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12/24/20

Stressful Care of Limberlost Garden in High Duration Heat and a Pandemic

The Earth Arch with 75% weave of Aluminet on top, 50% weave below that, and high tunnel of hydrophobic row cover inside.

I built an arch shade house in March 2012 to help heat stressed squash survive fierce sunlight. That shade house got me thinking about the future of my garden. I could forecast problems already showing up under long-duration heat and drought. The arch shade structure seemed like it might be a good framework for experimenting with shade to control temperatures of the bed. I raised about $5000 in four rounds of crowdfunding using Kickstarter and Indiegogo platforms. I documented the creative process that produced ten arch variations that were part of a business development process using prototypes. Four of those prototypes were commissioned by supporters. The Earth Arch design took advantaged of insights gained from all of these experiments, as well as my own history with solar heated housing.

Summer of 2019 would put a different kind of stress on my forest garden and the Earth Arch (EA). It was time for Acacia and I to escape the summer heat. We planned a series of trips that would keep us out of the desert most of June, July and August. I employed a rotating triad of friends of friends to care for the food forest, the animals and the EA. The plants were dependent on hand watering, completed early in the morning. I was nervous about this plan, knowing much attention was needed. Its success was a roll of the dice.

The first week of June 2019 we got to see my granddaughter Hailey graduate high school in California. After that we flew to Seattle and got to spend two weeks with Bob and Donna of Rokalu farm on the Kitsap Peninsula. Bob and Donna host two young couples who lease land for organic gardens that feed the surrounding semi-rural population. Bob operates a thriving composting operation and drives a tractor that scares me half to death. It was great contrasting a small farm operation to my house garden.

The remainder of our 2019 July and August trip plans were upended by the health emergency of a family member. On our return to Tucson it was clear that our backups were not able to cover all that was needed. The garden made it through 3 weeks, but I had no solution for a several month absence. That experience led me to build a drip system that would lessen the stress of early morning waterings on housekeepers. Bob introduced me to hose-end water timers. I would bring that concept back to Tucson and spend a year implementing it, completing four zones in early July 2020. By March when the pandemic came along I completed two of four sectors of irrigation. Any plans for a summer get-away would soon be overwhelmed by the Covid-19 pandemic, and the one of the hottest summers on record. July 2020 was the hottest and 10th driest on record. On June 5, 2020 a lightning strike started the Bighorn Fire in the Catalina Mountains northwest of Tucson, Arizona on the Coronado National Forest. It would burn 119,978 acres, adding smoke and air quality concerns to the heat. It wouldn’t be 100% contained until July 23rd. This was followed my record all time heat in August, September and October. All told, 2020 was the 2nd warmest on record, setting a yearly record of 108 days of high temperatures 100˚ or hotter.

The Weavers Bamboo (Bambusa textilis) responded with robust growth to the switchfrom handwatering to drip irrigation

The Water Mystery

Hose-end water timers

Late in June in order to complete the drip irrigation I hired a contractor to install the third and fourth sectors of my hose end water timer system. It was completed July 2nd. When my water meter was read on August 5th, I was sent a bill for $742. The property typically uses about 25 to 30 CCF in July. This bill showed 60 CCF. We used an additional 30 CCF (One CCF = 748 gallons) which is 22,440 gallons. Keep in mind that I and the world around me were reeling from the stay at home orders due to the Covid-19 pandemic. Arizona was one of the states with the widest spread of the virus. I did my best to keep a distance from the workers, fearing for my own health. The result was that I had no real idea how many emitters were installed. My first impulse was to check the four toilets on the property. None showed any sign of leaking. My next impulse was to think the installation of the drip system was the problem. Yet I couldn’t see any evidence that a swimming pool’s worth of water was leaking, I was stumped. To make a long story short, after reading my meter and ruling out my household use and drip systems, I went back to a toilet in the separate studio building that had practically no use during the summer. This time I scrutinized the studio toilet carefully. Again there was no sign of it leaking when I flushed. I flushed it twice and the chain got hung up. I flushed it again after resetting the chain and the source of the leak was revealed. The handle did not return to the full down position, leaving the float valve hanging. That is how you lose 22, 440 gallons in a month – 748 gallons a day, 31 gallons an hour, half a gallon a minute, for 30 days.

Scott and Edna’s Arch Gets Restored

Scott looks at new gussets.

