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By Bruce Rottink, Volunteer Nature Guide & Retired Research Forester
Western trillium (Trillium ovatum) flowers are a major attraction at Tryon Creek State Natural Area (TCSNA). I’ve already written three Naturalist Notes about this plant. In the process I’ve accumulated a host of materials that didn’t fit too well with any of those previous notes; the time has come to share them.
How big do trilliums grow?
From May 4 through May 6, 2016, I conducted a survey of trilliums that were growing more than 10 feet from any trail. The areas I surveyed were near the Equestrian and North Horse Loop Trails in the northern part of the park, Center, Big Fir and Old Main Trails in the central part of the park, and Iron Mountain Trail in the southern part of the park. For each triple-leafed trillium I encountered I measured the distance from the ground to the attachment point of the triple “leaves.” I also noted whether or not each plant was flowering. The results are shown below.
Ten inches is about the height where the plants shift from non-flowering to flowering, although a couple of very short plants flowered, and a few fairly tall ones didn’t.
What happens to the trillium’s flowers and seed pods?
Ideally, the flowers are pollinated, the seed pods (or capsules) mature, then open and release their seeds into the forest. Of course there are other possibilities. Deer, it has been reported, sometimes eat the flowers. The contents of the maturing seed pod are very nutritious, and researchers have reported that both deer and mice sometimes eat the seed pods.
To assess this, I conducted surveys in two different years. The first survey was conducted between June 23 and 28, 2015. Two groups of trilliums were surveyed. “Trailside trilliums” were those growing within 10 feet of the trail. “Mid-forest trilliums” were those growing more than 10 feet from the trail. It should be noted that at this time the seed pods are well along the path to maturity. The plants were placed in three categories: a) capsule intact, b) pedicel only, meaning the plant had flowered, but the flower/seed capsule was missing, and c) did not flower, as indicated by having no pedicel or capsule. Illustrations of each class are below:
The results are shown below:
A statistical analysis (Note to nerds: I used the Chi-squared test.) clearly shows that a significantly higher percentage of the trailside plants flowered compared to plants growing more than 10 feet from the trail. The cause of this difference cannot be determined by this study. The other statistically significant difference between these two groups is that a higher percentage of the “mid-forest” trilliums only had a pedicel (“flower stalk”), which means that either the flower or the seedpod was removed. Animals likely ate these seed pods or flowers. Perhaps the deer are more comfortable eating in the middle of the forest than trailside.
In 2016 I undertook a second trillium survey, this one was conducted May 4 through May 6, at a time when the last of the trillium petals had just recently fallen off the plants. This time, however, the “trailside plants” I tallied were within 3 feet of the trail. The “off-trail plants” were growing more than 10 feet from a trail. At this time the seed capsules were small and immature. The results are shown below:
Once again, the percentage of plants flowering was statistically significantly higher in the trailside plants compared to plants growing “off-trail”. A slightly smaller percentage of the flowers/seed-capsules had been eaten than in the previous study, probably because there was a shorter period of time for the animals to eat them, or perhaps, being smaller, they were of less interest to the animals. The one thing that clearly stood out in the data is that the percentage of reproductive structures missing was significantly higher along Old Main Trail than along the other trails. (Geek note: Statistically, there is less than a 1 in 10,000 probability that the higher percentage of missing capsules observed along Old Main was due to chance.) The fact that Old Main is one of the most heavily traveled trails makes it tempting to speculate that people were picking these flowers, as shown in the picture below, but this study cannot prove that.
An alternative explanation for the empty pedicels is that the flower was defective and the defective bloom was aborted. I recently saw a single dysfunctional bloom in the forest. It appears that the plant started to produce a functional flower, but something bad happened along the way, as in the example below, where you have what appears to be an attempt at a flower, but no actual petals.
Does it really take 7 years for a trillium to recover after the flower is picked?
Many people believe that if you pick a trillium it will be 7 years before the plant flowers again. I unexpectedly got a chance to test that theory when someone picked 6 trillium flowers on a plot of trilliums I had been studying for 5 years. I concluded these had been picked, because the remaining stems did not exhibit the type of cut associated with animal browsing. One of the stems from which the flower had been picked is shown below:
Although very unhappy, I decided to capitalize on the tragedy. (“When life hands you a lemon, make lemonade!”) I carefully documented the exact location of the trilliums. Based on the location of the six flowers, it appeared that all of them were twin stems, arising from a total of only three rhizomes (rhizomes are like a flower bulb).
