Our Organic Technology – High Altitude Rhubarb

The first 150 mounds made with shovel and wheel barrow…We were younger then.

Perennial crops are seldom addressed in popular discourses on organic technology. Crop rotation, tilling and other aspects which dominant most organic technology have little relevance to perennial crops. Fruit orchards and grapes are examples of other perennial crops. Many farmers are in a somewhat unique situation, often dealing with at least one variable unique to their combination of crops and environment. This note outlines our situation and our unique method of organic agriculture. We anticipate healthy food production will be of growing strategic importance to our mutual existence on this plant. Therefore, we freely offer details of our technique, costs and income in hopes they will be of value to others in meeting that challenge.

rear-tine TroyBilt Horse tiller in action

Tilling in compost with an 11hp TroyBilt Horse

Our driving goals were: Be organic, reduce maintenance costs and effort and conserve water. The technique has proven extremely successful since 2002. I’m sure we’ve reinvented some wheels common in pre-modern agriculture but the combination of techniques may well be unique among current practices. This page will explain the motivations and details of that technique and the results it has produced. We’ve never used pesticides. We farm in Black Forest, CO, a semi-arid⁵ forest at 7750′ near the easternmost foothills of the Rocky Mountains. We farm in USDA zone 4. The forest stands in stark contrast to the surrounding high plains grassland. It exists due to an east-west ridge, the Palmer Divide, almost 3000′ higher than the plains to the north (Denver), and the south (Colorado Springs). The elevation provides for additional precipitation on the Divide. Precipitation, however, is inadequate for watering our crops.

Overview

Top soil Amended With Compost

We first implemented this technique in 2002. When all plants are at full maturity we expect yields of 7000 pounds of rhubarb per acre at a market price of $3.50 per pound, less for bulk sales. The market is 95% local, within a one-hour drive. People pick their own, even commercial customers. Our field is partitioned into plots containing from 25 to 80 rhubarb plants each. Horseradish is grown in isolated, small plots. This information refers to our technique for growing rhubarb. It is a till-once approach that results in zero top soil erosion, zero runoff and considerably improves the local soils. In 2016 we used about 10,000 gallons of water to produce 3000 lbs. of food and a couple hundred nursery plants.

The setup process is:

1) Native soil is intensively amended by tilling in mature compost. Our soils are shallow, arkosic loam. For rhubarb it is too shallow and deficient in nitrogen and organic material. It also varies greatly over small distances. Sandy one place and full of clay only 10′ away.

2) Each plot is surrounded by a walkway at least 6′ in width. A layer of landscaping fabric is laid to define this walkway. This is primarily a barrier to weeds.

Top soil mounded, ready to be surrounded in a sea of pine mulch.

3) Newly enriched soil is mounded to 18-36 inches, 4-8′ apart on center, depending on variety. Wider spacing seems a waste for smaller varieties but better accommodates equipment access early and late in the season. The top of the mounds are leveled to about 12″ diameter.

4) Mounds are surrounded in a sea of pine mulch a few inches higher than the mounds. It will compact and compost in place. The sea tapers down to the walkways, which only a few inches deep in mulch.
5) Mounds are topped with mature compost, formed into a water ring
6) One rhubarb root is planted in the center of each mound
7) Over time the mulch and mounds both settle to a minimum depth of 12″.

We grow perennial rhubarb. Pick-your-own sales dictates that the plants must be uncommonly well established before the first harvest. We cannot control how much of each plant is picked. Indeed, most plants are picked to the ground. This dictates that the plants be at least 4 years old before their first harvest. Otherwise, excessive picking would stunt their growth. Even under controlled conditions, perennial rhubarb should be at least 3 years old before commercial picking, 2 years in a garden where you can limit picking to 50% of the biomass for the first few years. This creates considerable barriers to entry for rhubarb farming. Few people can wait that long to see a return on their investment of time and money.

