6 Tips to Grow Healthy Seedlings

March 29, 2018

Healthy seedlings!  It’s what every gardener and homesteader strives for, but growing and keeping those seedlings healthy isn’t as easy as it sounds.

Low germination rates, leggy plants, yellowish color, damping off disease and simply not thriving are just some of the issues that can plague seedlings sown at home, even for experienced gardeners.

You might find this helpful: Sprouting Seed Potatoes Before Planting

Don’t plant too soon

If you’re anything like me, as soon as the calendar turns from January to February I am ready to plant!

However, most of the time, seeds aren’t.

It might be warm and perfect inside your home or greenhouse all year long, but it’s usually best to wait until there are only 4-6 weeks left until your last frost date before you sow those seeds.  That’s because there’s not enough light during the day in late winter to keep your seedlings happy.  And the longer they grow inside your house, the faster they’ll outgrow their starter cells or pots.  You’ll have to transplant them at least once, and risk shocking them.

Of course there’s an exception to every rule, and onions do best when started about 8 weeks before the last frost date.  Cucumbers and melons, on the other hand, shouldn’t be sown indoors until three weeks before planting out, which in my zone isn’t until late May or early June (a good 4-8 weeks after my last frost date!).

And then there are the seeds that shouldn’t be sown inside at all, like carrots or other root crops.  Always check your seed packets for more detailed planting information.

Read this for more information: Sowing onions in February

Using the healthiest soil to grow healthy seedlings

Healthy seedlings need healthy soil

To grow the healthiest seedlings you have to start them off on the best possible foot.  And that means healthy, nutritious soil.

If you’re starting your seeds indoors, it’s important to use fresh, sterile seed starting mix or potting soil every year, in containers that have been cleaned thoroughly.  Used soil or dirty pots could contain diseases or have insects living in it.

You should also make sure that the soil you’re using is nutritious for your seedlings.  Many of the most budget-friendly sterile seed starting mixes found in grocery or big box stores lack any nourishment for your growing plants.  Make sure you check the packaging to see if there are any amendments such as compost, blood or fish meal, manure or greensand.  If not, you can easily add those in yourself.

It’s also important to add another kind of fertilizer when your seedlings are about a month old and really starting to grow. Fish emulsion is my favorite, as it’s extremely mild to tender young plants and can be mixed with water and used as a foliar feed.  It has slightly more nitrogen in it than phosphorous or potassium, so it promotes vigorous growth.

Use the right amount of water, and soak seedlings from the bottom

Over- and under-watering are really common problems for gardeners.  Too little water, and the seedlings wither up.  Too much water and a whole host of problems can crop up!

It’s best, of course, to always use the right amount of water a seedling needs, but it’s often hard to know what that right amount of water is, especially when they’re growing in peat pots or tiny plastic cells. If it’s been very sunny, the soil can dry out quickly, even if you just watered.  And if you’re using grow lights, sometimes the top of the soil can appear to be bone dry, while underneath it is saturated.

It’s so frustrating!

The best rule of thumb is just to keep a close eye on them, and check daily to see if the soil is drying out by sticking your finger into the soil up to your first joint if possible.  It’s good to let it dry out a bit between waters.

Also, always make sure to soak seedlings from below, by filling the tray reservoir with about half to an inch of water.  This way you won’t dislodge delicate seedlings and you’ll substantially lessen the risk of mold,  damping off disease, and those pesky little fungus gnats.

Keep healthy seedlings from damping off

The number one killer of otherwise healthy seedlings is damping off, which is sort of an umbrella term for any number of soil-borne fungi which attack the germinating plants.

Seeds sown in soil infected with the pathogens will fail to germinate or emerge.  Seedlings will sometimes discolor and suddenly wilt.  A fluffy cobweb-like growth can occasionally be seen on the seedlings.  Often, the stem of the plant withers away right at the surface of the soil.  Usually they die.

Luckily, there are lots of ways to prevent damping off.  First of all, make sure your soil is fresh, sterile and well-draining.  Don’t use soil from the garden!  It almost always has the pathogens in it.

