Q: A friend gave me some tomato seedlings her friend started in eggshells. Should I plant them in the shells or remove the shells? Should I start my seeds in shells next year?
A: I had never heard of starting seeds in eggshells, so I looked it up. I found lots of hobby and gardening sites talking about doing this, but could not find any scientific research on it. There is research about starting seeds and about using eggshells in the garden, though, and based on that research, I’m going to recommend that you at least crack up the shell before planting. Removing it entirely is probably a better bet.
Some of the websites I found said that planting tomatoes in eggshells will add calcium to the soil and thereby help prevent blossom-end rot, but research doesn’t bear out that claim. Blossom-end rot is caused by calcium deficiency, but eggshells won’t add an appreciable amount of calcium to the soil unless they are ground fine. In any case, blossom-end rot isn’t usually caused by a lack of calcium in the soil, but by uneven watering that makes it harder for the tomato to take up and use the available calcium.
Your seedling’s roots may be able to break through the shell and stretch out and grow, but it’s a good idea to give them a head start by at least cracking the shell. The shell won’t break down on its own. Consider removing the shell entirely and discarding it. Eggshells in the garden may attract pests such as skunks or raccoons. Slugs are also attracted to eggshells.
You can start seeds in almost any container; seedlings will grow in all sorts of things. The advantage to eggshells is you don’t have to buy containers, and you don’t wind up with plastic pots you have to throw away or wash for next year. The disadvantages are their small size and lack of drainage holes. We recommend starting seeds in a container with holes in the bottom, set in a tray, so that you can water from the bottom. Tomatoes are going to quickly outgrow a container as small as an eggshell, so if you were going to try this, you’d want to start them not too long before you planned to plant them in the garden, or plan on transplanting them to a larger container.
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Written by U of M Extension Master Gardeners in St. Louis County. Send questions to features@duluthnews.com.
