Seedling Care Tips- 5 Ways to promote stronger, healthier seedlings


You’ve sowed and nurtured your seed babies to the stage where they have developed their first set of true leaves! As gardeners, we know that the work is still not done. We need to get these seedlings strong enough to plant out in the garden. Below I’ve summarized my favorite tips for growing strong seedlings. Some of these are mentioned in my Seed Basics article, but I go into more detail below. I’d love to hear what you do to grow strong seedlings.

The tips below apply to seedlings that have been started in pots/pellets/or containers to be transplanted into the garden. If you have directly sowed your seeds into the garden, some of these tips will be applicable (like thinning seedlings) but not all. If you’d like to read about the benefits to both kinds of seed sowing, please check out Direct Sowing Versus Transplanting.

 1. Thin your seedlings

My first tip is one that many of us are already familiar with, but it is absolutely important to the future of your seedlings. Once your seeds have all sprouted, take a close look at each pot/pellet. Did all of the seeds you dropped in the hole germinate? Is one looking stronger than the others? When multiple seedlings share the same space, they will be competing for nutrients and space for their roots to grow. In order to give one seedling the best chance of growing strong, you need to snip away the seedlings that are competing with it. Simple take a pair of tiny scissors (see photo) and thin your seed pots/pellets down to one seedling per space.

The tool I use most for thinning are actually not for the garden! They are these small facial hair scissors! Haha. Scissors are a useful for thinning seedlings because sometimes, when you pull seedlings out by the root, it can disturb the roots of the plant next to it.

2. Provide a breeze

Often times, the conditions where we grow our seedlings are devoid of any wind or breezes (ie. indoors, greenhouses, coldframes). Your seedlings may look strong, but their stems have been protected from battling any sort of wind which means that they might be too weak to live in your garden. I sometimes like to turn on my ceiling fan or place a small desk fan near my seedlings. If it is a warmer day, you can open a nearby window. Exposure to these slight breezes will make the stems grow stronger and healthier. You don’t need to run a fan all the time, but just know that this is a great technique for increasing stem strength. Note: the process of hardening off your seedlings will also help them adjust to the natural breezes, but this tip is about making your seedlings even stronger before going outside.

 3. Feed your seedlings

Yes, you should feed your seedlings. Many seed starting mixes do not contain any food or fertilizer for your seedlings. There is a good reason for this. Many fertilizers are high in Nitrogen which can burn your delicate seedlings, and also the presence of a lot of nutrients can be a breeding ground for fungus or pathogens to grow. When to feed your seedlings? You want to feed them after the first set of true leaves have developed. If you are unsure what the “true leaves” are, see the diagram below. “True leaves” are the set of leaves that emerges after the baby cotyledon leaves have first emerged (cotyledon leaves are also known as embryonic leaves).

What should I feed? There are a few choices, and this is a personal decision for each gardener. I will say, my general rule is this: whatever you feed should be liquid, so you can simply water your seedlings while feeding them at the same time. Also, whatever you feed should be diluted with twice as much water as recommended. Your seedlings are fragile and can’t survive full strength fertilizer at this early stage. Here are some options for what you can feed your seedlings:

Fish emulsion– I have tried a couple different brands, but my most recent favorite has been one by GS Plant Foods. NOTE: fish emulsion definitely has a smell. You could also choose a fish and kelp blend.

Liquid Kelp– Again, I like to try different brands but I have been very happy with GS Plant Foods plus they make a kelp and fish blend.

There’s even a great fertilizer that is a mix of fish & kelp!

All-purpose, water soluble fertilizer– Sometimes it’s nice to just use an all-purpose plant food. I’ve used one by Jobe’s Organics before and was happy with the results.

Remember to dilute with TWICE the amount of water recommended. I like to feed this half-strength fertilizer about once or twice a week. Over time, you’ll be able to observe your seedlings and determine how often they like being fed. Remember, more fertilizer is not always a good thing.

Here’s a video tutorial on how I feed my seedlings↓

4. Don’t let your seedlings get root bound

When a plant is root bound (also known as pot bound), that means the roots have reached the bottom of the container and are forced to continue to grow around and around until they are basically stunted. Sometimes the roots poke out the bottom of the pot/pellet and are exposed to the elements. We don’t want our roots to be exposed or be forced to grow around in circles! If you start to notice that roots are coming out the bottom of your seed pots/pellets, it is time to transplant them to another, larger container. If Spring has arrived, you could plant them in the garden and forego the larger pot. Giving the roots space to reach out and grow will make your seedlings stronger.

5. Mycorrhizae-Encourage strong root systems and help prevent transplant shock

This is something I have been incorporating into my garden when transplanting seedlings for years now. The topic of mycorrhizae and it’s role in the garden probably deserves an article of its own. I found out about mycorrhizae through a series of events. One day I ran out of my homemade compost and needed to go buy a bag. As I picked it up, I noticed the label said it included mycorrhizae! This coincidentally happened right after I had read an older (2011) article from the UC Master Gardeners. The author had assessed the effects of mycorrhizal funghi on vegetables over a season. She found that the addition of mycorrhizae fungi into the soil lead to plants growing bigger, having better disease resistance, and possibly having better taste! If you want to read that article and assess for yourself, see here.

Why are mycorrhizae so beneficial to your plants? Mycorrhizae fungi exist in healthy soil. They basically form a mutually beneficial relationship with the roots of plants. As the fungi grow, they increase the surface area of the root system which allows the roots to absorb more nutrients and grow stronger. This ability to absorb more nutrients allows the plant to have a better defense against diseases (much like humans and our immune systems).

How do I apply mycorrhizae to seedlings? Well, when you go to transplant your seedlings into the garden, add a sprinkle of Mycorrhizae Fungi into the planting hole. I have been using a granular product by Plant Success Organics* that I really enjoy. If you want to try mycorrhizae fungi, you can use this granular that is easy to sprinkle into your planting hole. *Use my code: randi15 for 15% off your purchase!

Show those seedlings some love!

I want to end this article by mentioning that seed starting and seedling care is very personal. Many gardeners fine tune their process for years and years. Each one is so unique and sometimes the philosophy behind it has been handed down through generations of farmers and growers. I hope you found something here to help you develop your unique process. Have fun and happy growing!

Meet Randi

Urban gardening is my jam. I’m Randi, California girl who obsessively gardens to grow food and flowers around my urban home. Seasonal, simple living is what inspires me~ I hope it will inspire you too. Join me in crafting a life and home connected to the garden Read More>>>>

For Growers & Gardeners from High Mowing Organic Seeds