Properly clean all your tools and pots that were used before.  Make sure to wash your hands before you sow seeds or work with or touch your seedlings in any way.

It’s best if your seedlings’ soil is warm (I always recommend using a bottom-heating mat, like this one by Vivosun), because the damping off fungus thrives in cool, moist conditions.  In addition, low light, crowded conditions and over watering can increase the chances.  Be sure to take any plastic wrap or clear plastic lids off your trays or flats after your seeds have germinated as it will keep things too humid.

Always water from below, and water just enough so that the soil becomes damp but not soggy.

And last, but not least, I like to sprinkle a fine dusting of cinnamon over the soil after I sow.  Cinnamon has anti-microbial and anti-fungal properties, and combined with the other measures should keep your seedlings healthy.  Plus, it smells good!

Lightly brush seedlings to keep them strong

Have you ever noticed that seeds sown outdoors never seem to get leggy?  They’re almost always stocky and sturdy; strong enough to withstand the winds that blow.

Do you want to know why?  Well, it’s because of those winds (and bugs and birds and other things brushing up against them).  Called the “thigmo response,” it’s basically the plants ability to adapt it’s growth rate, avoid barriers, assist pollination, and even change it’s anatomy based on a reaction to touching or being touched.

Lightly brushing your hand over your new seedlings a few times a day, or having a fan blow gently over them helps the plants stems to become stronger and less leggy.  It sounds weird, I know, but it’s true.  So pet your seedlings!

Rotate seedlings in the windowsill

Not everybody can afford or find grow lights.  The next best thing is just to stick your seedlings in a south-facing window.

Here’s the bad news: plants grown in the windowsill will almost always become leggy and somewhat weak.  There just isn’t enough unfiltered light coming through to produce extremely healthy seedlings.

The good news is that that’s OK.  Seedlings are actually pretty hardy, and will mostly bounce back and turn into great plants when planted outside.

Plus, there’s something you can do to help them on their way!  Sort of like the touch response I wrote about above, rotating your seedlings every day will help them to grow stronger and more evenly.

If you don’t rotate your seedlings, you might notice that they lean toward the sun, which will make them more prone to snapping or falling over.  Rotating them a quarter-turn every day will help them grow upright and keep their stems strong.


And there you have it!  Growing healthy seedlings is almost an art unto itself, but these tips (learned the hard way after 14 years of gardening!) will help you out substantially in your quest to grow!


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  • Aimee

    March 31, 2018 at 4:56 pm

    Hey did you know that when viewing your blog as a WordPress follower the comments page does not come up? I had to “visit site” to be able to comment.
    And now for the comments ! Love learning about the cinnamon – I knew that about keeping ants off the countertops in the kitchen but never thought bout it with my seedlings- sweet!
    I found grow lights for pretty cheap at Home Depot – I think they were $20 and they have been SO helpful compared to windowsills, plus I splurged on a timer which is worth its weight in gold. 🙂

    PS – I thought your new blog name sounded familiar, then realized I just splurged on some pretty cloth napkins at http://www.hearthandharrow.com/ 🙂

    1. laceyhoyer

      April 1, 2018 at 5:08 pm

      Weird, I don’t know why it does that! I’ll tinker a little and see if I can if I can fix it, but no promises 😛

      I have a couple of grow lights, but Jasper has banned me from buying more 🙁 I’m going to get him to build me a seed-starting greenhouse instead though, lol.

      And I found hearthandharrow.com after I registered this domain, too! I wish I’d thought of that one first! They’re products are so beautiful!!

    2. laceyhoyer

      April 7, 2018 at 3:22 pm

      OK, I’ve been fiddling around and hopefully I got it fixed! Let me know!

  • Cecilia BuysWheeler Gunther

    April 1, 2018 at 1:47 pm

    Good Morning,

    Your site is lovely, well written and the photographs are superb. It was a pleasure to visit. Many thanks and have a wonderful day! cecilia

    1. laceyhoyer

      April 1, 2018 at 2:15 pm

      Thank you! I’ve long loved your blog as well!

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