5-6 Chapter 1; Large common liverworts
Finding and growing Marchantia, Lunularia and Conocephalum.
7 Chapter 2 ; Bags, Jars &Sandwich boxes
Short-term ways of keeping mosses alive.
8-10 Chapter 3; Sphagnum
Where to find them, how to grow them. A few common species.
11-13 Chapter 4; Polytrichum and other large mosses
4 common species. Lime accumulation, its causes & remedies.
14-19 Chapter 5; Garden mosses.
Attitudes to gardening. Recording and recognising the most likely species, how to grow them. Creating outdoor moss habitats.
20-25 Chapter 6; Acid woodland mosses & hepatics
Notes on 30 species, including 10 hepatics, with cultural needs. Collecting and using soils.
26-29 Chapter 7; Mosses on walls
Variety of wall habitats. Seasonal growth, tolerance for heat & sunshine. Soil- free "mounted" cultures.
30-32 Chapter 8; Chalk & limestone mosses
Descriptions & cultural notes on 20 species.
33-37 Chapter 9; Definitions & descriptions
Mosses, liverworts & hepatics. Sex cells, chromosomes and fertilisation. Capsules. protonema, bulbils & gemmae. The problems of growing very small bits of things
38-43 Chapter 10; Ethics
Victorian fern plunderers. Moss Exchanges. The herbarium. Record keeping & labelling. Legal restraints on collection. On growing and naturalising rare or exotic spp. Habitat creation. Introductions. Regulations on imported plants. Recording & defending habitats.
44-49 Chapter 11; Epiphytes
Air pollution "Mounted" cultures. Acid & alkaline tree bark. Notes on 30 species, including riverside mosses.
50-52 Chapter 12; In Vitro
Discoveries in test tubes. Use of test-tubes, nutrient gel & bleach.
The difficult plants, Bryums, ephemerals. Advantages to students etc.
53-59 Chapter 13; Mountain mosses
Where to look; western oakwoods, streamsides, banks. Rock and boulder plants and their cultural needs. Humidity, temperature, refrigeration. High arctic & alpine hepatics.. Using a refrigerator. Oceanic hepatics, rock cleft spp..
60-70 Chapter 14; Managing a Collection
Possible frameworks; patio, garden, test tubes, jamjars, windowsill, propagator, aquarium. Examples & management.
Greenhouse ideas. Reflective aluminium sheeting. Temperature differences within a greenhouse. Drought resistance. Management during holidays etc...
Temperatures. Critical temperatures. Carbon loss and gain. Plants needing low temperatures.
Use of fluorescent lights. Refrigerator management. Frost resistance.
Weeds; dealing with moulds, mosses, algae & lichens.
Unexplored ideas & equipment.
Growing mosses and liverworts is a big subject. With nearly 1000 species in the British Isles alone, and well over 15,000 worldwide, they exceed in numbers the known species of cacti, succulents, alpines, or ferns.
Also, mosses occupy habitats more diverse than the whole flowering plant kingdom. From the depths of a dark cave to the twigs of a tall free, each niche has its specialised plants. Some grow on the mainland of Antarctica, where nothing else save lichens and algae can survive, and some in the world’s hot deserts.
They began to interest me in the early 1960s. My interest took an obvious and familiar form, as a living collection. I soon saw that these humble plants were the biggest horticultural challenge I had ever found. There is a small but devoted band of botanists who have an especial love for and interest in mosses, and who make a lifetime’s study of them, but for some reason a tradition of growing them had never become established. Indeed mosses were generally considered so specialised that the cultivation of most species was virtually impossible. That idea has still not been fully dispelled.
Certainly their needs in cultivation are unfamiliar and varied, yet as much as 90% of the British moss flora can be grown with techniques and equipment well within the reach of most amateur gardeners. Indeed many mosses are incredibly tough and persistent, if treated in the right way.
This is in one sense a difficult book to write. I offer it especially to people who are already skilled or dedicated growers of other specialised plants, be they succulents, orchids, or alpines, but who may be complete beginners so far as mosses are concerned.
Such people will want help in naming their plants as they find them, yet this book obviously cannot be an adequate guide to their identification. It aims to give hands-on encouragement, starting with the commonest plants, the easiest to name, and the easiest to grow.
