drought tolerant plants

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My Carrion Flowers

In April of last year, a box of stem cuttings arrived in my mailbox. They were sent to me by a friend in Colorado called Sandra (you may know her from one of her many ventures: Greenwoman Magazine, Greenwoman Publishing, Flora’s Forum, etc.). Sandra’s carrion flower had bloomed that spring, a stinky but delightful occasion. In her excitement, she asked if I would be interested in growing some carrion flowers of my own. Not one to turn down the chance to try my hand at cultivating something unusual, I gladly accepted her offer of a few cuttings sent via Priority Mail. Six cuttings arrived shortly thereafter, and upon reading through some instructions on the internet, I nestled them into their new home and hoped they would put down roots and stay a while.

carrion flower cuttings

There are several species of plants that are referred to commonly as carrion flower. The plant parts I received from Sandra are in the genus Stapelia (family: Apocynaceae or dogbane family), also known commonly as African starfish flower. There are around 100 species in the genus Stapelia, and they all originate from tropical and southern Africa, mostly in arid regions.

Stapelias are short-lived, low-growing, perennial succulents. Their stems typically stand erect and are produced along stolons (above ground runners), creating a tight clump of stems that appear cactus-like. Each stem has 4-6 flattened vertical flanks, giving it a cross or star shape when looking down from the top. On the outside edges of the flanks are a series of rudimentary leaves protruding from tubercles (wart-like growths), giving the stems a spiny appearance. The stems are usually green but can also be red or mottled with red or purple.

The flowers of Stapelia are the real show. They are produced at or near the base of the stem and have a star-shaped corolla with five fused petals that come to sharp points. The corolla has a wrinkly look and is often hairy, especially along the margins. Flowers can be variations of red, brown, yellow, and purple. In some species they can reach up to 18 inches wide. It is a unique looking flower, but even more unique is its scent. Because Stapelia flowers are pollinated by flies, they emit the scent of rotting animal flesh, an odor that flies can truly appreciate. In fact, flies can be so deceived by the appearance and scent of the flowers that they occasionally lay their eggs on or near them, expecting them to be a food source for their emerging larva.

Stapelia variegate (photo credit: eol.org)

Stapelia variegata (photo credit: eol.org)

Stapelia is easily propagated, especially by stem cuttings. Allow cuttings to dry in a cool, shady location for 48 hours and then stick them in a well-drained potting soil mix. Water moderately (preferably from below by placing the container in a tray and then filling the tray with water). Cuttings should root easily. All six of mine did.

Keep Stapelia in a sunny or mostly sunny location. If you live in USDA hardiness zone 9 or above, you can grow Stapelia outdoors. Otherwise, keep it indoors near a window that gets lots of sun. The main thing you will have to worry about is stem rot due to over watering. Grow Stapelia in a well-drained soil mix, water from below, and allow soil to dry out between waterings in order to avoid this.

Stapelia variegata (photo credit: eol.org)

Stapelia variegata (photo credit: eol.org)

As for me and my carrion flowers, like I said earlier, all six cuttings rooted. I transplanted one of them. Of the five left in the original pot, one rotted a couple weeks ago and another rotted during the writing of this post. The remaining ones still look healthy, but none of them have grown much since they rooted. The main problem I am having is that my house does not let in much sunlight. What appears relatively bright to me is probably cave-like to my carrion flowers. Until I remedy that situation, they may not grow much, they could continue to rot, and they probably won’t flower any time soon. However, if anything changes and I do get a flower out of them, I will make it a point to let you know. And Sandra will be proud.

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Drought Tolerant Plants: Blue Sage

If you are considering installing a drought tolerant garden on your property or including more drought tolerant plants in your landscape, one plant that should come standard is blue sage. Its silvery-green foliage, large, abundant, purple-blue flower stalks, and attractive mounded shape, make it an excellent feature in any water-efficient garden bed.

