Tuesday, April 9, 2013

About Using Sphagnum Moss for Carnivorous Plants

Sphagnum_snowWild Sphagnum cf. cristatum  growing wild in the Brindabella Ranges above Canberra. Most Sphagnum species are cool-growing species from temperate climates (note the snow!), although I have seen a species (probably Sphagnum perichaetiale) growing in Wallum heathland in southern Queensland.
Why use Sphagnum moss?
Sphagnum moss makes a great CP growing medium, but it is not the only option for great plants. The main benefit it offers is providing an acid and very pH stable soil for CPs, which typically grow in very acid (and therefore nutrient poor) conditions. The reason for the stable pH is that live Sphagnum continually pumps acids (hydrogen ions) into the environment. These acids react with soil nutrients and prevent large plants (tree species) from outcompeting the Sphagnum and overgrowing its environment (light being the limiting factor). Because of its acid production, Sphagnum is an ideal media for CPs.

Read this before you think about using live Sphagnum for your CPs in Australia...
Sphagnum was, until recently, harvested from Tasmania in huge quantities. A minimum wholesale order comprised several pallets of 200L compressed bales of live moss. This is no longer happening because the licenses for such operations have reportedly been cancelled. As a result, you will now be very hard pressed to obtain useable quantities of live Sphagnum. The dried Sphagnum you get at Bunnings is of NZ origin, and has been treated with gamma radiation to ensure it is free of weed seeds. This means it will not regrow, no matter how well you take care of it. I can really only recommend live Sphagnum for two purposes - use as a medium for plants that absolutely need it (eg. Darlingtonia, highland Nepenthes - but you can grow these plants in other media), or for growing in its own right as an attractive and natural companion to other CPs. The latter purpose is something every CP grower should try, as a billowing carpet of Sphagnum is beautiful and adds to the aesthetics of your collection, as well as helping to maintain a stable growing environment for your plants.
About Sphagnum in Australia
Brindabella habitat_webMore wild Sphagnum growing in the Brindabella Ranges. Note the Utricularia dichotoma flower at top right of this image.
The genus Sphagnum contains 250 named species, with just 6 growing in Australia. Most of them occur in temperate regions, although one species growing here is a subtropical or tropical specialist that occurs in Queensland and the Northern Territory as well as in tropical Asia. All Sphagnum are niche specialists and most create their own ecosystems (ie. Sphagnum heathlands). These environments form a tiny fraction of Australia's biological diversity and are very sensitive to environmental change (including climate change for alpine and sub-alpine species). Sphagnum is protected in all states and territories of Australia, meaning you cannot just go an dig some up. As licenses in Tasmania (the only state that permitted recent harvesting) have reportedly been cancelled, the only mosses now available are those already in cultivation by CP and orchid growers.
The six named Australian species are:
· Sphagnum cristatum (subalpine NSW, ACT, TAS & New Zealand); robust, tussock forming species, green or occasionally light tan to light purple. Almost certainly the dominant species in cultivation.
· Sphagnum perichaetiale ( N.T., QLD and N.S.W. Also in New Zealand (North Island), India, SE Asia, Malesia (as opposed to Malaysia!), Melanesia, Fiji, South America, the Caribbean, eastern U.S.A., southern Africa, Madagascar and Mauritius); tropical/subtropical species, associated with flowing water over rock or acidic substrates in shaded areas. Probably not cultivated.
· Sphagnum australe (lowland to subalpine N.S.W., A.C.T., VIC. and TAS., also in South America, southern Africa and New Zealand); prefers relatively well drained sites. Leaves pendant, whitish green. Possibly in cultivation.
· Sphagnum falcatulum (NSW, VIC & TAS; ?QLD), very fine foliage, in wet to submerged conditions. Sea level to subalpine altitudinal range. Probably not cultivated.
· Sphagnum fuscovinosum (Tasmanian endemic); red foliage, grows submerged, subalpine and true alpine conditions.
· Sphagnum novozelandicum (WA, NSW, ACT, VIC & TAS; also NZ); yellow-brown to brown-purple, sea level to subalpine, cushion forming species. In wet conditions in shrubland, grassland and even roadside ditches. Possibly cultivated.
The most commonly encountered species as far as Australian CP growing is concerned is probably Sphagnum cristatum, which is one of the most widespread Australian species. This moss is a green type, with plants growing in strong sun occasionally becoming purplish at the growing point. Sphagnum novozelandicum is probably also in cultivation (possibly mixed with S. cristatum), and I suspect some NSW growers have Sphagnum australe as well.
Only one Australian species (Sphagnum fusconivosum) is strongly reddish in colour. Follow this link to see a photo of this species on Flickr. As you will see, it is almost entirely aquatic and a rather bushy plant that lacks a strong stem. It appears to rely on water's buoyancy to hold it erect, much like water plants like Elodea or milfoil. Given this unique habit, it is probably not suitable for CP cultivation. We do not have the terrestrial red Sphagnum that the United States has (or if we do, it is as yet unnamed and unknown to Australian moss taxonomists). Do not even think about importing live Sphagnum, as it will be illegal under our Quarantine laws. In addition, it is a major pathogen risk, and not just from a plant pathology perspective. Sphagnum can cause human health issues (see Barry Rice's page on sporotrichosis).
The major taxonomic work on Sphagnum in Australia is by Rodney Seppelt. You can access this work by clicking on this link (ANBG site).
Plants cultivated in Australia by CP growers
As noted above, most Sphagnum in cultivation appears to be either Sphagnum cristatum or S. novozealandicum, but some NSW CP growers have a much finer, more slender looking species with hanging foliage that may be S. australe. No-one seems to have bothered keying out their mosses (see the Seppelt work above for a taxonomic key if you want to try - you will need a microscope)!
