Prothonotary Warbler

Prothonotary Warbler

Monday, 18 August 2014

A highly endangered native orchid

One of the highlights of my season, is to check on one of the rarest orchids in Canada. It is so rare, that it was first discovered in a privately owned woodlot in Essex County as recently as 1950, and a few years later was noted in Rondeau Provincial Park. In spite of periodic monitoring, the Essex County population may no longer exist, resulting in the only Canadian population being at Rondeau.

The orchid I am referring to is a tiny, diminutive and difficult-to-see native species with the common name of Nodding Pogonia, a.k.a. Three-bird's Orchid  and a scientific name of Triphora trianthophora. And this is what it looks like up close.....real close.

Nodding Pogonia

It is quite a pretty little thing, with the emphasis on little, especially if you find one that has that magenta tinge to the petals. Most specimens are white, but I am always attracted to the magenta ones when I can find them. Some years there are hardly any magenta ones with predominantly white ones being all there is to see, such as this next one.



I have had the privilege of following this plant population ever since 1973, when it was first pointed out to me by my naturalist colleagues during the first summer I was on the seasonal naturalist staff at the park. The numbers have fluctuated greatly over the decades, perhaps partly because it is so tiny and difficult to see especially when it isn't in flower, which is most of the time. During one of the best years for it in the mid 1980s, I counted more than 1400 plants, which was amazing. The 2008 year was probably the second best year I have noted. The poorest year was in 2012 when, although I found a couple of dozen plants, absolutely none produced open flowers and therefore none produced seed. I have had study plots set up for this population ever since 1986 and have monitored the population almost annually.

Look at the next image.


Make the image as large as you can, and count how many Nodding Pogonia plants you can see. Do you see any at all? This photo was taken with a standard focal length lens, from only a couple of feet away, which is a lot closer than you would normally be viewing the ground flora at. This is what the plant looks like most of the time, for reasons I will explain shortly. In actuality, there are about 15 plants in this cluster!

Did I say that this plant is little? The average height of this plant is no more than 12 cm, or about 4.5". The flower itself, when fully open, is typically less than about 2 cm high. There are usually only one or two small, roundish leaves, each of which is less than 1 cm in diameter. Clearly macro photography equipment is required for this diminutive denizen of the Rondeau forest!

It puts out, in a good year and if it is a healthy plant, about three flowers over the course of the season (hence the Triphora trianthophora, the latter epithet meaning three flowered). The greatest number of flowers I have ever seen on a single plant over the course of the season was 7. Many flowers only put out one or two, and it is surprising how many grow but do not put out any flowers at all! The next photo - one of my favourites -  shows a very rare occurrence, with three flowers on the same plant being open at the same time. And a magenta one at that! This was taken in August of 2008, the most recent year when there was a fabulous showing of the species at Rondeau and included a few magenta ones to choose from.



The earliest I have ever seen a flower was on July 31, and the latest I have seen one is about September 20. However the peak of flowering is about the third week of August.

A bit earlier I mentioned that the plant is in a non-flowering condition for most of the time. It has a very curious flowering strategy. The plants will develop flower buds at their own pace, but will not open right away. Instead they will remain unopened, waiting for an environmental trigger. When there is a significant drop in night-time temperature, then usually on the morning of the second day to follow, all of the flower buds that are at a certain stage of readiness, will open. They will remain open for only a day (or less if they are pollinated sooner), then close up. If they are pollinated, then seed development begins, but if they are not pollinated, they will dry up and that is the end of it......there are no second chances!

The next set of buds will develop, and after a similar weather related trigger, will open several days after the first set opened. Often that is at least a week later, but it all depends on the weather.....those cool August nights are highly beneficial to this species. The benefit to this flowering strategy is that since the plants are not plentiful, if they are all open at the same time, they are more likely to attract pollinators and be successfully cross-pollinated. Of course it begs the question: why don't the flowers remain open for more than a day, as most other plants do? This would increase the rate of pollination, one would think. I haven't come across any explanation for this one-day flowering, so as far as I know, it remains a biological mystery.

This next photo shows a nice magenta flower in peak condition. There is another flower bud (the lowest one) that opened a few days before, and another developing flower bud that will hopefully open in another few days.



The plants may be scattered singly or in clusters. Here is what a small cluster may look like when opened. This photo was taken with a 100 mm macro lens, from a distance of about 2 feet. They are certainly more visible here than in the third image of this post. But in the dappled light of the forest floor, even when they are in flower they can be next to impossible to see. They are very small!



Some other interesting aspects of this tiny orchid include:
-they don't have roots like many other plants. Instead they have a tuberous root that is situated between the leafy humus layer and the sandy soil. They have a very close association with mycorrhizal fungi, which is established in the leaf mould, from where they get some of their nutrients.
-the main pollinators are small bees of the Halictidae family.
-adequate moisture well before the growing season is highly important to support the mycorrhizal fungi as well as the plants themselves. In dry years, as it was in 2012, flowering is greatly diminished or even non-existent.
-these plants can be dormant for quite a few years. Even in the heart of their range, in the southeastern US, colonies or at least parts of the population can be dormant for several years at a time. More than one population which was believed to be gone, has re-appeared.
-after a flower has been open, it droops (hence the Nodding aspect of its name). If it has been pollinated, the seeds develop, and when the seeds are ripe, the seed capsule will extend straight up. Eventually the capsule will split at several points, allowing the extremely tiny seeds to escape and be carried away by even the gentlest breezes. If the seeds land on a suitable substrate, a new plant may begin.



Now that I have you all excited about this plant, I have some unfortunate news. You probably won't get a chance to see it.

Due to its extremely limited occurrence in Canada, its extremely erratic flowering behaviour, its diminutive stature (did I say it was very tiny?), and the strong likelihood that even careful visitors could inadvertently trample it, the small area where it occurs is not accessible to the public. It is well off the beaten path and difficult to access in the first place. It is legally Endangered, under both the federal Species At Risk Act (SARA) and corresponding provincial Endangered Species Act (ESA). Due to the highly protective intent and language of those pieces of legislation, great efforts are being made by Ontario Parks staff to ensure that no harm will come to this important element of Rondeau's, and Ontario's, flora.

So even if you never get a chance to see this wonderful little plant in real life, hopefully you can enjoy knowing a little more about it via this post, and know that it is still present at Ontario's second oldest and most species rich provincial parks.

Rich forest habitat near the Triphora population




3 comments:

  1. I was just thinking about this flower the other day when I noticed a cool evening in August. I wondered how/when the flowering would happen this year, since we have had quite a few cool nights all summer. Did you see them this year?

    Deb

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    Replies
    1. Hi Deb....there have been a few noted in flower, but it hasn't been a great year for them. However much better than in 2012!

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  2. An interesting orchid! Thanks for giving us some insight on the species.

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