water rings and newly planted seedlings

This approach is labor and resource intensive in creation of new plots. It is economical in the maintenance and growing phases, which last decades. For example, a new plot was created in 2017. 40 cubic yards of mature compost and 210 cubic yards of mulch produced 80, 3′ high mounds 6′ apart with a large walkway/driveway partitioning the plot into two sections. It took about two man-weeks to prepare, virtually all done with a small tractor with a loader. Planting involves digging up mature plants and splitting the roots. A water ring is formed on the top of each mound from the compost applied in step 5 above. The roots are inserted in the middle of the rings and watered. The eventual yield from this plot will vary depending on the variety of rhubarb. We expect 2-3 tons annually once the plants are in situ 5 years. Ideally, this plot would have been watered and allowed to go fallow for the first year. Then another application of compost would have preceded formation of the mounds.

We do not practice animal husbandry and do not create our own compost. We also do not have a dump truck. The up-front cost of the 2017 plot of 80 plants was $2,400. That is for compost, mulch, landscaping fabric and staples.

garden kneeler

Annual Maintenance

1) Plots are watered 3-6 times per year. Our mature plants yield up to 90 lbs. of rhubarb annually. In dry conditions those plants receive 25 gallons of water with each watering. New plants and smaller varieties receive 2-10 gallons per watering. This is sufficient to reach the majority of the root zone, which extends down 12″ for most varieties. Watering is accomplished by filling the water rings. No water is applied to the surrounding mulch and all water is focused on the primary root zone of the plants. With only a few plots we accomplished this with hoses, watering plants while we removed seed heads and weeds. We are now experimenting with a system using drip hoses controlled by timers and remaining in place throughout the growing season. We fear drip tubes would be inadequate to reach the entire root zone whereas a hose, circling the entire plant just inside the water rings, will accomplish saturation similar to filling the water rings. The root balls of mature plants can be 3′ in diameter. Also, in our pick-your-own

Slime molds (fungus) growing on the mulch help compost the mulch in place.

environment typical drip tubes would be a maintenance problem and tripping hazard whereas we can easily remove the entire drip hose system for harvest and for winter storage…underground critters tend to gnaw on hoses left out under snow cover.) In our semi-arid climate a heavy rain is uncommon and would be 2″. Even in those conditions there is no runoff from the plots. All water is absorbed by the deep mulch and water rings.
2) Each fall the plants go dormant, dead debris is removed and the top of the mounds are covered in a 2″ layer of compost
3) Just as growth appears the compost is pulled back, by hand, to form a new water ring. A garden kneeler is very useful whenever one must get on their knees to weed or form or maintain water rings.
4) Plants grow about 2 months and are harvested at about 70% full growth

5) Every 5-7 years it is necessary to top off the mulch with another 3-5″ of mulch as it composts and settles in place.

Soil tests show healthy, organically rich soils at least 12″ deep. However, there is a consistent deficiency of nitrogen, common in most agricultural activities. Until 2017 the only additions to the soil was the annual, surface application of compost, which later forms the water ring around each plant. In 2017 late blizzards all but destroyed the crop and Organic Nitrogen was applied in the water and via foliar feeding to stimulate recovery. Our high yields up to that point have been paradoxical. How do the plants produce 90 lbs. of rhubarb in nitrogen-deficient soil? My guess, the nitrogen is leached from the water rings into

Dormant for the winter, the leaves must be removed/discarded and the plants covered in 2″ of compost.

the soil when the plants are watered and immediately used by the plants. I’d love to hear from anyone who has another idea. The intervening, deep mulch does indeed compost in place and receives only rain and snowfall for moisture. In plots started in 2002 the overburden of noncomposted mulch is only a few inches deep. Below that is soil which tests similar to the amended, native soil. We plan to plant a cover crop in those walkways, legumes that will enhance the nitrogen content of that soil.

Weeds are beginning to be a problem in some of the walkways. Though shallow, that mulch also composts in place and creates soil. After 15 years we have taken to removing those walkways, landscaping fabric and all, and replacing them with new walkways…a tractor with a loader makes short work of this.