This Sphagnum was (hopefully) obtained as live moss harvested from Tasmania under state-issued collection permits, or before permits were required. Sphagnum moss was also harvested from the Brindabella Ranges above Canberra, but stopped many decades ago. It is unlikely any of that moss remains in cultivation.
My experiences with growing Sphagnum Moss
I obtained my live Sphagnum moss either via Bunnings (as Brunnings or Amgrow brands, who got their live mosses from Tasmania) or via members of the AUSCPS in Sydney who also brought direct from one of the Tasmanian operations. My first success in growing it was as a substrate for Sarracenia under windowsill cultivation (nearly a decade ago when live moss was cheap!), but I have also grown it well in greenhouses and terrariums with Sarracenia and Nepenthes/Drosera/Pinguicula, respectively.
Wild Sphagnum nearly always grows underneath a open canopy of other plants. For example, the ACT Sphagnum heaths are covered in low growing tea trees (Leptospermum) and other small, scrubby plants generally less than 60 cm tall. In this habitat, Sphagnum grows in humid and well lit conditions that are protected from drying winds. In cultivation, these conditions can be emulated using the cover provided by foliage of Sarracenia or Nepenthes. Although wild moss grows in very bright light, full sun is detrimental to its growth. Water must be maintained at high levels during summer, especially if there are drying winds, as live moss looses water both via transpiration and also from honeybees that drink moisture directly from the moss. I always find numerous bees doing this in mid summer; they can also learn how to get into greenhouses through even a small gap.
In cultivation, Sphagnum grows well in standard CP mix of 1:1 peat:sand. To plant, insert or otherwise bury live strands deep into your CP mix, making sure the growing point is about 1 cm above the surface.  Chopsticks or a pair of forceps will help you to plant your moss out. This method will ensure the moss stays wet enough to grow well, as the buried moss will act like a wick from which it will absorb moisture. Be patient when planting; if you simply dump live moss on top of peat moss, it may grow well for a while but will be vulnerable to the first hot days of summer, when it will probably dry out very fast.
If you want to grow Sphagnum over potted CPs, you should also consider using trays that extend 5-10 cm or more above the height of the pot used. Solid-bottom broccoli boxes are good in this regard, because they can be cut to suit your setup. Be sure to drill drainage holes at the desired height to allow the tray to drain adequately and not submerge the pots.
Sphagnum grows well in bog gardens too. In my gardens, I made sure the peat and sand mix I used stopped about 5 cm below the level of the bog to protect the live moss. I then planted out the live moss from my potted collection as described above (I used the stem of a plant label to poke holes), inserting the live moss between Sarracenia rhizomes for extra protection. The result: deep, lush and billowing green carpets that fast overgrew the Sarracenia growing points. I am hoping it will soon bury some Sarracenia purpurea, as the effect is amazing: pitchers buried in moss with only their mouths poking through!
In terraria and climate controlled greenhouses, Sphagnum can grow much faster than under either unregulated greenhouses or outdoor conditions. However, these environments are usually less well lit than for truly outdoor plants due to problems of overheating from too strong light. This means greenhouse or terrarium grown moss can be more stringy or etiolated due to a relative lack of light. Nonetheless, terraria are a good way to quickly produce a reasonable volume of moss that can be planted out into potted plants or bogs if humidity is maintained. I have used Cool White 24 or 48 watt compact fluorescent with the highest Kelvin temperature available to grow Sphagnum in terrariums; the Phillips Tornado series has worked well for me previously. My setup used small lengths of PVC pipe (2 inch lengths) and some acrylic light grid (ask a pet store that specialises in reptiles) to create a platform that I covered with coir. I filled the terrarium with water to the platform depth and placed a small aquarium heater underneath to maintain a temperature at 28*C. Sphagnum was then placed over the top of the platform to a depth of about 1 inch and allowed to grow. Using this method, I produced enough moss in 6 months to top dress many Sarracenia pots.
If terrarium cultivation is not practical, try growing it in drained broccoli boxes (sterilised with bleach and well washed first!). I'd suggest planting strands of live Sphagnum moss into peat. Grow it in a shaded location that is cool. Make sure you keep the soil very moist to wet. If sun and desiccation is a problem in your conditions, try covering it with a light coloured shade cloth (ca. 70%). The ACT government used this method with good success to rehabilitate Sphagnum heath at Mt Ginnini that was burned after the 2003 bushfires (this heath is a RAMSAR listed wetland and the last major habitat of the northern corroboree frogs).
If you are lucky enough to have a climate controlled greenhouse for Nepenthes that is kept humid via misting, Sphagnum should be no problem to grow, and you should aim to progressively increase the amount you grow and make some available for other growers.
The Australian National Botanic Gardens (ANBG) have a webpage for cultivating Sphagnum moss, which you can view here (although you do not need the stringent conditions that link specifies, as described above). Bluegrass Carnivores also have a good website with some alternative methods for Sphagnum growing, which you can view here. Some of these may or may not be appropriate for our drier climate. But note the 12 cm water table depth that the latter resource recommends.
*This comment drew criticism when I posted this page on a CP forum. Yes, you can occasionally buy a small, baggie of live moss from many growers off the web. This is not the same as buying a 200L compressed bale of live moss that was harvested out of a Sphagnum bog in Tasmania, with the bale in itself just one in the several hundred bales that made up a minimum order. By volume, living Sphagnum for horticultural use is now very restricted in its availability. If you manage to get hold of some, treasure it!