Two Correas

by Jim Nelson

Correa backhousia stamens

Correa backhousia stamens

On our April excursion to Greens Beach, we walked along the coastal reserve track. Probably the biggest excitement of the day was watching a large group of gannets diving for food. They are amazingly graceful and beautiful to watch.

The coastal reserve flora was pretty much what might be expected, and with very little flowering in autumn. One exception was a single Correa bush with a yellow flower. Deb looked at it and said 'That doesn't look like Correa lawrenciana!' I replied that it must be because the only other choice for a yellow flowering Correa is Correa backhousiana, a species which occurs only in the south, west and northwest coasts.

It has been a few years since I had seen C. backhousiana in the area from about Rocky Cape and west. But as I looked more closely at the bush I too thought it was a pretty strange looking lawrenciana and thought perhaps it might be backhousiana. Thus, I took a small piece to key it out.

Correa stamens
Correa stamens

Both C. lawrenciana and C. backhousiana have yellow flowers, but I thought I remembered that there was something different about their stamens. Back in Devonport, we looked at the C. lawrenciana flowering in Deb's garden and I immediately saw that its stamens were sticking much further out of the top of the corrolla tube, while the sample from Greens Beach had its stamens barely exerted. The leaves were also different, but leaves can be quite variable and can thus be unreliable. Having flowers in hand is always the best way to come to an accurate conclusion, because botanic keys work mainly with floral characteristics.

I initially went to the Correa key in the RUTACEAE Family in my well-worn Student Flora (Curtis and Morris). There are four species of Correa native to Tasmania. The common coastal Correa is C. alba, which is often a large shrub with white bell-shaped flowers (rather than tubular ones) along our coasts. This obviously wasn't a candidate. There is also Correa reflexa, which is fairly widespread and is a popular garden cultivar (especially in its red flowered form) with its typical reflexed and rather hairy leaves, and again, not a consideration. That left C. lawrenciana and C. backhousiana as the two considerations.

In both of these species the leaves can be quite variable. The characteristic that quickly sorts them out is their stamens. In C. lawrenciana, (as we had noted) the stamens are exerted some distance above the petals. In C. backhousiana, the stamens are barely exerted. Additionally, some of the filaments of the stamens are expanded at their base in C. backhousiana.

This keying out to species probably took about 15 minutes reading through the key and then the descriptions while looking at the dissected flowers under a 20 power microscope. This time was fairly short because I already knew what family and genus I needed to look up.

I then decided to try out a new native plant key for Tasmania available on the internet . This key assumes very little knowledge, and is probably best used by having the plant in question in front of you. In less than 5 minutes I had the answer by making repeated choices which progress you to the next step. Each choice is illustrated with a photo, and if you go down the wrong track, you can easily go back. At the end, I had a photo with a dissected flower showing the stamens of C. backhousiana, and this clearly demonstrated the expanded bases of the stamens.

When keying out the plant in the Student Flora, I read the full botanical descriptions of the plants in the genus, and refreshed my knowledge about a number of differences between the two species in hand. This requires a reasonable working knowledge of botanical terms and the use of botanic keys. For those who take botany fairly seriously, this ritual is carried out with the same kind of relish that wordsmiths apply to cryptic crosswords. The more you do it, the more it starts to all make sense and becomes a pleasant challenge.

However, many people just want the answer to what a particular plant might be, and don’t want to have to learn basic botanic terminology to do so. The plant key website seems to offer this potential shortcut to accurately finding out the name of a plant. It will be interesting to see how people find it to use. I would suggest perhaps starting with plants that you know in order to work through the process.

But back to C. backhousiana, just what is it doing so far from its known distribution along the north coast? Well, one possibility is that it is an escape from one of the nearby gardens of the holiday houses next to the reserve, since the plants can be purchased from native plant nurseries. It would be interesting to see if any specimens turn up further along the coastal track away from these gardens. If you happen to take a walk that way, keep your eyes open. There is always a chance you may find evidence to expand the distribution information for the species.

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