5 Tips for Growing Super-Fit Seedlings

Seedling season is upon us, when we populate our lives with dozens of little plants with all kinds of quirky needs. We check on them daily, do our best to keep up with pricking out and potting on, but there is more you can do to grow stronger, healthier seedlings for your garden. From reciting poetry to rotating lights, here are five tips for growing super-fit seedlings that are ready start growing the day they are set out, with no setbacks from transplant trauma.

1. Keep Them Moving

Complete stillness is neither normal nor healthy for plants. Terrestrial plants are moored in place by their roots, but they are surrounded by constant forces from wind, rain, and gravity. Starting when the seeds sprout, I place solar dancers under my grow lights alongside my seedlings. The little toys move when the lights are on, stirring the air enough to make a slight difference.

When you gently touch the tops of seedlings, so the stems gently bend without breaking, it is called brushing. As the seedlings right themselves, their stem cells become more twisted so they can better withstand the next brushing, which should resemble a strong gust of wind. If you have only a few seedlings, simply pass the back of your hand over their tops first in one direction and then in another. If you’re concerned about breaking stems, use a light piece of cloth to brush tender seedlings. In my experience, onion, leek, and other seedlings that grow from a basal crown benefit from brushing more than peppers and other plants that make new growth at their tips.

Some gardeners use small fans to improve the fitness of their seedlings. Fanning plants for ten minutes or so several times a day helps them develop stronger stems that can better handle wind and rain after they are set out in the garden. A fan can go a long way toward discouraging fungus gnats, which are very weak fliers. Drying of the soil’s surface can also reduce the risk of damping off and other fungal diseases.

2. It’s Good To Talk

In a 2009 study in Great Britain, recordings of human voices reading various texts were played to tomato plants each day for a month. Tomatoes that “listened” to women’s voices grew larger, most likely in response to favorable sound vibrations in the 55-decibel range. The tomatoes’ favorite voice belonged to Sarah Darwin, great-great-granddaughter of Charles Darwin.

At one time it was thought that talking to plants enhanced their growth by enriching the air with carbon dioxide, but this has never been validated by research. However, it is a fact that the outdoor world envelops plants with sound. A summer rain shower runs about 35 decibels, birds chirping is 40, a brisk spring wind could be 50 decibels. Plants may be soothed by common nature sounds the same way we are, and they may be alarmed by loud ones. I suspect my strawflowers can hear the sound of thunder.

3. Keep It Light

Vegetable seedlings grown under grow lights enjoy constant, unchanging light, a far cry from the high and low light intensities they will face when transplanted outdoors. Even when seedlings have weeks of indoor growing time to go, I think it is helpful to rotate them to different lighting situations to get them accustomed to change. Gentle LED lights seem pleasing to seedlings that are just finding their feet. Older seedlings grown under fluorescent lights get rotated to a bright south-facing window as transplanting day draws near. There is nothing like direct sun to help leaves load up with chloroplasts, the organs that change light into energy.

4. Don’t Overfeed

We animals get most of our energy from food, while plants run mostly on light. Little seedlings find the nutrients they need in the soil, but small sips of supplemental fertilizer can be helpful after seedlings have at least three true leaves. Use a water-soluble plant food mixed at half the rate recommended on the label, and apply when the growing medium is already nicely moist. The best way to judge the moisture level in seedling containers is to pick them up to see if they feel heavy (wet) or light (dry).

5. Don’t Give Up!

Seed starting involves successes and failures, even when you do everything right. As the days become longer and warmer, starting seeds gets easier because the plants can spend more time outdoors. Keep sowing seeds of fast-growing cool-season crops, then move on to peppers and tomatoes, then cucumbers and squash. You will get a short break, then start over with cool-season crops for late summer. It’s the best way to have an interesting, productive garden.