Each section introduces a few new plants and a few new ideas on growing them. I hope many readers will also find these ideas useful in growing other kinds of plants, as I have done.
On the other hand I hope this handbook will interest people who already know a great deal about mosses, but who have not yet grown them successfully. I ask them to forgive the very elementary descriptions and sketches of the very commonest species, and the emphasis on such mundane objects as flowerpots and garden sprays. Though they have inspired so much interesting and sophisticated experimental work, mosses are not high-tech plants. They will grow as well in a jamjar or cold frame as in a laboratory, -better perhaps. Unique collections, of genuine scientific interest perhaps, can be built up on a windowsill. They need patience and understanding, not money.
That is part of their attraction.
1. Large common Liverworts.
One of the largest, the commonest, and surely the strangest looking of all liverworts, is Marchantia polymorpha. Through a lens, it’s flat crawling stems, its elegant cups full of oval green "eggs", and its umbrella-shaped male and female fruit stalks look like something from science fiction, rather than from a suburban garden. It has probably been grown more often than any other liverwort. There was once a Dutch cactus nursery, specialists in strange plants, which offered a Marchantia for sale - at a high price. Its catalogue did not even say which species.
However there is no need to send off an order to Holland. It can be found in any garden centre, growing on paths or around container plants. It is a horticultural weed, but can be found almost anywhere where there is wet soil - by rivers and streams, under gutters, or in wet shady garden beds. It is even commoner in towns than in the countryside, especially where there is an extra source of water, such as a dripping gutter. While looking for it, a gardener will be likely to find another species. Lunularia cruciata is fond of garden paths and soil in and around greenhouses, but can tolerate drier places than Marchantia. It is smaller and shinier, of a bright fresh green, and without any darker central band. The most obvious difference is that it has little egg-like gemmae, not held in circular cups, but in structures shaped like crescent moons, hence its generic name.
Botanists used to think that these were primitive plants, but it seems they are among the most complex and highly evolved of liverworts. Though leafless, the creeping stems, called thalli, are thick, with a tough upper skin and breathing pores (stomata,) through which they can breathe and regulate water loss, just as most flowering plants do. These pores can easily be seen even without a lens, as tiny spots on the smooth upper surface of the plant.
Underneath, both of these plants have a fuzzy white growth of fine root like hairs (rhizoids) which penetrate into the soil and draw up water, just like the roots of flowering plants. Marchantias and Lunularias can be grown in the same way as conventional plants. They simply need to be pressed onto soil - any reasonable soil will do - in a flowerpot, and watered, just like a geranium or a Primula, or any other pot plant. They will tolerate hot sun, though they do not particularly like it. Because they are small - by normal gardeners' standards - they tend to get rather soggy and messy if kept too wet, if for instance, they are stood in a saucer of water. Marchantia will shrivel up and die if you let it dry up completely, but a few of the little gemmae, or a small piece, will often survive and regenerate. Lunularia, being smaller, is more easily overgrown or spoilt if kept too wet, but is rather more drought-resistant. As a wild plant it grows in drier places, often on slopes or banks. If kept out of the sun, it can even be left dried out and dormant in the summer.
Leafy or shrubby flowering plants are cooled by air circulating among the stems and leaves. So long as the air is not heated above about 50C, and they have plenty of water, they will probably not be harmed by sunshine, though some ventilation may be necessary in a sunny greenhouse. Compact leafless plants such as globular cacti are not air-cooled in this way, and despite coming from deserts, may paradoxically be more vulnerable to sunburn. These liverworts are vulnerable for the same reason. Therefore, in a greenhouse, or indoors, and certainly in an enclosed frame or propagator, they must be shielded from hot sunshine. The nearer to the greenhouse roof they are, where hot air collects, the more vulnerable they are.
These two were the first liverworts I ever noticed and started to grow. They are likely to arouse the curiosity of any plant lover. Someone who is interested should look for Marchantias in early
summer, when the difference between the male inflorescences (left) and female (right) is obvious. A third common species is Conocephalum conicum. It is larger than the first two. It has no gemma cups, and fruits are rare. The upper surface is smooth, and of a fresh green colour. When brushed or bruised, it gives off a refreshing smell - a little like the smell of apples, but more pungent. It is not an urban weed, but is found in more natural habitats, usually by streams and riversides, on permanently moist soil, rocks or brickwork. It is a very easy plant to keep. It does not mind water logging or deep shade. However the soil must always be moist. Drought will kill it, as surely as it will kill a fern or a Primula. It is even large enough to hold its own in a garden bed or on damp bricks, so long as the ground never dries out completely. A 20-year-old patch on a brick border in my Reading garden died in the summer drought of 1989.
