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.
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.
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.
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.
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″.
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.
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
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
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
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.
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.
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.
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.
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.
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 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.
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.
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.)
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.
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.