Along the Oak Trail: Searching for New Forms of Southwestern Native Oaks

The idea of doing this trip came from Allan Taylor, professor emeritus at the University of Colorado, Boulder, where he taught linguistics and Russian. Allan is not only a brilliant linguist who speaks six languages besides his native English, but also a passionate plant lover who has been propagating trees as a hobby for ages. I met him in August 2001 on an oak exploring expedition to New Mexico, together with a dozen other oak people from The International Oak Society (I.O.S). Since that exciting trip, Allan and I have maintained regular contact by e-mail and from time to time he has sent me seed or herbarium material from selected oaks from the U.S. Southwest.

After our trip together to New Mexico, Allan invited me to visit Colorado so that he could show me the many beautiful places in his native state and beyond. Gradually the idea of going to Colorado took shape and things were thoroughly planned in the months before my departure. I bought a number of books and carefully studied the flora of the regions that we would visit. I made a list of the plants that I really wanted to see and photograph. We decided to avoid the places frequented mostly by tourists since I preferred to go to wild places where oaks and other endemic species of trees grow.

On Saturday, September 18, 2004, I was all packed and ready to leave my lovely wife Katrien, my three sons, my family, friends and nursery for a whole month. The first three weeks I was going to travel with Allan, after which I would join a tour through Illinois organized for the Belgian Dendrological Society by Guy Sternberg, former president of I.O.S. I flew from Brussels to Chicago and then on to Denver, Colorado where I arrived around four o’clock in the afternoon. Allan was waiting for me with open arms; just like me he was excited that we would finally meet again and that we would soon start our journey of exploration and discovery. He wondered if I didn’t feel the altitude since I’m used to living only a few meters above sea level and indeed I did feel a little light-headed, but that could have been because of the long plane ride.

Boulder is in the foothills of the Rocky Mountains, about an hour’s drive northwest of Denver, and while we were driving, I could see these impressive mountains gradually getting closer and closer. Allen lives in a quiet neighborhood in central Boulder, where broad streets are flanked by big old trees like Quercus rubra, Acer saccharinum, Fraxinus americana and many others. We had a delicious evening meal in a local Vietnamese restaurant, after which Allan drove me up to Flagstaff Mountain, from which we had a wonderful view of “Boulder by night.” Because the local football team had just won a game, there was a huge fire works display down below, making my first night in Boulder even more magic.

The first couple of days we decided not to do anything much, so that I could adjust to the new time zone and altitude and get rested from the trip. So on Sunday morning I took a look around Allan’s garden and nursery. It was still a little chilly but the sky was clear blue and it promised to be a beautiful day, something that is quite normal here, in a region where, according to Allan, the sun shines 360 days a year. In front of the house there is a lovely rock garden with maples, dwarf rhododendrons, manzanita’s (Arctostaphylos), succulents and a few shrubby oaks like Quercus sadleriana from the Siskiyou mountains in Oregon and
Q. vaccinifolia from the Trinity Alps in California. There are also a few bigger shrubs and trees such as small group of mature Populus tremuloides, Quercus x undulata ‘Boulder Blue’ and some lovely hybrids of Q. turbinella with other oak species such as Q. lobata. Q. turbinella is the hardiest evergreen oak for this region. I wonder what this oak will do in our maritime Belgium climate? Behind the house I noticed scores of potted trees and shrubs that Allan has collected during his trips around this fascinating region. Pinus contorta ‘Taylor’s Sunburst’ and Juniperus horizontalis ‘Two Medicine’ are two of Allan’s selections which have found their way into the nursery trade; the first of these can occasionally be found here in European nurseries. A small greenhouse serves as winter storage for the most tender plants and also to protect the most precious plants from squirrels, which can do a lot of damage in their incessant search for acorns and other food. In front of the greenhouse Allan has an interesting collection of cacti that he keeps in pots until he can give them a permanent place in his desert garden, which features native plants of the U.S. Southwest. A striking open roof construction in Japanese style over a sunken patio on the north side of his house hangs full of bells of all kinds and shapes which gently chime when there is a breeze. Surrounded on three sides by elevated beds of rhododendrons and other ericaceaeous shrubs, this is an ideal spot to sit and talk or read or just enjoy the peacefulness of this beautiful place. A low-branched Cercis canadensis makes the picture complete.