These three species grow quite fast. A few shoots will expand to fill a pot or pan within a few months. Presently new shoots will have to grow over the old ones, and become more loosely attached, and more vulnerable to drying out. Within a year or two, the whole culture needs to be cleaned out and restarted, by pressing the best shoots firmly onto fresh soil.
In Britain, there are not may other species in the same family as these - the Marchantiales - though British M. polymorpha now comprises three similar species. Some other species are dark green translucent plants of permanently wet places. Of those resembling Marchantia, some are rare, but more resistant to summer drought. Smaller, but widespread on bare clay soil, are Riccias, of which the two commonest are R. sorocarpa with a groove down the middle, and R. glauca, without. I do not have an up-to-date worldwide list of the genus Marchantia. I have grown up to 20 distinct ones, mostly from other living collections. They are all rather similar, and so far as I can judge, can all be grown in a similar way. The family Marchantiales as a whole is much larger and more varied, containing several hundred species, all of them leafless, and most with creeping thalli. The greatest diversity of species is in warmer and drier climates, as in the Mediterranean and South Africa. Several striking species of other genera have been grown here or elsewhere in Britain, though nobody has yet built up a comprehensive collection.
2. Bags, Jars, and Sandwich Boxes
When I was a university student, from 1958 onwards, I had no plants which could rely on regular care and attention. However I kept a few small ferns in jam jars with a handful of peat in, standing on my desk, or in a corner of the room, not too far from a window. There they sat quite happily, with the lid firmly closed, even during the long vacations. Without realizing it, I had re-invented the Wardian Case, so popular in Victorian times. Water, air, and even dead insects, were slowly recycled in a little enclosed ecosystem. The only attention they needed was a light spray of water every few weeks, and the wiping away of algae on the inside of the glass.
When I had a flat with a small garden, in 1962, I put a glass tank with a lid in the shade of a bush, and soon filled it with ferns, club mosses and mosses, especially from North Wales. As I became aware of the wide variety of mosses which existed, I found that most could be kept alive in that tank, or in a jam jar, or even a clear Perspex sandwich box. However it soon became obvious that keeping mosses alive was quite a different matter from actually growing them well, and that the spindly little shoots in sandwich boxes were quite different from those of the wild plants. At the time I did not yet realize just what a horticultural challenge these plants would prove to be. Yet there are probably thousands of people who have kept bits of moss in this way, for a time. A collection of bits and pieces in jam jars, or even in plastic bags, is not a long-term proposition, but it is a beginning, and with patience and careful observation, anyone who is interested can build on the experience gained in this way.
A more convenient way of keeping a lot of material is in seed trays, each covered with a sheet of glass or a plastic propagator. Nowadays stiff transparent plastic is widely available from hardware shops. It is safer to handle than glass, and with care, can be sawn to the desired size. Easiest of all, seed trays can be draped in polythene. They can then be put in the open air, in a shaded place. When I first became interested in mosses, I soon filled several trays like this. If I have a lot of new material to look at, and not much time to deal with it, I may still put everything into a tray, cover it with a piece of glass or a plastic bag, and spray it thoroughly. This is fine as a temporary measure, for a few days, or even weeks, but I soon saw that it was no way to keep mosses permanently. I remember being frustrated and puzzled by their poor response, however thoroughly I watered them.
For a start, it is obvious that many mosses do not grow in damp enclosed places. Some of the most interesting ones - and often, the hardest to grow - are found on dry rocks and trees, or exposed to full sunshine. For these, an enclosed tray or cold frame is quite unnatural. It is only a matter of time before they decay or become overgrown. Yet even these drought-resistant species seemed to dry out and to become dull and tired, however cool and damp their surroundings. Keeping the trays wet, or putting a layer of peat in the bottom to hold water, only seemed to make matters worse. They appreciated an occasional spraying with water, but that still left the problem of what to grow them on, if anything. Gradually it became clear that the way we plant and water "normal" plants is irrelevant for most mosses. They are fundamentally different in their needs, which are far more varied than the needs of the more familiar flowering plants.
