Monthly Terrestrial Orchid Culture—March
As stated last month, this is the second in the series of terrestrial culture notes for growing orchids in Adelaide.
The growing season is underway although much of the activity is underground out of sight early in the month. Repotting should be completed by now. Repotting tubers with long shoots is a tricky business requiring very gentle handling. Broken shoots and the death of some plants can result. It is better to leave them until next summer.
The weather can be hot up until equinox on about March 21st. Be aware that autumn is a time of rapid change. Day-length decreases by 2 hours in the 6 weeks from the 1st of March. Our orchids respond to the longer cooler nights faster than we do. All pots should be in their growing positions for the coming winter. Increase watering in March so that by equinox the mix is damp right through to the bottom of the pot. The first Eriochilus cucullatus flowers are usually open by the last day of March with the majority blooming in April. The buds resemble a grain of wheat when they first emerge.
Thrip can be a major problem this month. Thrips love to suck on the flowers and will cause the flowers to shrivel up in a day or two. If using a pressure pack fly spray to kill thrips, hold the can at least half a metre away or you can freeze the flowers with the propellant. Repeat the spray every few days.
Pull out any weeds that germinate while they are still small. The early Greenhoods will be showing leaves and some of the blue tag Diplodiums may be showing buds. The Greenhoods will like a weak soluble fertiliser sprayed on their new leaves as they develop.
Deflasking can be done after equinox. April is the best month to deflask terrestrials as it is cooler and more humid with enough sun to harden the leaves before the cold and damp of winter. Flasks are often the only way to get the slow multiplying terrestrial orchids. Seedlings in flask that have tiny tubers establish more successfully.
Remove the second layer of shadecloth at the end of the month or first week in April. Keep up the night time hunts for pests which get more active as the nights cool.
Autumn is a good time to build or extend a terrestrial growing area. A terrestrial house should be sealed to keep out birds and animals and have shadecloth or wire mesh sides to allow the breeze to move through. I prefer a roof of angled 50% shadecloth. Other growers use a solid roof of plastic sheeting. A solid roof means you have to water your pots by hand, which is more work. It is very important that winter sun reaches your plants so site the shadehouse away from the winter shadows of buildings, high fences and evergreen trees. Galvanised mesh benching about 750 mm high will deter slugs and snails and is a convenient height for observing the pots.
Genes, seasonal conditions or pure chance?
Leo Davis is an orchid hunter. He is meticulous in his observations and notes details that many of us may miss. In this article he muses upon the variations that he sees in the field.
You, as I do, must occasionally come upon an orchid or an orchid event that is a little outside normal experience. When I do, I wonder whether this is a purely chance event or is it caused by recent local environmental factors, or is it due to the genes of the plants. Or a combination of these?
I’ve been watching a couple of patches of fire orchids (Pyrorchis nigricans) that many of you will be familiar with, one at Knott Hill N.F.R., the other at Monarto C.P., where a few plants flower every year, without the normally required stimulation by fire. I need to check whether it is the same plants that flower each year.
The tall leek orchid (Prasophyllum elatum) puts up leaves at Scott Creek C.P. every year but does not flower. A fire swept through in early 2014 and most plants flowered in October. They’ve not flowered since. But over at Ramsay Way, west of Pt. Vincent, a few plants flower each year without fire. I assume genes are involved.
In April 2014 I chanced upon a patch of Adelaide Hills parson’s bands (Eriochilus collinus), along Moore’s Road, at Morialta C.P., in which the majority of plants had three flowers per stem. Was this because of favourable conditions or genes? Over the next two seasons I saw only the occasional double header and mainly single flowered plants. I will continue observations and records.
In July 2015 I found a dense patch, about 3 m2 in area, of hundreds the common mallee shell orchid (Diplodium dolichochilum), in Ferries-McDonald C.P. As usual less than ten plants were in flower, but two of them were double headers. I’ll be checking this season and expect this not to be a chance event but one due to genes.
On May 27, 2012, Bob Bates led a NOSSA outing to Scott Creek C.P. and as ever, when he leads, we saw and learned a lot. He showed us a patch of fringed hare-orchids (Leporella fimbriata) that he assured us should not be growing there on that steep rocky site and that the plants would not flower most years. Unfortunately he was right, as usual. I could not find plants in 2013 and 2014 and it took three searches in 2015 to find a very few leaves. On May 10 this year, over an area of less than 10 m2, I found perhaps 50 leaves and just seven plants in flower. Three of these had three flowers and a tiny unopened bud (check the photo) and the others were doubles. I’ve never seen a triple flowered plant in hundreds I’ve seen at Knott Hill N.F.R. Are genes in an isolated population at play here? Given the paucity of flowering at this site, it may take me years to sort this one out.
An Eriochilus study in the Southern Flinders Ranges: 2010
Until 2009 when NOSSA did an orchid study of Wirrabara Forest Reserve the parsons bands or Eriochilus were thought to be rare in the Flinders Ranges, but that year Eriochilus were found all the way north to Mount Remarkable and were often seen as locally common.
In 2010 I did two visits, one in April and one in May to see how well they flowered after a wet spring the previous year.
Results: all colonies at Wirrabara flowered spectacularly in April 2010 but at Mt Remarkable flowering was poor. No leaves were visible at the time. The flowers were white with some strong colour and stems were quite bristly, see image. At Wirrabara plants were sturdy with up to four flowers per scape yet at Mt Remarkable plants were spindly and flowers mostly single.
It was thought that the reason for this difference lay in the wet spring of 2009 at Wirrabara with much less rain at Mt Remarkable.
