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10 Common Seed Starting Mistakes (and fixing them)

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Starting from seed has advantages, yet so many people avoid it and buy started plants. And while there’s nothing wrong with that, starting your own opens up so many different varieties and choices. However, there are some common seed starting mistakes, and knowing what they are in advance so you can avoid them, or fix them if they happen, can help you grow from seed successfully.

Gardening is a learn-as-you-go endeavor for most of us. My mother loved to grow plants, but she taught herself and mostly grew perennials… I never learned much as she took on the endeavor when I was into adulthood.

While the fear of failure can paralyze us when we see all of these perfectly curated seedlings and gardens on Instagram, truth be told even the best gardeners have likely killed more plants than they’ve grown to maturity successfully. It’s just the nature of things.

There’s nothing wrong with killing seedlings, though. We live in an era where going to a local nursery to purchase started plants is usually an option, a more expensive option, but an option nonetheless. We can take these mistakes we make and turn them into lessons to do better next time.

Thankfully, there are some very common seed starting mistakes that are very easy to identify so you can avoid them happening at all or fix your plants before they meet their demise if you do mess up. So, let’s go over the top ten mistakes I’ve made or seen made when it comes to starting seeds.

Mistake #1: Ordering (or starting) too many

We’ve all been there… you pick up the seed catalog and start drooling over all the amazing varieties they offer. So, you buy one of virtually everything.

And then spring fever hits and you plant a half dozen of everything and two dozen of the rest. After you have your entire house bombarded with seedling trays that you really don’t have enough room, time, or patience for.

While growing enough food to feed your family is an admirable goal, you can’t grow everything, all at once. Just like with anything else, you have to practice some restraint.

Maybe you try a few varieties of tomatoes this year, and you plant one or two of each variety. Maybe instead of starting your own pepper seedlings, you purchase them at the local nursery. And then you purchase some of the fresh produce you need at the local farmers’ market.

There’s no shame in any of that. Self-sufficiency is a myth, it takes a community of people to make things work well. No man is an island and we can’t do it all on our own.

How to Avoid or Fix It

Having a plan for your garden in place, as well as a place to put all of the things you want to grow is paramount. Then, of course, you should only start what you can realistically maintain on your own (or with the help of your family). If starting 200 seedlings seems overwhelming, just start small (think 10) and go from there.

If your ambition gets the better of you, either give some of the seedlings away to neighbors, friends, and family to make it more manageable or compost some (or feed them to your chickens).

Starting Seeds too Early

I get antsy to start my seeds so early in the year. I generally plan my garden on the winter solstice and finalize my plans in early January. The seeds start coming in and I’m ready to go…

Except, the plants aren’t. Each type and variety will be slightly different. Some vegetables like lettuce and peas, like cooler weather and can, withstand cooler temps. Others, like tomatoes, eggplant, and peppers like it hot.

When you make your garden plan, I always recommend you take note of when you need to start them based on your projected last frost date. Your seed packet should contain the information you need for this along with your gardening zone.

I write everything down on a calendar, what date I plan to start, how many I plan to start, when they should be hardened off, and when they should be safe to transplant.

Take note of your last expected frost, count backward, and start seeds at the proper time so they aren’t growing indoors becoming root-bound before you can get them outside, or needing potted up into huge, gallon containers before you can get them outdoors.

Using the Wrong Potting Medium

Contrary to popular belief, a seed starting mix really isn’t necessary to start seeds. In fact, if you use a seed starting medium, you will likely have to pot up into potting soil fairly soon after germination.

Yes, seeds contain all of the nutrients and information they need to germinate, but they will need nutrients soon after in order to thrive. Those nutrients can be found in potting soil and similar mediums.

While you do need to be mindful and make sure the soil you’re using is not full of diseases, pests, and weeds plenty of people start seeds in straight-up compost. While we have made our own starting mix in the past, we typically start seeds with soil blocks now, and the seed starting mix just won’t hold up. So, I use clean potting soil or compost to make my blocks.

If you do use seed starting mix, you’ll want to add compost, worm castings, or transplant seedlings into potting soil medium once your seedlings have a set or two of true leaves.

Planting too Deep (or not deep enough)

Your seed packet contains a lot of valuable information when it comes to starting your seeds. One of those tidbits of information is how deep to sow your seeds.