Anyone can collect twenty or thirty species and keep them alive for a few months in the way just described. That gives time to experiment, and to learn. What the next few chapters will do is to introduce different groups of mosses and liverworts which even a beginner can find in Britain with little trouble. For each group, I shall introduce one or two ways of keeping and propagating them on a more permanent basis.
3. Sphagnum growing
Most gardeners are familiar with dead Sphagnum. It is stuffed into hanging baskets to hold moisture. Its remains form peat, which has long been ripped up and marketed as the panacea for all gardening problems. Yet the live plants deserve a better fate.
All Sphagna need a habitat which is wet and acid. They will not be found elsewhere. In the South and East of England, some of our few remaining acid heathlands, with their characteristic flora of heather, bracken and birch, are still being threatened. Only the wetter parts of these dry lowland heaths support Sphagna. These areas of boggy ground are often quite small, and vulnerable to drainage or disturbance. For conservation reasons, the sale and the use of Sphagnum peat is being phased out, for these are among the most characteristic of all British plant habitats, and their continuing loss is one of Britain's greatest conservation problems. If you know of such a place, where sundew and Sphagnum grow, do not trample or disturb it unnecessarily, and collect only very sparingly. Technically, the collection of even a few shoots of a common moss can be illegal, especially in nature reserves, in which some of our remaining lowland Sphagnum bogs are now protected. Another threat to these Sphagnum habitats is commercial peat extraction. I have used Sphagnum peat for many moss cultures, but have found that the coconut-fibre substitute is an adequate for this purpose. If kept soaked in acid water, it supports excellent growth of Sphagnum, and of all other mosses and liverworts of similar habitats I have yet tried growing on it.
Most of our upland and mountain regions have high rainfall and acid soil. Here Sphagna are to be found almost everywhere, and the variety of colours and forms is obvious. Even a casual visitor should find several species in a short time. It is fair to warn that Sphagna are easy and delightful plants to grow, but often hard to identify. There are about 30 species in Britain, and very few people who can confidently name most of them on the spot. Sometimes two gatherings of quite different size, colour and general appearance prove to be the same species. The very common S. subsecundum and its varieties are especially variable.
Firm identification needs a microscope, a good textbook, some experience, and the methodical examination of leaf and stem characters. The main stem has leaves which can only be seen by pulling off the branches, or in some cases, the head of the plant. Stem colour varies, as does the presence of a translucent outer layer of enlarged cells around the stem. The branches may be erect or hang down, sometimes being pressed against the main stem. The differing shapes of the branch leaves, from rounded to sharply pointed, are easy to see with a lens, as is their arrangement, sometimes in well-defined rows. The most obvious features, the varied and attractive colours, are unfortunately unreliable in naming many of the common species, and even the most experienced Sphagnologist must check some gatherings under a microscope. The delightful pictures in some popular books may give some idea of the beauty and variety of our 30 or so British Sphagna, and may enable a few intelligent guesses to be made about their names, but little more. However, there can be no better way to arouse an interest in these plants, and a desire to identify them, than to start growing them.
They must be kept wet, which is easy. Plastic flower pots can be stood in a shallow tray, a seed tray without drainage holes perhaps, which is kept topped up with standing water. That is a familiar idea to most plant growers, though Sphagna, unlike familiar plants, have no roots, and simply soak up water like blotting paper. It is equally important to keep the conditions acid. Sphagna should be grown on peat. Normal soil, or anything containing lime, is fatal to them. The biggest practical problem is to ensure an acid or lime-free water supply. Hard tap water, being alkaline, will kill them, not immediately perhaps, but certainly within a few weeks. In one university greenhouse I know, a drum of distilled water stands on the staging. Most gardeners will opt for the cheaper traditional solution - a water butt - the larger the better. The cleaner and higher the roof from which rainwater is collected, the better also. Most greenhouses have not a large enough catchment area to reliably supply all the plants they may contain. I collect water from the main roof of the house. One refinement which many gardeners will find a labour-saver was that the tap in the water butt by the house in Reading could be connected to a hose which ran down the garden, to fill another water butt in the greenhouse, seventy feet away. This may seem rather a lot of trouble to take if all you want to do is keep a bit of that bright red Sphagnum (probably Sphagnum recurvum) from last summer holiday, but there is a bonus. Anyone who arranges a good store of rainwater and can grow Sphagnum, can also grow other mosses, also insectivorous plants such as sundews, Venus flytraps and pitcher plants, and other interesting things which other less enterprising gardeners find difficult or impossible to keep. The essentials are so simple.... A bag of peat or acid fibre, a waterproof tray, and a supply of rainwater.
