Redwood Botany

It’s always the fate of a lecturer in a series like this to look at the audience and see a real expert on the subject in the audience, and I see Bill Libby sitting there. And when I will have to leave to catch my plane I’ll hand the fielding of the questions over to him and you’ll see he’ll do a much better job than I shall. Well, this talk, indeed, this series of talks is going to deal with the redwoods of California. And the first talk is intended to put these redwoods in their context, the historical context, as well as the botanical context.

Nowadays we recognize the existence of three separate genera of redwood. We think of them as three separate genera because we have reason to believe that they represent the end points of three long lines of separate evolution. Most of the species in those lines are now extinct. The three which remain are the ones we know as Metasequoia, Sequoia and Sequoiaderdron. Each of these genera nowadays consists only of one single species. In the genus Metasequoia, it is Metasequoia (glyptostroboides). In the genus Sequoia, Sequoia sempervirens. And in the genus Sequoiadendron, Sequoiadendron gigantea. And these three species are respectively the dawn redwood, Metasequoia (glyptostroboides), the coast redwood, Sequoia sempervirens, and the Sierra redwood, or big tree, Sequoiadendron gigantea.

Metasequoia, of course, is the most recently recognized of this group. And does have, indeed, a very strange history, having first been recognized as a fossil by a Japanese botanist in 1941. And, subsequently being found, also while World War II was in progress, as a wild tree in a single valley in central China. Metasequoia (glyptostroboides), the dawn redwood, which is the only one of the redwoods now not found living as a wild plant in California. Well, it’s easy to distinguish the dawn redwood, Metasequoia, from the other two because the dawn redwood is deciduous. You’ve probably noticed all these short twigs bearing leaves have been dropping off whilst I’ve been holding this up. Metasequoia (glyptostroboides) is a deciduous tree. The other two are evergreen. Furthermore, Metasequoia has its leaves arranged along the twigs in opposite pairs, whereas in Sequoia, along the twig. Metasequoia is a native of China, the other two are natives of California. Metasequoia is also a considerably smaller tree than the others, seldom apparently reaching above about 100 feet in height. Whereas, both of the other trees are capable of topping 300 feet.

Well it’s pretty clear why Metasequoia is in another genus than the others. But it’s not clear to the outsider why these two trees Sequoiatendron and Sequoia should be separated generically. And, indeed for most of the 100 years that they have been known to science, they were not separated generically. They were kept together in the genus Sequoia.

But as more and more careful studies have been made of these trees and particularly as botanists have used their microscope to peer into the developing seed, they have seen significant differences between these two kinds of trees so significant that there should be two different genera recognized.

For us, however, the most important thing is not whether they are placed in two separate genera, but whether we can tell them apart. And on most occasions when we meet a redwood tree in the wild, there is not much difficulty in telling them apart. When we see them in a state of nature, we do not have too much difficulty because the coast redwood we find only in areas in a narrow strip running parallel with the Pacific Coast generally within the range of the summer fogs. The Sierra redwoods on the other hand is confined to the western slope of the Sierra Nevada and as a consequence, one wouldn’t have much difficulty because of ones geographical position in telling which kind of redwood tree one was looking at.

Nevertheless the rangers of the State Division of Beaches and Parks every now and again have reports made to them by hikers or hunters or others who prowl around the wild places of California, that there are Sierra redwoods growing amongst the coast redwood trees. Part of the trouble in this case seem to come from the appearance of one of the trees. The Sierra redwood has adpressed leaves, little scale leaves which are adpressed along the branches. The coast redwood has leaves which stand out from the branches in two rows, so-called distichous arrangement. This is clear enough in the way of a difference. But at the bases of each one of these branches and in the branches which are borne high up on the trees or on young trees, there is often is a tendency for the coast redwood leaves to be arranged along the stem in a manner very much reminiscent of the arrangement in the Sierra redwood. And it’s probably this which occasionally gives rise to stories of Sierra redwoods growing in coastal regions.

