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5 Common Seed Starting Problems & How To Easily Fix Them

by on March 25, 2024
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If you’re reading this, you may be in a panic because your beloved seedlings are suffering in one way or another. If this is the case, first take a deep breath! It will be ok. Most gardeners typically experience issues when seed starting, so you’re not alone. The good news is that you can likely solve the issue and save your seedlings or at least learn what not to do for the next tray of seeds you start. So put the panic to rest as you read on.

Indoor seedlings under grow lights

New To Seed Starting? Start Here!

If this whole seed starting concept is brand new to you, you’re in luck! I’ve got a handful of posts that can help level up your seed starting from beginner to expert status.

Be sure to check out my other seed starting blogs:

Where To Buy Seed Starting Supplies

I’ve curated a list for you featuring all my fav seed starting products over on my Amazon Storefront.

Here you can find everything I love and use for at home seed starting from soil and organic fertilizers to trays, fans and grow lights.

I’d also encourage you to visit your local garden centre if you can! Small business needs our love. If you’re local to Manitoba, check out my post The 10 Best Garden Centres & Greenhouses In Manitoba.

5 Common Seed Starting Problems & Issues

Let me start by saying that there are in fact more than just 5 problems that can occur when seed starting. In fact, there’s probably dozens. But don’t let that scare you!

I’ve instead identified the 5 most common ones that you’ve likely experienced or are maybe even experiencing right now.

I’ll break each one down in further details, but here they are in in summary.

1. Damping Off

An air born or soil born illness caused by a lack of air flow.

2. Mold

Typically caused by too much humidity.

3. Leggyness

Seedlings with stems that appear stretched out and long.

4. Yellowing Leaves

What is sounds like, seedlings that lose their green hue and turn yellow.

5. Stunted Growth

When seedlings stop growing.

Now let’s get into each seed starting issue further and look at some ways you can solve the problem!

What Is Damping Off And How To Solve It

As mentioned above, damping off is an air born or soil born illness that typically happens to seedlings if they don’t have enough airflow.

Lack of air circulation leads to fungi and other bacteria attacking the plants before, during or after germination.

The bad news is that once seedlings are affected they typically don’t bounce back. Sorry!

So if you’re in a situation where your seedlings are already damping off, your best option is to put them in the compost pile and start back at square one.

But the good news is that damping off can be easily avoided. Here’s how!

How To Avoid Seedlings From Damping Off

Avoiding seedlings from damping off is easy!

I suggest following these three guidelines:

First, remove your humidity dome and/or cover from your seedling tray as soon as germination occurs. This will allow your new seedlings to get the oxygen needed to stop bacteria from forming.

Second, once your seedlings are well established and have put on their true leaves (second set of leaves), put a small fan on them to increase air circulation further.

I love this clip-on fan from Amazon. It works great and can easily hang off a seedling shelf.

And finally, be cautious with watering. Overwatering and/or seedlings that are in sitting water is another reason damping off can occur.

Try my bottom watering method covered in this post to ensure your seedlings are getting the perfect amount of water.

What To Do If Seedling Soil Gets Mold On It

Luckily, mold is not a big deal when it comes to seed starting and happens to the best of us!

There’s a few reasons why your seedling soil is getting moldy:

The first could be because of the soil you used. If you like to make your own seed starting soil blend like I do, you may be adding in compost and/or other organic soil mediums which might not be sterile.

This is okay and just means you have more living microorganisms in your soil blend. It’s actually a good thing!

If this is the case, simply remove any mold that appears and then try repotting your plant with additional, new, fresh potting soil.

Alternatively, your soil may have mold on it because of, once again, lack of air flow.

If this is the case, follow my tips from above, including adding a small fan for more air circulation.

When Should I Be Concerned About Mold On Seedlings?

Mold on seedlings can get a little dicey if it’s white and fuzzy and begins to cover the plant entirely.

This often happens when using compostable containers, such as peat or cardboard pots as they naturally start breaking down with the water and soil, becoming a breeding ground for mold.

White mold on seedlings won’t necessarily make you sick as there’s still much time to go before these little plants are ready to produce food to consume.

But white mold may damage your plants and/or stunt their growth.

So if you see white mold growing on your seedlings, be sure to move them away from the others and provide adequate air flow immediately.

Additionally, be sure to water only the soil rather than the entire plant. Again, my bottom watering method covered here works great for this!

What Causes Seedlings To Get Leggy And How To Fix It

Leggyness is an issue many gardeners deal with and it can be frustrating!

Leggy seedlings is when the stem of the plant gets stretch out as it is reaching for the light. You’ll quickly know if this is happening as your plants will look stretched out. They may also fall over and be very weak.

Instead, you want a seedling that is sturdy, stalky and has some rigidity to it so that when it heads outside into the great outdoors it can withstand wind.

