Container Garden Water-Saving Tips From a Soil Scientist

Over the last year or so I’ve noticed a lot of websites, blogs, etc. offering water-saving techniques for container gardening. Some tips are useful and scientifically sound, but some are just plain wrong. As a person with a Ph.D. in soil science (and a minor in water resources), this drives me crazy. Because of that, I wanted to put some tips out there that will actually work!

If you’re reading this blog post, it’s likely that you are a gardener that, like me, is either lazy or forgetful when it comes to watering. Despite my lack of a rigorous watering regime for my container plants, I still have a wide variety of beautiful specimens, mainly because I’ve found that these simple tips just plain work.

1. Pick the right plant

This is the biggest decision you’ll face for container gardening, and the best way to make it easy on yourself. Get to know your local landscape and floral supply store (a real one, not a department store gardening section). Workers there will likely have some good advice on what plants do well with very little water. I highly recommend sticking to “succulents“, which are generally adapted to dry climates with little rain. Some great examples are Aloe vera, Crassula ovata (Jade plant), Euphorbias,Schlumbergeras (Christmas cactus) and any other cactus species.

Schlumbergera, Source: Wikipedia Commons

Succulents are generally “CAM” plants, meaning that they open their “stomata” (pores) at night instead of the day so that they can adsorb CO2 with minimal water loss (as opposed to opening stomata during the day like most other plants). Succulents also tend to have waxy skins that further limit water loss, and store lots of water inside their stout leaves or stems. Be sure to investigate the plant thoroughly before you buy it to see what it’s lighting, watering, and space needs are or might be once it matures.

2. Choose the right container

When it comes to containers you generally have two choices – terracotta (clay) pots and plastic containers. Both have advantages and disadvantages when it comes to limiting how frequently you will need to water your container plants.

Source: Wikipedia Commons

The traditional terracotta clay pots are porous, meaning that water can, and does evaporate through the side of the pot, and not just through evaporation at the soil surface, or transpiration through the plant. This can be desirable for a few reasons. For one, the color of the pot will actually tell you how wet or dry the potting soil is, at that moment. The wetter the soil is, the darker the clay pot will be.  Some plants (succulent plants in particular) prefer moist but not wet conditions. Terracotta pots do a great job of preventing saturated soil in the bottom of the pot, which may damage plant roots. The downside of terracotta pots is that the plants will need to be watered more frequently than with plastic pots.

Plastic pots are not porous, so no evaporation occurs along the side of the pot. If you have plants that can tolerate wet conditions reasonably well, then using plastic pots is a great way to limit how frequently you need to water. If you don’t like the look of plastic pots, try placing the plastic pot on the inside of your container of choice.

3. Pick the right location for your pot

The less sun your plant is exposed to, the less water it will use. Shade reduces the temperature of the plant and soil, and thus the transpiration rates. Find out what sun/shade tolerances are of your plant of choice, and aim for something on the shadier side. Your plant may not grow as fast, but at least you won’t have to water it as much.

Source: Wikipedia Commons

Also, try to place the plant in a location where you will see it everyday. This will make it more likely that you will notice that the plant(s) needs watering. More than once I’ve forgotten to water a plant that I don’t see everyday. Picking the right location is a great way to make sure that won’t happen.

4. Use mulch


Every single drop of water that you add to your container goes one of three places. It can be transpired through the plant, evaporated from the soil, or drained out the bottom of the pot. Adding mulch to the soil surface reduces how much water is evaporated from the soil. This is because the mulch shades the soil from the sun, which keeps the temperature down, and in turn reduces evaporation from the soil. One thing to keep in mind is that adding mulch is equivalent to adding a carbon-rich, nutrient-poor substance to the soil. This isn’t a problem, but be sure to add some fertilizer at the same time that you add mulch so that the plants don’t become nutrient-limited.

5. Don’t worry about the potting soil

There are a lot of gimmicky potting soils out there claiming to work miracles in terms of retaining water. Honestly, there’s not much difference between potting soils. I’d recommend just buying the potting soil that is the cheapest. If you follow the first four tips, then the type of potting soil you buy won’t make much of a difference. If you really want to go cheap, use topsoil from a corner of your back yard. It will work the same, as long as you lime and fertilize as needed.