Although the longevity of these beds has yet to be demonstrated, we anticipate these fields will produce commercially for at least 20-25 years. This is based on historical records of rhubarb farms in the 19th century. We may well be able to prolong the productivity of our beds. 19th century farmers did not have our ability to test and amend soils. Longevity, however, is also influenced by variety. We have experimented with a score of varieties. Some lasted only 8 years in the same soils as the ones that have lasted 15 years without slowing down.

Goals, Constraints, and Resources

dormant rhubarb plants covered in compost for winter

Dormant for winter and tucked away under a compost blanket

This section describes our local environment and the motivation for the aforementioned process. Published information on organic systems gives evidence that successful systems often exploit resources or opportunities somewhat unique to that farm. For example, most of the published techniques are unusually labor intensive and are practiced by families with working-age children. Many publications address only annual crops, such as wheat and corn. Some systems involve components of animal husbandry, exploiting expertise in those disciplines as well. We therefore started our quest for an organic system by identifying our local constraints and resources with attention to those unique to our situation.

Choice of Crop: Why rhubarb? This ideal crop revealed itself to us without much effort on our part. We had planted most typical U.S. food crops in our garden. Most proved unsuccessful due to some combination of cool nights, a short growing season, frequent mid-summer hail storms, underground critters or deer. Rhubarb, on the other hand, so enjoyed our situation we could almost hear it growing during the quiet nights!! Go figure. Perennial rhubarb, as opposed to annual plantings, was indicated as plant growth was limited by early hail and hot summers. Plants needed at least one full year of growth before producing commercially viable stalks. A perennial crop obviated crop rotation, which is of little value without alternate crops anyway. We considered an organic greenhouse but in 1997 that appeared to be an oxymoron and, regardless, would require too much water. The crop was to be perennial rhubarb.

A tractor speeds mound building, mulch/compost spreading, etc.

Our goals were few and simple: Generate enough money so we can afford to retire on the farm. We also wanted a healthy living and working environment, which lead to the goal to be 100% organic. We also hoped it would be fun. The results have exceeded our expectations.

Our constraints included: A small, part-time, aging labor force (both born in 1949); a scarcity of water; shallow, highly varied and always poor soils rich in weed seeds; a dense extant population of prairie vegetation; the certainty of invasion by noxious weeds when the soil is disturbed; a semi-arid climate; an omnipresent potato blight which had ended all commercial potato production on nearby land a few decades ago; a short growing season, zone 4; frequent summer and spring hail storms, sometimes up to 8″; and hostile winters. Our winters are a formidable problem for most perennial crops. They are defined by mostly cold, sometimes snowy days, a few sub-zero events, and a week or two of 60^o days in January! Perennials can wake up during the false spring only to die in the subsequent freezing temperatures. As you might imagine, farming is uncommon here.

Noteworthy resources included an inexpensive supply of high quality pine mulch, 14 hours of intense, daily sunlight throughout the growing season, high quality, mature compost and many years of gardening experience from longtime locals.

Pests: The fungus and insect known to threaten rhubarb appear in short supply locally. Wild dock is in the area and is a host to those pests. We kill it whenever we find it. Deer and other herbivores typically ignored our rhubarb until after the Black Forest Fire of 2013. Subsequent changes in the ecosystem drove them to decimate our crop beginning in 2016. They consume the toxic leaves, not the edible stalks! Underground critters do not consume the roots but they do burrow around them causing a winter desiccation. Still, we’ve not experienced any major loss from this problem. Additionally, rhubarb demonstrated itself to be a rare perennial which easily survived our weird winter conditions. All that remained was to reduce the typical water requirements and find an organic method to address the risks.

The inexpensive mulch offered a solution to the problems of water scarcity, organic feeding, and weed control. After several years of experimentation, we had found effective strategies for soil amendment and maintenance which addressed the remainder of our goals and constraints…low maintenance but high yield. Turns out we love working outdoors and producing food. Also, a pick-your-own sales strategy adds considerable fun to the whole operation. More details of the system follow.

History and Future Plans

Hail damage normally occurs after the main harvest.

