Should You Fertilize Seedlings? 5 Considerations and Tips
Seeds contain some nutrients, but after growing for a few weeks, they quickly run out! Maintain a regular feeding schedule, and your seedlings will stay healthy until transplanting. Seasoned grower Jerad Bryant shares five tips for successfully fertilizing tender seedlings.
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Fertilizing seedlings is a necessary step towards healthy, productive crops later in the growing season. All plants need nutrients to thrive, including nitrogen, phosphorus, and potassium. Other secondary and micronutrients are beneficial for plants in small doses.
How much and when to fertilize depends on the seeds you’re planting and the soil you’re using. Some dirt mixes have nutrients in them already, while others are void of fertilizer. Knowing your plants and the soil type you have will help you decide when and how often to add nutrients.
5 Considerations and Tips
These pro tips will help you discover which fertilizers are best for home use and how to apply them to tender plants. Follow these five fertilizing recommendations to grow healthy, robust seedlings every season.
Don’t Fertilize Seedlings at First
Seeds have a tiny packet of energy and sugar, allowing young plants to grow without needing extra nutrient sources. Adding fertilizer at planting may do more harm than good, as it overwhelms young seedlings with more resources than their small roots can handle.
Though some potting mixes have plant nutrients in them already, they’re often organic. Organic types need time to decompose before they release themselves to young plants. You can safely plant into organic soil mixes if they have some fertilizer, so long as it’s not synthetic.
Synthetic types are dangerous for tender plants, as they can cause burning and scorching on the leaves and stems. Rather than overloading your specimens, wait until they sprout true leaves before considering fertilization.
True leaves differ from cotyledon leaves, the first types that emerge from sprouting plants. Cotyledons are the seed leaves—the seeds have them inside before they germinate. Some plants have one while others have two; single-leaf plants are monocots, while two-leaf types are dicots.
Let Seedlings Reach 3”
After sprouting, vegetable and fruit crops quickly mature with continuous access to light, water, air, and nutrients. Ensure they have sufficient light so they don’t grow spindly or leggy. A bright window with indirect light works well; grow lights are excellent substitutes for sunlight in dark homes.
With consistent moisture and light, your seedlings will reach three inches tall in no time. After they reach three inches tall and have two or more true leaves, they’re ready for a regular fertilizing regimen. Young plants are no different from mature ones; they need nitrogen to grow leaves and phosphorous to grow roots.
When fertilizing, choose a water-soluble mix with a low nutrient content or dilute one with a high concentration. Tender species require fewer resources than mature plants, and their dosage should reflect their needs.
All plants need the following nutrients to survive. The primary kinds are the most important; your specimens need them more than others. Secondary and micronutrients are also crucial for plant health, though the plants need them in low doses.
- Primary
- Nitrogen
- Phosphorus
- Potassium
- Secondary
- Sulfur
- Calcium
- Magnesium
- Micronutrients
- Zinc
- Iron
- Copper
- Manganese
- Boron
- Molybdenum
- Chlorine
Synthetic or Organic Fertilizer?
There is a lot of disinformation about synthetic and organic fertilizers. Though synthetic types are easy to use, they strip the soil of microbes and create dead zones. Dead zones lack beneficial microbes that convert organic matter into plant nutrients. A lack of microbes leads to synthetic-dependent plants in the long run.
So, why do growers choose synthetic kinds over organic ones? The main reason is their guarantee—the numbers on the packaging of synthetic products equate to the exact number of nutrients your plants will receive. In organic kinds, the numbers represent how many of each nutrient the product contains. Whether or not they reach your plants’ roots is dependent on how active the soil microbes are.
When active, the microbes convert the organic matter into a form that seedlings can use. In soils with few microbes, organic matter may not decompose fully. It’ll stay unusable in the dirt until microbes convert it into usable forms for your growing crops.
If you fertilize with a little bit of synthetic fertilizer, it’s okay, but organic types with mycorrhizae are better for young seedlings. Mycorrhizae are fungi that work like other soil microbes, except they partner with plant roots. They exchange their nutrients for sugar from plant roots, creating a symbiotic relationship underground. With a little mycorrhizae, seed starting mixes are ready for organic fertilizers; they’ll convert them into forms your seedlings can use.
Weekly Nutrients
Seedlings benefit from a weekly dose of low-nutrient fertilizer. A formulation with a number like 2-2-3 is perfect! If the number is higher, use a half or quarter-dose to avoid overwhelming your growing species. The numbers refer to a percentage of the total. 2-2-3 equates to 2% nitrogen, 2% phosphorus, and 3% potassium.
Liquid fertilizers are optimal for seedlings. They’re easy to mix and apply. Simply follow the package’s instructions for proper dosing, dilute the fertilizer with water, and apply the blend to your budding crops once a week. Fish and kelp emulsions are excellent liquid organic types you can use at home.
Skip a week of fertilizing if you notice signs of overfertilization. Leaves may turn yellow and wilt, or they’ll have patches of yellow among green and brown. Some leaf tips may turn brown or yellow before moving down the leaf. If you suspect you have overfertilized, run cool water through the soil to leach out the excess, and wait two weeks before adding another dose.
Repotting and Transplanting
Seedlings are generally ready for transplanting or repotting once they reach six inches or taller. With plenty of true leaves, stems, and shoots, they’ll excel in a larger pot or garden bed. Their roots begin circling in the small containers, and they need more space to thrive.
Transplant tender specimens by gently lifting them out of their containers and placing them into new ones with fresh soil. If you’re transplanting outdoors, ensure the temperatures are optimal for your growing crops. Tomatoes, peppers, and eggplants need warm night temperatures to thrive outdoors, while cold crops love growing during late winter, early spring, and autumn.
If it’s not warm or cold enough for your seedlings, transplant them into larger containers and continue fertilizing them. They’ll continue growing healthy, fresh shoots that will take off once temperatures reach their optimal range.
Frequently Asked Questions
When do you fertilize seedlings?
Add fertilizer once the specimens reach three inches tall or higher with two or more true leaves.
How often should you fertilize seedlings?
Add a low dose of fertilizer once a week to growing seedlings.
How do you fertilize seedlings?
Liquid fertilizer is the easiest type to use. Simply dilute it in water and add it to the dirt. Powder and granule types exist too, though they’re better for mature specimens.