Scott and Edna’s Arch was completed in 2013. Scott and Edna love this garden structure. It sits on a steel plate over a culvert that diverts the monsoon streams of rainwater from above their house down a steep desert mountain hillside facing south. This location gets plenty of solar radiation as well as canyon whipped winds. A few years after construction they installed a mist system to help cool the interior. This structure used the original prototype arch design built with 2’x4″ lumber using exterior plywood gussets sealed with acrylic primer paint. The gussets sustained severe water damage from the mist system. In November and December 2020 I’ve replaced every plywood gusset with steel plate gussets and aluminum sheeting to cover the space where the plywood once was. Quarter inch concrete board lining the raised beds lacked a backing of plywood, and as the soil became wet and expanded, cracked the board in multiple places. The expansion also pushed side-walls outwards, forcing corners to spread. Fixing this damage involved placing new concrete board over the old, and waterproofing. This experience illustrates the value of learning from a prototype. I’d never built a raised bed structure out of 36″ high side walls before. Now that I’ve been back to repair the structure, I’ve learned alot about how it should be built.

The Writing Challenge

I finished my last commissioned arch for Rod and Carol in March 2017. The Earth Arch, which was started in December 2014, wasn’t completed until April 2018. The amount of finish work (sanding, sealing, priming, painting) for over 200 components was simply overwhelming. In the end it was an endeavor I couldn’t manage by myself. So I assessed the situation, knowing I was not going to risk taking on debt to grow Nurse Tree Arch as a business. I decided that the best way forward was to document the learning from the Nurse Tree Arch project, in writing – perhaps as a book. There is a good story here to be told about the challenge of home gardens under conditions of high-duration heat and drought. It is reasonable to ask the question: how will we continue to support gardens when the cost of water becomes 25% more expensive. Already the quality of potable water is problematic, due to chlorine disinfectant and high mineral contents. Given that I am using rainwater as much as is available, the record drought conditions means that I ran out of rainwater in June, and as of December when I write, I’ve got no more rainwater stored than I had in June.

In spite of tough conditions, the Nurse Tree Design project reveals that we can control heat and water loss through managed applications of shade, humidity containing row covers and fans moving the air. The research results are finding their way into writing. Stay tuned for more reporting of results on this blog site in 2021.

     

   

Winter into Spring is a rite of passage for this desert gardener. Some of our kale is in its second year with long stalks. Kale planted in the fall of 2018 is maturing, providing a reliable source of greens for breakfast eggs. Our household is beginning to realize the vision of a reliable year round source of greens. On February 2nd, in advance of a cold front bringing rain, I planted lettuces, stir fry greens, arugula and purslane. On February 22nd we had that rare snow event, put the Solexx covers on the Earth Arch, drawing the high tunnel row cover closed. This kept temperatures ten degrees warmer for peppers and tomatoes on the following night of below freezing temperatures. Plants in the hugelkultur beds outside got covered with old bed sheets.  Late in February, with the help of my granddaughter Hannah, we assembled a balloon mapping kit from Public Lab, a community where you can learn how to investigate environmental concerns. I wanted to get a clear view of the food forest canopy, as well as the four arch structures on the property. This proved to be possible by launching at sunrise, when winds are light. By April, golden beets, kale and dill are filling in the hugelkultur bed. Tomatoes and overwintered bell peppers are producing fruit. The next challenge will be the onset of high heat in June through September. We were fortunate to have a mild May, due to the jet stream being forced south by the high pressure over the arctic. Of course, this meant Alaska was much warmer than normal, and the midwest and southern states suffered damaging rains and winds.

 

This will catch my readers up on continued work, most of which has revolved around completion of the desert adapted solar greenhouse that I call the Earth Arch. A solar greenhouse is defined by Lindsey Schiller in the Year-Round Solar Greenhouse as “a structure that works with local climate and resources, using the sun as the predominant energy source not only for growth but for the structures  energy needs.” In this case I use the massive earthen walls surrounding the raised beds to keep bed temperature at around 80 degrees throughout the hot summer, where ground temps outside the arch easily reach 150˚ F. Rather than collect solar energy, the arch helps reflect it back into space using Aluminet shade cloth, while slowing transpiration and evaporation by draping hydrophobic (water restraining) row cover beneath the shade. Solexx glazing used in the winter is removed, or put in an awning position for maximum ventilation. A fan moves AC cooled air from an adjacent room through the south wall and into the Earth Arch. Together the temperature inside the Earth Arch is 94˚ F. – reliably 14 or 15 degrees cooler inside compared to temps outside (108˚ F. ).  Though not complete, I have installed an additional Ground to Air Heat Transfer (GAHT) system in the ground on the east flank of the Earth Arch. I will get it completed later in the year

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“Oversummered” tomato plants ready for second harvest in the Earth Arch

The Early Girl tomato plants made it through one of the hottest summers yet, and have set a second crop of about 70 fruit in the hottest fall ever. A 122 year old record fell as well, along with witnessing the latest ever 90+ degree in November, recorded on November 27th. The combination of Solexx, Aluminet and hydrophobic row cover helped control the effects of sunburn, evaporation and transpiration in raised beds on a south facing wall. Preparations are being made to complete the Solexx arch cover and install framing on the southern opening – as colder weather is on the horizon.

