You’ve sown your first indoor seeds, set them in a bright and sunny location and they finally germinated!
What a feeling it is to witness a baby seedling unfold from a tiny seed! The cycle of life is mysterious and magical. It always amazes and excites me to witness tiny green shoots emerge from newly planted soil.
This is something that never grows old.
But what to do next? How do you care for these fragile and delicate seedlings, so they may grow into healthy transplants, ready for outdoor transplanting?
Many people have trouble with this next stage of a seedling’s life. Although seed germination often seems like the most difficult part of seed starting, and this is often witnessed when certain seeds refuse to germinate, it is caring for the baby seedlings that is actually more challenging.
By following a few simple techniques, your seedlings should have no trouble transitioning from newly sprouted to hardy enough for transplanting outdoors.
Whether you’re a novice seed starter or a seasoned expert, you’ve probably had a few seed starting failures in your experience. If it is one or two seedlings, or an entire variety, I seem to lose a number of seedlings each year. However, this is not always the gardener’s fault, some varieties are touchier than others. By providing your seedlings with the optimal growing environment, it will help them to grow healthy and strong.
The following 10 steps will provide your indoor seedlings with the ideal growing conditions:
- Full sun for a minimum of 15 hours – Seedlings require a minimum of 15 hours of direct sunlight in order to grow strong and healthy. However, early seed starting takes place in the winter, when daylight hours are shorter than 10-11 hours per day. For our seedlings to have enough sunlight to grow successfully, we either need to supplement with artificial lighting hung 2-inches above the plants, or wait until the days are long enough to obtain sufficient light from a sunny window or greenhouse. Insufficient light is evident in plants when they grow long, thin and lanky, leaning towards a light source. These seedlings usually have a difficult time transitioning to the outside environment, due their delicate and fragile nature and succumb to the slightest environmental changes, such as too much water, wind and pests.
- Proper air circulation – Outdoor plants are rarely affected by a lack of air circulation, because they live outside and are exposed to a constant airflow. The inside of our homes, especially during winter, lacks this natural air circulation. Without proper airflow, indoor plants grow weak and fragile, making it difficult to harden them off prior to outdoor transplanting. (For more information on “hardening off”, please see my post.)
Proper air circulation also helps to prevent mold from growing on the soil and insect pests from invading plants. In order to create proper air circulation around your seedlings, either place an oscillating fan in the room and run it all day, or brush your hand over the tops of your seedlings. The motion of the fan will create wind, which will blow over your plant stems, causing them to strengthen. Brushing your hand over the seedlings will create a similar effect.
- Regular watering and maintaining a consistent moisture level in the soil – Seedlings require regular watering, to prevent them from drying up. Unfortunately, cell packs, trays, modules and other containers are shallow in nature, containing a small quantity of soil. Overhead grow lights, running for 15 hours per day, warm the soil and dry it quickly. Don’t allow the soil in your trays to dry up, or your seedlings will follow and won’t recover. Be sure to check your seedlings daily and water them thoroughly, always aiming to maintain a consistent moisture level.
- Drain off any standing water in cell trays – After your seedlings have been watered and the water has drained through to the bottom, be sure to drain away any water left behind in the seed trays. Water left in the seed trays will create a moist and humid environment that leaves your seedlings susceptible to dampening off disease. Dampening off is a disease that affects healthy plant stems, causing them to rot at the soil line and collapse. Water in the seed tray also encourages other seedling diseases and pests, such as fungus gnats.
- Don’t wait to pot up your seedlings into larger containers – Familiarize yourself with your seedlings. If you’ve planted your seeds in 1-inch cell packs, they will be ready for potting up into larger containers after they’ve developed their second set of true leaves. If they were sown thickly in a tray, be sure to prick them out and pot them on before they develop their first true leaves. The more leaves they develop, the thicker and longer their roots. The earlier you get them out and into a larger container, the easier it will be for you and won’t damage the roots of neighbouring seedlings. Provide your seedlings with the appropriate size pot. Check your seedling’s roots. If they are coming out the bottom of the container or have started wrapping themselves around the root ball, pot them up to the next size container. If you leave them in the small container for too long, it may stunt their growth. Recovery is not always possible.
Provide your seedlings with the appropriate size pot. Check your seedling’s roots. If they are coming out the bottom of the container or have started wrapping themselves around the root ball, pot them up to the next size container. If you leave them in the small container for too long, it may stunt their growth. Recovery is not always possible.
- Fertilize your plants after they’ve developed their second set of true leaves – Once your seedlings have developed their second set of true leaves, they are ready for a weekly fertilizer. Use a light strength all-purpose fertilizer. Dilute it in a watering can based on the instructions of the fertilizer bottle. Ensure the liquid runs out the bottom of your pots when fertilizing, or it may burn your plant’s roots. I prefer to use a fish emulsion, since it is gentle on the seedlings. Fertilizing isn’t a must, however. I often skip this step and only fertilize if my seedlings show signs of needing an added boost.
- Keep the room at a constant temperature of at least 21 celsius/70 fahrenheit – Although cool-season vegetables will germinate at a lower temperature, the ideal indoor temperature is 21 celsius. Cooler temperatures may stunt the growth of delicate seedlings and even damage them. If temperature drops below 8 celsius/46 fahrenheit, plants will stop growing. Once they react to the lower temperatures, it is often difficult for them to recover.
- Label all your seedlings – Be sure to label all your seedlings. No matter how excellent your memory, it is very easy to forget exactly what you planted in each tray and many seedlings look similar, especially if they belong to the same plant family. Labelling them will make it easier for you to properly care for your seedlings.
- Don’t take on or start too many seeds – Only start what you can handle. It is very tempting to start everything you like, but keep in mind where you will plant them all. It is very easy to run out of space under your grow lights and in your garden. Also, the more seedlings you start, the more work you will have in watering them. This may cause you to become frustrated and regret taking on all that you have. This leads me to my last point…
- Don’t give up on your seedlings – Frustration may lead you to giving up on your seedlings. Don’t give up after all the work you put into starting them. A little patience will reward you at the end. There is nothing like the taste of homegrown veggies!
These 10 steps will arm you with what you need to maintain and grow the healthiest seedlings. We all have failures and some can’t be explained. That’s ok. If you have enough variety, you should have enough seedlings to balance out the ones that didn’t make it. Just keep trying each year and don’t give up. With trial and error comes experience, and experience leads to confidence. In the end, you will be rewarded with the most delicious homegrown vegetables.