Collecting and Growing Texas Native Plants for Conservation and Climate Change Adaptation
Throughout 2020 while the United States Botanic Garden was closed to the public, the Horticulture team continued stewarding its plant collection. Several Horticulture team members were paying special attention to a new batch of plants grown from seeds harvested during a plant-collecting trip to Texas.
The team found and collected seeds from the rare Glen Rose yucca (Yucca necopina), native only in a few counties in Texas.
For 200 years, the United States Botanic Garden (USBG) has grown and shared thousands of plants with the public. While seasonal plants like poinsettias delight and inspire, the USBG's biggest treasure is the approximately 10,000 plants that form a permanent collection -- a basis for the USBG's status as a living museum. These plants include rare and endangered plants, orchids, medicinal and food plants, U.S. native plants and others from around the world.
In 2018, the USBG's former Plant Curator Bill McLaughlin (now retired) joined colleagues on a collecting trip organized by the Plant Collecting Collaborative, a group of public gardens dedicated to propagating wild-collected plants from around the world for the purposes of increasing diversity in horticultural displays and collections and contributing to plant conservation. The 2018 trip sought to find and collect seeds from several locations in central Texas.
The team gathered seeds from these wild sunflowers (Helianthus annuus) at the Cedar Hill State Park south of Dallas, Texas.
You might wonder why a garden in the mid-Atlantic would be interested in gathering plants native to Texas. According to McLaughlin, some areas of Texas have similar climates to Washington, D.C. "I was surprised because we started pretty far west in Texas, where I expected the plant life to be much more adapted to dry air," said McLaughlin. "But we woke up to 70 percent humidity that didn't burn off until afternoon. I saw immediately that many plants there could live in D.C."
A major goal for the USBG was to locate Texas native plants that could grow well in an urban heat island like downtown Washington, D.C. and be part of adapted planting designs in response to a changing climate. "Many Texas plants, if they have a modicum of cold hardiness, can make great garden plants," said McLaughlin. Some plants from Texas display heat and frost tolerance, as well as drought tolerance, which could be very useful into the future.
After participating in a successful collecting trip to the Philippines in 2017 that supplemented the USBG's indoor Conservatory collection, McLaughlin was excited for this domestic trip where he could gather plants to grow and showcase outdoors. "Plants like wild sunflowers and blanketflowers -- I love when the Garden can show the straight species and exactly where it came from," said McLaughlin. The provenance data indicating when and where a plant was acquired makes it valuable for conservation and breeding.
Every day, the team had to clean the seeds gathered to provide the best conditions for storing and future germination. Former USBG Plant Curator Bill McLaughlin is shown second from left.
The Plant Collecting Collaborative team had some specific plants they were hoping to find but were also keeping their eyes out for other opportunities as they arose. Partners on the trip included Chicago Botanic Garden, Chanticleer Garden, The John Fairey Garden and the Botanical Research Institute of Texas. It wasn't always glamorous, McLaughlin reported -- there were several 100-degree days. "You don't have to worry about ticks and chiggers in those scorching temperatures. They recede!" said McLaughlin.
Despite the long, hot days, the group was successful in locating many plants fitting the heat- and drought-tolerant, cold-hardy target. The USBG has added seeds from more than 150 plants collected during this Texas trip into the plant collection. The Horticulture team has been determining the best courses for getting those seeds to germinate and then growing them into strong plants that can be planted in the outdoor gardens.
Gardener Anna Mische John is a member of the Gardens and Grounds team and is one of the key people responsible for growing the Texas plants. "I am really excited for the potential drought tolerance," Mische John said. "We need plants that can handle climate change and areas like the rain gardens in Bartholdi Gardens where plants need to be able to handle both inundation but also the long periods of dryness in between."
The Horticulture team plans to incorporate some of the plants into current garden areas like the rain gardens and dry, full-sun areas, but also plans to swap out current plants that might have come from a horticultural greenhouse with unknown provenance with these new wild-collected plants. Mische John already has one such swap out planned -- replacing a Texas persimmon in the Southern Exposure courtyard in the Conservatory with one brought back from the trip.
Redwhisker clammyweed (Polanisia dodecandra), above, and prairie fameleaf sumac (Rhus lanceolata), below, are a few of the many USBG has successfully grown from seeds collected on the trip.
A number of the plants were exciting for the Horticulture team for a variety of reasons. Texas milkweed (Asclepias texana), was Mische John's favorite. "It's a beautiful garden plant with a great size and flowers for a long time," she said. "It's not a plant that I've really seen growing in other gardens or in the horticulture industry to purchase."
Some plants like halberdleaf rose mallow (Hibiscus laevis) and lemon beebalm (Monarda citriodora) are already large enough and have been planted outdoors. Try finding them on a future visit! Other plants like a little prickly pear cactus (Opuntia engelmannii var. lindheimeri) that germinated this winter is only the size of a pea. Cacti typically are slow growing, so the gardeners will have to care for it for many years before it reaches a size that can be displayed in the public gardens.
Caring for special plants is one of the things public gardens do best. The USBG is newly focused on updating its plant collection to replace unknown-origin plants with wild-collected ones, continuing to make the plant collection available for research, and expanding partnerships to further support science and conservation. People rely on plants for food, clean air, medicine and so much more. These vital organisms are facing threats such as climate change, a growing human population, and land loss due to development and agriculture. Bringing native plants into cultivation and expanding the genetic diversity of living collections is a critical component of ensuring plants survive these challenges. The USBG is proud to be part of the public garden community that is at the forefront of American native plant conservation.
BY DEVIN DOTSON | JULY 2021