What you’ll learn about starting seeds in this post:
- How to set up your seed starting area
- Options when choosing your medium and containers
- How to prepare your seeds with soaking, stratification, and scarification
- How to take care of your seedlings
- How to harden off your seedlings for transplanting
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As winter winds down to a close, we find ourselves flipping through seed catalogs and daydreaming about this year’s garden. Soon it will be time to come out of hibernation and start the back breaking, but enjoyable, work of digging in the soil.
“Not only is starting your own seeds less expensive than buying starts, but you’ll have so many more options.”
Until then, we can get a jump on our garden by starting our seeds indoors. Not only is it less expensive than buying starts, but you’ll also have more options. Garden centers tend to carry limited varieties, but when you germinate your own seeds, you have the opportunity to experience flavors you would otherwise never taste.
Starting your seeds indoors also gives your plants a head start with fewer risks. They won’t have to contend with harsh winds and rains, slugs, or hungry rabbits. You can keep them safely protected in an ideal environment until they are old enough to be hardened off and planted outdoors.
However, starting your own seeds indoors isn’t foolproof. Most people who have tackled this project have had seedlings die or not germinate at all. The process is simple, but it can be somewhat of an art form and it pays to learn from others’ experiences.
Set Yourself Up for Success
First things first, it is important to get your timing right. A common mistake is to start your plants too early. Different plants require different time frames, so you’ll want to do a little research on each plant you plan on growing. For example, broccoli, cauliflower, and tomatoes should be started about 6 weeks before your last frost date. Artichokes, celery and onions should be started about 10 weeks before your last frost. Pumpkins, cucumbers and cantaloupes only need about 3 weeks.
“You’ll want to make sure your seedlings have the right environment to thrive.”
You’ll want to make sure your seedlings have the right environment to thrive. Most importantly, you need to consider the amount of light they receive and their soil temperature. Most seeds need darkness to germinate, although there are exceptions. For example, lettuce, poppies and snapdragons need light to sprout. Your seed packet should tell you what your individual seeds need.
Once your seedlings breaks through the soil, you will need to make sure they have enough light. Oftentimes, a window is not sufficient. You will have better success if you use a grow light on a timer. Place the light about two inches above the seedlings so they don’t grow long and leggy, and give them 12 to 16 hours of light per day.
Most seeds will germinate between 65 and 75°F, however each plant has its own optimal soil temperature. For example, peppers will germinate in 8 days at 86 degrees, but take almost two weeks at 58 degrees. Eggplants, melons, pumpkins, squashes and tomatoes all have optimum soil temperatures between 80 and 95 degrees.
You can test soil temperature by inserting a soil thermometer 3 to 4 inches deep in the soil. You might be able to achieve these temperatures by placing your seedling trays on top of the refrigerator, however if you want to be more precise, I recommend using a heat mat with a temperature controller.
Choose Your Medium and Containers
Next, you’ll want to gather your containers, clean them, and fill them with the proper medium. Most garden centers carry seed starter trays with individual cells you can fill with a seed starting mix. They usually have matching trays to catch water and clear plastic domes that will help your soil retain moisture between watering.
“Seedlings need more air flow than standard potting mixes provide.”
You can also use small paper cups, rolled up newspaper, or toilet paper rolls to create tiny pots if you would like to stay away from plastic. Whatever container you use should hold about 3-4 ounces of seed starter mix and have drainage holes. Instead of purchasing clear plastic domes, you can simply use plastic wrap to cover your seeds. Puncture the wrap with a few holes to allow for air flow. If you are using plastic pots or trays, be sure to clean your containers with a bleach solution in order to prevent fungal diseases.
Used spinach clamshells from the grocery store can be used to create a humid environment for seedlings.
The medium you use is very important. Seedlings need more air flow than standard potting mixes provide. You can buy a soilless seed starting mix, or you can prepare your own with equal parts peat moss and vermiculite or perlite. Presoak your medium, fill your trays and containers to the top, and then tamp down on the mix to get rid of air pockets.