But there is a very definite separation of the distribution ranges of these two species. The coast redwood running along near the coast form southern Oregon down to the Golden Gate, appearing again in the San Francisco Peninsula and the Santa Cruz Mountains and appearing once again south of Monterey Bay for a distance down into the Santa Lucia Mountains. The coast redwood also occurs in eastern Sonoma County and western Napa County and is native in the Oakland Hills. In the Santa Lucia Mountain area the distribution of coast redwood is a series of valleys at right angles to the coast line. This gives you the general idea of the distribution of the two trees.

The Sierra redwood has adpressed scale-like leaves. Whereas in the coast redwood there are scale leaves adpressed at the base of the branches but then there is an alternate arrangement of leaves which stand out from the twigs.

There are other differences between the species. The cones of the Sierra redwood are considerably larger, being two to three inches long compared with a single inch or even slightly less in the case of the coast redwood. The cone scales of the Sierra redwood are more numerous – about 35 to 40 in each cone compared with 25 or so in the coast redwood, and each cone scale in the cones of the Sierra redwood bears as many as nine seeds upon it, whereas the less numerous cone scales. In the coast redwood bear smaller numbers of seeds each, only two to five. Add to this the fact that the sierra redwood seems to be more regular in producing seeds — it has a better crop every year than does the coast redwood. Altogether, there appears to be a considerably greater seed output per tree of the Sierra redwood than of the coast redwood.

But the coast redwood has its compensation for this. The coast redwood trees are able to sprout from a cut stump or from the roots of the tree and achieve a measure of vegetative reproduction in this way which is not shown by the Sierra redwood which relies for reproduction to a much greater extent upon the establishment of seedlings. An interesting difference between the trees of the coast redwood and the Sierra redwood species is that the seeds ripen and shed in the same year that pollination takes place in the coast redwood, whereas, in the Sierra redwood the ripening does not take place until the season ; after pollination. And in the Sierra redwood cones may hang on the trees for many years with seeds still inside them.

I’ve mentioned that all three of the redwoods — Metasequoia, Sequoia and Sequoiadendron — have long fossil histories in which they showed, once, much more extensive distributions than is the case at the present day. The genus Metasequoia, the dawn redwoods nowadays in restricted to a single valley in central China. It has a history which goes back to the Upper Cretaceous Period, a matter of 110 million years ago. And its history from that time until the present has been one of continual contraction in its natural range. From a maximum distribution in the Northern Hemisphere during the beginning of the Tertiary Period, about 65 million years ago, it has shrunk down to this single valley in central China. You can see that the dawn redwood was once quite commonly found in western North America as well as in eastern Asia. And there are records of the dawn redwood from Greenland and from Spitsbergen. This is indicative of the fact that the climate in Greenland and Spitsbergen war distinctly more clement at a time in the past actually at the beginning of the Tertiary Period when the Metasequoias lived up there. It seems that the dawn redwood was never native in Europe.

For the coast redwood, the Sequoia, the picture is almost as traumatic. It too shows a history that reaches back to the Cretaceous Period. And the genus Sequoia was widespread through the Northern Hemisphere during the early part of the Tertiary Period, 60 million years ago. But with the cooling and the drying of the climates of the . Northern Hemisphere which took place during the Tertiary Period, the genus Sequoia became progressively restricted to western North America, western Europe, the Himalayas, and Japan. And then it seems to have been eliminated entirely, everywhere except western North America, by the onset of the Pleistocene Period, one to two million years ago, with the glacial advances. In western North America we know that at the beginning of the Tertiary Period the coast redwood was found in the region of Alaska and British Columbia.

This was the beginning of the Tertiary Period where a subtropical or even tropical climate was to be found in California, the present home of the Coast redwood. At that time it existed considerably farther north and also existed considerably farther inland. But during the cooling and the drying of the climate during the Tertiary Period, it gradually became eliminated from its inland stations. It gradually moved farther south from its Alaskan and British Columbian stations down into California.