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Soil Science in the News: Eating Dirt

I came across an interesting story from NPR today, entitled “The Old And Mysterious Practice Of Eating Dirt, Revealed“. It’s about the ancient practice of eating soil (or mineral deposits), often called Geophagy. I’ve heard about this practice in a few of the soil science classes I’ve taken over the years, and in a “World Food Issues” class I took as an undergrad. It’s an interesting phenomenon, and from what I understand the cravings to eat soil, or kaolinite specifically (a phyllosilicate clay mineral) occur mostly in expecting mothers.

Source: The Augusta Chronicle

There is a documentary coming out soon that highlights this normally under-the-radar practice entitled “Eat White Dirt“. Here is the trailer for the film:

I’m looking forward to the documentary. If I ever see this Kaolin sold in a store, I just might have to try it out (for purely scientific purposes of course). Have you ever eaten “white dirt”? Tell me about your experiences in the comments.

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Top-Ranked Priority Research Questions for Soil Science in the 21st Century

In 2012 and 2013 I had the privilege to work with a fantastic group of graduate students on a project focused on identifying the top-ranked priority research questions for soil science in the 21st century. It was a great learning experience, and an opportunity for me to collaborate with fellow graduate students from all around the USA – most of which I had never met. The results from our work are now available to the public in the Soil Science Society of America Journal. Please follow that link and read it. I’m interested to know what you think. Let me know either in the comments section here, or tweet at my @ColbyDigsSoil.

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Citizen Soil Science: Cropland Capture

If you’re looking for a fun game for your mobile device but want to help science at the same time, then I know the app for you. “Cropland Capture” is a fun game designed to help classify areas of land on our planet as either cropland or not cropland. With over 7 billion people on the planet it is important that we accurately assess the resources available to feed a growing population. Even with the fanciest computer software, sometimes it’s difficult to accurately identify land uses without the human brain. The makers of Cropland Capture took this daunting task and made a great game out of it, as shown in this video:

The Cropland Capture app contributes data to the Geo-Wiki project, which has the following description on it’s website:

The Geo-Wiki Project is a global network of volunteers who wish to help improve the quality of global land cover maps. Since large differences occur between existing global land cover maps, current ecosystem and land-use science lacks crucial accurate data (e.g. to determine the potential of additional agricultural land available to grow crops in Africa). Volunteers are asked to review hotspot maps of global land cover disagreement and determine, based on what they actually see in Google Earth and their local knowledge, if the land cover maps are correct or incorrect. Their input is recorded in a database, along with uploaded photos, to be used in the future for the creation of a new and improved global land cover map.

The app is available in Google Play for Android devices, and iTunes for Apple devices. I’ve been playing with the Android app for a while now. It’s a lot of fun, and a great way to kill time. Try it out, and save the world!

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New Job!

Source: Wikipedia (c) University of Washington

Hello everyone,

As many of the followers of know, I’ve been working on my PhD in soil science at NC State for a while now. I’ll be finishing up in December, so I’ve been in the midst a thorough job search over the summer and the beginning of the fall semester. That job search is officially over now as I have accepted a position as a postdoctoral researcher in the University of Washington Civil and Environmental Engineering Department. I will be working with Dr. Rebecca “Becca” Neumann. I will be working on a project studying methane oxidation in the rhizosphere of wetland plants.

Methane is a greenhouse gas that is 20 times more effective at trapping heat in the atmosphere than CO2. Methane is produced in wetland soils. Plants can act as both a route for methane to move from the soil into the atmosphere, and as a way for oxygen to enter the soil and oxidize the methane in the rhizosphere (the zone of soil immediately surrounding roots). The objective is to put a solid number on the percentage of methane that’s oxidized in the rhizosphere in order to refine climate change models. We also want to predict how that number changes with different plant communities, and how those communities might change as the climate warms. The field site is about 40 minutes west of Fairbanks, Alaska. The field site has two types of wetlands – a bog and a fen. It is called the Bonanza Creek Long Term Ecological Research Station. I’ll be in Alaska for their growing season (June-September), and in Seattle the rest of the time working on laboratory experiments. 

The position is exactly the type of postdoctoral research position I was looking for in my job search, so I’m really happy I got it. My wife and I are both excited to see what the West Coast is like, and we now have an excuse to visit Alaska.

My start date is January 6, so my wife and I will be moving over the holidays. This new stage of my career will affect this blog a little bit. My first priority is to finish and defend my dissertation on time in December, so I won’t be able to add many blog posts between now and the end of the year. However, once I make the move I should have all sorts of interesting material and pictures from Alaska to post on this blog.

