Sunday, August 30, 2015

Seeds: The Next Generation

The blooming season is in the last quarter now and plants are busy making or ripening their seeds. Some seeds, like those encased in the fleshy fruits of spring plants such as plums and cherries, are long gone, gobbled up by hungry critters. Other seeds take a long time to form. For example, acorns on oak trees in the red oak group are ready in the second fall after they were fertilized and witch hazel (Hamamelis) seeds are ripe when the flowers bloom the next year. Other plants, particularly annuals and perennials, are ripening and dropping seeds throughout the season.

Milkweed seed gets ready to fly

Now is a good time to keep an eye out for ripening seeds that you might have wanted to collect. I keep a list for myself so that I can remember what I wanted to gather. 

Seeds are a particularly fun topic to help kids learn more about the natural world. After all, seeds are the next plant generation just like kids are the next human generation.

I’m currently reading The Triumph of Seeds: How Grains, Nuts, Kernels, Pulses, and Pips Conquered the Plant Kingdom and Shaped Human History by Thor Hanson. The author offers some fascinating information about these things which are, in essence, “baby plants in a box with their lunch.” Why are some seeds so big and others so small, don't they all need the same thing?

Impatiens capensis flower

With seeds on my mind, I noticed some particular seeds this week. I saw the summer blooming jewelweed (Impatiens capensis) which makes its seed pretty quickly and then disperses it at the slightest touch. 

In fact, it’s called “touch me not” because the seed capsule shatters when touched. It's a fun seed to share with kids.

Impatiens seed in pod
Impatiens pod after exploding

Silphium seeds are the dark spots

There are seeds that ripen but stay hidden until just the right birds come along to pry them out. Sunflowers (Helianthus) and rosinweeds (Silphium) are such plants.

The seeds are actually large enough for young hands to explore as you take a flower head, pull it apart a bit and point out where the seeds are hidden. The large plants are sturdy enough to hold the weight of the goldfinches that seek out the seeds.

Sanicula canadensis seed under microscope
Some plants have seeds with tiny hooks on them so that they attach to the fur of animals and the clothes of humans who pass by. This mechanism helps the seeds be dispersed over a greater area. You can use a magnifying glass to see them up close.

Other special considerations might affect how a seed is packaged. The overcup acorn (Quercus lyrata) has a larger than usual cap which acts as a floatation device. These oaks naturally live near river floodplains and poorly drained bottomlands so the ability to float is probably helpful. Maples and other trees have wings on their seeds to help them disperse. Milkweeds and dandelions have little bit of fluff attached. All these parts are not the seed itself but rather extra packaging.

Blueberry fruit with tiny seeds
Some seeds are meant to be eaten so that stomach acid and traveling by the organism that ate it provide two services: scarification and distance of dispersal (when the eater poops, of course). 

Blueberries are a fleshy fruit that contain many tiny seeds. The seeds are small enough that the eater doesn't mind eating them. Kids might be interested to know that, by eating seeds, they are doing just what the plant wants! The tasty fruit is the plant's reward to us.

Passiflora lutea seed under microscope

Still other seeds have intricate designs if you examine them up close. Surely there must be a purpose!

Next time you come across a seed, take a moment to appreciate and be curious about how and why it is what it is. And if you’ve got a young human nearby, take the opportunity to spark their curiosity too.

1 comment:

  1. Love this post! I have so many passiflora seeds and I am trying to figure out how best to collect them. Do you have any experience with this Ellen? I have so much fruit and I'd love to pass along seeds to friends.