In April 2017, one year after the tragedy, I surveyed the site again. I went to the site and measured the location of the trilliums. Based on their location, 2 flowering stems were within ½” of the location of the flowering stems that were decapitated last year. Thus I concluded that only 2 out of the 3 effected rhizomes produced flowering stalks again this year. However, whereas last year they were twin-stalked, this year they only had one stalk each. At the location of the third picked trillium, there was nothing. Scientists have determined that some years a trillium will occasionally just take a rest, and not produce an above ground stem. So that is what this one did, OR it died. I don’t know which. Either way, for at least two of the plants, the “7 year” myth is debunked.
Does anything eat trilliums?
Deer are commonly reported to eat trilliums. But it turns out that isn’t the whole story. This spring I ran across one of our slimy forest friends deeply engrossed with a trillium. Note that this is not our native banana slug (Ariolimax columbianus) but appears to be one of the non-native species.
You’ll notice that considerable chunks of the trillium petals are also missing, and these may only have been the prelude to the slug’s full scale attack on the heart of the trillium flower.
What pollinates trilliums?
Most of the plants we hear about are pollinated by bees, like our Pacific waterleaf (Hydrophyllum tenuipes), or by the wind, like Douglas-fir (Pseudotsuga menziesii). Trilliums are a little different. A study of Trillium ovatum in southern Oregon determined that pollinators included several species of beetles, honey bees, bumble bees, crab spiders and geometrid moths1. Since the trillium doesn’t produce nectar, at least some of these creatures are here to eat the pollen, and they spread the pollen as an unintended side effect.
The forest is endlessly fascinating, when a person just stops to observe. Looking back on my old trillium photos, I now see lots of the “little brown bugs” deep down in the bloom. How could I have missed that so often? When you’re out in our forest, stop for a minute and look around. I think you’ll be amazed, as I was, at how many interesting things are out there.
1Jules, Erik S. and Beverly J. Rathcke. 1999. Mechanisms of Reduced Trillium Recruitment along Edges of Old-Growth Forest Fragments. Conservation Biology 13:784-793.
By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester
Mother Nature is the world’s first, largest and best recycler! Each year in Tryon Creek State Natural Area (TCSNA), tons of organic matter like trees, dead animals and coyote feces are recycled. This recycled material is used by the forest to grow new trees, birds and mice, to name just a few. If it weren’t for recycling, the surface of the earth would be covered with unimaginable amounts of dead organic matter. In addition, it would be tough for any new organisms to grow because so many materials vital to life would be locked up in the litter.
Two years ago, I started a small study at TCSNA to determine just how fast the recycling process is in our forest. The first year’s results were published in a Naturalist Note last fall. To access this previous note, use this link, and then scroll to the bottom. This second Naturalist Note takes a look at the results after two years.
How it works…
As indicated in the previous Naturalist Note, samples of five different kinds of fresh organic matter were collected from the ground in TCSNA in the fall of 2014. Collecting them from the ground insured that they were naturally ready to start being recycled. The samples included a) red alder (Alnus rubra) leaves, b) bigleaf maple (Acer macrophyllum) leaves, c) western redcedar (Thuja plicata) branchlets, d) Douglas-fir (Pseudotsuga menziesii) branchlets, and e) scales from a Douglas-fir cone that had been chewed apart by a squirrel. Two samples of each thing were collected, for a total of 10 samples.
Each sample was placed inside a flat “bag” made of standard plastic window screen material. The bags were then taken into the forest, placed down flat on the forest floor, and fastened down by inserting a nail through the corner of each screen down into the ground.
From September 2015 through September 2016, pictures were taken on a quarterly basis. The results after two full years can be seen in the photos below. The first photo shows the array of litter bags before I disturbed them to take the photos. The silvery-gray bits seen in the photo are the exposed part of the screen bags. As you can see, there were also some plants growing up through the litter bag array.
They’ve really changed!
The rate of decay of materials from the different species varies dramatically. Specific samples are shown below. The first two sets of pictures show the two different red alder leaf bags. I’ve included both sets of red alder bags to show that there is a certain amount of bag-to-bag variation in the rate of decay. For the remainder of the species in the study, I’ve included only one of the two bags. You may observe that due to my picking up these bags periodically for photos, the position of some of the materials in the bags has shifted a bit.
While most of the leaf blades are substantially degraded, some of the veins are still intact. This is typical of many different leaf decay studies.
The following photos are of one of the bags containing bigleaf maple leaves. Again, you can see that the leaf blades themselves are pretty well decayed, but some of the veins, and petiole (the “stem” that connects the leaf blade to the branch) are still identifiable.
