Photo of the Week – November 18, 2011

Entire-leaf rosinweed seed heads in late September, 2011. Lincoln Creek Prairie - Aurora, Nebraska.

Entire-leaf rosinweed (Silphium integrifolium) looks much like a sunflower when it’s blooming, but it and its close relatives are actually pretty different from sunflowers.  One major difference is the shape and location of the seeds.  Sunflowers produce seeds in the center of the flower head, but rosinweed, compass plant, and other Silphiums have seeds that are located on the outer border of their flowers.  In this photo, the white dots on the left flower are the tips of those seeds. 

Rosinweed seeds are built differently than sunflower seeds as well.   Everyone is familiar with the kind of sunflower seeds sold as snacks – with a two-part shell covering the “meat” of the seed inside.  Prairie sunflowers all have variations on that same structure.  Silphiums, however, produce very large seeds that are encased in a kind of papery sheath about the size and shape of a fingernail.  The photo below shows another rosinweed head on which the seeds are exposed.

This rosinweed seed head shows the ring of seeds around the center of the flower.

The size and shape of the seeds of rosinweed (and other Silphiums)make them easy to identify in our restoration seed mixtures.  They’re also a good example of why it can be challenging to use some kinds of seed drills when planting diverse prairie seed mixtures.  Large flat seeds like those of rosinweed can’t squeeze through small tubes or other small openings.  Combined with other seeds that are fluffy, smooth and hard, or just plain tiny, it can be difficult to get all the seeds to feed smoothly, or at consistent rates, through some kinds of equipment.  Because of this, many of our older prairie restorations were seeded by hand -which works just fine – though now we mainly use a drop spreader (a fertilizer spreader such as an EZ-Flow that is essentially a long box with holes in the bottom and an agitator inside).

13 thoughts on “Photo of the Week – November 18, 2011

  1. That’s a pretty tiny seed and I’ll bet it weighs practically nothing. How many acres of plants do you need to get a pound of seeds?
    Are these edible? What do they taste like?

      • Mel – as Ted said, they’re pretty big. I don’t have any idea whether they’re edible to people or not. I’ve never heard them discussed, but I’m sure someone knows.

        It doesn’t take too many plants to get a pound of seed, but a pound of seed would take up more volume in a bucket than one might expect because the seeds don’t pack together very tightly. A rough guess is that 20 or 30 big plants would yield a pound of seed.

        • I’ve eaten the seed of a congener, compass plant Silp[hium laciniatum — Very much like raw sunflower seeds in taste and texture, but flatter, so without as much volume.

          In answer to a question below, this type of seed (actually a dry, one-seeded fruit) is a achene with marginal wings. Samaras have a single, long, terminal wing, as those of a maple, ash or tree of heaven.

          • Thanks James. Apparently the seeds aren’t too toxic, then, if you’re around to make the comment. Had/have you heard or read anything about their use as a food item?

          • I tried a silphium (don’t remember which one) and was not impressed; more work than a sunflower but less “meat” and taste.

  2. Is the seed case a samara? Would that indicate that seed dispersal is mostly by wind? Leopold has a good essay on Silphiums in the Almanac. Tom P.

    • Tom- I’m not sure if it’s a true samara, but it has a similar appearance. In terms of dispersal, I’d guess it does get blown short distances, but it also has two little appendage-like points at the top that can help it stick to fur a little. It doesn’t appear to be optimized for either wind or animal dispersal, but has a little of both. And yes, I like Leopold’s piece on Silphiums too.

  3. When the seeds become ready to collect, we look for the tiny white tips to verify the existence of good viable seed. If the seed is not viable, you will not see the white tips and we will not pick it. You would think that such large seeds need to have a soil covering them to germinate but I have noticed that just casting them into the wind over existing plantings or bare ground will give surprising results. Be careful not to broadcast Compass Plant a handfull at a time into one spot as most will germinate and they will come up too close to one another and may not bloom for 10 years or more.

    Compass Plants can live up to 100 years. The roots can grow 9 to 14 feet in depth. An elderly gentleman named Roland Bernau owned a 100 acre native prairie near Algona, Iowa. He has since passed away. He was in his 90’s. His comment to me was that he used to harvest hay from that same prairie and some was sold to the Chicago market. Hay that contained Compass Plant always secured a higher price as it’s food value for cattle was considered to be the best. Roland called the plant “gumweed” and he said that he used to chew the resin produced by the plant as it was nature’s chewing gum.

    • Great comments! I’ve never used the white tips as an indicator, but will have to watch for that. We usually just check to see if the seeds are “lumpy”. If they’re completely flat, they clearly didn’t fill.

      You’re right about the surprising results from broadcasting. Rosinweed is one of a handful of species I’ve noticed that can move into my bluegrass yard, even. I’ve been hoping that means I can establish it in some of our more degraded prairies that are dominated by bluegrass, but results have been fairly spotty so far.

      • thanks for the great photos ! I had a “volunteer” I wasn’t sure of (Florida Greeneyes vs Rosinweed) but was able to identify the tiny white dot and then peel away to find the my case, however, it is tiny – about the size of a baby’s fingernail…possibly as different sort than uou grow out west ? Mary 9-2

    • I remember from my early childhood eating something we called indian chewing gum, which was the inside of a stalky plant that grew in the vacant lot behind my parents house. Reading your post just helped me to make the connection that the plant was probably a silphium. Of course they’re long gone now.


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