After a lavish Sunday brunch we drove into the mountains to admire the fall color on Populus tremuloides, and at an altitude of 2500 meters we arrived in a mountain village quaintly named “Nederland” where we made a stop to take a few pictures and enjoy the vista. We could already spot the first aspen in their yellow and sometimes red autumn dress. Besides this quaking aspen most of the trees at this altitude are conifers such as Pinus ponderosa, Pinus contorta, Pinus flexilis, Pseudotsuga menziesii and Picea pungens, but near Boulder Falls we found some Betula fontinalis and a few Acer glabrum. In the late afternoon, after our return from the mountains, we went downtown to the “Boulder Mall,” an auto-free zone where we strolled among street musicians, acrobats, and magicians who were cheered on by the crowds of people out enjoying the mild evening. Because of jetlag I felt a little tired by late afternoon during those first days in Colorado, so I went to bed rather early Sunday evening, around 9 o’clock.

On Monday we visited the Denver botanic Garden where Allan’s brother-in-law, Panayioti Kelaidis was our guide. Panayioti, who is Director of Outreach at the Gardens, is a walking encyclopedia and he is an expert on North American alpine plants and high altitude plants of South Africa. The botanic garden is extremely well maintained, and at that precise moment it was the host of a fine collection of modernistic African sculptures displayed all over the garden. In a heated greenhouse we admired the Gardens’ extensive collection of epiphytes such as bromeliads and orchids; outside, our guide showed us a rich collection of crabapples, oaks and cold desert vegetation but also a wide variety of trees and shrubs from all over the world. A majestic Quercus shumardii, a red coloring Carpinus caroliniana, a Sorbus scopulina laden with bright red berries and a large group of Q. turbinella were but a few of the many trees that caught my eye.

In the afternoon Allan had wanted to drive all the way to the top of nearby Mount Evans (4347 m), but the road the final distance to the summit was already closed for the winter, so we had to park our car near Summit Lake, which is itself at a very respectable altitude, well over 3500 meters. At the lake we were well above timberline and it was very windy and freezing cold. On our way back down from near the top of the mountain we stopped at a stand of Pinus aristata where some of the trees are estimated to be about 2000 years old; needless to say, these ancient trees make a man stand mutely before them, full of respect and admiration. One can clearly see that the winter ice storms coming from the north-west through the many centuries of their lives have polished one side of the trunk almost clean of bark, the white of the xylem showing through on almost the entire north and west side of the trees. In some cases, only a thin line of living bark keeps the gnarled, tortured tree alive.

The next morning we left Boulder for Salt Lake City, Utah, where we hoped to visit the oak collection of the late Doctor Walter P. Cottam. We also hoped to see many interesting things along the way. Our goal for this Tuesday was to reach Grand Junction, on the western side of the mountains and already in the Colorado Plateau, one of the most beautiful sections of western North America. But after only a couple of hours of driving into the mountains it started to snow heavily and we wondered if we would get as far as we had planned. But the snow stopped after we began to descend from the two high mountain passes we needed to cross to reach the western side of the continental divide.

According to my flora it was likely that we would be able to find Crataegus saligna and Fraxinus anomala in some of the places we would pass through. Crataegus saligna develops a striking coppery bark with white cherry like horizontal lenticels and a graceful willowy habit, hence the Latin epithet (“willow”). Reason enough to look for the plant, but I had really hoped to find a few berries, especially since this species is highly praised in James B. Phipps recent book on hawthorns and medlars. (Our former I.O.S. president, Ron Lance, also contributed to this interesting work.) So I kept looking for creeks and draws, hoping to find this haw. As we descended along the Colorado River we made a few stops where we thought we might find our Crataegus, but always without success. We even left the freeway and followed a little creek to Rifle Falls, where we found a dense vegetation of Populus angustifolia, different willow species, Rhus trilobata, Cornus, Acer negundo and Quercus gambelii, but again no willow Hawthorn. The triple waterfall and its endless splashing made us forget our fruitless search for a while. Along Roan creek, a little farther on, we saw only a few willows and poplars but we were lucky to see some of the local fauna: a young bear, a coyote, a deer and a cottontail rabbit. Not everyone who comes to the U.S. is so lucky as to see a wild bear, so let’s be optimistic! We didn’t find the hawthorn today but we did see a rare sight, the young black bear, which returned our stare before he ambled off into the brush. Farewell, little Bruin, have a long and interesting life!