And its journey southward seems to have reached the maximum during the Pleistocene glacial advances. At that time the coast redwood seems to have reached some 200 miles farther south than its present distribution and has been recorded from Carpenteria in Santa Barbara County as a fossil.

With the partial recovery of warmth after the Pleistocene glacial episodes, the coast redwood seems to have retreated northward a little to its present day distributions where it is located just about on the overlap between subtropical and warm temperate on the Pacific coast of North America. Its present range is from the Santa Lucia Mountains in Monterey County along parallel with the coast to Curry County; the southernmost county of Oregon.

In addition to the latitudinal shifts in the genus Sequoia, it also was eliminated from its inland localities and persisted as a relic only in the coastal regions. This seems to have been due to increasing dryness especially in the summer months from the middle of the Tertiary Period onwards. So it became extinct in such states as Montana, Idaho, Wyoming, Nevada. It finally was restricted to the foggy coastal hills of central California. And during this contraction in region several species of Sequoia appear to have become extinct leaving us with just the single surviving species, Sequoia Sempervirens, the coast redwood.

At present it seems that the coast redwood is prevented from expanding its range by a different kind of limiting factor according to whether you go to the northern limits, the southern limits, the western or the eastern limits. According to Forrest Shreve, a famous botanist – the southern limit of the coast redwoods in the Santa Lucia Mountains is determined by the severity of the period which is to be experienced between the cessation of the winter rains and the onset of the summer fogs. There is a dry period at the beginning of the summer and this gets longer and longer the farther south you go, In the Santa Lucia Mountains there comes a time when this becomes too severe for the coast redwood, a tree which likes good moisture supply. If you have this long dry period between the end of the winter rains and the beginning of the summer fogs, it is unable finally to grow. It is noticeable as one goes down Highway 1 south of Big Sur that the redwood trees become restricted to the bottoms of these valleys or at least to the valleys themselves which run at right angles from the coast inland. In these valleys the trees get extra drainage water. They get shelter from the winds which blow over the area and a higher humidity as a result. But even that does not suffice to save the redwoods beyond a certain point and so we have the southern limit to its distribution.

As far as the eastern limits of the narrow coastal strip of coast redwood distribution are concerned it seems very likely that it is the low rainfall and particularly the hot winds which sometimes blow off the lands, especially in the fall which determine the inner limits of this distribution. The Western limits are pretty obviously imposed by the Pacific Ocean. But even so, the redwoods do not usually reach right down to the Pacific Ocean. Usually they are separated from the ocean by a little stretch. And it is to be suggested that the rainfall on the immediate coast is probably insufficient for them. It is only when the rain bearing winds are forced up over the mountains that sufficient rain falls. In addition, the fog cap tends to be on the mountains rather than on the immediate coast. And, in addition, in all probability the redwood is susceptible to damage from salt spray.

And then the northern limits of the coast redwoods may very well be set by severe winter conditions. In Humboldt County the trees on the outsides of the forests, the edges of the forest, may be damaged by the winter frosts. But the forest as a whole is protected by the very nature of being a forest. But further north over the Oregon County line, it has been suggested, that frost damage becomes more severe and particularly frost damage to young trees imposes a limit on the northern distribution of the coast redwood. Certainly, one would imagine, it reduces the competitive power of the coast redwood so that it is unable to compete with such trees as the Douglas fir which takes its place farther north and incidentally which also takes its place at greater elevations farther south.