Our operation began non-organically. We have never used pesticides but did use conventional fertilizers and herbicides in the years before we decided to go into commercial production. We applied RoundUp selectively to weeds near the crop and Weed-B-Gone was broadcast to the areas surrounding the plots. We also used general purpose vegetable fertilizers.

We normally have only one harvest due to hail and hot weather, though there is sometimes a small, second harvest. Hail can be guarded against with hail cloth but it has never done significant damage to the first harvest. It has often, however, completely destroyed the plants subsequent to the harvest, leaving the plots looking like we’re making rhubarb sauce rather than rhubarb plants. Heat, however, normally renders the second growth poor tasting so we’ve not worried about hail protection…knock on wood.

Establishing a bed or field with our approach requires considerable labor and cost. Subsequent maintenance, labor and costs, however, are very small. Water requirements are lower than traditional flood irrigation and weeds a few in contrast to other no-till organic operations. Pernicious for many crops, the odd bindweed is our most robust green adversary. Yet even bindweed is impotent against rhubarb as it generally gains size only after the harvest and can be manually controlled, though not eliminated. The few weeds unfortunate enough to start in our only surface soil, centered directly under the rhubarb plants, live an anemic existence and seldom even find the sun. Rhubarb creates a thick canopy. The exposed soil is at most 3 feet in diameter. Our larger plants have leaves up to 30 inches in diameter and the plants reach 8 feet in diameter, 50 inches high–A hostile environment for any green competitors, though welcome shelter for rabbits from the local eagles, owls, hawks and falcons.

We plan to experiment using orange oil and other organically approved substances to reduce the need for manual weeding. Mechanical control of weeds is not feasible among the mature plants. Likewise, removal of the mulch between plants would involve removing soil as well. We will first pull all visible weeds and then apply the oil as they attempt to reemerge. Orange oil and other approved remedies only kill the visible growth, they are not systemic. Roots will persist, particularly in the more annoying, noxious weeds. But persistent removal of the growth will eventually deplete the roots of energy and kill the plant, we hope.

Mold blooming

Our non-organic startup applies to only the first of our many plots. The soil required considerable amendment. It was overgrazed to the dirt by horses for years. Prior to that it had been high prairie grassland. Our native soil is “Kettle-Pring-Peyton association: Deep sandy loam and loamy sand soils on arkosic sandstones.”¹ The top soil was 1-2 inches thick and an unfriendly mix of clay and sand, amended with horse urine and compacted…just add straw and you’d have a parking lot of adobe brick.

The initial beds were prepared in 1995 in a non-organic manner. First, 3″ of compost was tilled into the top six inches of existing soil and this was further amended with sufficient high nitrogen fertilizer at concentrations of 10 times the recommended amount. Additional, non-composted pine chips were also tilled into the soil. The idea of the excessive nitrogen was twofold. It was to add fuel for a bacterial bloom to compost the wood chips and to kill any weeds extant in the soil. The beds were left fallow but were broadcast watered several times during the growing season. Weeds and grass germinated but were promptly killed by the high nitrogen concentration. The following year the Colorado Extension Service reported they had “never seen such ideal, rich soil but it was rather high in organic material.” For the next several years the soil and plantings, which included 12 rhubarb plants, were maintained in a non-organic manner…chemical fertilizers were used twice per year to produce harvests of a variety of crops suitable to our area, including beans, peas, squash, carrots, beets and garlic. There were no weeds. We experimented with numerous crops which failed in our climate. We must deal with a short growing season, cool nights and frequent hail storms.

Organic growing began in earnest in 2002. We stopped using chemical fertilizers. The first bed, our final experiment, was started with 35 plants from the roots of two of the original 10 plants. (Rhubarb can be propagated by seed or splitting the roots. Roots are recommended to ensure plants with character identical to the original plants. We do, however, experiment with seedlings as well. Indeed, it is difficult to import root-stock from foreign countries.) It was the prototype for all future beds. The unique aspect of our technique deals with soil preparation, composting and watering.