Thanks for stopping by,


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Citizen (Soil) Science: Predicting 17 Yr Cicada Arrival

Magicicada septendecim. Photo credit: Wikipedia Commons

The 17 year cicada (genus Magicicada) will emerge on the American east coast again this year in just a few days. As nymphs (grubs) they feed on the xylem fluid of deciduous tree roots. The xylem in plants is basically the tubes through which water and nutrients flow as it moves from the roots to the trunk, branches, and leaves. After staying in their nymph stage for such a long time, the emerged after 17 years as their adult form for four to six weeks. During this time their primary goal is reproduction. The buzzing sound you hear in the air during this time is their mating call as they desperately look for a mate. This genus of cicadas is one of the only insects that to follow such a lengthy and regular schedule.

Life cycle of the cicada. Photo credit: Wikipedia Commons

NPR’s affiliate, WNYC has a citizen science page called Radiolab. Radiolab has a great post regarding how you can track the emergence of the cicada. Cicadas emerge from the soil once the soil reaches a temperature of 64°F (18°C) eight inches (20 cm) below the surface.

If you go to Radiolab’s cicada website (, they have a spot in which you can enter the current temperature of the soil in your backyard. You can either measure it using a soil temperature thermometer you can purchase at a local garden center, or you can construct your own soil temperature monitor using some supplies available for purchase from your local Radioshack. Radiolab’s page says the parts all together cost about $80 total, and can be constructed in about 2 hours. Soil thermometers can be bought for around $10 to $20 at a garden supply store, but aren’t quit as fun as hacking your own soil thermometer.

Radiolab’s Soil Temperature Monitor

I thought this was a really fun and interesting citizen science project, mainly because it helps people get experience in soil physics, soil biology, entomology, and even engineering in a fun and exciting way. Let me know if you participate in this project by posting in the comments on this blog post page. If you take a picture of your project, send it to me and I’ll add it to the end of this post.

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SWCS: Time Well Spent

SWCSnewlogoRGB_2829BDA961538Tonight the Soil and Water Conservation Society at NCSU (the NCSU student chapter of the SWCS) held our 2013 officer elections. For the first time since 2006 (seven years) I am not an officer or board member of the SWCS, or any affiliated chapters, whatsoever. I’ve really enjoyed my time as a leader in this society, but it’s finally time to step back, let others have a chance to lead, and focus on the next step in my own career.

The SWCS is an international professional society focused on the science of soil and water conservation. It’s mission is “to foster the science and art of natural resource conservation.” As a sophomore at Iowa State University, I attended my very first meeting of the Soil and Water Conservation Club (the ISU student chapter), and was immediately elected as the secretary of our chapter. I later became the chapter president, then the student representative to the Iowa Chapter of the SWCS. In 2008 I was elected as the student director of the SWCS, and served on the board of the directors for the society. Once my second 1-year term came to an end, I turned my attention to founding a student chapter at North Carolina State University. We were chartered in 2010, at which time I was elected as the founding chapter president. After that I became the treasurer in 2011, and the secretary-treasurer in 2012 (we merged the secretary and treasurer officer positions). Tonight, as I said, we held our 2013 elections, and I will finally be handing the ropes to the next generation of SWCS leaders.

I’ve had an incredible time in all of these officer positions, and it’s helped me build my network, learn new skills, and especially develop my leadership abilities. I’ve performed community outreach through teaching people of all ages about soil science and water quality. I’ve also had the chance to travel to many of our society regional and annual meetings, visiting places like Tucson, AZ; St. Louis, MO, Detroit, MI, Okalahoma City, OK, and of course Ankeny, Iowa (where the SWCS is headquartered). Of all of these experiences, I value the friendships I’ve made through the society the most.

I plan to stay involved with the society in the future, likely as an adviser role to a student chapter (if I get a job in academia), as well as a role more focused on the science end of the society – publishing and reviewing papers for the Journal of Soil and Water Conservation (that is, if they request that of me).

Here’s a couple of pictures from my SWCS adventures:


Me teaching a little girl about hydrology, and water quality at ISU’s VEISHEA


Me with a Saguaro cacti during the Tucson, AZ SWCS annual meetings in 2009.


Me and my buddy Jerry Pearce at a Cardinals game during the 2010 SWCS annual meeting in St. Louis.


Some SWCS at NCSU members during our first ever rain barrel builds (we build and sell rain barrels for a fundraiser).


Me teaching FFA students about hydrology and water quality using the Iowa State Soil and Water Conservation Club’s groundwater flow model.

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