Last August, the Research and Conservation Department received a grant from the Institute of Museum and Library</a> Services (IMLS) to “advance the North American Botanic Garden Strategy for Alpine Plant Conservation” (MA-255890-OMS-24). The Alpine Strategy</a> is a document that was published in 2020 by the Gardens and Betty Ford Alpine Gardens to serve as a blueprint for protecting alpine plants and ecosystems in North America. The funded project will support a nationwide endeavor to document and preserve the natural heritage of vulnerable and treasured plant species, specifically targeting the role that botanic gardens play in advancing this mission. The objectives of the project will engage the botanic garden community and those working in alpine plant conservation, while moving us closer to our goal of understanding and conserving alpine habitats and plants in North America. </p> Changing environmental conditions threaten plant communities worldwide, with alpine plant species being particularly vulnerable. Temperature fluctuations are projected to be most severe at high elevations and species will be displaced to higher and higher elevations, or highly restricted microsites, until there is nowhere left in which to migrate. The limited space for plants to migrate to track suitable environmental conditions, coupled with the potential inability to adjust traits or phenology, may increase extinction risk. Alpine species are in desperate need of conservation action. </p> Understanding seed dynamics is arguably the most important piece of ex situ (outside of the natural habitat) seed conservation. Successful management of ex situ seed collections relies on understanding seed quality, viability and seed banking behavior. Prior to seed banking, it is important to have an estimate of the quality of each collection so that resources are not wasted on a non-viable collection and to understand how viability may change throughout the duration of storage. The most efficient and least destructive way to assess seed quality is through x-ray imagery. X-ray imaging is especially appropriate for small seed collections or for those of globally threatened species so as not to destroy any of the seeds in the collection. X-raying allows the inspection of the inside of the seeds, providing images that show whether a seed is filled with an embryo/endosperm, empty, or predated upon by an insect. With this information we can have an initial estimate of seed collection quality, which is impossible with visual inspection alone. </p> The funding from IMLS allowed us to purchase a Kubtec X-ray to image all our alpine seed collections, which ranged in collection year from 1988 to 2025. Overall, our alpine seed collections are of good quality, with 87% of the collections having above 70% estimated viability (filled with viable tissue and potentially capable of germination). </p>
There are many ways to increase soil health in your garden. One of those is using deep mulch to cover beds.</p> Often used in combination with other sustainable farming practices</a> like crop rotation and intercropping, deep-mulch farming uses a thick layer of organic material, such as straw or wood chips, to cover soil. One of the main benefits of deep-mulch farming is that it can reduce the amount of time and energy needed for weeding and watering, as the mulch helps to retain moisture and suppress weed growth. Additionally, as the mulch decomposes, it feeds the soil ecosystem and improves the structure and fertility of the soil. </p> The initial cost of purchasing or gathering enough mulch material can be a significant upfront expense, particularly for larger farms or gardens. However, you can often find landscape companies that will drop off truckloads of wood chips for little or no charge.</p> Certain types of mulch, such as straw, can harbor pests like slugs and pill bugs. This can be a problem if the pests become a nuisance or cause damage to crops. However, mulch also provides habitat for beneficial insects, like spiders, that help control pests. </p> Overall, the pros and cons of using deep mulch will depend on the specific circumstances of your garden, such as the size and type of crops being grown, the local climate, soil conditions and the availability of mulch material. </p> Ready to deep-mulch? Here is some additional reading to help you prepare:</p> Types of Mulching, Advantages of Mulching in Farming</a></li> Deep Mulch Gardening – The Good AND The Bad</a> </li> </ul>