Prepare Your Seeds
If you have seeds that are a few years old, you can check their viability with a couple of different methods. The first is to place your seeds in water. It is likely that the ones that float will not germinate. This method is not always accurate, so if you want to have a better idea if your seeds will sprout, place 10 seeds from the packet between two wet paper towels and place them in a plastic bag on top of the fridge for a little added warmth. If only a couple of the seeds sprout, then there is a good chance you may be wasting your time planting the entire packet.
To improve your chances of success, you can prepare your seeds with stratification or scarification. These techniques can take days off the normal germination time.
Depending on their natural habitat, seeds may require certain environmental factors before they germinate. For example, seeds native to deserts usually need a good soak from the rain before they pop. Seeds whose native climate has cold winters benefit from time spent in a cool, moist, dark place. You can learn what each plant needs by reading the seed packet and doing some minimal internet research.
Stratification is when you trick seeds into thinking they are experiencing winter by putting them through a period of moist cold. You can do this by soaking them, putting them into a plastic bag filled halfway with moist seed starting mix, and placing the bag in the fridge. When you see the roots peeking out, use a spoon to scoop out the seed with some medium and plant it in a small pot.
Scarification is ideal for bigger seeds with a thicker skin. It is when you break the seed’s skin with either a pocket knife or a little sandpaper so that moisture can reach the embryo inside and start the germination process.
“All but the smallest seeds usually benefit from soaking them for about 24 hours.”
All but the smallest seeds usually benefit from soaking them for about 24 hours. Be sure not to soak them for longer than this or they could rot. Once they swell up, plant them right away and keep them moist.
Garbanzo bean seedling
Planting and Care
Whether you decide to prep your seeds or not, you’ll want to press the seeds gently into your pre-soaked seed starting mix. Plant 2-3 seeds per container and thin them later by snipping them at the base with a pair of scissors so you don’t disturb their roots. The general rule of thumb is to plant them three times as deep as their size. If they need light to germinate, press them lightly into the soil and barely cover them. Cover them with plastic wrap or a dome until they sprout, and then remove.
Be gentle when watering your seeds so you don’t disrupt them. Mist them with a spray bottle, use a turkey baster, or water them from the bottom.
Jiffy Natural & Organic Starting Mix inside of cut up toilet paper rolls.
Seeds contain enough nutrients to feed themselves until they sprout, however once they break through the soil, give them plenty of light and feed them with a diluted fish emulsion or seaweed fertilizer. I also recommend using compost tea to water your seedlings for accelerated growth. The sooner you can establish microbial colonies on their root systems, the more effective the microbes will be.
When your plants have two or three pairs of true leaves and are ready to go outside, I like to foliar spray them with a neem oil treatment to prevent pests from attacking them right away. I dilute the neem oil a little more than I usually would since they are so young. This may stress them slightly, but it may also save them from hungry bugs. Preventing pests is a lot easier than fighting a full blown infestation.
In the back are 10 x 20 inch black plastic cell trays covered with saran wrap, waiting for seeds to pop. In the front, I’ve already transplanted some seedlings into Solo cups with Black Gold Potting Mix.
Hardening Off Your Plants
Before planting your babies in the garden, you need to acclimate them to harsher outdoor conditions. You can “harden them off” by putting them outside for a few hours every day.
“Before planting your babies in the garden, you need to harden them off by acclimating them to harsher outdoor conditions.”
For the first few days, put them in a shady spot that is shielded from wind for a few hours. Over the next week, gradually increase their time outside, and the amount of sun and wind exposure they receive. Once they have toughened up, transplant them into the garden on a cloudy day or in the late afternoon so the full sun doesn’t shock them.
Starting your seeds indoors can save you money, give you a head start on the growing season, and offer you more options than your local garden center provides. These tips will help you avoid failure and start your garden with happy plants.
This article was originally published in the February 2019 issue of Maximum Yield Magazine.
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Some of My Favorite Seed Starting Supplies: