Contents Page 4 Introduction 5-6 Chapter 1; Large common liverworts

Much human activity involves collecting and classifying things. A typical shop or household will contain thousands of objects. Except in the untidiest home, they are not left in amorphous heaps, but arranged and classified into a series of sub-collections, set within a framework of rooms, furniture, and the house itself. Cutlery is in a kitchen drawer, clothes in a cupboard, books on a shelf, and so on.

A few tubs or flower pots on an outdoor patio can constitute a collection. They do not have to be filled with Lobelias and Pelargoniums. The large liverworts, Marchantias and so on, will do as well, though they are not so colourful. Any reasonable soil will suit them. If they dry out completely, they are damaged. The big common liverworts are better kept in the shade, since drought and hot sunshine will kill them, just like Lobelias. They take a few weeks to get well rooted, and until they are, they need more careful watering. like anything that is newly planted. I had half-a dozen such pots on a north-facing cement border in Reading. In dry summer weather they got washing-up water tipped over them every few days. For most of the year, rain was enough. When going away on summer holidays, I covered them with a plastic bag to keep them moist. There are of course more elegant ways of growing such plants, as in the Reading university greenhouse, where a collection containing many fine pots of Marchantias enjoyed a daily wetting with distilled water.

An old brick walltop in the garden, and some cement, were home to some non-local mosses, some long-established, some stuck on in later years with silicone bath sealant. It hardly amounted to a collection, but about 10 non-local species persisted and in some cases spread, though slowly. All were pleurocarps of dry rock or tree habitats. Notable successes for ten years or more were Pterogonium gracile (abundant) and Leptodon smithii (slow but steady). Later trials of several other species, especially of Racomitriums and Hedwigia ciliata were promising. Most were transplants of surplus material from greenhouse cultures. As suggested in chapter 5, it would be irresponsible to collect any except the commonest mosses for such transplants, but their persistence and growth on an ordinary wall near the middle of Reading was surprising, suggesting that there is still a great deal to be learnt about their ecology.

An aquarium with a plastic lid proved a more convenient home for an indoor collection. It was on a landing, and contained some houseplants. They included forms of Begonia rex. Winter in the Reading house was rather cool for this plant, with January temperatures on the landing averaging 13C, ranging from (+5)-10-15C., and the Begonia sometimes suffered catastrophic leaf loss in the late winter, though the hardier species, Begonia boweri and B. maculata flourished. Most bryophytes failed. Only a few hepatics would grow in these very dim and almost constantly humid conditions, but some of them were of great interest. They included several rare and very minute hepatics of the Lejeunea family, notably Cololejeunea calcarea, Aphanolejeunea microscopica, and Drepanolejeunea hamatifolia, also a Frullania. Calypogeia arguta was an abundant weed, and some small rare Lophocoleas did well. Even fewer mosses survived, among them Leucobryum glaucum. It was convenient to keep nearby a small handspray full of rainwater, and to spray them every few days, when passing up and down the stairs. Even here, desiccation played a part. For a few weeks in April and August, sunshine got in for 20 minutes or so each day. This was enough to gently dry out the mounted cultures, to check or kill Calypogeia arguta, and to stop it overrunning the other small hepatics. One curiosity was a small patch of Lejeunea patens which grew over a Begonia leaf, just as tiny epiphyllous Lejeuneas grow over leaves in tropical rainforests. It lasted two years, until the leaf died. None of these survived tour years neglect during my more recent illness.

Plants were moved to a conventional greenhouse in 1986. It was in an unpromising site near the centre of Reading, in a south-facing brick-walled garden with a warm dry urban microclimate. The greenhouse itself was aligned east to west, and closely hemmed in on the east and south sides by walls. Until 1994 it was overhung by two large lime trees, and partly shaded on all sides by other trees. It became very dark in summer, though some afternoon sunshine still got in, making it very hot indeed. After the lime trees were felled, it got full sun almost all day. The door and ventilator ware opened a little in summer, but there was usually less ventilation than one would expect in a greenhouse, even one devoted to heat-loving plants.

Thermometers scattered around showed a surprising situation, though something similar must occur in most greenhouses. On a sunny day, the upper part was far warmer than the outside air, even with ventilation. There was a steep temperature gradient, and the floor, especially at the more shaded end furthest from the door, was cooler than outside on warm sunny days. I once, for instance, recorded a shade temperature of 50C on a top shelf, and at the same time, 21C on the floor, with an outside temperature of 25C. The water butt was a heat sink, the water in it cooling the air around, which sank and collected on the floor. These great temperature differences have to be reckoned with, and can be exploited. Delicate hepatics - mostly mounted cultures of small leafy liverworts - survived on the floor, in aluminium trays covered with polythene sheets. They were cool in summer, and in the constantly high humidity grew well, though they would have died almost instantly in the heat of the day on an upper shelf. Meanwhile the drought-resistant plants on the top shelves were being baked, among them even some Arctic and alpine mosses which seemed no less drought-resistant than their relatives from milder climates. Yet these in turn were warm enough to grow on sunny winter days, even in the severest cold weather.

Yet it takes some conviction to impose such apparently harsh treatment on these tiny plants. Even some hepatics are drought-resistant. Most hepatics have always been on the floor, or on the third shelf down, but even some of these dry out gently in hot weather. Much could depend on the site of the collection. In a greenhouse with a cool north aspect, especially in the north of the British Isles, most mosses could be kept growing all summer. Plants like Sphagnum were kept wet but exposed, and the hotter and drier the weather, the more often their trays needed checking, and topping up with water. However the one essential piece of advice is that most mosses or hepatics, if conditions get too hot or dry, cannot in general be saved by waterlogging. That will often kill them, faster and more thoroughly than desiccation. One of the great advantages of mounted cultures can be that they dry out so quickly in summer. A plant that is watered just before the sun comes out can be dry and dormant again within minutes. The same plant in a flower pot may stew in wet soil for hours, after the temperature has risen high enough to damage it.

Many plant growers fear some disaster while they are on holiday, and have to make arrangements for watering, shading and ventilating their precious collections.. Most of this moss collection could be left to dry out quietly at any time of the year, whenever I was busy, or away from home. Geraniums, houseplants and pet animals all proved a bigger headache at holiday times. In this respect, mosses and hepatics are easier to keep than many houseplants. Such watering and attention as they need can be fitted around a busy or irregular routine.
The top shelves, despite being warmer and drier, have always been crowded. Most Sphagna, permanently waterlogged, but best shaded in summer, were there. Any hepatics on the top shelf were best kept shaded in summer. Cephaloziellas and Riccias were allowed to dry out in summer, others such as Anthoceros and Riccardias needed to be always kept wet. For the rest, the top shelf contained xerophytes. Tortulas, Bryums, Barbulas, high epiphytes and plants of exposed rocks were mostly on mounted cultures. Management for these was simple. Nothing was watered in the summer. Sometimes, on a cool cloudy day, they got a spraying, but there was little point in regular watering, since they were usually dry again within a few hours, and could make no useful growth. To moisten any moss when the temperature is above 25-30C will damage or weaken it, though mosses that are already moist and growing may continue to grow, apparently happily, in temperatures as high as 35C. Unless they can grow, repeated wetting and drying are more stressful than remaining dormant. The higher the temperature, the more stressful it is.
That, at least, is my general impression. A moss or hepatic that is damaged, as by crushing or cutting, or by exposure to harmful chemicals (such as bleach), or by being moistened when too warm, or after a damaging drought, will usually give off a characteristic smell. I do not know the cause, save that it is obviously the smell of some substance which is bound inside a healthy plant, but which escapes from an stressed one. I take it as a sign that the plant is being stressed or damaged.

In September or October, regular watering became worthwhile for these exposed plants. They were, and are, still mostly covered with polythene, and kept almost continuously moist until next March or so, with little or no direct sunshine to dry them out. Early autumn is a good time for replanting those which have not been growing well. The plants on these top shelves were at their most interesting in the darkest part of the winter.

All normal plants fix carbon by photosynthesis. There is an optimum temperature range for photosynthesis. Few plants can fix much carbon at below 5., though they include most mosses. Most grow best at temperatures above 10C. Many plants, especially tropical ones, use a form of photosynthesis which works best above about 16C. On the other hand, plants lose carbon by respiration. The loss increases with temperature. There is therefore, for any species of plant, a best daytime temperature for growth, a temperature at which it gains most carbon. Above this best temperature, carbon loss increases. If it gets too hot, the carbon loss exceeds the gain, and the plant cannot grow at all, however good the conditions are otherwise. This best temperature varies between species. Obviously, it is likely to be higher for tropical plants than for arctic and alpine ones.

At the other extreme are plants of strongly lit cold habitats. They obviously include many alpines. The small alpine cactus, Pediocactus simpsonii, from the high mountains of Colorado, long had a reputation as ungrowable. No combination of compost or watering could be found which would prevent it from wasting away in England, until an enterprising cactus grower took four plants, grew two normally, and put the other two in a refrigerator each night for a summer season. Unlike the controls, they gained weight and flourished.

Many mosses seem to have an optimum temperature for growth at around 10-15C., but seem less troubled by hot days than by warm nights, during which time carbon loss presumably continues. Also, unlike cacti, an entire moss plant can become desiccated and inert. In this state, many mosses, even Arctic and alpine ones, can stand temperatures that would be lethal to most flowering plants. However, after growing well in spring, and not suffering too much in hot June weather, mosses may languish or go mouldy in late summer. The worst weather for them is warm and overcast, with high night-time temperatures. The plants most affected have been those with a northern or alpine distribution, plants which cannot be dried out and left dormant in summer, and especially plants of cold watery habitats, mountain streamsides and so on. Some are mosses, but most of these problems have been alpine hepatics. Some were discussed in the chapter on mountain mosses.

A preoccupation of many greenhouse owners is to keep things warm in winter. The mosses have always been unheated. They freeze when outside temperatures go below about -2C, usually get chilled to -5C most winters, and have been as cold as -13C. One rare Sphagnum from NW Scotland, S. strictum, may once have been damaged. The astonishing thing is that I have seen no other obvious damage to mosses from frost, not even to the many tropical ones. With hepatics, the position is not so clear. Many Marchantias and their relatives are hardy, but may show marks on their thalli after frost, which seems to check their growth. Pellia epiphylla and Riccardias seem unaffected by cold, but some hepatics of similar appearance, such as the erect frondose Pallivicinia xiphoides from New Zealand have become quite miserable after a severe winter. The related genus Moerckia has thin translucent thalli with a thicker midrib. It is a warm-temperate genus with few British species, and does not like severe winters. Strangely, there is a very striking species M. blytii with a crisped and curly thallus, which is almost confined to Scottish snowpatch vegetation. I lost my first culture of this species one winter, in a way which suggested frost damage. In habitat it is of course covered by deep snow for most of the year. Anthoceros, a strange genus of thalloid hepatics, tend to disappear in cold winters, though some species are British natives. They re-appear in spring, and grow best in warm summer weather. On the other hand, in midsummer 1992 I put two cultures of Scottish snowpatch plants into a freezer at -15C. They were being overrun by weedy mosses and hepatics. They were pretty thoroughly destroyed by the sudden freezing, mosses as well, but out of the dead mush emerged some surviving shoots of a high alpine Marsupella.

Anyone who maintains a large plant collection must be concerned about weeds, pests and diseases. I have encountered no obvious diseases peculiar to mosses and liverworts. In warm weather, cultures may go mouldy. This is perhaps the most obvious problem. The damage can be sudden and fatal, but moulds are very delicate, and can usually be checked or stopped, either by drying out the plant completely, or by spraying it thoroughly, and if possible, moving it to a cooler or better-lit place. If that fails, try replanting, or await cooler weather, and watch for recovery.

Other larvae, probably of moths, have been far more damaging. They eat decaying material, but may spread fungus decay as they burrow through moss tufts. Between 1987 and 1989 they were an increasing problem, damaging and destroying many healthy plants, especially those growing on peat. A spraying with a long-lasting insecticide containing dimethoate and permethrin eliminated them.

As for weeds; It can be quite difficult to establish a pure culture of any one moss. Anyway, there is usually not much point in it. So long as conditions are right for the plant which is intended, it should hold its own against competitors, with one reservation - that many mosses are quite short-lived. Ephemerals may have a life cycle measured in weeks, which is why they are the hardest to keep for a long time. Many others languish unless given fresh soil every year or so. Replanting is an opportunity to pull out and discard unwanted species. In cultures on waterlogged soil, things can also happen quite fast, and some species, especially Marchantias and Bryums, can be very invasive, completely covering them within a few months. It is often worth weeding out the unwanted plant with tweezers. The exact technique depends on the species involved, but invaders can rarely be exterminated in this way. At worst, the desired plant can almost always be refound, and a new clean culture started. Once again, the invader will often reappear, but so long as the desired plant has some room to grow, it is rarely lost.

More troublesome weeds are algae. A test-tube culture contaminated by algae is eventually doomed, yet algae are everywhere, and it is not possible to make any greenhouse culture without them.

Another basic problem can be to recognise the species one is actually trying to grow, and it can be a real problem. Just as a helpful child who does not know the difference between chickweed and Dahlias can wreak havoc when weeding a garden, so a person who cannot distinguish immature shoots of difficult-to-name mosses will never be confident of keeping them. In flower pots of soil, I have sometimes found myself growing the wrong species - of Bryum and Dicranella especially. On mounted cultures, this is much less of a problem. Far commoner is the basic problem, familiar to all bryologists, of not being able to identify what you collected in the first place. But then, of course, the plants that cannot be named are often the most interesting.

There is one very good reason for not even trying to make pure cultures of freshly collected plants. Many mosses and hepatics have an remarkable affinity for a particular habitat. Where one unusual plant is found, there will often be others. If the main species grows well, its original associates will probably survive as well. Many of my own cultures contain several species from the original habitat. Some were not noticed when collecting, and were only discovered as long as ten years after. Sometimes these are more interesting than the main plant. It is worthwhile to deliberately mix and cross-culture mosses from the same site in a way which would be impractical with larger plants. In this way, any one species is far less likely to be lost completely, and can be observed growing in different cultures, interacting with other species, and under a range of conditions. Much of what I have learnt about growing these plants has come from seeing things survive or grow where they were not expected. Nevertheless, unwanted mosses and hepatics will overrun many cultures, perhaps, in time, most of them. Never despair. Even if 99.9% of a culture is dead, or is of the wrong species, the desired plant can almost always be refound. Be prepared to use a good lens to search for it, and a pair of tweezers, to remove and replant any possible surviving shoots.

In the 1970s I wrote to many people, and discovered only about a dozen collections of live mosses and hepatics, worldwide. Most belonged to professional botanists, and most, though not all, were in highly artificial surroundings, in test tubes or growth chambers. Even so, I was surprised at the diversity of these few collections. Another surprising and embarrassing thing was that some of these people generously sent me new and fascinating plants, which they had in some cases grown successfully for many years - and that some of those plants died as soon as I got them. That does not mean that bryophytes are especially temperamental, for many gardeners have had similar experiences. A plant that flourishes for one grower will often inexplicably die in the hands of another. It is a reminder that a collection of plants, just like the collection of objects in a house, reflects the personality of its owner, both in the choice of plants, and in the way they are treated.

There are many pieces of equipment available from horticultural suppliers, some of them unavailable a few years ago, which might be worth trying. The most interesting is probably mist propagating equipment. I have not been tempted to use it, partly because it is expensive, but mainly because hard tapwater is so obviously unsuitable for most mosses. Also, even soft tapwater may be contaminated by copper or other substances harmful to mosses, dissolved from the supply pipes. There is also the thought that any collection that relies on high-tech equipment may face disaster - should that equipment fail. Nevertheless, I have seen some fine large pleurocarps grown under a mist propagator.

There is probably no other group of plants about whose cultivation so little is known, or which offers so much scope for experiment. And there can be few other groups of plants which an enthusiast can so easily see in their natural habitats. It is not that too few people are interested in them. I have sometimes found, in casual conversation, that someone admits to having tried to make and keep a moss garden, usually in a jamjar or a saucer. Many children are fascinated by the world of minibeasts and tiny plants which is revealed by a good lens. Yet these interests too rarely develop into a more sustained interest in mosses, let alone an interest in growing them.
While many orchid or succulent lovers can only daydream about visiting distant lands and seeing their plants growing wild, a couple of dozen mosses, including some quite interesting ones, can be found, even in central London. It is not of course that central London is an especially exciting place for plant hunters, nor that distant lands are not worth visiting. It is, rather, that an interest in wild plants, or in any other branch of natural history, is an incentive to visit, to look at, and to enjoy places and landscapes. I doubt if there is any other group of British plants, the study of which could draw a student to visit a greater variety of extraordinary and sometimes beautiful places.

Some botanists, when they visit places of interest, bring home herbarium specimens of their plants, some notebooks, and some photographs - while some are content with only memories. I hope this handbook shows that, if it is done responsibly and intelligently, any serious student of mosses can do something even more worthwhile. He, or she, can keep and make as many photographs, as many herbarium specimens and notebook entries as desired. But best of all, it is possible to bring back, to keep - and to study, propagate and enjoy - the living plants.