The second visit in May showed a different picture. Very little rain had fallen at Wirrabara in autumn and the stems of all plants had hardly elongated. Yet seed capsules were plentiful. In contrast, Melrose near Mt Remarkable had received good autumn rain and stems there had doubled in length.
So it seems that the number of flowers and strength of plants depends on rain the previous season whilst height of stems depend on rain during the current flowering season.
Curiously, in both areas a second flush of flowering occurred in May with the second flush at Wirrabara producing tiny flowers on short spindly stems (see image) while those at Mt Remarkable had larger flowers on tall stems.
Flowers seen in both areas were similar in appearance and both had leaves which were large, apiculate, dark green, ribbed and hairy above, purple below. Both the April flowered and May flowered plants belonged to the same taxon and clearly flower size and number, and scape length, are not useful in separating species as they are so variable.
On the other hand leaf shape, texture, ribbing and colour below are important in identifying the species as these are constant features.
Conclusions: only one species of Eriochilus occurs in the Flinders Ranges and this is the same as the common woodland species in the Mt Lofty Ranges. This species has never been named officially but is generally known as Eriochilus sp Hills woodland and is best identified by it’s leaf … see image.
This is the most common of three or four Eriochilus species in SA.
Surveying in the South East
In recent years a number of N.O.S.S.A. members interested in field work have been involved in surveys for orchids. These include surveys for individuals as well as government or semi-government organisations.
Late in March this year we undertook an Autumn survey of a forest in the South-East known as The Marshes. As the name suggests the area is well served with swamps as well as forest of Stringybark with sandy soil. Several members met the day before to check some areas in the upper SE. Here in sandy-heath there were two species of Corunastylis in flower, often not very distant from each other, but each favouring different habitats. In the heath were C. aff. rufa in flower and capsule. In mallee open forest C. tepperi had recently commenced flowering.
In areas dominated by granite outcrops were found Eriochilus cucullatus flowering and perhaps another un-described Eriochilus species. Leaves were not present, so no distinction could be made from flowers alone. However, in mallee the flowers were larger and supported on much taller stems. Those on the granite were small flowered on short stem, there being no apparent difference in the flowers themselves. Here also the C. aff. rufa was seen in flower and capsule.
In the lower SE a sojourn into Honans Native Forest Reserve produced yet different species, some in flower. C. ciliata was already in capsule, the distinctive greenish-yellow lateral sepals still evident and under magnification hairs could be detected on the labellum. C. despectans had the very last flowers on the top of the scape as well as capsules on earlier flowering specimens. Speculantha obesa had just commenced flowering. In most cases the inward facing, smallish flowers had only the bottom one open with buds on the stem above. Rosettes were not yet present. We were amazed to find Pterostylis nutans rosettes already emerging. A little less surprising was Leporella fimbriata, but the number of flowers seen at this early stage was few.
The Marshes is not renowned for being prolific in Autumn flowering orchids but our visit was scheduled to try to locate as many as we could. By the second day we were rewarded with the discovery of plenty of Spiranthes alticola, which were represented in most of the swamps in the western sector. It is interesting to note that years ago they were found prolifically in the eastern sector but this appears to have dried out too much for them these days. S. obesa was found in very low numbers and this time one of the plants already had a capsule.
Perhaps the greatest excitement was afforded when two members thought they found Cryptostylis subulata leaves. All the surveyors collected for lunch and soon were down at the site considering if the leaves lived up to the name. Much discussion ensued. If only there was a flower to confirm the diagnosis. After what seemed like an age a “tired” flower was located! C. despectans had previously been recorded for the forest and a considerable amount of time was spent in searching known locations but to no avail. Not Autumn flowering but the other orchid found was Dipodium roseum which was heavy with capsule. Some of the stems had up to eight large pods hanging on them.
At Mt. Lyon Native Forest Reserve we were able to view many Cryptostylis subulata in flower and capsule. Another trip was made to Honans to locate C. subulata from provided GPS readings. After a bit of interesting navigation both swamps were located. However we were unable to find the target species, one swamp appearing to now be too dry to sustain this species.
A quick trip was made to Telford Scrub Conservation Park following one of the survey days. Here we saw Eriochilus sp. in flower. This time they were large flowers with tall, almost robust stems. Leaves were yet to emerge. Another surprise was to await us here. Bunochilus spikes were well up and it was evident there were two species represented. Some of the spikes were quite pinkish with leaves still tightly furled on the spike. Flowering will clarify more for us; some of the spikes will have a long growing time.
Upon completion of the surveys some members headed for Piccaninnie Ponds Conservation Park in yet another attempt to locate Eriochilus in flower. This time we were successful. It is a long way to travel when not knowing the exact flowering time for the area, and those times can change with each season! On short thin stems, small flowers with still the same general appearance were what greeted us. There were buds and capsules present as well, but most interesting to us was the presence of obviously earlier capsules. One had already dehisced and all were far more robust and distinctly different from the smaller red-striped hairy capsules of the currently flowering species.
On next to more Native Forest Reserves. Once again the target species was Eriochilus but we were hoping to find among the flowers some colourful pink specimens. It seemed this time we were a little too early because few flowers were seen. However, a strong coloured pink flower was located and so became much photographed. The next area was low open forest with bracken and heath understorey. Showers caught up with us and lowered the visibility very considerably. This made it hard to look for small greenhood type flowers but possible to find, once again Eriochilus sp. Some lovely double headed flowers were seen but no leaves were evident.
At this early stage of the year it was amazing how many orchids were seen, albeit over quite a wide ranging area. Perhaps some worthwhile early rains in the lower SE had been useful, but most of the species are not heavily dependent upon this for their Autumn appearance.