 

 

There are times in my life  a citizen scientist when I wonder if the prototype arch is robust enough to meet the challenge I set for it: making it possible to grow healthy vegetables through extreme conditions, working with the forces of evaporation and transpiration.

My philosophy is hopeful, akin to that of a practitioner of Aikido, expressing gratitude for the universe, our ancestors, fellow human beings, and the realm of nature. I sought out martial arts that stressed unarmed grappling techniques: Jujutsu first, and its derivative Aikido later. This was a response to my labored breathing, a consequence of my young life lived in fear of my father, and of bullies I encountered at school. The word Jujutsu can be broken down into two parts. “Ju” is a concept. The idea behind this meaning of Ju is “to be gentle”, “to give way”, “to yield”, “to blend”, “to move out of harm’s way”. “Jutsu” is the principle or “the action” part of Ju-Jutsu. In Japanese this word means science or art.[9]

The science and art of gardening in extreme heat and dry conditions involves grappling with the ways in which plants breath and lose moisture.

Rather than use fossil fuel power to create cool conditions, instead I look to use the natural exhalation of the plants to cool themselves. This is done by containing the rate of evaporation, and keeping the evaporative process close to the bodies of the plants. This has evolved into a layered approach that holds water close in the soil, holds the evaporation and transpiration of the water close to the ground, and employs shade cloth and row covers to hold temperatures down to or below 86˚ F. – that point where plants experience stress as the loss of water through transpiration exceeds the water available from the soil. These elements of heat, water, soil and breath (air) are blended with the gentle restrictions of the arch structure, just as the canopy of a tree provides similar conditions. The results I hoped for would be tested by the Summer of 2017 in Tucson, Arizona: a time of record setting heat.

Early on in my first prototype Nurse Tree Arch I used an Arduino controlled set of ground and air sensors taking both temperature and humidity readings. Today in the Earth Arch I use calibrated SensorPush cubes placed in sensor shields of my making, sometimes at just above ground level (and below understory canopy) and other Meade sensors at five feet in shaded patios near my arch structures. These are cross-referenced to National Weather Service temperature and humidity reported at Tucson’s Airport. I use a hand-held laser infrared thermometer for gathering surface soil temperatures.

In January, 2017 I completed the arch frame on the Earth Arch. I completed four Solexx panels for the west face of the arch, and in April I added a 50% weave of Aluminet shade cloth on the east face. Keep in mind that the Earth Arch extends out 8 feet from the south facing wall of a 1930’s era concrete block ranch garage and storage building. This face of the building receives direct sun for 8-9 hours a day. Outside temperatures recorded by the SensorPush instruments are higher than airport temps as a result.

On April 26th, 2017, with temperatures expected to reach 100˚ within a week, I ran an experiment using hydrophobic row cloth as a cover for a bed of Parris Island Cos lettuce, Oak Leaf Loose leaf lettuce, and Arugula. I was very pleased with the production of lettuce, given that desert adapted varieties of lettuce are typically stressed and bolting at this point in the season. On June 6th at 4 pm, SensorPush and Meade instruments measured air temperatures just above ground level under the row cover, outside the row cover but still inside the cover of Solexx and Aluminet, and outside the arch. I was surprised how much difference I got with the several layers of cover.

  • Outside at five feet under porch T = 106˚ H = 5%
  • Inside Earth Arch cover of Solexx (west) and 50% Aluminet (East) T = 95.6˚ H = 26%
  • Inside Earth Arch cover and under the hydrophobic row cover T = 90.1˚ H = 57.2%

That is a difference of 16˚ where it matters most – on and near the ground where the roots and plant leaves are. I am able to measure 5-8 degree differences in temperature attributable to the 50%-75% Aluminet. This suggests that the 16˚ difference is at least half a contribution of plant and soil evaporation cooling both mediums. In addition we know that removal of Biomass (the leaves and stems of living plants) raises temperatures due to both loss of shade and transpiration-based cooling in these hybrid green to screen houses (see blog report on June 28, 2013 spider-mite infestation that removed cucumber from south face of Prototype #1 – resulting in a 6˚-8˚ rise in ground temperatures the next day).