You may have heard of the Plant Select® program—a collaboration between Denver Botanic Gardens, Colorado State University and green industry partners. Its mission is simple: to introduce plants that are not only beautiful, but also tough, water-wise and perfectly suited for gardens in the Intermountain West.</p> Behind the Scenes: How Denver Botanic Gardens Shapes Plant Select®</strong></span> </span></h3> At the Gardens, we play a big role in this work. We trial new plants onsite (see an excellent overview of the process here</a>), manage demonstration gardens at both York Street and Chatfield Farms, and offer Plant Select plants at our annual Spring Plant Sale.</p> But here’s something you may not know: the Gardens also helps discover and develop new plants for the program. With over 17,000 plant varieties in our living collections, we have an unmatched resource to draw from. In fact, more than 70% of Plant Select introductions begin here at Denver Botanic Gardens with our staff.</p> Better Plants for the Intermountain West</h3> In recent years, our horticulture research team has launched a focused plant breeding program to create cultivars and unique varieties tailored for our region. Sometimes this means selecting naturally occurring traits from wild populations; other times it involves advanced tools that allow us to shape plant genetics more precisely.</p> Plant breeding is hardly new—it dates back nearly 10,000 years, when early farmers began selecting plants for better yield, flavor, or appearance. At its simplest, it’s just crossing two compatible plants to combine desirable traits. Over the last century, techniques such as mutagenesis and ploidy manipulation expanded what breeders could achieve, and today, gene editing and transgenics allow us to target traits with unprecedented accuracy.</p> At the Gardens, most of our work still relies on traditional breeding methods. That means crossing plants with traits we want to combine—say, the flower color of one species with the drought tolerance of another. By pairing a highly ornamental plant with a drought-hardy relative, we hope to create varieties that are both beautiful and better adapted to hot, dry conditions. It’s a long process, often requiring multiple generations before the right combination is achieved.</p> We also use mutagens, substances that can trigger changes in a plant’s genome. While these changes are random, they often produce predictable outcomes, such as compact growth, novel foliage color, or reduced fertility. We use this technique with plants that already have strong ornamental appeal and environmental tolerance but may benefit from a unique twist or refinement.</p> Beyond Beauty: Our Breeding Goals</h3> Unlike ornamental horticulture at large, our breeding priorities go beyond aesthetics. We aim to develop plants that are not only striking in the garden, but also resilient in our increasingly harsh climate and supportive of pollinators and ecological health.</p> In other words, we’re not just breeding plants to survive here—we’re breeding them to thrive. </p>
Scattering a few ounces of seed onto dry Colorado soil can feel more like hoping than planting. Folks who’ve tried store-bought wildflower mixes might know the frustration: despite following instructions, results are often inconsistent. Mixes may bloom for a season or two but can be patchy, lack coherent design, are soon overrun by weeds, or collapse into stands dominated by one or two aggressive species.</p> Still, direct seeding remains one of the most appealing ways to transform non-functional turf, medians and other tough spaces. Seeds are inexpensive, species are easy to source compared to potted plants, and installation is simple. Our horticulture research team at the Gardens has been investigating ways to make direct seeding more reliable, creating mixes that are beautiful, resilient and long-lasting.</p> Setting Parameters</h3> One challenge with many commercial mixes is the lack of crucial details. Sowing rates are often given in pounds per acre, which is nearly impossible to scale to a backyard or small urban lot. Even worse, weight is misleading: a gram of lupine seed equals about 30 seeds, while a gram of Artemisia can be nearly 10,000. To improve accuracy, we calculate sowing rates based on the number of seeds per unit area (i.e., 300 seeds per square foot). This method allows us to balance species more precisely and adjust mixes to specific sites.</p> Another problem is growth form diversity. Most mixes emphasize only wildflowers, overlooking grasses and shrubs—two of the most resilient growth forms in Colorado ecosystems. However, the right ratio of these various growth forms is crucial. Too many aggressive grasses or shrubs, and diversity disappears. But when balanced, each growth form contributes to a stable and enduring plant community.</p> Choosing the Right Species</h3> Species selection is just as critical. Every plant has unique traits: germination timing, bloom period, lifespan, stress tolerance and competitiveness – among many others. Many mixes rely heavily on species that sprout quickly, which may look good at first but fail to sustain long-term diversity or season-long blooms.</p> Our approach uses trait-based design. We include fast-germinating species that suppress weeds in the first year while leaving room for longer-lived species to establish. We also screen new species for how they perform over multiple seasons, tracking which ones persist, coexist well with others, and extend bloom time from spring through fall.</p> Timing Matters</h3> We’ve also studied how sowing season affects establishment. Standard advice is to sow in autumn so cold weather can break seed dormancy. But our trials show that spring sowing—using seeds pre-treated with cold in refrigeration—often yields higher germination, especially when paired with supplemental irrigation in the first year. Losses from winter die-off, predation, and moisture stress may explain why fall seeding performs less reliably.</p> Built to Last</h3> Direct seeding may never be as predictable as planting nursery-grown perennials. But with thoughtful design, it can be just as successful. By refining sowing rates, balancing growth forms, carefully selecting species, and timing sowing strategically, we’re creating custom mixes that are diverse, resilient and built to last in Colorado’s challenging conditions.</p> </p>