Just before we arrived in Grand Junction, we visited Allan’s native community, a peaceful neighborhood of orchards west of Palisade, Colorado, in the “banana belt” of the state where the cultivation of fruit is the main activity. The wooden houses between the orchards have their typical porches and in front of the houses there are majestic poplars, perfectly round Salix babylonica var. pekinenis and stately columnar catalpas (Catalpa speciosa). We bought ourselves a bag of delicious juicy peaches and while eating them we silently enjoyed the quiet rural scene of orchards and vineyards dominated by the brooding mass of Mount Garfield, an 800 meter “palisade” which rears its mighty head just to the north of here, the beginning of the Grand Valley. I suddenly perceived a look of nostalgic reverie in Allan’s eyes, but after a moment he broke the silence and said: “Let’s move on, Buddy” and off we drove to Grand Junction where we found a quiet motel. Grand Junction is so named because it is there that the Gunnison River flows into the Colorado River, formerly called the Grand River. This old name of the river is also the source of the name of the Grand Canyon.

The next morning we drove to Fruita where, at the foot of the Colorado National Monument, Allan had an appointment with a fellow cactus collector. Strange how cacti can survive in this dry climate with winter temperatures down to -24 °C while in our humid maritime climate they would succumb at a few degrees of frost. Allan exchanged a few cacti with this avid plant collector and I took a few photos of an old Catalpa bungei standing in front of the man’s house.

By noon on Wednesday we had arrived at Green River, Utah where we had a quick lunch. Only a few kilometers west of here we could see the towering rock formations of the San Raphaël Swell, one of the most beautiful sights in the Colorado Plateau. Right after we began to climb up the swell we stopped at a rest area where we had a wonderfull view of the swell and the encircling mountains. At this stop, Allan quickly spotted some desiccated Fraxinus anomala which were in seed; this is a small ash with single roundish leaves, hence its common English name “single leaf ash.” But despite its “anomalous” leaves, it has all the other characteristics of the genus such as opposite buds and winged fruit. I was really glad to obtain seed of this curious ash.

From this point on we drove through a spare but unbelievably beautiful landscape dominated by towering cliffs and deep canyons in all kinds of shapes and colors. Sometimes sharp and gray-green like an old Gothic cathedral, sometimes flattened, red-brown and bulbous like gigantic wheat breads, again square as if we had driven into an abandoned brick works with bricks as big as buildings! The freeway winds farther through this unearthly landscape until it suddenly starts to descend and gradually a lusher vegetation reappears. From the car we could clearly see small groups of Quercus gambelii but we decided not to stop as we still had a long way to drive today. At Salina we left the freeway, I-70, to drive north to Salt-Lake-City. We did not stop in Salt Lake City but continued a little farther on to Ogden, where Allan had reserved a room for the night.

The setting of Ogden is also breathtaking: just to the east is a huge rocky rampart composed of rock strata in all shades of red and buff. On the mountain slopes around Ogden
we could clearly see stands of Acer grandidentatum, just beginning to don their fall foliage. This is a western, drought-tolerant form of Acer saccharum, the famous sugar maple. So after checking in we drove out of town in the direction of Huntsville, hoping to get a little closer to this maple. When we reached a nice group of these maples we discovered that there was no seed at all. We continued and stopped a few more times, but none of the trees had any seed. But all was not lost: I suddenly perceived a small but graceful looking hawthorn and I was almost sure that we had found Crataegus saligna. Later, after a closer study with keys and pictures, it appeared that it was C. rivularis. On another spot nearby we find the same hawthorn with beautiful orange-colored leaves, a striking smooth orange bark and dark purple berries waiting to be picked. We also saw a deer, peacefully grazing in the evening sun.

It had been a long and tiring day with a lot of driving, but we had seen a number of beautiful vistas and were lucky enough to find two new acquisitions for my collection of North American trees and shrubs: Fraxinus anomala and Crataegus rivularis. I was very contented, and I slept very well that night.