Some seeds require light to germinate, like chamomile and lettuce so they should be very lightly covered with soil (or not at all). While other seeds require it to be dark and should be planted deeply in order to aid in germination like calendula.

The general rule of thumb is to plant a seed about twice the depth of the actual size of the seed. I use the knuckles of my fingers to help me decide on planting depth. Things that say 1/4″ get planted down to the first knuckle. Things that say 1/2″ I plant down to the second.

It is better, however, to plant something too shallow than it is to plant it too deeply. If it is planted too deep, it may not have enough energy to reach above the soil level and you’ll think it hasn’t germinated.

Planting too shallow, of course, has its disadvantages. The plant will not be very deeply rooted. However, this can be remedied by potting up and planting it deeper in order to encourage sturdier growth. Things like tomatoes actually root anywhere along the stem, so these should always be potted more deeply when potting up anyway.

Not Providing Warmth

A lot of seeds need around 70˚F to 80˚F to germinate. So, making sure your soil and environment are warm enough to support these temperatures and aid in growth is important.

This is especially true for warm-weather crops like eggplant, tomato, and peppers. While some herbs and cold crops (peas, lettuce, and several herbs) do not require supplemental heat, these hot weather-loving plants, do.

This is fairly easy to fix by utilizing a heat mat. They have some amazing heat mats that will operate only when the soil temperature needs them to, that way the soil is not overheated.

Note that too much warmth is also a problem, for any plant. 95˚F or warmer, you will sterilize your seeds and nothing will grow. Which makes a thermostat a nice thing to have.

If you do not have a heat mat, it’s not the end of the world. Your seeds will likely germinate once those soil temps get to where they need them to be. I’ve aided soil temps in seedling trays by using warm water to water the soil and gotten early sprouts that way. Sometimes, you just have to wait.

If you’re starting indoors, just make sure the ambient temperature inside is around 70 and your soil will naturally warm to around that temperature without any added heat.

Insufficient Light

Plants need light. And those tiny, vulnerable seedlings will stretch to find any light they can. Which, results in “leggy” seedlings.

We’ve all seen them, and we’ve all created them at one time or another, but taller isn’t always better in the world of seedlings. And those thin, tall, stretched-out seedlings were generally created by a lack of light.

Those cute little sprouts need a minimum of 12 hours of adequate light. I recommend 14 hours, never more than 16… they do need some dark time, too.

If you’re the type that forgets, a timer can be a lifesaver. Some grow lights come with timers, or you can simply hook one up to the lamps.

And yes, I do recommend grow lights. We have a ton of southern exposure in our home, and I plan to add a greenhouse soon. Yet, we still do, and will, continue to use grow lights. Today, for instance, is overcast and would not be providing adequate light for the seedlings. They’ll stretch over toward the window and become leggy pretty quickly.

Grow lights can be fancy and expensive, but they do not have to be. An inexpensive fluorescent fixture fitted with a T5 bulb will work. You’ll want to keep the light about an inch or so from the top of your plants and begin providing light as soon as you begin seeing those first sprouts.

A Note on Fixing “Leggy” Seedlings

If you notice your seedlings are looking a little sad and dumpy, not all is lost. You can fix leggy seedlings, as long as you get to them before they shrivel up and die.

To do this, I recommend “potting” up from the cells they’re in (see below). Plant them down to their first true leaves to encourage strong roots (this is especially true of tomatoes, peppers, and even brassicas).

Once you’ve got them potted up, maintain proper moisture levels and make sure they’re getting plenty of light! I keep leggy seedlings I’m trying to help under the light (one inch away, which is part of the reason for repotting) for about 15 to 16 hours for the first few days just to help them out. Then, you can go back to the 14 hours (or 12, I just prefer 14) you normally use.

Too much Water (or not enough)

While too much or too little water will kill off your seedlings, watering too much is a far more common problem than not watering enough.

Too much water can lead to dampening off disease which will cause your plants to die suddenly and it’s much more difficult to save overwatered seedlings than it is under-watered seedlings.

There is also the problem of watering them, then not, then watering them, and letting them dry out completely and begin withering before remembering to water them again. This results in stressed-out little plants that have trouble thriving.

And it’s difficult to keep the right level of moisture! This is especially true for those seed pods that come with the supposed biodegradable netting around them. I don’t recommend using them. They require far too much water and just about every time I’ve tried to use them, they’ve wound up having fungal issues.