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Salvia pachyphylla is in the mint family (Lamiaceae). It has several common names which it shares with several other plants: blue sage, Mojave sage, rose sage, mountain desert sage, giant-flower sage. For this post we will refer to it as blue sage; however, if you’re looking to purchase it, make sure to verify the botanical name. Blue sage is a subshrub that can grow up to 3 feet tall and 3 feet wide. It tends to remain smaller – around 1-2 feet tall – in its native habitat. It is found in the southwestern states of the United Sates on dry, rocky slopes and flats at elevations between 5,000 – 10,000 feet. The leaves are oppositely arranged and covered with fine hairs that lay tightly against the leaf surface giving the foliage its silvery appearance. Like all other sages, the leaves of blue sage are highly aromatic.

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The flowers appear in compact clusters on spikes that extend upward from the branches. The inflorescences can be several inches long. They have numerous large, purple bracts that appear in a whorled pattern along the spike. The violet-blue flowers are small but prolific and appear between the bracts surrounding the stalk. Flowering occurs throughout the summer (July-September in its native range). The flowers attract droves of pollinators including bees, butterflies, and hummingbirds. Blue sage is especially beneficial to native pollinators. In fact, while taking photos for this post, I noted that the flowers were being visited by several bumblebees. Its benefit to pollinators is another great reason to include this plant in your landscape.

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Blue sage is a very drought tolerant plant. Once it is established it requires only occasional watering throughout the summer in order to keep it looking good. It performs well in a variety of soil types, but like most drought tolerant plants it is best placed in well drained soil. Heavy soils can be amended by mixing in things like sand, lava rock fines, and compost at planting time. It prefers full sun and is winter hardy to USDA hardiness zone 5, especially if planted in an area where the soil is relatively dry throughout the winter. Blue sage is a long lived plant and can be kept in shape by cutting back the spent flowers in the fall. The folks at Plant Select recommend planting blue sage with, among other things, penstemon, coreopsis, and creeping veronica.

Photos were taken at Idaho Botanical Garden in Boise, Idaho.

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Drought Tolerant Plants: Fernbush

The first of many plants to be profiled in this series on drought tolerant plants is Chamaebatiaria millefolium, known commonly as fernbush or desert sweet. Fernbush is a shrub that is found in most western U.S. states, generally in locations that are dry and rocky with sandy or gravelly soils.  However, it also occurs in sights with loam or clay loam soils, making it a plant that is not too finicky about soil types. It is found at a wide range of elevations (from 3,000 feet up to 11,000 feet) and in a wide variety of plant communities, including lodgepole pine subalpine forests, juniper-pinyon pine woodlands, mountain mahogany-oak scrublands, and sagebrush steppes. It is occasionally browsed by certain animals, but not enough to be considered an important food source. Instead, its major wildlife value is providing cover for birds, small mammals, and antelope.

Fernbush is by far one of my favorite shrubs. Its the leaves that make it so interesting. As the common name suggests, the leaves look just like little fern fronds, and considering that ferns tend to be associated with shady, moist environments, it seems strange to see a fern-like bush growing in full sun in a dry, rocky site. Alas, fernbush is not a fern, but instead a shrub with very cool leaves.

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Fernbush grows to about as wide as it does high (between 1-3 meters), and depending on where it is growing it is evergreen or semi-evergreen, dropping the older leaves from the lower portions of its branches during the winter. Its bark is smooth and russet or cinnamon-colored. Flowers appear in clusters at the tips of branches in mid to late summer and are small, white or cream colored, and rose-like with five petals.

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The fruit of fernbush is called a follicle and contains very small seeds, mere millimeters in size. The spent flower stalks are attractive in their own right and provide great winter interest. They can be pruned off in the spring in preparation for new flower stalks and to keep the plants looking good.

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Fernbush is very drought tolerant. Once its established, it needs very little (if any) supplemental water. It is likely that the leaves of fernbush give it this trait. They are small and finely divided, as well as being hairy and resinous. Physical adaptations such as these reduce water loss through transpiration, which helps the plant use available water more efficiently. Though not very commercially available, fernbush, with its unique appearance and late summer blooms, is a great addition to waterwise gardens and landscapes.

Fun Fact: Chamaebatiaria is a monotypic genus, meaning that it is a genus consisting of only one species. In this regard, Chamaebatiaria millefolium is a true rarity.