On June 14th, 2017 I placed an additional layer of 75% weave Aluminet over the entire arch. This was in preparation for advertised temperatures of 105˚ to 116˚ F. for the week to come. The month of June, 2017 was the hottest June on record. The average high of 105.3˚ was 5˚ above normal. The average temperature of 89.5 set the all-time record. Six days were 110˚ or higher, tied for 4th most in year. The 116˚ recorded on June 20th tied for 2nd hottest day ever, just one degree below the all time record of 117˚.

On June 20th, that 116˚ record for the day, The SensorPush and Meade instruments recorded air temperature and humidity levels inside and outside the Earth Arch at 3 pm.

  • Outside temperature at airport = 116˚
  • Outside at 3 feet over garden bed near to wall (a heat source) T= 120.6, H=9.9%
  • Inside Earth Arch covered with 75% Aluminet T=102.4˚ H=26.3% (a difference of 13.6˚ from the airport, and 18.2˚ from the SensorPush instrument next to the Cistern.)

On June 21st, with a recorded high at the airport of 115˚, I tested ground temperatures with a hand-held infrared thermometer. This is what I found:

  • Ground temp outside the Earth Arch = 158˚
  • Ground temp inside = 84˚-90˚ (difference from outside of 68˚ to 74˚)
  • Ground temp under row cover = 76˚ (difference from outside of 82˚)

What’s happening here?

I lack any instrumented data on soil moisture. What I do know is that I apply 15 gallons of water to the 40 square feet of soil in beds that are 24 inches deep over a 12 inch deep bed of cottonwood and other dead woods some harvested on site. These beds have non permeable earthcrete and ferroconcrete walls with loamy sand soil at the base. They create a heat bank, slow to heat during the day, and radiating heat at night. The beds are always moist at 6 inches and often at the surface at well. Tomatoes are deep rooting broad leafed plants that sweat profusely. I’ve chosen both hybrid (Early Girl and Summerset) and heirlooom varieties (Punta Banda, Nichols). The deep composted soil, along with a soil temperature that is maintained in the mid-80˚s, have encouraged rapid growth of biomass. The cover created by Solexx, which scatters the intense radiation of the afternoon sun is complemented by Aluminet, which reflects heat away from the beds. This protects the beneficial effects of the plant canopy and transpiration, which create an evaporative cooling environment, and the open weave of the covering allows breathing and discourages fungal and other wet-environment problems, while also reducing evaporation away from the beds.

 

Work on the Entry Arch for Rod and Carol began in October with a design review and client approvals. This second Entry Arch Prototype focused on sun and rain proofing the exterior grade plywood using boat builder techniques. We used Smiths expoxy sealer with multiple coats of primer and acrylic. Rod helped with the additional labor that this required, as well as time needed for curing. We suffered delays from illness, weather, and competing commitments. The fun part is now in process: assembling the finished components against the east wall of the house in Tucson, AZ. Soon the blazing sun and wickedly wet monsoon season will test this prototype. Time will tell the story.

7-17-17 R&CEntryArchFinalTouches

Build out of the Earth Arch continues, a new fan installed in the first prototype, data gathering continues,

and a client’s Entry Arch is assembled…

One of the design principles for Nurse Tree Design is to keep electrical use to a minimum in cooling and heating the arch. I’m working on an evaporative cooling system with a 12 volt variable speed fan powered by a deep discharge battery. The battery will be charged by a 100 Watt Polycrystalline Solar Panel. These pictures show the development process thus far. Next step will be to build the housing for the evaporative medium and polytube water delivery system, which will be connected to the drip irrigation system.

The journey of Dale’s arch from initiation to completion was long (September 27th 2015 proposal, April 25th 2016 completion). The design and creation of pattern files for CNC milling took until January to submit. Errors in the initial files further delayed assembly of the components. New standards for marine grade epoxy sealer and varnish required long lead times for procurement and additional time for applying the finishes. A new approach to the end cap framing was also time consuming. However, Dale is pleased with the result, as am I.

The Nurse Tree Entry Arch is designed to cover a raised bed outside a patio door. This prototype is placed outside the entrance to the original Nurse Tree Arch, acting as an annex that expands the space available for growing.