How to Start Plants From Seed
It may not actually be Spring, but for the gardener, it’s so close we can taste it (and our coming produce) already. That means it’s time to get those seeds into some soil and started for the coming season. You can, of course, purchase started plants at your local garden center or nursery. But, there is nothing quite like starting your seeds yourself. Not to mention the fact that it opens you up to a much wider array of varieties than most garden centers carry.
However, if you’re new to gardening, or to seed starting it can seem a bit daunting. But, it doesn’t have to be. You don’t need fancy soils, or expensive pots either. The truth is, started correctly, a seed can sprout just about anywhere. So, today we are going to walk you step by step through the process of starting plants from seed.
When Should Seeds be Started Indoors?
Your seed starting date will be dependent on two primary factors:
The crop type or variety Certain crops such as lettuce and cabbage will go into your garden earlier than frost-sensitive items like peas and corn.
Your last expected frost date As a general rule, with a few cold hardy exceptions, plants don’t like frost. One of the most important things for any beginning gardener to know is what the first and last frost dates are for their area. If you’re not sure of your frost dates, you can find them by entering your zip code here.
You never want to sow your seeds too early. If you do, you risk plants getting too large to be kept in pots before putting them in the ground. Another reason is the potential for fungus. One year, we started everything too early and kept them in paper pots. After weeks of being kept in soggy paper, that paper molded. Which left me to start over from scratch way later in the season than I was comfortable with.
The desire to get a jump start on things is real, but in the long run, you’ll be much happier if you just hold off a little longer.
Reading a Seed Package
Before starting seeds indoors you’ll want to study the information provided on the seed packet. It should have everything that you need to know. (If information is missing, a quick Google search should fill in the gaps.)
Look for sowing instructions - “sow indoors x weeks before the last frost” or direct sow after all danger of frost is past.” It’s important to note if a seed is recommended for starting indoors. Some varieties such as corn do not like to have their roots disturbed and will not tolerate transplant well.
Other information you’ll need is sowing depth, days to germination, spacing, days to maturity, light, water, and soil/fertilization needs.
What are the Best Containers For Starting Seeds?
As we said before, seeds will sprout in just about anything as long as the conditions are right and no one container type is “the best.” You can invest in plastic pots, seed-starting peat pellets, or biodegradable paper pots. But they really aren’t worth the expense.
Seedings don’t need an overabundance of soil. Any small container will do as long as it has drainage. A few good options for DIY or upcycled seed starting pots include:
Solo or other plastic cups
Plastic water bottles, cut in half
DIY newspaper pots
Toilet paper tubes
Shredded paper mache pots
What is the Best Soil for Starting Seeds?
There are of course special “seed starting” soils that can be purchased. But just like with other gardening supplies, they can be costly and aren’t actually necessary. Additionally, they tend to contain chemical fertilizers.
The thing about seeds is that they are much like a chick inside an egg. Just like an egg contains everything needed to make a healthy chick, the seed itself contains all the nutrients your seedling needs. There is no reason to fertilize them at the germination stage.
The key to seed-starting soil is that it should be light, airy, and finely textured. We mix our own using organic potting soil, coconut coir, and worm castings mixed 50/30/20. When selecting a bagged soil avoid products that contain pine chips, wood fiber, or other chunky materials that can prevent delicate roots from breaking through the substrate.
Also, never reuse potting soil. It could contain soilborne disease held over from previous plantings. And, don’t mix in garden soil, it doesn't drain well, tends to be too heavy, and can contain pests, diseases, and weed seeds.
Let’s Get Sowing!
Now that we have the basics of when and what we need to know to grow seeds, it’s time to get down to the business of how to start plants from seed.
Gather Your Supplies
Seed-starting pots containers or trays
Seed starting mix (homemade or store-bought)
Spray bottle or squirt bottle filled with water (rain or well water is best, if you must use city water, let it sit out overnight to dissipate chlorine.)
Bucket or large container for soil (optional)
Moisten Your Soil
You’ll need to start off with moist soil. Start by dumping your seed starting mix into a large tub or bucket. Next, pour in a generous amount of water, and mix to combine with your hands or a trowel. As the mix starts to absorb the liquid, add more as needed until your soil mix is uniformly damp.
Fill Your Containers or Trays With Seed Starting Mix
Once your seed starting mix is nice and damp, fill your seedling pots with this pre-moistened seed starting mix. Fill the pots up to the top, and very lightly press down. Do not compact the soil but ensure that it is firm enough to keep your seeds and seedlings in place.
Sow Your Seeds
Now that your seed containers are prepped, it’s time to sow! Be sure to check your seed packet for planting depth. A good rule of thumb is to plant the seed at the same depth as the seed itself. So a ½” seed should be planted ½” deep. For very small seeds like basil and mustard, you can actually leave them uncovered.
To plant, make a small indentation in the center of your pot or tray cell. Place 2 to 3 seeds in each hole.