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Drought Tolerant Plants: An Introduction

Water is a precious natural resource and an essential element for life on earth. Demand for water increases dramatically as human population grows and fresh water sources become polluted. Awareness of our reliance on water is especially heightened during times of drought, like the one that California residents are currently experiencing. Some regions of the planet are inherently dry. The region where I live (Boise, Idaho) receives on average about 12 inches of precipitation annually. Compare that to a place like Pensacola, Florida which receives around 65 inches annually, or El Paso, Texas which is lucky to get around 8 inches of rain a year. So whether it is out of necessity (enduring a drought or living in a dry climate) or simply the desire to be a responsible citizen of planet earth, many people are choosing to incorporate more drought tolerant plants in their landscapes in an effort to conserve water.

In the early 1980’s, landscaping with drought tolerant plants was given the name xeriscaping by the Denver, Colorado water department. These days terms like water-wise gardening and water efficient landscaping seem to be more popular. The initial vision that many people may have of a landscape planted with water efficient plants is one filled with desert plants like cacti, yuccas, and other succulents along with drab shrubs like sagebrush. While landscapes like these can actually be quite attractive (see Plantasia Cactus Gardens), modern water-wise gardens do not have to be so cacti-centric. As interest in water efficient plants has grown in recent years, the horticulture industry has been busy introducing a wide variety of plants that are not only drought tolerant but are lush, green, and full of color.

Plantasia Cactus Gardens -Twin Falls, Idaho

Plantasia Cactus Gardens – Twin Falls, Idaho

Plants that live in regions with frequent or extended droughts are called xerophytes. They have developed a variety of mechanisms that allow them to survive and even thrive in these regions. Ecologists call these mechanisms strategies, or sets of coordinated adaptive traits. In future posts I intend to profile specific drought tolerant plants so that we can get to know them on a more individual basis. For now I will provide a brief overview of the strategies plants use to cope with low water environments.

-Alternate Photosynthetic Pathways: Conventional photosynthesis is inherently inefficient when temperatures are high and water availability is low. Plants that evolved in hot and/or dry environments have developed alternate photosynthetic pathways in order to overcome these inefficiencies. These alternate pathways involve utilizing a different protein to fix carbon, splitting the photosynthetic process into two separate cells, and collecting carbon dioxide at night then converting it to sugars during the day. Learn more about the different photosynthetic pathways here.

-Drought Avoidance: Many desert plants live most of their lives as seeds hanging out on the desert floor waiting for rain. These are seeds of short-lived annual plants that sprout and grow when the rainy season comes around. They flower and set seed and are gone by the time the dry season returns. Birdcage evening primrose (Oenothera deltoides) and desert sand verbena (Abronia villosa) are examples of these desert ephemerals.

-Drought Dormancy: Some desert trees and shrubs shed their leaves during dry periods, and then put out new leaves when rains return. This is called drought deciduous. Other desert plants live out the dry season as fleshy roots or underground stems, putting out foliage only when conditions are favorable. Arrowleaf balsamroot (Balsamorhiza sagitatta) is a good example of this; it spends much of the year as a taproot with little or no sign of its existence above ground.

Arrowleaf Balsamroot - Balsamorhiza sagittata

Arrowleaf Balsamroot – Balsamorhiza sagittata

-Physical Adaptations: Desert plants have many physical adaptations that allow them to survive in hot, dry climates. The thick, fleshy leaves of cacti and other succulents store water for future use. The roots of some desert plants are shallow but horizontally extensive in order to capture water more effectively when rains come. The roots of other desert plants extend deep into the ground, some (like the roots of mesquite, Prosopis spp.) even reach as deep as the water table. Palo verdes (Parkinsonia spp.) are drought deciduous trees or shrubs that have photosynthetic bark that can keep photosynthesizing even when leaves are not present. Other adaptations include small leaves, hairy leaves, dull colored leaves, and waxy leaves all of which help to reduce water loss and improve the efficiency of photosynthesis.

Drought tolerant sedums (Sedum spp.) with their shallow roots and succulent leaves are ideal for use on green roofs where temperatures are often high and water is limited.

Drought tolerant sedums (Sedum spp.) with their shallow roots and succulent leaves are ideal for use on green roofs where temperatures are often high and water is limited.

Learn more about how plants cope in low water environments from Arizona-Sonora Desert Museum.