Greenhood orchid taller, greener, later

Ah, orchid taxonomy! Nothing like it to put 99.9% of readers to sleep and the other 0.1% into apoplexy correcting me (in all other circumstances I proudly include myself in this latter percentile). So here we go, and it's a rerun of an old post, but this time getting things right - or at least a little more correct.

Three years ago I returned to an old orchid hunting haunt and rediscovered some Tall or Leafy Greenhoods, all of which used to be called Pterostylis longifolia (and some include in their own genus Bunochilus). It's a tricky group, at least for me after a hiatis away from Victoria.

Don't worry too much about the names but back then in mid-August what I thought at first was Pterostylis melogramma turned out to be most probably Pterostylis smaragdyna. It was all to do with the two petals that fuse to form the hood being flanged inside so that the opening (if you look into the hood) was mostly closed.

This year I revisited the same site, Professors Hill in Warrandyte, on the outskirts of suburban Melbourne, and found one large, deep green Tall Greenhood at full maturity (and about to fade), and another nearby which was pale green, smaller, and in the early stage of its flowering. I wondered if one was melogramma and one was smaragdyna. Not a particularly important life question but I was curious.

This time I went straight to the online key to Victorian plants, which you track down through VicFlora. If you correctly interpret that flanging inside the hood - which I didn't do in 2013 - you get to a pair of species: Pterostylis chlorogamma and Pterostylis smaragdina.

They don't seem particularly distinct from one another with the diagnostic features a small difference in the length of the labellum (the fuzzy surfboard-like structure that flicks back into the hood when touched by an insect, or human hand - it's closed in the picture above), the colour of the hood ('pale transluscent green with dark green lines' v. 'dark green with darker lines') and the two fused 'sepals' dangling downwards narrow oblong or narrow elliptic.

Now if I interpret things correctly, this is Pterostylis chlorogamma (the Green-striped Leafy Greenhood).

And this is Pterostylis smaragdina (the Emerald-lip Leafy Greenhood)

I'm not super confident, but I reckon my pale, smaller, later-flowering entity is chlorogramma and the other smaragdina. If you track back to the Flora itself there is a paragraph under chlorogamma explaining that it differs from smaragdina in having small, paler flowers and a smaller labellum with less developed 'lateral lobes' (the small flange on each side of that lumpy surfboard...).

As additional support, the flowering time for chlorogamma is July to September, and for smaragdina, June to August. I read that as the former flowering later than the latter, which is exactly what I found.
So two sprinter flowering Tall Greenhoods, one early in the season, one late. That'll do me for now. All correspondence received with gratitude and great expectation. Sorry everyone else.

Images: All except the last two are, apparently, Pterostylis chlorogamma. The others are, of course, apparently, Pterostylis smaragdina. Both have leaves sticking out of the stem and no basal rosette at the time of flowering, but then so do all those other species of Tall or Leafy Greenhood they might just be.