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.

 

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2013: Year in Review

The start of a new year is traditionally a time to be reflective and resolute. Awkward Botany is now a year old, so it is in the spirit of a new year that I look back at a year of blogging and look forward to the years to come. I did not initially set any concrete goals for this blog nor do I plan to. I am passionate about plants, and I enjoy writing – hence the blog. Any attention this blog receives is not only welcome, but celebrated. It is one of life’s great joys to be able to share your passions with others.

In 2013 – surprisingly enough – I managed to publish 42 posts. These posts covered a wide range of topics, including plant profiles (mountain kittentails, Lewis’ mock orange, sundews), wildflower walks (Spring, June, September), the latest in plant science research (cushion plants, northern pitcher plants, plant communities of the Catalinas), a book and movie review (What a Plant Knows & What Plants Talk About), gardening tips (starting seeds indoors, assessing your soil, pruning rosemary), and so much more. The years to come will bring more of the same, plus whatever else comes to mind or is requested (leave a comment below).  More importantly, my plan is for past and future posts to be organized into pages according to major categories – such as botany, horticulture, and ecology – which will make it easier to find posts on the topics you are most interested in. Also, a new year brings a new tagline – “for the phyto-curious” – because it is a deep, abiding curiosity about plant life that really drives this blog.

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If you feel so inclined, please leave comments below and let me know what you like/dislike about the blog and/or tell me if you have any ideas for future posts. You can also leave comments and ask questions by visiting my Contact Page. Also, check out my twitter feed. Please be in touch, and let’s make 2014 our year!

For the plants, etc…

Growing Plants on the Moon

You’ve heard about gardening by the moon – an ancient approach to gardening based in folklore and superstition in which planting times are scheduled according to moon phases and astrological signs. Now, how about gardening on the moon! No pseudoscience necessary here. NASA scientists are currently on a mission to determine what it will take to grow plants on the moon in anticipation of setting up a permanent lunar base. After all, if we plan on sending people to the moon to live for long periods of time, we will need to figure out how to grow some food for them up there, right?

The first phase of the study will examine seed germination in a lunar environment and will observe seedlings during the first week or so of their lives. The seeds of cress, basil, and turnip have been selected as the first to be grown on the moon. However, these seeds will experience an environment that seeds of their kind (or any other kind for that matter) have never experienced before, because, unlike the earth, the moon has no atmosphere. Gravity on the moon is one sixth of what it is on earth; solar radiation is intense and direct; and fluctuations in temperature are extreme to put it lightly (about 150°F during the day to -150°F during the night). Oh, and there is one other important limitation: moon soil is dead. To start with, it’s virtually moisture-free. It also has no organic matter content, and it is void of life (compared to a tablespoon of earth soil, which is said to harbor about 50 billion microbes, many of which help sustain plant life).

NASA scientists have considered these limitations. That is why the first seeds on the moon will be grown in a lunar plant growth chamber. This growth chamber is designed to regulate temperature and light and will contain a filter paper inoculated with plant nutrients. Water will be stored inside the growth chamber and released when the chamber reaches the moon. There will be just enough water to induce germination and allow the plants to grow for 5-10 days. Plant growth will be monitored with an onboard camera and then compared to plants grown in a similar growth chamber on earth. Scientists will be observing how well the seeds germinate and grow in a low gravity, high radiation environment.

The first lunar plant growth chamber is scheduled to head for the moon in late 2015. It will be hitching a ride with the winners of the Google Lunar X-prize competition. Based on the results of the first phase of the experiment, following phases will observe sexual reproduction in a lunar environment. If sexual reproduction occurs, what effect will high levels of radiation have on subsequent generations? Only time will tell, so this will be an exciting project to monitor for years to come.

moon

photo credit: wikimedia commons

Do you want to help design future lunar plant growth chambers? Go here.

Consider yourself introduced…

Winter is in full-force (at least for us northern hemisphere dwellers), so it may seem like an odd time to start blogging about the plant world. Everything has gone dormant. All color is gone. From now until the first signs of spring, we mostly just have gray days and frozen ground to look forward to – little in the way of life. But a blog has got to start somewhere and at some point, right? Especially when it’s been brewing in the back of my skull for so long. So why not now? And why not with this measly post announcing its arrival?

Plants have been my passion for years now. They have also become my career. This general obsession I have with them has led me to start this narrowly (yet in some ways quite broadly, as you will see) focused blog. My intention is to write about plants…but what about them exactly? A quick brainstorming session yields this list of topic ideas for posts: the science of plants, rare and endangered plants, the wonders of plants, my favorite plants, tips on growing and caring for plants, places to go to see plants, the benefits of plants, plants in the news, etc. It turns out there is a lot to say about plants – they are an extremely fundamental part of our existence on earth after all. Without plants, we certainly would not be here.

Whether the things about plants that you enjoy most include the science, the cultivation, the recreation, or simply just the aesthetics, there really is something that anyone can relate to when it comes to the world of plants. This blog will attempt to explore all of those things from the perspective of an educated yet still amateur and awkward botanist. I will endeavor to be approachable, interesting, and entertaining. Please feel free to post any comments and suggestions that you may have along the way, and let’s all have a friendly conversation and enlightening experience as we explore the endlessly fascinating and wildly rich world that is plant life.

white oak