…Or maybe not so much!
The remaining samples are all from conifers, which retain their foliage for more than a single season. If you could feel their foliage, you could tell it was definitely tougher. This becomes evident in the photos below.
The western redcedar foliage has not only not decayed very much, but also, many of the leaf scales are still attached to the branchlets. I’m impressed!
Most of the Douglas-fir needles in the bag shown below have fallen off the twigs, but they still appear to be largely intact. Detailed scientific studies suggest that while there has probably been some substantial decay inside the needles, the outer tough surface of the needle has been somewhat resistant. One unfortunate thing with the Douglas-fir branches is that once the needles have fallen off the twig, they can easily slip through the mesh screen when they are jostled very much. I have no doubt that some of the needles that were originally on the twig have fallen out of the bag.
The final set of photos below show the tough cone scales of the Douglas-fir which appear to be only minimally changed over the course of two years on the ground. This is not surprising, given that the cones are made tough to protect the seeds of the tree. Also, the cones tend to have high resin content, and thus resist decay.
Litter as fertilizer
Litter contains vital nutrients that help trees grow. One of the advantages of relatively slow litter decay is that the litter then acts as a “slow-release fertilizer” a method of ensuring that the living plants will have ample opportunity to absorb it to assist with their growth.
But long before the nutrients trapped in the litter help the next generation of trees and shrubs grow, those nutrients help the fungus and bacteria that decay leaves grow. And just like you, the microorganisms are more attracted to a lavish banquet than to a bowl of thin soup. The more nutritious the litter, the faster it decays1. For example, red alder leaves have 4 times the nitrogen content of either western redcedar or Douglas-fir foliage. Bigleaf maple litter has more than 3 times as much phosphorus as either western redcedar or Douglas-fir. Both red alder and bigleaf maple have more than 10 times the amount of potassium as Douglas-fir litter. Viewed from the perspective of nutrient contents, it’s no surprise that the red alder and bigleaf maple foliage decays faster.
It was found in the mid-1970s that applying urea fertilizer containing 200 lbs of nitrogen per acre to Oregon’s Douglas-fir forests, significantly increased their growth rate. As noted above, red alder leaves, due to the nitrogen-fixing nodules on the alder roots, contain relatively high levels of nitrogen. The photo below shows the amounts of urea fertilizer (the typical nitrogen fertilizer for forests) and alder leaves that would be needed to provide 200 lbs/acre of nitrogen. So the decaying leaves, especially the alder leaves, are acting as a slow release fertilizer.
The box of dried alder leaves contains as much nitrogen as the small vial of white urea.
The dead plant parts like tree trunks, branches, leaves and even the unseen roots, are important parts of the whole cycle of life at TCSNA, as well as in other forests. In their role as nutrient recyclers, the fungus and bacteria that decay the forest litter play a vital role in helping maintain a healthy and vigorous forest. Recycling is an important example of how different parts of the forest work together to create the TCSNA we love so much.
1Valachovic, Y. S., B. A. Caldwell, K. Cromack Jr., and R. P. Griffiths. 2004. Leaf litter chemistry controls on decomposition of Pacific Northwest trees and woody shrubs. Can. J. For. Res. 34:2131-2146.
By Bruce Rottink, Volunteer Nature Guide and Retired Research Forester
If you’re reading this, there’s an excellent chance that you have hair! Well, you’re not alone! Amazingly enough, many species of plants have “hair” too. Technically, plant hairs are called “trichomes” and they’re different from mammalian hair in many ways. They come in a variety of shapes and sizes, and perform many different functions. The plants at Tryon Creek State Natural Area (TCSNA) have a variety of different kinds of trichomes. Based on their physical properties, trichomes can protect plants from a variety of herbivores, reduce the loss of water and help spread the plant’s seeds.
Simple Plant Hairs
Let’s start out with the basic plant trichome. These simple trichomes can be found, for example, on the petiole (“petiole” is the little stem that attaches the leaf blade to the branch) of TCSNA’s own red elderberry (Sambucus racemosa L. var. racemosa), as shown below. These are simple, straight, unbranched hairs.
Plants, like most things in nature, are rarely frivolous. If they expend the energy to produce plant hairs, those hairs most likely have a purpose. One of the benefits of plant hairs is that they help reduce the rate of water loss from the plant. Imagine a water molecule trying to escape from the elderberry pictured above. The thicket of plant hairs on the stem dramatically slows down air movement right at the surface of the plant. This mass of plant hairs is essentially a maze that the escaping water molecules have to slowly wander through before it leaves the plant.
