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How to Care for Seedlings: Growing Healthy Seedlings

Starting plants from seed is a great way to start a garden. It’s cheaper than buying starter plants and you can choose unique varieties that you might not be able to find in stores. Plus, it’s a lot of fun!

If you don’t have a lot of experience starting plants from seed, the process can seem overwhelming. If that’s you, don’t worry, I’m here to help! This guide has everything you need to learn how to care for seedlings.

I’ll go over how much to water, when to fertilize, how to tell when it’s time to transplant seedlings outside, and more. Keep reading and soon, you’ll be an expert at caring for seedlings!

A starter tray of watermelon seedlings.

How to Care for Seedlings

You’ve planted your seeds and carefully tended them to make sure they sprout. Now that the little seedlings have emerged, you may be wondering what to do next.

Caring for seedlings is an important part of growing a garden from seed and I’m here to show you how to do it.

There are a few basic things you need to do when taking care of seedlings. Follow these tips, and your seedlings will grow strong and healthy.

Watering Seedlings

All living things need water, and plants are no exception. Most gardeners know that water is an essential part of providing proper care for seedlings but figuring out when and how much to water is the tricky part!

Before seeds sprout, make sure your growing medium stays moist at all times. You don’t want it to dry out at all because seeds need to stay moist in order to germinate. Water once a day or every other day. If your seedlings are in a sunny location or on a warm heating pad, they’ll dry out sooner and need water more often.

Use a spray bottle to water seeds and young seedlings. Spray bottles produce a fine spray that won’t disturb or displace small seeds. Once seedlings have grown a bit, you can use a regular watering can.

Using a spray bottle to water seeds is one tip for how to care for seedlings.

After seedlings emerge, water is still really important. Check on your plants at least once a day and water any time the top layer of the soil starts to look dry.

It’s possible to go overboard and water too much. Too much water can drown your plants and cause problems like mold so try not to overwater! The soil should be thoroughly moist but not soggy or dripping. Wait until it starts to look dry on top before watering again.

Fertilizing Seedlings

When seedlings have their first set of two true leaves you can start fertilizing. Since these are just baby plants, they don’t need a full dose of fertilizer. Use a very small amount of liquid fertilizer like Fox Farm. 1/4 of the regular dose is plenty.

Organic fertilizers are usually more effective than chemical fertilizers and you have less chance of burning the plants that way. If you’d like more information, we have an article all about the best fertilizers for seedlings.

Fertilizing isn’t absolutely necessary but it does provide an added boost to strengthen seedlings and help them grow into strong and robust plants.

Thinning Seedlings

If you planted several seeds per cell, they’ll eventually need to be thinned to just one plant per cell.

A tray of basil seedlings.

As they grow, seedlings start competing with each other for resources like light and nutrients. This results in weaker seedlings overall.

Once seedlings have developed true leaves, you can start thinning them. Choose the healthiest plant in each cell and use scissors to snip the others away at the soil level.

I know it’s such a bummer to cut away healthy plants. I don’t like to do it either but keep in mind that having fewer healthy plants is better than having a lot of unhealthy plants. Thinning is an important part of learning how to care for seedlings!

Providing Adequate Light

Proper care for seedlings includes providing adequate light. Indoor seedlings aren’t exposed to natural light the way outdoor plants are, so we indoor gardeners have to provide it for them.

If seedlings don’t get enough light, they try to reach for it resulting in leggy seedlings with long, thin, and weak stems.

Seedlings under a grow light.

Using a grow light is the most effective way to ensure young seedlings have plenty of light to grow. There are many different grow lights you can choose from in all different price ranges. If you’re not sure where to start, we’ve put together a list of grow lights we recommend, especially for seedlings.

Give your seedlings 12-16 hours of light per day. A timer is handy for programming grow lights to turn off and on so you don’t have to remember to do it at the right time every day.

Providing Good Air Circulation

Good air circulation is important for preventing fungal disease and similar problems. You can ensure good air circulation by making sure plants aren’t too crowded, regularly rotating the trays, and using a fan.

