How to take care of your indoor seedlings

Spring is officially around the corner! Although the weather may not have begun warming significantly where you live, there’s no reason you can’t start your growing season a little early. After visiting my local nurseries for the past month now and repeatedly being told that no new herb or vegetable plants had come in yet, I decided to invest in a few simple tools and start planting some seeds indoors. Whether you’ve got the itch to grow right now, or you’re interested in getting a jump start on your gardening, there are a few things you can do today to start growing something good and make sure that it thrives well into the warm season.


What tools do you need to start seedlings indoors?

The planting medium

How to take care of your indoor seedlings

Many newbie gardeners (and even a few experienced ones) think that all you need to germinate some seeds is pot, dirt, water, and maybe a sunny window. Well technically, that’s true, but if that’s all you’re doing, your seedlings won’t get off to a good start. In fact, they’re more likely than not to grow leggy and weak, lacking both the spectrum of nutrients they need to thrive and the strong immune system they should be developing in order to fight off pests and diseases.  

Strong, healthy seedlings start with a good soil mix. Virtually any potting soil that is formulated for container gardening and seed starting will work, but if you are using a potting soil that is not also formulated for seedlings, you should amend the soil with nutrients like compost (used coffee grounds also work well) and inert materials like vermiculite and/or perlite to help with soil aeration, drainage, and nutrient absorption. A good seed starter soil mix is the best commercial choice for germinating seeds indoors, as it contains all the materials you need to ensure your seeds get off to a strong start.

You can also make your own seed starter mix. This post by Grow Journey explains how to do it.

The planting container

Seedlings can be planted in many different types of containers, but if you plant them in a container that is large, you will run into problems when it’s time to transplant them, since removing them may damage their roots, which can become entangled. Instead, choose seedling starter containers and trays. The containers contain individual compartments for 6 or more seedlings. These sit inside of a larger tray that holds several containers, making it easier to water your seedlings. You can also buy individual peat pots: some are pellet pop-ups that lok like round, flat disks. These expand when you pour water on them, and are contained by a fine mesh restraint. Others look like small plant pots (single or connected pots) that you fill with seed starting mix before planting. In both cases, the pots can be transplanted – seedlings and everything – directly into the soil, so that the shock of transplanting does minimal damage to your plants.


Lighting: natural or artificial?

This is the detail that trips many a novice gardener up. Your indoor seedlings need a full-spectrum grow light (which contains the colors we can see, namely red, orange, yellow, green, blue, indigo and violet, as well as UV light, which is produced by the sun). Using a full spectrum grow light will make a tremendous difference in helping your indoor seedlings start off faster and produce a bigger harvest, as this kind of light comes closest to harnessing the full power of the sun. Most of the time, multiple trays of seedlings especially sun-loving herbs like basil and oregano and vegetables like tomatos, will not start off well in a sunny window alone: as they tend to grow very leggy (develop long, thin, weak stalks) as they stretch towards the light.

How to take care of your indoor seedlings

There are 3 types of grow lights to consider: HIDs, CFLs, and LEDs. HIDs, or high-intensity discharge lights, include high pressure sodium (HPS) and metal halide (MH) lights. These lights are expensive and heat-intensive, meaning that you’ll need to put a greater distance between them and your seedlings. CFLs, or compact fluorescent lights, emit red and blue spectra light and don’t emit much heat. They are most efficient with crops that don’t have high light requirements. LEDs are the most efficient and least costly of the 3 types of lights, as they use half the electricity of the others, require a modest investment, and do not get hot. Full-spectrum LEDs also help with photosynthesis, or the process whereby plants convert sunlight into nutrients, which ordinary grow lights can’t do. Want to learn more about lights? Check out this super-informative blog post by Urban Vine.

Water and air

Watering can either make or break your seedling operation. Water too much and your seedlings will rot before they come up, or if they already have sprouted, will suffer root rot. Don’t water enough and the seedlings will never pop up or worse, your delicate shoots will die before they’ve even had a chance to show you what they can really do.

Watering your seedlings is actually pretty simple, if you take a brief moment to observe them every day. Consistency is key here: if you are using peat pots, you can tell by looking at the outside of the pot if it’s wet. Let it dry out very slightly between watering: you may need to water once a day, or once every other day, but rarely less often. Feel the top of the planting medium with a finger: does it feel more than just a little dry? Then add a little water, using a small watering can or mister from the top. Watering from the bottom is often more efficient than watering from the top, as top-down watering may damage your delicate shoots or promote the growth of mold (and rot). Use a small fan to keep air circulating and to discourage the growth of mold on your seedlings. Some say that using a fan also helps the stalks of your plant grow stronger as they learn to resist the current around them.

Some growers use a cover or germinating dome to help with the process of sprouting seedlings, but I have always found that these contributed to the growth of mold or rot. You’ll have to see what works best for your growing operation.


Nutrients – when should you add them?

At what point should you begin feeding your seedlings? The pod that the seedling emerges from contains all the nutrients that the plant needs when its first set of leaves, called cotyledons, emerge. Once the second leaves, the “true leaves,” emerge though, you should begin watering with a diluted fertilizer. For organic gardening, a liquid fertilizer containing fish emulsion and kelp will give your plants all they need for a strong start. Synthetic fertilizers can be tricky to use for the novice gardener and can easily burn your plants. In either case, it’s best to dilute the recommended amount of fertilizer by at least half (and as much as ¼ for synthetic fertilizers) before giving to your seedlings. Fertilize once a week. If your seedlings begin to look lanky and tender, cut back on the fertilizer.

Want to learn more?

I’ll be sharing information like this and much more in my new online course, Container Garden Like a Pro. Want to take a peek at the course curriculum and view some of the free content? Click the image above to sign up for the mailing list, which will give you access to the course as well as to my library of Free Resources for healthy living.


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