Growing seedlings properly will help to ensure that you have strong, healthy plants for transplanting.
And that's a key to successful gardening.
Using grow lights and seedling heat mats can help.
But the most important thing is to understand what your seedlings need.
And your seedlings will give you what you want: Strong, vibrant, healthy plants that will be beautiful and productive.
Once you've started your seeds and they begin to germinate, you'll need to give the seedlings the proper amount of light, heat, water, nutrients and air circulation.
Whether they’re vegetable seedlings or flower seedlings, if you give your growing seedlings these things in the proper quantities, your success is all but assured.
Most seeds do not need light to germinate. But once the seedlings emerge from the soil, light becomes crucial.
Without the proper quantity and quality of light, a seedling will not be able to produce the food that will fuel its growth.
Of course, there are only two possible sources of light: Natural light from the sun, or artificial light supplied by indoor lights.
Obviously sunlight is the cheapest source of light for your seedlings.
But is it the best? Not necessarily.
Relying on sunlight to power the growth of your seedlings is fine -- assuming that it is reliably available in sufficient quantity.
Well, that depends somewhat upon the type of plant you're growing, but generally anywhere from 12 - 16 hours per day is optimum. You're not going to get that much light from the sun if you're starting your seeds indoors during late winter because the days simply aren't that long.
But growing your seedlings on a sunny windowsill can still work.
Just be sure that the windowsill receives sunlight most of the day. That means that it will need to be a south-facing window (unless, of course, you're reading this from the southern hemisphere, in which case it will need to face north).
Also, you’ll need to rotate the seedling flats or containers a quarter turn every day. This will prevent the seedlings from growing at an angle as they reach for the sun.
One note of caution about growing seedlings on a windowsill: Make certain that the seedlings aren't getting too cold at night. It's possible for the temperature to drop quite drastically right next to the window once the sun goes down. If that's happening, it won't do your seedlings any good.
Even if you have access to a nice south exposure for your seedlings, you may still have problems in relying upon the sun.
If your area is prone to long, dreary cloudy spells during the time you will be growing seedlings, then they will be hurting for light during those cloudy spells. Without an alternative source of light, their growth will be impeded.
Using indoor grow lights is usually the best alternative for supplying light to your seedlings.
Growing seedlings under grow lights gives you the obvious advantage of being able to control the hours of light that your seedlings receive each day. No matter how much cloudy weather you have, your seedlings won’t miss a beat as they luxuriate in the abundant light you provide them.
You can grow seedlings under grow lights without breaking the bank with expensive grow light setups. If you’re interested in learning more about grow lights, click here and I’ll help you sort out the options (coming soon).
Most plants don’t require quite as much heat for growing seedlings as for germinating seeds. But if you used a seedling heat mat to germinate your seed, don’t turn it off.
Depending upon the type of plant you’re growing, you can probably turn down the heat mat a bit. Most seedlings grow well at temperatures of 65 – 75 F. But seedlings do need to be kept warm for optimum growth, and applying bottom heat is a great way to keep your seedlings warm.
If you use a heat mat to warm the growing media of your seedlings, the air temperature is less important (though you still don’t want the air temperature to be extremely cold, of course). If you’re not using a seedling heat mat, you’ll be relying upon the air temperature to warm your seedlings.
Once your seeds have germinated, keeping the moisture level constant isn’t as crucial. In fact, it’s actually good to allow the top of the growing mix to dry out a bit between waterings.
How often will you need to water?
Unfortunately, there’s no easy answer to this question. A number of variables will determine how frequently the growing seedlings will need watering.
The surest way to know when to water is by frequently checking the moisture level of the growing medium. When the top surface feels dry to the touch, it’s time to water. You can water either by placing the seedling tray or container in a shallow pan of water or by spritzing water over the top surface with a spray bottle.
Take care not to brutalize your seedlings when you water them.
Even large water droplets applied with a forceful spray from a spray bottle can be damaging to very young seedlings. If you use a spray bottle, be sure that it emits a gentle, mist-like spray.
If your water comes out of the tap cold, let it set awhile and warm to room temperature before using it to water your seedlings. Growing seedlings don’t appreciate a cold shower any more than you do! If your water is chlorinated, letting it set awhile will also reduce the amount of chlorine remaining in the water.
It’s important that you maintain constant air circulation around your seedlings.
Because air circulation will help to decrease the humidity level around the seedlings. And keeping the humidity down will help you avoid unpleasant encounters with fungal diseases such as damping off disease.
Running a small fan continuously to provide a gentle, constant pattern of air circulation is a great idea. You don’t need to blast the seedlings with a gale force wind, of course. Just a very gentle breeze is all that’s necessary.
If you can see the leaves of your seedlings just barely being jostled by the air current – that’s perfect. You simply want to avoid dead air.
A secondary benefit of providing air circulation is that the gentle jostling of the growing seedlings will help to produce stronger stems.
While germinating, seeds consume food stored within the seed, and don’t need any supplemental fertilization.
Soon after a seedling emerges from the ground, though, it will have used up the food that was in the seed, and will be getting hungry! So you’ll need to fertilize your growing seedlings on a regular basis.
Most potting soils and seed starting mixes are fairly inert – they contain few or none of the nutritional elements your seedlings need. And even though some seed starting mixes contain a small charge of fertilizer to help the seedlings get started, it will soon be gone.
So you’ll need to give your seedlings all of the nutritional elements that they need.
This means that you’ll need to supply not only the macronutrients like nitrogen, phosphorus and potassium, but also all of the trace micronutrients that all plants require.
Most all-purpose fertilizers such as Miracle-Gro will contain all of the nutritional elements that your seedlings need, but check the labeling to be sure. Also check the labeling to find out what strength to mix the fertilizer at for your seedlings. Usually a ½ strength mix is sufficient for seedlings. A full-strength mix will likely be too strong.
If you want to use only organic fertilizers, most fish emulsions will give your seedlings all of the major and minor nutrients they need. Caution, though: If you’re growing your seedlings in the house, the odor of fish emulsion can be rather intense and lingering!
Again, always check the label, but usually a once-per-week application of fertilizer is sufficient for young seedlings.
Yes, you read that right!
After all, everyone needs to feel appreciated and loved. Even your little seedlings!
Well, Ok…That’s not really why you should pet them (as far as I know, at least!). There’s actually a very logical and scientifically sound reason for petting your seedlings.
Think about it.
By growing your seedlings indoors, you’re growing them in an unnatural environment. They don’t get the mechanical stimulation they’d get outside: wind, rain, animals, etc.
And that’s mostly good.
But all of that mechanical stimulation that the seedlings would get outdoors helps the seedlings to grow stronger in response. You can duplicate that response by just brushing the flat of your hand over the tops of the seedlings once or twice per day. Your seedlings will grow stockier and stronger, and be better able to hold up in the outside world when they’re transplanted.
And if you want to sweetly whisper to your seedlings how much you love and appreciate them as you pet them – I’m quite certain that won’t hurt anything!
Usually, you’ll plant more seeds than the amount of plants you actually want to allow for seeds that don’t germinate or grow properly.
At some point, you’ll probably want to thin out most of the extra seedlings (I’d keep a few extra until after they’ve been transplanted, just in case). Usually, you’ll want to thin before the seedlings are touching each other.
You’ll pick the weakest looking seedlings to thin out, of course.
But you need to be careful about how you thin so that you don’t damage the remaining seedlings.
DON’T dispose of the rejects by pulling them out. If you do that, you’re liable to do serious damage to the roots of neighboring seedlings. Instead, simply cut or pinch off the thinned seedlings at soil level. Don’t worry about the roots remaining in the soil.
It will probably take some time for you to get a good feel for how much to water your seedlings.
But while you’re learning the ropes it would be better to err on the side of under watering than over watering. Consistently over watering is FAR more damaging to young seedlings than is getting a bit dry.
Before you know it, those growing seedlings will be ready to take their place in the outdoor world.
And that’s where all of your careful work in planting and nurturing those seedlings will begin to pay off.
With a bit of luck, your little seedlings will soon be busily producing the bountiful harvests that you’ve dreamed of all winter.
But let’s not get ahead of ourselves!
Let’s spend a little time preparing for perhaps the most critical phase of your gardening season: transplanting.