vegetable, herb and flower seeds need two key things to readily sprout: consistent moisture and steady warm temperatures.
- The soil or potting medium that the seeds are planted in should be maintained nicely damp. Never allowed to fully dry out, but not overly soggy either.
- The majority of seeds prefer a temperate range between 70 to 80 degrees Fahrenheit for optimal speedy germination. However, most seeds can and will sprout in the 50’s to 60’s, but at a much slower and less consistent rate.
- Furthermore, keep in mind that a few select vegetables actually prefer slightly cooler soil conditions for germination (50 to 70F) – including lettuce, arugula, onions, peas, carrots, radishes, and turnips. Many of these seeds are ideal to direct sow outside.
- For the best results, seeds should also be started in a fluffy, fine-textured soil. Or, in a sterile soilless seed-starting medium.
- Once seeds germinate and start their life as a seedling, they need ample bright light right away. Seedlings may also need protection from pests or inclimate weather.
- Indoor-raised seedlings should always be hardened off before transplanting outside to avoid shock and damage.
Benefits of Starting Seeds Indoors
There are a number of notable benefits to starting seeds indoors over planting them outside, highlighted below. Most avid gardeners start at least some of their seeds inside. Even more, northern gardeners and those with short growing seasons absolutely must start seeds indoors in order to successfully grow and harvest certain crops at all!
Get a Jump Start on the Season
By starting seeds indoors, you are extending your growing season and giving your plants a jump start. When it is still too cold and dark to plant seeds outside, raising seedlings indoors can give the plants weeks or even months of time to begin to mature. This is a huge advantage, particularly for folks with a short growing season! If you plan it right, you will have big, robust, healthy seedlings ready to go in the ground when the growing season begins. While indoor seedlings are still growing in their containers, it also provides you extra time to decide exactly where you want to plant them.
Take cool-season crops like broccoli, cabbage, or cauliflower for example. All of these brassicas take several months from seed to harvest, and are not big fans of high heat or temperature swings. So, if you wait until the spring weather is suitable for planting seeds outdoors, the plants likely will not grow quickly enough to produce a harvestable head before hot weather sets in and causes issues.
Heat-loving summer crops also benefit from getting an early start indoors. Tomatoes, peppers, and eggplant can take many months before they begin producing edible fruits. Starting them indoors means you’ll be harvesting sooner and longer before chilly fall weather returns once again. Additionally, playing with seeds indoors is a fun way to keep in touch with your gardening hobby during the cold and darker days of the off-season.
Not sure when is the “best time” to start seeds? Reference your Homestead and Chill planting calendar for a visual guide on when to start seeds indoors, transplant seedlings outside, or direct sow seeds outdoors – for every USDA hardiness zone.
Easier to Control Conditions Indoors
When starting seeds indoors, gardeners are able to provide them an ideal controlled climate. Clearly, indoor temperatures are more steady and moderate than outside. Even more, optimal seed-starting conditions (described above) can be achieved with the use of a specialized seed-starting soil medium, seedling heat mats, humidity domes, and grow lights. The result is quick and even seed germination, and accelerated seedling growth compared to the direct sow method.
Outdoors, cool soil or inconsistent water can lead to spotty or slow germination. Cold temperatures and limited daylight hours during the winter months will also make seedlings grow less vigorously, even in frost-free areas. By having all your seeds and seedlings in one concentrated area, it also makes it easier to remember to look after them!
Protection from Pests & Harsh Weather
Baby sprouts are especially vulnerable to damage from frost, pests, or other external threats. We’ve had several garden beds full of just-sprouted seedlings taken out by birds in a single morning! Devastating. Pest insects may also pose a threat, especially soil-borne pests like cutworms and pill bugs. Starting seeds and raising seedlings indoors offers them protection from these things during their most vulnerable time.
If you plant seeds directly outdoors, be prepared to protect the seedlings as soon as they emerge as needed. The same goes for small indoor-raised seedlings after they are hardened off and transplanted outside. Hoops and row covers are the most useful tools we’ve come across for protecting seedlings from birds, insects, critters, frost, extreme heat/sun, and more.
A final benefit of starting seeds in containers is that it buys additional time for any other plants that are still growing in your garden. For example, say you want to grow a fall garden (my favorite!) Most fall garden seeds need to be started during the summer, when you likely still have healthy summer crops occupying your garden beds. Even though summertime is a far easier time to direct sow seeds outside than during the winter, starting seeds indoors instead (or even outside in seedling trays or small pots) allows the other established plants to continue to grow for an additional month or two – and feed you in the meantime!
Benefits of Direct Sowing Seeds
As you can see, there are a number of benefits to starting seeds indoors… but direct sowing seeds outdoors has its advantages too! Most notably, planting seeds directly outside requires fewer supplies or equipment than starting seeds indoors. Also, you won’t need to fuss with the added step of hardening off seedlings when you use the direct sow method. Last but not least, certain types of plants do not like to be transplanted at all (see the list below). In that case, directly sowing seeds is clearly the best choice for those!
