- Look at your last frost date (find yours here) and check the recommendation for how many weeks before this you should sow your seeds. Varieties like Snapdragons can take upwards of 6-8 weeks to grow before the last frost, whereas varieties like Cosmos and Zinnias should be planted just 3-4 weeks before the last frost date.
- Seeds with hard shells may need to be scarified or soaked before planting. Learn how to do this in our blog.
- Find the best spot to start your seeds. A warm, sunny spot indoors is the perfect place to place your trays. If you don’t have direct sun, simply use a grow light. Just be sure that your light is positioned close (within 6 inches) of your seedlings so that they remain short and stout and don't become leggy from trying to reach for the light. This means that you'll need to move your light source frequently, as plants begin to grow.
- Add water to your soil and mix it with your hands. You want the soil to be moist enough that it can be formed into a ball, but not too wet that it isn’t solid. If you don't pre-wet the soil mix, you may notice that water simply runs off the top and doesn't soak in as you'd like.
- Place your soil in your cells (plastic, peat, newspaper, or egg carton). Pack the soil down with your fingers, add more, and pack it down again. You want to make sure the soil is compact and comes almost to the top of your cell.
- Put your seeds on a small dish to easily pick one up at a time. A small white plate works great as it’s easy to find the seeds!
- Plant your seeds according to the recommended depth. Most seeds should be placed directly on top of the soil with just a light dusting covering them. We recommend planting two seeds per cell. This ensures you’ll at least have one seed germinate and if both do, you can remove the weaker seedling once they are an inch high.
- Water from below into the tray. The holes in the bottom of each cell will allow the plant roots to wick up water as needed.
- Add a plant marker to the tray so you don’t get your varieties mixed up. You can use popsicle sticks or wooden markers you can find at the garden center.
- Cover with a plastic dome or saran wrap to help speed up germination.
- Place on a heat mat if you have one, or place on top of your refrigerator (or in a warm area of your home).
How To Start Seeds: Growing/Caring For Seedlings
Once you’ve planted, be sure to check your trays each day to ensure they are moist enough. You’ll want to water from below every day (or every other day) depending on how quickly your soil dries. Once your seedlings emerge, remember to remove the plastic dome or saran wrap. Care for the seedlings by watering below when necessary and use a spray bottle to mist the tops. If you have two seedlings growing in one cell, once they are about an inch tall you can remove the weaker (smaller) one by either gently pinching at the base of the stem or snipping with a small pair of scissors. Your goal is to leave the roots of the seedling you plan to keep undisturbed, in case the roots of both plants are intertwined below the soil. This is an important step to make sure the remaining seedling has plenty of room to grow healthy roots.
Once your seeds sprout and two seedlings emerge in one cell, gently use your fingers to remove the weakest one.
One of the most common problems with starting seeds is legginess. You can tell if your seeds are leggy if they are extremely thin and growing taller faster than they are filling out. Leggy seedlings are often extremely fragile and need extra care. The biggest cause of legginess is lack of direct sunlight, so if you’re noticing your seeds are looking leggy, make sure to move them to a sunnier spot or add another grow light to your setup. Leggy seedlings can usually grow into healthy plants, but you will want to give them as much sunlight and TLC as possible.
How To Start Seeds: Planting Outdoors
Once there is no more danger of frost in your area, it’s time to plant your seedlings outdoors! Whether you’re planting in containers or directly in the ground, you’ll still want to make sure there is no more chance of frost in your area.
One of the most important steps to ensuring your seedlings grow into healthy plants outdoors is to harden them off before you plant them. Hardening off is a gradual process where you acclimate your seedlings into the harsher sunlight and temperatures outdoors so they don’t get shocked from the different growing conditions:
Use a wheelbarrow or garden cart to harden off your seeds, bringing them outdoors for a few hours each day to get acclimated to outdoor temperatures.
How to Harden Off/Plant Your Seedlings Outdoors
- Starting with a mild day, bring your seedlings outside into dappled sunlight for 2-3 hours, making sure to protect them from harsh sun, cold temperatures, and extreme wind.
- Each day for about a week you can add one more hours to the time your seedlings spend outdoors, while also gradually watering them less.
- After about a week of this, make sure you choose a mild day to plant your seedlings outdoors.
- Dig a hole about the size of your cell and make sure to plant the seedling at the same depth as it is in the cell.
- Apply a watered-down solution of organic fertilizer to your new plantings.
- Water thoroughly.
Your seedlings should be acclimated to the weather outside through the hardening off process and will start to take off in your garden beds or containers! Remember to keep the new plants watered regularly and keep an eye on them for the first few weeks. Once you’ve started seeds once, you’ll get the hang of it and many of your tools (including plastic trays, cells, and domes) can be used year after year. Simply wash them in a diluted water/bleach solution to disinfect before planting the next season.
What are your favorite tools/methods for starting seeds? Please share in the comments below!