On Thursday, September 23 we had an appointment with Eddy Dawson at the Red Butte Garden, which is the state arboretum of Utah. As I mentioned previously, we had come here in order to take a close look at the Cottam hybrids. This calls for a little explanation. The genesis of this ambitious hybridization project began on May 23, 1954, which just happens also to be my date of birth; on that day, Rudy Drobnick, then a student of Dr. Cottam, discovered a wild oak with small leathery leaves that were sharply toothed. This oak was growing in the Oquirrh mountains about 30 kilometers west of Salt Lake City. Quercus gambelii, the only oak species now growing in northern Utah has larger and thinner leaves with rounded lobes. Through contact with other botanists in California it was quickly concluded that this must be a hybrid between Q. gambelii and Q. turbinella, an evergreen species that can now be found only in Southern Utah. Some 7000 years ago at the time of the Altithermal, when warmer and drier conditions prevailed in the Great Basin, Quercus turbinella had migrated north. During that period Q. turbinella had a range which overlapped with that of Q. gambelii, and hybridization between the two occurred. As the climate became colder again, approaching the climate that we have today, Q. turbinella gradually died out, but the hybrid, which had inherited the cold-resistant genes of its other parent, was able to successfully withstand the colder climate. As a test of this hypothesis, Dr Cottam wanted to artificially pollinate Q. turbinella with pollen from Q. gambelii. This was carried out successfully and the leaves of the artificial hybrid looked almost identical to the leaves of the natural hybrid found by Rudy Drobnick.

The success of this artificial hybridization experiment encouraged Dr Cottam and his team to try more of these, and so forty-three different crosses were tested between 1961 and 1971. The following four species were used as female parent: Quercus gambelii, Q. macrocarpa, Q. turbinella and Q. robur. Where in earlier attempts to artificially cross pollinate oaks, the pollen was usually applied to the stigma with a brush, Dr. Cottam and his team simply used waxed paper bags, in which a handful of mature catkins were inserted just when the stigma was receptive. The sack was then carefully sealed and shaken every two or three days, for about a week, to ensure good distribution of the pollen. A great number of these attempts were successful and all of the acorns were sown for further evaluation. The main purpose of this ‘Grand Orgy’ was to create new hybrids which might become acceptable as ornamentals. We all know that by hybridizing oaks, like other plants, one can create surprisingly beautiful and interesting novelties like Quercus x ‘Pondaim’ (Q. pontica x Q. dentate), Quercus x hispanica ( Q. cerris x Q. suber) and a few recently introduced American selections like Q. x bimundorum ‘Crimschmidt’ (Q. robur ‘Fastigiata’ x Q. alba) and Q. x warei ‘Windcandle’ (Q. robur ‘Fastigiata’ x Q. bicolor). The latter was selected by Guy Sternberg for its pyramidal shape and good mildew resistance.

Most of the progeny of Dr Cottam’s hybrids have been planted out in Red Butte Garden, and the area where these hybrids were planted is called “Cottam Grove”. I am very interested in hybrid oaks and I had long dreamed of visiting Dr Cottam’s collection. And so here we were, armed with notebooks and camera, eager to see these interesting trees about which I had already read so much. Eddy Dawson, curator of the arboretum, first showed us around the very well maintained garden where we also admired a statue of Dr W. Cottam surrounded by a variety of leaves of his first hybrid (Q. turbinella x gambelii). For the next four hours I wandered around this exciting collection of artificial hybrid oaks, which is especially interesting when you know how it was created. I took a lot of herbarium material and carefully wrote down the data for the crosses which I wanted to receive scions of later. The following hybrids particularly attracted my attention because of their attractive habit or striking foliage: Q. robur x Q. lobata; Q. robur x Q. macrocarpa; Q. turbinella x Q. mongolica; Q. turbinella x Q. robur; Q. turbinella x Q. virginiana; and Q. turbinella x Q. gambelii.

Since returning home I have received scions of several of these hybrids and the grafted plants will be planted out here in Belgium for further evaluation; I hope that they will adapt well to our maritime climate. To be continued!

Late in the afternoon we left Salt-Lake-City and drove all the way to Rawlins, Wyoming with a stunning sunset in our rear-view-mirror and a threatening thunderstorm before us coming closer and closer as we drove east. That evening it was hard for me to fall asleep because all those hybrid names keep spinning through my brain; when I finally fell asleep I dreamed I was “Doctor D. Benoit,” creating bizarre hybrids with gigantic leaves that had flamboyant fall colors and huge edible acorns.

The next morning we left early because we still had a long way to drive, and we also wanted to visit a nursery in Fort Collins, Colorado along the way. We avoided Cheyenne by leaving the freeway at Laramie, and drove into Colorado by back roads; gradually the monotonous landscape of Southern Wyoming became more hilly and greener as we neared Colorado, and it reminded me of our Belgian Ardennes, though much drier, of course.

