Seeds: Which Side Goes Up?

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Nasturtium seeds (Tropaeolum majus) are lumpy, wrinkled and vaguely round: how should you orient them when you sow them?

You’ve got a seed pack in one hand and you’ve poured a few seeds into the other. The seeds can be of almost any shape: round, oval, long and thin, shaped like a scimitar, etc. All you have to do now is to sow them, but which side should face up?

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Squash (Cucurbita maxima) seeds: the first root will grow from the pointed end. Photo: RoRo, Wikimedia Commons

There is, on every seed, a spot from which the first seed root, the radicle, will appear and it would appear logical to plant it so it faces downward. And sometimes, it’s quite visible. A lot of oval seeds (squash, cucumbers, corn, etc.) have a point and that’s the “down side.” Beans have a depression of a different color from which the radicle will emerge: logically it should point down. Some long seeds, like marigolds, have a tuft at the upper tip, so the opposite end should point down.

Then come round seeds and all those odd-shaped seeds, plus the very fine dustlike ones you can barely see. With these seeds, there is often no particular indication, or a least, no obvious one. What to do about them?

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The seed root will always grow downward, the sprout, upwards.

In fact, though, seed orientation really makes little to no difference. In nature, most seeds end up facing any old way and they still germinate. Geotropism (geo = ground, tropism = growth) takes care of assuring they sprout correctly: the radicle (seed root) will always grow downward, showing “positive geotropism,” while the shoot (plumule) will grow upwards (negative tropism). Auxins (plant hormones) present in the seeds “tell” the root to follow gravitation pull and grow downward and sprouts to defy it and grow upwards.

Interestingly, light is not a factor. Seeds that sprout in the dark will still orient themselves correctly. However, if you sprout seeds in space, where there is nearly no gravity, the radicle and sprout will grow any which way, sometimes both even heading in the same direction!

Is Seed Orientation Important?

You’ll seed Web sites that claim seeds will sprout best if planted with the radical side downwards, as it saves the young seedling time and energy (the root of a seed planted “upside down” would have to travel half way around the seed to head downwards, and vice-versa for the seed sprout). In fact, though, and you can easily test this by sowing the same seed in different positions, it actually seems to make no difference at all. If there is any difference, it is so slight as to be insignificant.

So when you sow seeds, just place them any old way: they’ll do fine!20170509A

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