The Black Forest slash/mulch program provides residents the opportunity to drop off tree debris and pick up mulch for a nominal charge.

The mulch and maintenance: We make extensive use of pine mulch partly because it is available inexpensively. ($200/35 cubic yard, delivered). The mulch composts in place and thereby contributes to plant nutrition. Some of the composted nutrients undoubtedly leach into the soil around the plants and the lowest levels of mulch compost to directly provide a home for future root growth. We avoid mixing noncomposted mulch into the soil. This would bind nitrogen into the bacteria decomposing the mulch and deprive the plants of the same nitrogen until the bacteria’s demise. Nevertheless, soil and new compost from the mounds mix around the periphery of the mounds. This forms a very rich soil. Wetter environments would undoubtedly result in faster decomposition of the mulch. The mulch not only continues as a weed barrier and constant source of fresh compost but it also retains moisture in the soil, considerably decreasing the frequency and volume of water applications.

Slash piled and ready for mulching

After 14 years, we discovered weeds getting out of control where the mulch had significantly composted, particularly in the walkways where roots intruded from the surrounding field. Repeated toppings of mulch resulted in a weed-friendly layer of compost just beneath the surface mulch. Fortunately, the walkways are wide enough for a tractor. We scooped up the mulch, compost and landscaping fabric, spread it where it would be useful, and replaced it with new fabric and fresh mulch. Old fabric is discarded and the old mulch is spread elsewhere on the property, where weeds are of no concern.

Young man with armload of giant Victoria rhubarb

Phenomenal results: Victoria plants produce 90lbs. annually.

The mounds expand slowly over time. The mature Victoria mounds are now almost 2-3 feet in diameter, narrowing the path between plantings to 3-4′. Future Victoria plantings will be farther feet apart on center so the aisle between will accommodate a small tractor…anticipating weeding and other needs. The is due to the annual application of compost and creation of water rings. This is a good thing. It accommodates the natural expansion of the rhubarb root mass. It also contains and limits that expansion. Even out 15-year-old plants have never experienced the center root death reported by others. That is possibly due to our varieties but more likely because of the saturation watering technique and expansion-limiting effect of the mounds and surrounding sea of deep mulch. We let some sunflowers grow wild between the plants. Makes for a pretty field and they don’t start growing until after the harvest.

In years of normal precipitation we water 3 times per year, about 2/3 of the years since 2002. Our water comes from an aquifer 150′-450′ in depth. During drought years or under special circumstances we water 5-6 times per year. Special circumstances happened in 2017 when late blizzards destroyed the crop and we found it necessary to stimulate additional growth. The mature plants yield 90 lbs. of rhubarb at full growth and recieve 25 gallons at each watering. Younger plants and smaller varieties receive 10 gallons. We normally harvest when the plants are about two-thirds of their maximum size. This is to optimize quality. Rhubarb can get stringy as it matures. So we see harvest yields of about 60 lbs. per plant. (We have allowed a few plants to grow to maturity in order to measure total yield...That’s how we know the total potential.)

For close-up photos of the results see phases of growth.

We will gladly answer any inquiries and assist anyone in adopting a similar approach to organic growing. We also invite you to share your own experiences with us and to comment on the information contained herein. We welcome help. We are new to farming and there is much we do not know or understand. Please contact us with your questions and information.

1: “Soil Survey of El Paso County Area, Colorado”, 1961-1974, U.S. Department of Agriculture, Soil Conservation Service
2: “Pie Plant Culture”, by Fred S. Thompson, 1894, J. H. Yewdale & Sons, Co, Printers
3: Economic pressures and the rigors of organic certification have motivated us to establish new plots without adding nitrogen or allowing the ground to sit fallow for a year. We will first try planting the same year the field is amended in 2017
4: For larger varieties of rhubarb this spacing proved inadequate to provide room for a tractor between rows of mounds. Mounds expand as the plants mature.

5:“Semi-arid”: 13″ of rainfall-equivalent per year. Much of it snowfall in our area…of no value to our plants as it sublimates.