So we have the probable limits on the distribution of the coastal redwood. It has been suggested that a rainfall of some 40 inches per year is minimal for this tree. But in many of the areas where the coast, redwood grows, the rainfall is considerably less than this. So deficient rainfall can be compensated for in two ways. Firstly, by increasing the amount of water supply to the roots. And a tree which grows along the margins of a river may be able to grow in an area where the rainfall itself is inadequate for the support of the tree. On the other hand, you can compensate for deficient rainfall by summer fog. But up on the outer coast range, not only is there a greater rainfall, but there is also the summer fog. And through the fog drift, the condensation of fog on the leave, and then dripping onto the ground or running down the trunk, to the ground, we do have a supplementation of the natural rainfall. In addition to this, which Oberdoffer, a worker from San Francisco State College working on the San Francisco Peninsula has concluded may add as much as the equivalent of 50 inches of rain around the base of a tree,

The fog also cuts down evaporation and transpiration and cuts down the heating effect of the sun during the summer months. So this fog is not only a potent source of water for the trees, but also comes just at the time of the year when it is most needed, in the dry summer months.

Now the Stanford campus area is inadequately supplied with rain for the growth of redwoods. But, of course, there is the Palo Alto tree growing by San Francisquito Creek in the Stanford area well away from the outer coast range. But it is by the side of the creek. And in the days when San Francisquito Creek carried more water than it does now, that might have been a significant aid to those trees in their growth.

This then is the fortunate concatenation of climatic circumstances which has given us the redwood forests and the associated redwood flora, the sword ferns under these trees, and the oxalis and other ferns which abundantly carpet the soil under these great trees in Humboldt County.

Actually, however, despite this long history, it wasn’t until the Spanish explorers came to California that a European or person of European descent had ever seen a redwood tree. It had to wait until the 18th century for its discovery even though its history is so tremendously long. But Englishmen, Sir Francis Drake, did have the opportunity of being the discoverer of the coast redwood in 1579. Had he not been so obviously a sailor, rather than an explorer of the land, he might have taken the opportunity whilst the Golden Hind was being careened in the vicinity of Point Reyes of penetrating just 10 or 20 miles inland, where he would have seen the coast redwoods in the area which we now think of as Samuel P. Taylor State Park. But Sir Francis Drake was deterred by the fog and the cold from making such a journey and it seems certain that it was through Spanish eyes that the Palo Colorado or redwood was first seen by Europeans. Father Juan Crespe, the Franciscan missionary who was the diarist of the Portola expedition, the first expedition by land up the Pacific Coast, in 1769, recorded the existence of coast redwood trees when he was in the vicinity of the Pahara River in Monterey County. And he used the following words, in translation, of course: “The area is well forested with very high trees of a red color, not known to us. They have a very different leaf from cedars and, although the wood resembles cedar somewhat in color, it is very different and has not the same odor. However, the wood of the trees that we have found is very brittle. In this region there in a great abundance of these trees and because none of the expedition recognizes them they are named redwood for their color.” Palo Colorado, of course, in the original Spanish. You remember it was the Portola expedition which also discovered the Palo Alto tree when they reached San Francisco Bay.

But the first collection of the coast redwood seems to have been made by Thadeys Haenke, botanist of the Malaspena expedition in 1791. And it appears there is at least one tree derived from the seed which he went home still growing in Spain. The Malaspena expedition was a Spanish financed expedition but Malaspena, its captain was an Italian, and Haenke, its botanist was a German. The redwood trees from which they collected seed, in all probability, grew near Santa Cruz. And indeed most of the early collection of seed which were sent back to Europe and have given rise to cultivated trees there, were collected in the Santa Cruz area. Nevertheless, it was a Scot, Archibald Menzies, who played the role of botanical discoverer, because it was his specimen sent back to Britain which formed the basis of the botanical description of the coast redwood tree. In 1794, Menzies collected a herbarium specimen and for a long time it was unknown just where the collection was made. The specimen, however, still exists in the British Museum in London and the story is that one day Professor Willis Jepson of the University of California here was looking at that herbarium specimen in the British Museum and he happened to turn the herbarium sheet over and on the back side of the sheet, it said Santa Cruz, Menzie. It seems that through all the years they’d had the sheet, nobody had thought of turning it over. Well, this specimen was carried to Britain in 1795, but a description of it with a botanical name was not given until 1823 when the name was published by a botanist named Lambert. And because the material looked to Lambert like the already known genus taxodium, he called the redwood taxodium sempervirens. It’s sometimes thought that the name sempervirens refers to the long life of the tree, which indeed may be upward of 2,000 years. But this is not the case. Lambert, after all, was describing a specimen from a hyberium sheet and he knew nothing of the longevity of the tree. And he was merely concerned to record that the tree was evergreen. Sempervirens meant evergreen in distinction to those taxodium speciea like the bald cypress, taxodium discusum, which are deciduous. The generic name became changed subsequently because a German botanist, Steven Endlicher, recognized that indeed it was not a species of taxodium. And in 1847, he called the coast redwood Sequoia sempervirens, the name which it still hold today.