To demonstrate this effect, I set up the following demonstration. I took two small identical plastic tubs and completely filled them with water. The first tub (pictured below) is totally open to the atmosphere.
For the second tub, I inserted a scrub brush, bristle side up, into the top of the tub. The bristles of the brush created a maze similar to that created by plant hairs. The water molecules had to move through this maze in order to escape (evaporate) from the tub of water. And, yes, just like in plants, it did slightly reduce the open surface area of the water.
I weighed the containers as shown before the experiment started. After 36 hours of evaporation, I weighed the containers again. The open container lost 39 grams of water, while the “hairy” container lost only 25 grams of water, 64% as much as the open container.
Get a Grip!
Some of the trichomes found in the plant world are simple, but not straight. A good example found at TCSNA is the seed of the bedstraw (a.k.a. “cleaver”) plant (Galium spp.). The seed, which is shown below, is covered with stiff, curved trichomes.
In case you’re wondering why the seed has these hook-shaped hairs, take a look at the picture below.
The hook-shaped hairs allow the seeds to attach themselves to some innocent passing animal and hitch a ride to a new location. Presumably they will be brushed off, or rub off somewhere after the passing human or other animal has traveled some distance and “voilà” the plant spreads itself to a new growing place.
Plant hairs can defend against insects and other pests that want to eat the plants. Sometimes, the sheer density of the hairs can serve as a deterrent to hungry herbivores. Some insects might not be able to get through the hairs. Some larger herbivores might just experience the hairs as “sharp pokey things” and decide to leave the plant alone. A good example is the ultra-hairy seed of TCSNA’s bigleaf maple (Acer macrophyllum) as seen below.
Sometimes, defensive plant hairs are a little more complicated. One of the premier examples here at TCSNA is our beloved stinging nettle (Urtica dioica) which is pictured below. The stinging nettle uses some of its plant hairs defensively. The larger trichomes have a largely silica (like glass) hollow needle (blue arrow) mounted on a relatively soft green pedestal (red arrow) which contains toxins. When some animal carelessly brushes against it, the tip of the needle breaks off and the movement of the animal against the plant bends the needle over, squeezing the toxin out of the green tissue at the base of the needle. The toxin is thus injected into the offending animal. The toxins in this species include histamine, acetylcholine, serotonin, and formic acid. Typically they cause an itching sensation that for most people lasts no more than 24 hours. Note that the stinging nettle also has much smaller hairs (yellow arrow) that are common on many plants.
While humans tend to be very sensitive to stinging nettle, apparently it isn’t 100% effective against all animals. The banana slug (Ariolimax columbianus) pictured below crawling on stinging nettle seemed to be pretty calm and unconcerned by the trichomes. It may be that the slug is either immune to the chemicals in the stinging nettle, or its famous slime layer is protecting it or it moves so gently that it doesn’t break the nettle’s needles!
Human hairs are all unbranched. This is not necessarily so for plant hairs. The English Ivy (Hedera helix) has hairs that are branched. The pictures below show these branched hairs from two different perspectives.
Finally, there are glandular hairs, which produce chemicals in a small gland at the tip of the hair. One of the most interesting examples at TCSNA is the invasive plant commonly known as “herb Robert” (Geranium robertianum). Another name for this species is “stinky geranium.” If you ever pulled one of these plants, you’ll know why it’s called stinky geranium. On the tips of the hairs (blue arrow) on the stem below, you can see a small red dot. This red dot is actually a gland that produces the stinky chemical. One of the traditional ways humans have used the chemical produced by herb Robert was to rub it on their skin to repel mosquitos. It probably keeps insects away from the plant as well.
A second example of glandular hairs on a plant at TCSNA is hazel (Corylus spp.) Both of the hazel species that we have at the park have a significant number of glandular hairs, as shown in the photo below. The chemicals are located in the brown tips of the hairs. In both pictures below note that in addition to the glandular trichomes, the hazel also sports a large number of very small hairs on the midrib on the leaf.
Many interesting chemicals are produced by glandular hairs on plants. The trichomes of the sweet wormwood plant (Artemisia annua), which is not found at TCSNA, produce the chemical “artemisinin” which is an effective drug against malaria. And the psychoactive chemicals in marijuana (Cannabis sativa) are produced in the tips of the plant hairs of that species.
All in all, the hairs on plants are quite diverse, and have many functions. As has shown here, plant hairs can slow water loss, help spread the seeds to new locations, and protect the plant from herbivores. For the plants, the many functions of these trichomes do indeed make them a big hairy deal!