Texas Oak Open Days - October 12–16, 2023

The IOS Texas Oak Open Days were held over 5 days in October, 2023, at different locations in east and central Texas, moving from Houston through Hempstead, Austin, and San Antonio, and ending with a one-day field trip in the Hill Country on the Edwards Plateau. A total of 28 participants attended at least one of the events, while three stayed the course from beginning to end.

The event kicked off at Houston Botanic Garden where Horticulture Director Fran de la Mota gave us a guided tour of this new garden (inaugurated September 2020) that is exploring solutions to the challenges presented by Houston's grueling climate. Punishing low temperatures have killed back to the ground tenderer plants, but the extended hot growing season means they put on astounding growth when they recover. We were impressed by several vigorous Quercus rysophylla and other interesting oaks including Q. graciliformis and Q. laurifolia. The second part of the tour took us to some mature oaks (Q. nigra, Q. phellos, Q. texana, Q. virginiana) that date from when the site was a golf course. The first day ended with a visit to a venerable live oak (Q. virginiana) at Glenwood Cemetery. Estimated to be over 140 years old, this beautiful epiphyte-laden tree rests its longest limbs on crutches or has them fastened to stronger branches with steel wires, and several cables run down the tree to the ground, ready to deflect any "oak-cleaving thunderbolt".

Day Two saw us at the legendary John Fairey Garden (formerly Peckerwood Garden) in Hempstead, where we were hosted by Executive Director Randy Twaddle. The Mexican oaks steal the show at this garden, established by John Fairey in 1971, but there was so much more to see and learn from Horticulturist and Nursery Manager Craig Jackson, our expert guide. The wild-collected oaks sometimes defy identification, like the stunning Section Lobatae oak referred to as “San Carlos", after the mountain range where it was found, Sierra de San Carlos in Tamaulipas, Mexico. It is generally understood to be somewhere between Q. sartorii and Q. canbyi and is represented by numerous trees in different sections of the garden. An interesting Section Quercus species is referred to as Q. aff. pringlei. It was good to see some newer plantings of endangered oaks, including Q. acerifolia, Q. arkansana, and Q. brandegeei, as well as fine mature specimens like Q. crassifolia and a putative Q. tarahumara × Q. jonesii hybrid.

On the third day we visited the arboretum at the Lady Bird Johnson Wildflower Center (LBJWC) in Austin, which is building a collection of all the oaks found in the state of Texas. Arboretum and Natural Areas Manager Phillip Schulze showed us round, sharing his deep knowledge of Texan oaks and anecdotes of the Herculean tasks involved in creating the arboretum in hostile and unforgiving conditions. At the Hall of Texas Heroes we strolled between two concentric rings of young descendants of the state’s most famous live oaks (Q. virginiana and Q. fusiformis), imagining how this will one day become a shaded allée. We then moved to the new planting where native oaks are planted in tightly spaced small groups, but with ample space between them. Highlights include the endangered Q. graciliformis, Q. emoryi, Q. grisea, and Q. turbinella. A partial solar eclipse was part of the entertainment, casting a beautiful tapestry of dappled, crescent-shaped shadows through the canopy of mature post oaks (Q. stellata).

Michael Eason hosted Day Four at San Antonio Botanical Garden, where he is Associate Director of Conservation and Collections. The Garden features a spectacular conservatory designed by Argentine architect Emilio Abasz, next to which grows a fine Q. germana. A newly discovered quercetum contains mature specimens of native oaks, including Q. vaseyana and Q. marilandica var. ashei. Michael shared many oak treasures in his nursery that will soon be planted out in the planned oak collection, like the Critically Endangered and federally listed Q. hinckleyi and the rarely seen Q. chihuahuensis. The highlight was the famous and recently rediscovered Q. tardifolia and the equally significant Q. scytophylla, with beautiful white leaf undersides, found on the same expedition and previously not recorded in the US. The visit ended at the mature Q. hinckleyi trees at the entrance, which are thriving and copiously producing acorns and suckers.

In the afternoon we moved to the nearby (in Texan terms!) campus of Trinity University in San Antonio, to see three large Q. rysophylla said to be grown from seed collected by legendary plantsman Lynn Lowery. The largest tree must be around 25 m tall and possibly the US national champion. Also on the campus we found other impressive oaks, including Q. laceyi, Q. polymorpha (possibly sourced from Mexico rather than from introduced trees in Texas, as is the case with most other specimens in the state),¹ Q. canbyi, and a likely Q. gravesii with unusually shaped leaves. The day ended downtown at the Alamo, to view two enormous live oaks (Q. fusiformis), one of which was transplanted in 1913 as a relatively large tree by Walter Whall, a retired English seaman, at a time when it was thought that mature trees could not be transplanted.

The Texas Oak Open Days culminated with a field trip to the Hill Country led by Phillip Schulze. First stop was the formidable Big Tree Ranch near Concan, where we saw the second largest recorded Q. laceyi in the state of Texas and a massive bald cypress (Taxodium distichum), currently ranked third in the Texas Big Tree Registry for the species.

Doug McLean, proud and ebullient owner, pointed out that the bald cypress may merit a higher ranking. He showed us that there is no root flare on the tree, as it originally grew on the bank of the river which has since moved further away, and the base of the tree has been buried. If the soil were removed to reveal the base, the circumference at breast height may be significantly larger. We saw other large bald cypresses, including one with a hollow trunk, and scrambled up a slope for a view of tree tops and the river from above. There are several other trees on the property ranked by the Registry, including the National Champion netleaf hackberry (Celtis reticulata).

Next was one of the historic live oaks (Q. fusiformis) whose descendant we had seen at LBJWC on Day Three, the Rio Frio Landmark Oak, a beautiful ancient tree with spreading limbs, well cared for by its owner. The afternoon saw us cruising along country roads on the Edwards Plateau to see Q. marilandica var. ashei, Q. sinuata var. brevifolia (its acorns and cups had attractive orange-tinted hilum scars), an unusual Q. laceyi with unlobed leaves and another one with conspicuous lobing, even suggesting possible Q. stellata influence. We also paused to see Q. buckleyi and the local Q. muehlenbergii with narrow leaves, sometimes referred to as var. brayi, and for the final stop Michael Eason led us to a Q. muehlenbergii that had extremely narrow leaves and elongated acorns.

Our reluctant drive along the freeway to San Antonio brought to a close this intensive five-day event. Our thanks go to our hosts and guides at each venue, and to the enthusiastic group of participants who came out to join in the fun, including many local new members and others who visited from overseas.

Note: A detailed report of the Texas Oak Open Days will be published in May 2024 in International Oaks No. 35. You can view more photos of the trip on Instagram under #TexasOakOpenDays

¹Quercus polymorpha is native to Texas but only as one small population in Val Verde County near the Devils River. It is widely planted as a street tree in the state, but most of the trees are grown from seed obtained from cultivated trees.

Photos © Roderick Cameron unless specified