Label Your Seeds as You Plant
Trust me on this one. You may think that there is no way you’ll forget what you planted where. But let’s be honest, chances are high that you can’t remember where you left your car keys last night! All joking aside, it is easier than you think to forget what goes where.
Last year, I was so sure I knew what I was doing. In the end, I never did figure out which tomato varieties I had where and the only two I could identify on site were the Black Strawberries, and the Atomic Grape, which I ended up planting too close to each other. Meaning I ended up with cross-pollination and received Atomic Strawberries. Very pretty, and very tasty, but not what I wanted.
You can use a variety of markers for this task. You can purchase cheap plastic markers at your local garden center, or use popsicle sticks, or even plastic spoons or knives. If your seedlings are in plastic pots, you could also opt for labeling the container itself.
Keep the Seeds Moist and Warm
The best way to ensure good moisture content and warmth is to offer your seedlings a cover, or humidity dome. If you are using purchased seed starting trays they likely came with a clear cover. If you are using DIY pots, you can place them inside the plastic clam shells that salad greens and take outcome in, or simply cover them in plastic wrap.
We currently have seeds in plastic trays that are covered in the lids from the croissants we purchase at our local bakery. When I started our lettuce a few weeks ago I started them in a long pot where they will live on the window sill so I simply placed a clear plastic bag over the top.
What you use is fairly irrelevant. It must be clear(ish), and easy to move or remove so that water can be added as needed. Seedlings require warmth at this stage more than light so if your cover is not completely clear, it won’t hurt your germination.
Place your pots in the warmest area of your home for the duration of germination.
Let There be Light
Germination will take place anywhere from 4 days to 4 weeks so make sure you plant varieties with similar germination times together. Once your seedlings germinate and emerge from the soil, it’s time to add light.
Remove the humidity dome or plastic wrap, and move the seedlings to the sunniest spot in your home, or place them under grow lights.
Continue to keep the soil moist, but not too wet. Seedling roots are still fairly close to the surface so they don’t need a deep soak the way larger plants do. A mister or spray bottle is best at this stage since your seedlings are fairly delicate. Large streams of water can displace seeds or damage seedlings.
If you remember from sowing, you should have planted 2-3 seeds per pot. This was done in an attempt to hedge your bets on the germination rate. Chances are that you now have some pots with no seedlings, some pots with one seeding, and some pots with 2 or 3 seedlings.
Once your seedlings reach 2” - 3” inches, it’s time to thin your seedlings to one plant per pot. Inspect your seedlings for signs of health and strength. If a seedling looks weak, simply snip it off and discard it. If you are lucky enough to have multiple healthy starts, gently separate them and place them into their own pots.
This needs to be done to ensure that your plants have the room they need to grow without having to fight for space, light, water, or nutrients. The spacing information can usually be found on the seed packet.
Keep the Air Moving
Once your plants reach 3” - 4”, air circulation is an essential addition. A gentle breeze helps prevent disease, promotes stronger plants, controls fungus gnats, and keeps algae from growing on the soil surface. Add air circulation using a fan set on a gentle setting to provide airflow without blowing the seedlings over.
Up Pot if Necessary
If your seedlings have reached 4”-5” inches and it is still not safe to plant them outdoors, now is the time to “up pot” to larger containers to give your seedlings the room they need to keep growing indoors. When up potting, you can now switch from your seed starting mix to a quality potting soil and add in fertilizer and nutrients where needed.
Hardening Off Seedlings
This process will need to be done one to two weeks before you plan to transplant your new starts into your garden. Remember that they have lived a nice cushy life up to this point free from direct scorching sunlight, temperature shifts, wind gusts, and bugs. If you were to simply plant them in the garden now, they are susceptible to shock from the jarring change in their environment.
Begin this process by placing your seedlings in an outdoor spot protected from wind and sun for an hour or so. Over the next few days, move it from diffused sun to partial sun to full sun, increasing the length of exposure each day, until it’s finally kept outside all day, and overnight.
Before considering transplanting to your final destination, whether that is to your garden, or a large pot make sure that the seedling has its first true set of leaves.
Gently remove your seedling from the pot it is in by shaking it lightly or pushing it up from the bottom of the container. Never attempt to pull a seedling from its pot as this can damage the plant. Once your start is free from its original pot, dig a hole slightly bigger, and slightly wider than its original container. Add a handful of organic fertilizer, compost, or worm castings to the bottom of the hole.
Fill the hole with water then place your baby plant in the hole. Gently cover it with soil, pressing down and compacting it very lightly to ensure that it stays firmly in place. Next, give a good top-down water and lightly cover in mulch to ensure good moisture retention.
When I transplant my starts, whether they are grown from seed, or purchased from my favorite nursery I add a handful of worm castings and a pinch of bio-char to the hole with them. I then cover lightly with straw all the way up to the first set of leaves.
We hope the steps outlined above will help to start you on a long-lived journey of seed-starting success. If you are new to gardening, be sure to hop over to our Gardening for Beginners page for lots of helpful resources!
Feel free to ask any questions, and be sure to tell us all about your seed-starting endeavors in the comments below. And as always, until next time;