Katy's garden of herbs, peppers and greens is constantly expanding as she learns new techniques and tries new plants!
In the seedling stage, plants are delicate and require special care. They're growing stalks and leaves while establishing a root system. This takes nutrients like phosphorous, potassium and nitrogen.
Before we get into what fertilizer to use for seedlings and how often to add it, let's talk about whether it's really necessary. Many gardeners swear by plant nutrients to get vegetables with high yields and beautiful, prolific flowers every year. But just as many insist plants get what they need from the soil so they keep their gardens completely organic. So, which is it?
It is true that most plants can get the nutrients they need from the soil. But that is only the case if the soil has nutrients. If your garden plot has been over-planted without more compost mixed in, there's no more nutrients the future plants to absorb. If you pot and plant with regular dirt and not potting soil, it can't get everything it needs from just water. Even if the soil starts out nutrient rich, the plant will use up the nutrients throughout its life and need replenishing through compost or liquid fertilizer.
Seed Starting Fertilizer
Sow your seeds directly into soil that is rich in the nutrients it needs. Any store-bought potting soil will have nutrients already mixed in. That's sufficient for the early life of your sprouts.
Never apply fertilizer directly to a seed, whether it's been germinated or not. The seed has all the nutrients it needs for very early growth.
Next, we'll get into when you should be adding liquid fertilizer to your young plants.
When to Fertilize Seedlings
The timing of adding a sprout's first fertilizer is crucial.
First True Leaves: Diluted Fertilizer
The earliest you should give a sprout nutrients is when they put out their first true set of leaves. A sprout will grow a couple thin leaves first, and the next set is normally shaped and referred to as "true leaves." Wait until you see these leaves before adding any fertilizer.
The fertilizer you do add at this point should be diluted. Read the directions for normal dilution on the label. To be on the safe side, dilute more it with one part fertilizer and at least three parts water. There's no need to overload at this point; a little will go a long way.
Re-Potting or Transplanting Into the Garden: Full Strength
Once it's time to transplant, you can think about upping the nutrients to a stronger level. If they're going into a new pot, either plant them directly into potting mix or add some liquid fertilizer. If they're going into the ground in a garden, be sure to mix in with compost and add the recommended dilution of plant nutrients.
What Fertilizer to Use
The most reliable plant nutrients for seedlings are SuperThrive and Botanica's Grow formula. SuperThrive is a good all-round formula that is good for plants at any stage. Grow will help establish the stalks and leaves faster.
Both will need to be diluted beyond their usual amount until a sprout is well-established. Build up to full strength as the plant grows.
Miracle Grow for Seedlings
Is Miracle Grow formulated for seedlings?
Miracle Grow does have nutrients that are essential for seedlings. But they likely don't need much at the seedling stage, and you can actually harm the little sprouts by adding too much.
If you do use Miracle Grow at the early stage, wait until after the first set of true leaves as recommended above. At that point, still dilute it beyond what the label recommends, and don't add it often until the plants are closer to full grown.
How to Grow Strong Seedlings
If you're looking into fertilizer and nutrient supplements for your seedlings, know that at this stage their light exposure is most important. Most plants struggle to begin life in a window environment. So if you're starting your seeds indoors read about how to use a grow light. If you've never done it before, you'll be shocked at the results!
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2020 Katy Medium
Katy Medium (author) from Denver, CO on March 14, 2020:
Hi Liz, glad you enjoyed it!
Liz Westwood from UK on March 14, 2020:
This is an interesting and useful article.