When you’re starting your seedlings, you can utilize a humidity dome to keep the moisture levels adequate. Keep it on the tray until you begin seeing sprouts, then prop it open just a bit.

Once you have some seedlings established, try to keep them on a schedule. You’ll want to allow the soil mix to go from the dampness of a wrung-out rag to slightly dry. Then, water your trays from underneath. I fill the bottom tray with an inch or so of water and allow each cell to draw up some moisture. About half an hour to an hour after I provide water, I will drain any remaining water from the bottom tray to make sure the seedlings aren’t sitting in water (which will lead to dampening off and death).

Not all is lost if your seedlings are wilting from a dried-up starter mix. Gently water them from below and let them slowly soak up some moisture bits at a time, don’t drown them to try to make up for not watering them.

Not Thinning Seedlings

Depending on the germination rate contained on your seed packet, you may want to start one or two or three or more seeds in each cell. This helps ensure that each cell will likely have at least one seed germinated.

It can also mean you wind up with three tomato plants in every single little cell you have. This is great, if you like tomatoes, but not so great for the plants themselves. They will quickly begin competing for nutrients, water, and airflow and become root bound with each other and succumb to not having enough to go around.

To avoid this problem, you’ll want to thin them out and leave just one seedling per cell. You can do this simply by picking the strongest plant when the seedlings are around a week old and cutting off the weaker seedlings. I do not recommend pulling the weaker seedlings you don’t want to keep. It’s too much or a risk you’ll end up disturbing the strong seedling and cause problems for it.

What if you want to keep them all? Read on…

Neglecting to Pot Up

Seedlings shouldn’t be left to their own devices in the small cells we start them in, either. They’ll become root-bound which creates its own host of problems.

So, you need to pot them up into larger containers. And if you’d like to keep all of your seedlings that sprouted, this is a great way to enable you to do that.

If you have multiple seedlings in each cell you want to keep, you can gently remove the entire cell using a spoon to gently remove it. Then, you can gently remove the dirt from the roots and handle each individual plant gently to pot deeply into the larger pot.

Even if you only plan to keep one seedling and cut off the contenders at soil level, you’ll want to eventually pot up before the plants are likely to go outdoors. You can just remove the whole cell and put it in the larger pot.

Tomatoes do really well when they are transplanted into larger pots 2 to 3 times before they’re put in the ground. Some plants you may, or may not, start indoors should be started in larger pots, to begin with (generally biodegradable pots) because they don’t transplant well (peas and borage come to mind specifically, but there are others).

For most plants, though, you’ll want to begin potting up as soon as they get their first set of true leaves. You can plant the entire plant all the way down to these leaves in the soil to promote strong growth as well.

Not Properly Hardening Off Seedlings

I know I’ve done this a time or two. I’ve got all these plants, the weather starts warming up and I’m ready to put them out in the ground! It’s gardening season, yay!

Bad idea. They look beautiful, the sun is shining and you’ll go out in the next day or two and all that hard work will have been for nothing as you cry over your dead, lifeless plants.

Seedlings started and grown up until this point in a sheltered environment free from wind, direct sunlight, and rain hammering down and are likely to die if thrown to the wind, so to speak.

Even if you used fans, sprayed them with a hose nozzle, and put the light right on top of them, they’re incredibly sheltered. They need to acclimate to the harsh conditions of the real world instead of just being put in the ground.

Thankfully, it’s pretty easy to fix this and acclimate them to the real-world environment they will be spending the rest of their days. You can use fans indoors, or gently brush your hands against seedlings to help encourage strong stems and root growth so they can handle the wind.

But more than that, you’ll want to take a week to two weeks to introduce them to the great big world. This process is called “hardening” off.

I keep notes in my garden planner/journal for when I want seedlings to be transplanted outside. I then go back a week or so prior to that and make note that they need to begin to be “hardened off”.

Start with an hour or so outside, in a shady, halfway-sheltered location. Then, slowly increase the time and direct sunlight and other elements over the course of a week. The day before transplanting, I leave my seedlings outdoors overnight in their containers. Then, they will get put into the ground the next morning.

By gradually introducing them to the real world, you’re less likely to get transplant shock and a bunch of dead plants, it’s worth the time it takes to get them acclimated, trust me.

And there you have it, the most common seed-starting mistakes and how to avoid them so you can start your garden from seed with confidence!

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