Vegetables to always direct sow seeds outdoors:
Notice a theme? Most root vegetables and rhizomes don’t take kindly to transplanting. Attempting to do so will likely cause permanent stunting, or even death to the seedlings. Feel free to visit our grow guides on how to grow potatoes, carrots, radishes, turmeric, and garlic for more tips! Note that garlic, turmeric, and potatoes are not started from traditional seeds. Instead, individual garlic cloves, turmeric rhizomes, and small pieces of ‘seed potatoes’ are planted. These can be pre-sprouted indoors, but not in the same manner as other seedlings.
Vegetables that prefer to be directly sown, but can be carefully transplanted
Are you a “rule breaker” like me? The list of vegetables below are most often recommended to direct sow seeds outside. However, we don’t always follow that suggestion – and I know many other fellow gardeners who do the same! Yet these sensitive veggies do not like their roots ruffled, are more prone to becoming stunted, and may indeed thrive best when directly sown outside.
If you do opt to start these seeds indoors, they should be transplanted soon after, while the seedlings are still quite small. Take care to not disturb their roots too much. Never allow them to become overgrown in their container (aka root bound). To avoid this, either start them in decently-sized containers (such as small 4″ pots) or carefully pot them up as needed.
After a few years of trial and error, we now usually direct sow seeds for beans and peas outside (but not always). On the other hand, we start our shallots, spinach, leeks, beets, kohlrabi, and corn inside first – simply to get a head start. Experiment and see what works best for you. You could even do a side-by-side comparison of both methods!
(including Fava beans)
Start inside OR direct sow seeds outdoors (all others)
Essentially all other veggies or herbs can technically be started indoors or planted directly outside. However, keep in mind they’ll be subject to all of the pros and cons we’ve explored today! Most herbs are more successful when started indoors. For flowers, follow the recommendations provided on the seed package.
- Bok Choy (and other Asian greens)
- Brussels Sprouts
- Collard Greens
- Eggplant *
- Mustard Greens
- Squash (Zucchini/Summer Squash* or Winter Squash)
- Swiss Chard
- Tomatillos *
*Click on any of the highlighted vegetables in the list to visit the corresponding grow guide!
Ready to get sowing?
Well folks, that about sums up the pros and cons between starting seeds indoors versus the direct sow method. I hope this discussion and the list of vegetables to direct sow seeds will help you grow strong, healthy plants! Please feel free to ask questions in the comments below. If you found this information to be valuable, please spread the love by sharing or pinning this post! Happy growing.
Dr. Cynthia Nazario-Leary: Starting seeds for the garden to transplant outdoors in spring
Although the days are cooler and our landscapes may look a little less green after our recent freeze, now is the time to think about starting seeds indoors to get a head start on your spring garden. Not only will your plants be ready for the garden at the earliest possible moment, but you also will be able to harvest sooner. If you’re new to growing seeds indoors and want to give it a try, some good choices for beginners are tomatoes, marigolds, basil, zinnia, coleus, nasturtium and cosmos.
Getting started: Start with fresh seeds from a reliable source. Seeds can be planted in any clean, 2- to 3 1/2-inch-deep container with adequate drainage holes. You can use containers made of plastic, compressed peat or wood, or recycled containers. Using shallow trays or flats sold in garden supply stores saves space when you want to start a lot of a single-type of seed. Containers that have been previously used for planting should be thoroughly cleaned and disinfected to prevent disease.
Use a fine-textured soilless mix with no fertilizer to grow your seeds. You can either buy a seed-starting mix or prepare your own at home. Do not use garden soil since it may contain weed seeds or diseases, and it tends to compact and dry out, damaging the fragile seedlings.
Planting seeds: The goal with starting your seeds indoors is for them to be ready to be planted outside as soon as the weather is favorable, usually after the last predicted frost date. For our area, that is usually early to mid-March. Seedlings may take from 4 to 12 weeks, and the amount of time will usually be indicated on the seed package. Once you know the number of weeks needed for your specific plants, work backward from the frost date to determine when you need to get started.
To sow seeds, fill containers with moist growing medium (not soggy!) and gently press seeds onto the surface. A general rule of thumb is to cover each seed with a layer of growing medium 1 1/2 times as deep as the seed’s size.
Growing seedlings: Most seeds need warmth to germinate, usually a soil temperature of 65 to 75 degrees. Find a warm spot in the house, like on top of a refrigerator, or use heating mats to help ensure a consistent temperature. Avoid direct light — the key at this stage is to keep them moist and warm.
As soon as sprouts appear, move the seedlings into bright light. They need 14 to 16 hours per day of natural or fluorescent light to keep from becoming leggy. The growing temperature should be about 55 to 65 degrees.
The soil needs to remain evenly moist while the seedlings are young. Water from the bottom or use a very fine sprinkler to avoid damaging the delicate seedlings.
Transplanting to the garden: Young plants will need one to two weeks of hardening off before they go into the garden. Hardening off is the process of acclimating plants to outdoor conditions. Start by setting them outside for a few hours at a time in a protected, semi-shady location, such as on a porch or under a shrub. Gradually increase the time outdoors and the exposure to direct sunlight. Transplant your seedlings to the garden in the late afternoon, after the heat of the day has subsided, or on a cloudy day, and water them in well. Then pat yourself on the back and know that you are that much closer to enjoying the fruits of your labor.