Allan had made an appointment with his fellow plantsman, Scott Skoggerboe, who is in charge of production at the Fort Collins Nursery. This nursery has an interesting variety of trees which are partly propagated at the nursery either by sowing seed or from cuttings under mist. Scott and Allan often go out in the wild together, looking for something interesting or just to gather seed. Seedlings are kept in pots for two years and are then planted out in “root control bags.” This way of growing trees is new to me and Scott explained how you get a perfect root system in these bags so that the trees suffer very little when transplanted. Trees grown in root control bags keep about 93% of their roots when transplanted while trees with a rootball keep something like only 25% of their roots. Trees grown in these bags always need irrigation during the growing season, especially in Colorado where the summers are hot and dry. This year I have tried this system at home in my nursery in Belgium to see how it works in our climate and soil.

As we strolled through the planting fields, two Mexican workers were busy planting trees. Allan asked them in Spanish for some more details about their work and where they came from in Mexico. The trees are not staked because Scott wants firm trees with a natural looking crown. Scott had just picked the fruits of what he calls “Crataegus sinensis”; (he doubts, however, that this is the correct name of this cultivar). Anyhow the fruits have a delicious sweet flavor and Scott promised to send me a few scions of this and a few other Crataegus species grown at the nursery.

Fort Collins Nursery also has their own selection of Acer tataricum; it has dark purple fall color and is easily propagated by cuttings under mist. As we walked around inspecting the various growing areas, suddenly, in a bed of young seedlings, there it was: Crataegus saligna, the hawthorn that we had been looking for since we left Boulder! I would have preferred to find and observe it in the wild but I was very happy to have found it here and to be able to add it to my collection. They have also tried to grow oaks from cuttings under mist and Scott told us that this is best done with shoots from the second flush of growth, when the leaves are still small. This affable nurseryman had a busy schedule that day and so we left Fort Collins shortly after midday to drive back to Boulder. And with this, the first leg of our oak journey came to an end.

Before setting out again we wanted to rest a few days because Allan had caught cold and felt a bit tired from all of the driving. That is why, the next day, I decided to go for a long hike in the foothills all by myself. Allan took me to the mouth of Gregory Canyon, which is actually not far from his home. I promised to be back by 5 p.m., during which time Allan would prepare a Greek meal for us. (Allan’s late wife was Greek.) At the trail head an information panel warned that this bear country and that mountain lions were also sometimes seen here. I asked myself if it was wise to hike alone in such a place, but on the other hand the whiff of danger attracted me. Just suppose that I should meet a bear or a lion! Every 15 minutes or so I met other hikers and when I met two park rangers they gave me instructions on what to do if I should encounter a bear or a mountain lion. From that moment on, I felt completely relaxed and I began to enjoy this wild paradise with all my senses. Soon I perceived the juicy fruits of Crataegus succulenta, certainly bears would love those too. In a small side canyon I saw a Sorbus scopulina, which I had observed earlier that week in Denver Botanic Garden, and on drier sites there were yuccas (a spikey member of the Liliaceae), cacti and groups of Rhus glabra. At another spot there were Acer glabrum and Pinus ponderosa from which a dark blue bird observed me. In more humid places near a brook, Betula occidentalis and Corylus cornuta were more abundant; the latter looked a lot smaller than our native hazel (Corylus avellana). In my enthusiasm I forgot to keep an eye on my watch and I suddenly realized that it might be difficult to get back to Allan’s place by 5 o’clock. For that reason I began to hurry my steps, but it was rather dangerous to run heedlessly downhill where the track is full of rocks and tree roots. When I finally reached the main road I soon met Allan who had come to look for me; worried about my failure to appear on time. He had actually thought of calling the police to search for me. But the problem had not been bears or lions, it was simply the enchantment of a lingering hike in a primeval canyon full of new species of trees and other plants. To finish this first part of our trip we had some delicious Greek food and wine and Michiko, Allan’s Japanese girl friend, clearly enjoyed the report on our trip to Utah.

The diary of the second part of my trip with Allan, where we saw many more interesting plants, will come a little later this year. We drove from Colorado to New Mexico, Oklahoma and Texas, all the way down to the Chisos Mountains near the Mexican border.