If you’re using a humidity dome, leave it off for a few hours a day to increase airflow around the plants.

A humidity dome over a seedling starter tray.

Thinning seedlings and moving them to bigger containers as they grow both help with air circulation by ensuring plants have plenty of room and aren’t too crowded.

A Fan isn’t strictly required when taking care of seedlings but it’s one of the best ways to provide good air circulation. It’s also beneficial for strengthening seedlings.

Outdoor plants are exposed to wind all the time and as a result, they become stronger. Indoor plants don’t usually experience wind but you can provide your own by aiming a fan at your seedlings for a few hours a day. This simulates real garden conditions for plants and helps them get ready for moving outside.

Potting up Seedlings

Learning how to care for seedlings can be confusing if you don’t know the lingo, but that’s what I’m here for! If you haven’t heard the term before, “potting up” simply means to move seedlings “up” into a bigger pot.

Potting up provides many benefits for young seedlings. If your plants are getting too crowded or too big for the seed trays, potting up gives them more room to grow and more space to breathe.

Most of the time, plants outgrow seedling trays before it’s time to transplant them outside. Potting up keeps plants healthy as they wait for the right time to be planted outside.

Seedlings that have been potted up into containers.

When to Pot up Seedlings

Plants have a good way of letting us know what they need if only we can learn to read the signs. Here are some of the top signs to look for when deciding when to pot up young seedlings.

The first is size. If the seedlings are twice the height of the container they’re currently in, they need a bigger container. Second, If you see roots growing out the bottom of the seed tray that’s a sure sign the plants need more space.

Another thing to look for is thirsty plants. If your plants soak up water so fast that you can’t keep them hydrated, they need more soil. Lastly, if the plants look healthy but don’t seem to be growing anymore, that’s another sign that they need more space to stretch out.

How to Pot Up Seedlings

Select a larger container and fill it with potting soil, making a hole for the seedling. Carefully move your seedling into the hole and fill in around it with soil. Water thoroughly, and don’t forget to label the new container!

Gloves and a garden trowel are other useful garden tools to have for potting up your seedlings.

When to Transplant Seedlings Outside

Seedlings being hardened off in the garden.
Hardening off seedlings in the garden.

After taking care of seedlings indoors for weeks, it’s so exciting to finally plant them outside in the garden. For the healthiest plants, it’s important to make sure to transplant your seedlings at the right time.

The biggest factor in determining when to transplant seedlings is the weather. Different plants all have different needs, so check your seed packets to see when they can be planted outdoors.

For warm-weather crops like tomatoes and peppers, wait to plant seedlings outside until all danger of frost has passed. Cool-weather crops like lettuce and peas can be planted outside a little bit sooner.

Seedlings are large enough to transplant outside when they are a minimum of 2-3 inches tall and have at least one set of two true leaves.

A starter tray of cucumber seedlings.
Cucumber seedlings with the first set of true leaves forming.

Many plants can stay inside for 4-6 weeks before planting outside, so they might be quite a bit bigger by the time the weather is right. That’s perfectly fine too!

Harden Off First

Before transplanting outside, make sure to harden off plants for a few days or even a week. Hardening off gives your plants a chance to get used to the conditions outside slowly.

Learning how to take care of seedlings is hard work, you don’t want to waste your efforts by shocking your plants! Treat your seedlings gently and you’ll be rewarded with strong, healthy plants.

Wrapping Up How to Care for Seedlings

Seedlings and plant labels.

Taking care of seedlings after they sprout is an essential part of starting plants from seed. Now that you’ve learned how to care for seedlings, you’re ready to get growing! With these tips, your little seedlings will soon grow into healthy plants you can be proud of.

If you have more questions about planting and growing, be sure to visit the Seed Starting page on our website. We’ve put together tons of resources to answer all of your questions and give you tips and tricks to help your garden thrive. You’ll find planting guides, product recommendations, how-to articles, and much more to get your garden off to a great start!