Well, generally speaking, early visitors to California knew relatively little about the coast redwood. And some of them seem only to have seen the trees from a distance. And I think that at least a part of the reason for this is the nature of the terrain upon which the coast redwood trees grow. They do not grow on the south side of the Golden Gate where the Presidio and the Mission Dolores stand. And as a consequence, persons who landed there in early times did not come into contact with the redwood trees. Neither do they occur in the vicinity of Monterey, the other, even more frequent, point of call for these visitors that came from the sea. And when these visitors journeyed from Yerba Buena, the old San Francisco, to San Jose or to Monterey or to Salinas, it was much easier to make the journey by the Santa Clara valley route which lay through the oak savannah and the grassland rather than to go through the mountainous areas where the redwoods grow beneath their fog cap. Thus, when Captain Beechey of His Majesty’s Ship ‘Blossom’ visited California in 1826, he rode overland from San Francisco to Monterey. And he was not at all overawed by the redwoods. He merely noted them in the distance and gave them half a sentence of mention. By contrast he described poison oak with great forcefulness. And it is quite clear that this made much more impression on him, as did the fleas which existed in everyone of the settlements. The little things impressed him much more than the big ones.

On the other hand, the Sierra redwoods, the only big trees according to some people, have never failed to impress visitors who see them for the first time. And in part, I think, the greater impressiveness of the Sierra redwoods may be traced to the fact that in their case it is the enormous girth of the trunks readily appreciated against the scale of a human being which marked them out as utterly different from the other coniferous trees which grow with them. The girth in the important thing to notice.

The fossil history of Sequoiadendron, the Sierra redwood genus, has not been worked out with the same completeness as has the fossil history of the genus Sequoia. But we know it in sufficient detail to understand the general picture. Once again it appears to have been a progressive contraction in range for the genus which had its origin in the Cretaceous Period, but gradually diminished in area; during the climatic changes of the Tertiary Period. And before the end of the Tertiary Period, about two million years ago, Sequoiadendron, which had occurred in Europe as well as in Greenland and in North America, had become extinguished everywhere except in North America.

At the present time, Sequoiadendron gigantea is found in a series of groves in a narrow belt running some 260 miles in length on the western slopes of the Sierra Nevada. The elevation of these groves ranges from about 4,500 feet at the northern limit to about 7,500 feet at the southern limit. The northernmost grove consisting of about six trees grows on the middle fork of the American River in to Placer County. And the most southerly grove, a larger one containing about 100 trees, grows along Deer Creek in Tulare County.

The climate in these areas is both drier and cooler than that in which the coast redwood grows. The rainfall is 18 to 60 inches a year, which incidentally mostly comes in the form of snow. And in these groves Sequoiadendron grows mixed with other trees. Growing along the side is a much more slender Douglas fir.

Dr. Dan Axelrod of the University of California at Los Angeles, famous paleobotanist, has shown from the study of fossils that during the Tertiary Period there were forests of the Sierra redwood in the State of Nevada. But as the rainfall decreased at the end of the Tertiary Period, the Sierra redwood migrated westward to the western lopes of the Sierra Nevada. Not only was it becoming too dry for the Sierra redwood in Nevada, but the winters were also becoming too cold for this tree. For all that it grows in the mountains of California, it is known to be damaged seriously by prolonged spells of temperatures below zero degrees Fahrenheit. The accelerated uplift of the Sierra Nevada which took place during the end of the Tertiary and the Pleistocene Periods created still more of a rain shadow on the Nevada side and produced conditions which were completely unsuitable for the growth of Sequoiadendron. Consequently, when the Pleistocene Epoch came with its four major ice ages, just over a million years ago, the Sierra redwood was already restricted to the western side of the mountain.