What causes leggyness in seedlings?

Leggyness is almost always caused by not enough light or seedlings that are placed too far from the light.

Like I mentioned, they are ultimately getting leggy because they’re stretching up to the light to try and get more of it.

I’ve said it before and I’ll say it again, if you don’t have a grow light your seedlings simply do not have enough natural light to succeed. You need a grow light if you are growing seedlings indoors in a Northern climate. No if, ands or buts!

And no, a south-facing window is not enough! Seedlings need at least 12-16 hours of direct light daily.

My trusted and favourite grow light brand is Sun Blaster.

They offer high quality LED grow lights that will last you years and won’t add on much additional cost to your electricity bill.

My preferred grow light style is the Sun Blaster Prismatic Lens LED Strip Light.

The prism allows the light to be magnified so it reaches a larger surface area, meaning you only need one grow light per shelf rather than needing two as you do with traditional strip grow lighting.

But why are my seedlings still getting leggy even under grow lights?

If your seedlings are still suffering from leggyness despite being under grow lights, try raising them so they are closer to the light.

My rule of thumb is that from germination and throughout the initial establishment of my seedlings (approx. the first 2-6 weeks depending on the plant) I keep my seedlings directly below my grow lights.

There should only about an inch of space between the tops of them and the light.

Once my seedlings are established and have their true leaves, I lower them so there’s 2-3 inches above the top of the plant and the light as pictured here.

You may need to continue adjusting your grow light height as your plants grow.

Try hanging your grow lights with a heavy-duty electrical wire like this so it’s easy to adjust their height regularly.

What Causes Seedlings To Turn Yellow And How To Fix It

Most often, the main cause for seedlings that turn yellow is a nutrients deficiency.

Again, it’s luckily an easy problem to fix!

But first, if it’s your seedlings first set of leaves that are yellowing don’t worry. This is normal and sometimes those initial leaves may even just fall off.

If that’s the case, let nature run her course and don’t rush to take any action.

However, if your seedlings are well established and it’s their true leaves (second set of leaves) or additional growth that is yellowing, the fix is fertilizing! Organically, of course.

How Should I Start Fertilizing My Seedlings?

There’s several different schools of thought when it comes to how often you should fertilize your seedlings.

Some organic gardeners seem to believe that fertilizing should begin as soon as germination occurs. Whereas others will even go as far as to soaking their seeds in fertilizer before planting.

My rule of thumb is that I begin fertilizing once the second set of leaves (the true leaves) have appeared.

You can find my full approach to organically fertilizing seedlings covered here, but the big takeaway is to fertilize at least once per month and to use both an all-purpose organic liquid fertilizer as well as a kelp-based liquid fertilizer as they play different roles.

I suggest trying Sea Magic Kelp Fertilizer. It’s a liquid fertilizer that helps seedlings with root development, foliage growth as well as improve disease resistance. It’s one of my fav products!

The key thing to remember is that if you’re choosing organic, you can’t really over do it or hurt your plants with fertilizing.

If anything, too much fertilizer simply won’t have a greater effect. So it could just be a waste of your time and money.

However, don’t use a granular and/or all-purpose fertilizer on seedlings. It will be too powerful for the tiny plants and could hurt them. Wait until they’re transplanted in the garden to start fertilizing with something like that.

What To Do If Seedlings’ Growth Are Stunted

Small silver dollar eucalyptus seedling

It can be disheartening to see your beloved seedlings stop growing and get stunted. Such a bummer!

But you can typically help them put on new growth once again as long as you’re consistent.

First, consider increasing the size of container your seedling is in. They may just need more space to grow and their current home isn’t providing that.

You should be potting up your seedlings at least once if not twice while they are indoors to a 4-6 inch pot.

I like using these compostable peat pots.

Secondly, evaluate how often you’ve been watering and fertilizing your seedlings.

Consistency is key and getting them on a regular water/feeding schedule can help your seedlings put on new growth quickly.

We covered fertilizing above, but be sure to water at least every few days depending on where they’re located, if they have a fan on them and other environmental factors.

All this is covered in my blog How To Properly Water & Fertilize Your Indoor Seedlings.

And finally, look a little further into the plants specific care requirements.

  • Are they getting enough daily light?
  • Are they away from drafts and forced air heating/cooling?
  • Is the air temperature around them consistently 21°C/70°F?

All these things can impact seedling growth significantly!

And there you have it! Those are the 5 most common seed starting problems and tips for how to fix them.

I hope you found this article useful and can apply it to your own seed starting this season. If you have any unanswered questions, comment below! I answer all your comments and love hearing from this community.

You can keep up with my garden over on Instagram, Tik Tok and Pinterest too. I love building community with you over there!

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