It is that time of year again, here is some guidance for starting your Seedlings Indoors.
I know, most of New England is under a blanket of white and the last thing you have on your mind is your summer garden. You can grow a robust vegetable garden by buying young plants at your local garden center closer to the time you want to plant them outside, but your selection may be limited especially if you are an organic grower. On the other hand, you can have a much wider range of varieties if you start your own plants from seeds indoors. If this is you, now is the time to start planning and mapping your outside garden. Start plants like tomatoes with long grow times and requirements for warm weather now. Planting your own seedlings is very economical with many seed suppliers like Johnnyseeds.
While growing seedlings indoors for beginners can be a challenging endeavor, there are several helpful garden sites for the best chance of success on the internet. Regardless of the garden site, they all agree to start your seeds in fresh, sterile seed-starting mix that is light and fluffy and designed to hold just enough moisture. If the growing medium is too wet or not sterile, disease can strike. If it is too heavy or sticky, fine new roots will not be able to push through it. Remember when selecting your vegetable or flower seed to do so by the zone you live in for the best and hardiest result.
As you peruse the virtual garden centers, you will see a plethora of seed, soil, fertilizer, and other offerings. This can all be a bit daunting for a first-time gardener, hold strong, start out with a list of what you and your family eat before going online. Think of it like buying health in a box! Decide if you are going to be an organic gardener or not as this is all personal preference. Are you going to use compressed coir pellets (coconut husk fibers) that expand when wet or bags of loose seed starting formula. All these mixes have a trace of starter fertilizer in them so you will not need to start fertilizing until the seedlings have several sets of leaves.
Choosing the Right Container
Anything that will hold the growing medium and has drainage holes will work, but the most recommended especially for beginners is specially designed seed starting kits because they include everything you need to grow strong, healthy seedlings.
Others offer a variety of seed starting kits that include trays with cells, expandable coir pellets, a tray to set them on and a clear lid to hold in humidity during the early stages.
An alternative to using the kits is to purchase biodegradable pots that break down in the soil. You can plant them right in the garden and so avoid disturbing the young plant's roots. Some are shaped from organic wood fiber or peat, or you can make your own from newspaper. Don't confuse these with biodegradable resin pots; those will break down in a landfill or, eventually, in a compost heap, but you can't plant them directly in the garden.
Prepare the Potting Soil
Choose potting soil that's made for growing seedlings. Do not use soil from your garden or re-use potting soil from your houseplants. Start with a fresh, sterile mix that will ensure healthy, disease-free seedlings.
Before filling your containers, use a bucket or tub to moisten the planting mix. The goal is to get it moist but not sopping wet; crumbly, not gloppy. Fill the containers and pack the soil firmly to eliminate gaps.
Start Planting
Check the seed packet to see how deep you should plant your seeds. Some of the small ones can be sprinkled right on the soil surface. Larger seeds will need to be buried. For insurance, I plant two seeds per cell (or pot). If both seeds germinate, I snip one and let the other grow. It's helpful to make a couple divots in each pot to accommodate the seeds. After you've dropped a seed in each divot, you can go back and cover the seeds.
Moisten the newly planted seeds with a mister or a small watering can. To speed germination, cover the pots with plastic wrap or a plastic dome that fits over the seed-starting tray. This helps keep the seeds moist before they germinate. When you see the first signs of green, remove the cover.
Light, Light, Light
Seedlings need a lot of light. If you're growing in a window, choose a south-facing exposure. Rotate the pots regularly to keep plants from leaning into the light. If seedlings don't get enough light, they will be leggy and weak. If you're growing under lights, adjust them so they're just a few inches above the tops of the seedlings. Set the lights on a timer for 15 hours a day. Keep in mind that seedlings need darkness, too, so they can rest. As the seedlings grow taller, raise the lights.
How Much Warmth Do Seeds Need?
Seed starting happens in two stages: germination and growing. Germination is the sprouting stage when the root and leaves emerge from the seed. You won't need light at this stage because it occurs under the soil, but you will need gentle warmth (not harsh heat). You can provide heat by using special heat mats these will keep your seedlings about 10 degrees F warmer than the air temperature, allowing the seeds to germinate faster, and leading to healthier seedlings. Once you see green sprouts about half an inch tall, you need the plant lights. You can remove the heat mats if the room temperature is between 60- and 70-degrees F.
Water, Feed, Repeat
Plants consist mostly of water to keep them turgid, and they need it for the photosynthesis that gives them energy to grow. Water is also what starts the germination process. But while water is essential for plant growth, overwatering is the most common cause of seedling failure. Check your water source for heavy minerals and or other chemicals if your drinking water from the town. If you are not drinking from your kitchen spout, your seeds should not either.
Sow your seeds in an evenly pre-moistened mix. It should be moist but not soaking wet. Cover the container to hold in humidity while the seeds germinate with the cover from your kit, or a clear plastic wrap. Try to allow for some air circulation.
Once they sprout, uncover the containers and water them from the bottom by pouring water into the tray. Make sure air circulates freely so humidity isn't trapped around plants.
How Often Should I Check My Indoor Seeds?
This is the secret ingredient to successful seed starting: you should check your seeds daily. Check to see if the seeds have sprouted so you can remove the cover when it's time and make sure the seedlings have light; check to make sure they stay properly moist but not too wet; check your reservoir if you have a self-watering kit; check the seedlings’ growth and raise the lights so they stay 3-4” above the plants; and check to make sure the lights and timer haven't malfunctioned. If you are starting a few seeds on the windowsill, turn the plants every day so they don't bend toward the light.
As you plan your garden, factor in your convenience and habits. Will you really remember to check seeds in the basement daily? It might be wiser to start seeds in the guest room or kitchen where they will be handier, even if you have space for fewer seedlings.
Move Seedlings Outdoors Gradually
It's not a good idea to move your seedlings directly from the protected environment of your home into the garden. You've been coddling these seedlings for weeks, so they need a gradual transition to the great outdoors. The process is called hardening off. About a week before you plan to set the seedlings into the garden, place them in a protected spot outdoors (partly shaded, out of the wind) for a few hours, bringing them in at night. Gradually, over the course of a week or 10 days, expose them to more and more sunshine and wind. A cold frame is a great place to harden off plants.
Enjoy the process and the eventual fruits of your labor.