So why does it grow on groves on the western side of the mountain, rather than in continuous forests? It seems to have been the great naturalist John Muir who put forward the explanation for this a way back in 1875. Muir noticed that the groves are usually on unglaciated slopes separated by valleys which were heavily glaciated during the periods of ice expansion, of glacier formation, in the Sierra Nevada, during the Pleistocene Epoch. And he postulated that the Sierra redwood trees were wiped out in these valleys by the ice age that time and have never been able to get back in again. And we generally accept this view nowadays. We believe that the Sequoiadendron has not spread back into the valleys in post-glacial times because the valleys are still too cold in the winter for the trees. Thus we have the Sierra redwood growing magnificently, to over 300 feet in height, and to an enormous age, certainly to an excess of 3,000 years in its groves but not apparently being able to spread out from its groves except where man has planted the trees in other parts of the world, particularly as a decorative tree in the eastern United States and in Europe. But it’s interesting that this tree is not completely lacking in genetical variation. A large number of horticultural forms have been selected from it in cultivation including what I think is the ultimate, I almost said ultimate insult to the big tree, a dwarf form of the big tree suitable for growing in rockeries.

With regard to the discovery of the Sierra redwood in the 19th century we needn’t bother to argue too much by whom these trees were first seen. Was it Joseph Walker in 1833 or John Bidwell or any one of several other hunters who was the first non-Indian person to see them. The important fact is that the scientific discovery of the Sierra redwood or big tree dates from 1852 when once again seeds were collected and sent back to England by a collector named William Lobb. William Lobb had been sent out to California by the nursery firm of James Vetch to collect seeds of California plants suitable to grow as decorative plants in the British Isles. Lobb’s seed and his specimens formed the basis of the first botanical description of the tree by the great botanist John Lindley. Lindley named the tree Wellingtonea gigantea, in honor of the Duke of Wellington, the Iron Duke, the hero who defeated Napoleon at Waterloo. The reason was that Wellington had died the year before and a suitable memorial was needed. And being the giant amongst trees, it was inevitable that it should be claimed for a domestic hero. Interestingly enough, that has been its fate subsequently too. After Endlicher established the genus Sequoia in 1847 he added the Sierra redwood to the coast redwood in the genus Sequoia and this made the Sierra redwood become called Sequoia gigantea. But the hero worshippers were not to be outdone and some years later Sudworth, who felt that American tree. ought to be named after an American hero, proposed that the name be changed to Sequoia Washingtoniana. And even this was not enough for one patriotic New Yorker who wanted to be quite politically and patriotically straightforward about the thing and call it Americus gigantea. But, alas, all these names are invalid for one reason or another and we have it now Sequoiadendron gigantea.

But I don’t think there’s any reason to be sad about this. After, all Sequoia and Sequoiadendron are both names which commemorate a very great man, a Cherokee Indian named Sequoia who lived at the end of the 18th century and the beginning of the 19th century admittedly not in California but in the territory which is now Oklahoma. In 1821, this self-educated man completed an alphabet of 86 characters by which the Cherokee language could be written and printed As a result they were able to have a written law. They were able to have written newspapers and so on. He was far ahead of his time in helping his people, and I personally think that it’s just as good that his name should be commemorated in these trees as that of any military hero.

I think these are noble trees and are very well worthy of discussion in this series of lectures. But whilst we are thinking about the nobility of the tree, we might make a resolution never to allow this sort of thing to be done again to them. Nor indeed to allow the sort of situation on the next slide come about if we can possibly avoid it. If we possibly can, let’s have the situation which in pictured on, the last of these slides. Thank you very much.