When I talk about my work as a scientist in the Research and Conservation Department at Denver Botanic Gardens, I explain how I study the role of genetic diversity in conserving biodiversity. People often ask for examples of this or cite famous stories of disease resistance, genetic rescue or environmental adaptation. Indeed, there are great examples, such as how a lack of genetic diversity led to widespread disease and die-off of potato crops resulting in the 1800s Irish Potato Famine, or the successful recovery of the endangered Florida panther after introduction of new genetic variation from Texas panthers. I want to highlight a few real-world examples that are specific to plant biodiversity conservation. </p> First, adaptation to new environments is facilitated by genetic diversity. Examples of this include colonization of toxic mine tailings by certain grass species (e.g. Anthoxanthum odoratum</em>), adaptation of yarrow (e.g. Achillea borealis</em>) and other species to serpentine (low nutrient, high heavy metal) soils, and existence of new species or varieties of wild sunflowers (e.g. Helianthus petiolaris</em>) in sand dune habitats. These studies of natural phenomena are particularly valuable to understand in the context of conserving biodiversity under ongoing threats of environmental change. </p> Second, genetic diversity can increase ecosystem function. While the mechanisms for this are still debated, there is ample evidence that complementarity, or differential strategies by different species or genetic variants, allows for improved functioning of ecosystems. In grasslands for example, it has been shown that species that utilize above- versus below-ground space in complementary ways results in higher productivity overall. Or in the case of threats such as herbivores and climate extremes, different plant species can protect or facilitate each other via mechanisms such as nurse plant effects. Together, these examples emphasize the role of genetic diversity in plant communities and the importance of conserving it. </p>
In 2018, Denver residents voted to pass the citywide green roof ordinance, sparking excitement about a greener, cooler, livelier cityscape. Many rooftops transformed into gardens, farms, and pollinator havens. But despite their benefits, green roofs are notoriously difficult to establish—especially in Denver’s semi-arid climate.</p> On a rooftop, plants endure full-sun exposure, with substrate temperatures soaring above 90 degrees in summer and plunging below freezing in winter. The shallow, fast-draining engineered soil holds little organic matter. As a result, designers often rely on sod seeded with Sedum species.</p> While sedum roofs offer benefits, they lack the biodiversity, dramatic colors, and rich textures one might see while visiting Denver Botanic Gardens or hiking the mountain trails of Crested Butte in summer. Colorado’s native species are well adapted to such harsh conditions, yet their potential on green roofs remains largely untapped. Recognizing this, Colorado State University graduate student Maria Schonewise partnered with the Gardens’ horticulture research team to develop native seed mixes capable of establishing naturalistic, resilient plant communities on rooftops.</p> Working with Manager of Horticulture Research Michael Guidi, Schonewise designed a mix of 34 wildflowers, grasses and shrubs, varying seed densities to test establishment. Once developed, her mix was then sown into approximately 60 plots across three Denver green roofs: CSU Spur, Community College of Denver and in the Green Roof garden</a> atop Offshoots Café at the Gardens.</p> Throughout the summer, Schonewise tended plots and collected data on species presence, abundance and weed coverage. These findings will help answer pressing questions: Which plants are tough enough to thrive? How can we create biodiverse, low-maintenance communities? What pollinators use rooftop habitats, and what resources do rooftop native plant communities provide urban pollinators? </p> Her research could help improve upon the industry standard sedum mats used in green roofs by creating a reliable, hardy and biodiverse method for establishing plant communities, making them just as colorful and rich as Colorado’s various landscapes. Next time you visit the Gardens, stop by the Green Roof garden above Offshoots Café to see this living laboratory in action.</p> This article was contributed by Horticulture Research Associate Reece Bailey</strong>.</em> </p>