The most attractive feature of Sphagna, to a grower, is the range of colours they can show, ranging from the rare S. fuscum, of a dark khaki, through greens, reds and oranges, to the pale glaucous ochre of S. papillosum, found on rather dry heathlands. Unfortunately, one of the commonest, S. recurvum, is very variable in colour. These colours only develop well in sunshine, or at certain seasons. I have grown a few Sphagna in jars, but plants in such enclosed containers or in small frames or propagators are always in danger of overheating, and therefore must be shaded, so the plants will remain a dull green. If well ventilated, or in the open, Sphagna do not mind summer sunshine, though in a greenhouse they appreciate shade. They must never dry out completely. In their tolerance for water logging, Sphagna are unusual among mosses.
Over thirty years, I have on three occasions lost a number. In the hot summer of 1976 I forgot to move the trays into shade during a two week holiday. Many dried out, and some died. In 1986 I stood the trays in the open air, but did not put netting over them. Blackbirds turned the plants over, looking for grubs. The plants and labels got so mixed up that some were lost or never sorted out. During my more recent illness, all the cultures dried out during five years of almost total neglect, and most were lost. Birds can be a problem, as many gardeners know. Many mosses can be successfully grown in the open air. However they do need to be protected from disturbance, especially in spring, when birds will collect them for nesting material. The simplest protection is plastic netting. Wire netting should not be used, since the zinc leached out of it may be toxic to many mosses.
The biggest advantage of growing plants in the open is that they are washed clean by natural rainfall. Sphagna which are grown in a sunny site in a greenhouse lose a lot of water by evaporation in summer, and can become mucky and encrusted. Such sickly Sphagna can be seen in greenhouse collections of insectivorous plants. If the water is at all alkaline, these deposits soon disfigure and damage them. The cure is to spray thoroughly from above, and literally to wash them off. For doing this, a large garden spray is essential. For growing mosses on any scale, such a spray is the most vital single piece of equipment. It is a sad reflection on our destructive society that these pump-up garden sprays are promoted not primarily for watering, but for dispensing chemicals such as mosskillers and weedkillers. They are invaluable for watering, cleaning and spraying plants - not just mosses - and as a source of high-pressure water for D.I.Y. jobs.
Among the British Sphagna there are wide ecological differences. It does not seem essential to reproduce most of them. .S papillosum is a common large species of sunny sites, usually ochre-coloured. Medium sized, and very common, is S. recurvum, with stem leaves bent back (recurved). Its varieties can come in almost any colour, though the bright red forms are the most attractive. Trailing in pools, its fine branches’ having a look like “a drowned kitten” is S. plumulosum. Very common, in sun or shade, and with its many varieties, colour forms and related species, is S. subsecundum, with its branches often a little curved to one side "like cow horns". Preferring some shade, at least in drier parts of the country, is the large green S. palustre, like S papillosum, but greener. In boggy shaded woods is found the smaller S. fimbriatum, with ragged ends to the stem leaves, and with it, one of the smallest species, S. tenellum. S. squarrosum is quite distinctive, with recurved leaves giving the branches a prickly appearance. A few, especially S. quinquefarium, may be found on well-drained sloping banks in wet western woods, and on mountainsides. If well shaded, these can tolerate slight desiccation, and may be grown in shaded humid conditions, not waterlogged.
The more brightly coloured ones only develop their colours in sunny situations, and should be grown accordingly. Some species have a strongly northern or western distribution, though I never noticed any difference in their tolerance to high temperatures. Also, a few Sphagna from the Southern hemisphere, from Tasmania and Papua New Guinea were treated like the British ones. There are hundreds of Sphagna, worldwide. Many of them are variable or hard to identify, and some of their taxonomic problems still need study in culture. This genus alone could become the subject of a large, attractive and valuable living collection.