Marigolds and petunias which never require irrigation watering or weeding? Is It possible?
A beautiful marigold (Tagetes spp.) and petunia (Petunia spp.) in full bloom at the Douglas County Extension Service’s Community Garden located just west of the Philip S. Miller Library in Castle Rock is part of a plan to develop a revolutionary new way of raising flowers. Typically, such flowerbeds require watering 25-75 times a season and weeding 8-20 times at this 15″ annual rainfall site. But the goal of this test bed planted by Dan Wofford. Jr., owner of Western Polyacrylamide. Inc. (WPI). is total elimination of all irrigation watering and weeding for suitable annuals and perennials.
Wofford constructed the 60-square-foot bed on June 7, 1992, by working in six pounds of Hydrosource cross-linked polyacrylamide (a water-absorbing polymer) to a depth of six inches, and covering it with DeWitt PRO5 Weed Barrier. The water-absorbing polymer captures rainfall from summer monsoon-type rains, and the polyethylene weed barrier not only prevent weed growth, but also helps reduce moisture loss. To date no weeds have grown through the 3-4″ slits made in the fabric, but 2″ linear slits will further eliminate the possibility of weeds.
NOTE: DeWitt PRO5 Weed Barrier and DeWitt Sunbelt both have ultraviolet blockers, but DeWitt Weed Barrier is more expensive and more porous (meaning higher evaporation). These two products allow infiltration of water at the rate of 11 gallons per minute per square foot, but severely retard evaporation.
Wofford explained that success or failure of this NO-WATER flowerbed technology is solely dependent on the frequent, brief summer showers which sweep across Colorado’s Front Range delivering an average of one to two inches of rainfall each summer month. He hopes the rate of ten pounds of polymer per 100 square feet will absorb and store virtually all of the rain which falls on the bed. Because the higher levels of salt in most tapwater from wells or lakes are not generally present in rainwater. the performance of the polymer in the rainfed flowerbed is about 50% higher than with normal irrigation systems.
The bed received only a minimal watering when it was planted June 7th, and no rain since that date has been sufficient to fully charge the bed, which was designed to hold about four inches of extra water. Visual examination of the bed after each significant June and July rain by Wofford has led to his estimate that the polymer storage system in the bed has not yet been charged more than 75% to date.
While Wofford is generally optimistic about the Community Garden marigold and petunia test, he would not be surprised at a temporary failure of the system in August – as the plants get larger, evapotranspiration (ET) rates increase because of heat, and total rainfall drops slightly for the month.
If the bed suffers a single temporary failure, Wofford plans to exercise two options for subsequent designs: a.) increase the polymer rate by 30-50% and b.) work the polymer in to a depth of eight to ten inches instead of the six inches used in this test. He predicts the bed may perform better next year because it will go into the 1993 season fully charged with water from melting winter snows.
Balanced against increasing the rate of polymer is the fact that each type of plant appears to have an optimum hydrated polymer to soil ratio, generally in the 10-25% range. Pushing the percentage beyond the optimum range runs the risk of decreased plant growth and production. The marigolds in this test, for example, appear to be flourishing with the estimated thirty percent ratio of hydrated polymer to soil, while the petunias are doing well, but not spectacularly. A side benefit of these tests is obtaining more information about the optimum range for the type of plants tested.
Wofford explained that the idea for this “NO-WATER” flowerbed originated with a City of Westminster petunia / marigold median planting two years ago in which the Parks Department was able to stretch l-3-day watering intervals to 14-16 days. Last year a single petunia test using the technique (but without the DeWitt PRO5 Weed Barrier) was nearly destroyed by a nine-inch hailstorm on June 23, 1991. However, it recovered sufficiently to make us believe the “NO-WATER. NO-WEED” flowerbed concept would work – especially in conjunction with the DeWitt Weed Barrier. This year’s test, using the polymer and the weed barrier, combines the experience of the past two years.
Mike Bahm, Colorado State Forest Service, notes the DeWitt PRO5 Weed Barrier has been exposed directly to the sun on Colorado Living Snow Fence sites in Elbert County for seven years with little deterioration, and he suggests that the DeWitt material (which contains a UV blocker) should last for fifteen years or longer under bark mulch in such a flowerbed application. Wofford has some Hydrosource in a home garden which has gone through 5 1/2 years and six growing seasons with little loss of hydration capacity. Based on his estimate of an eight-to-ten-year lifespan for the polymer, and the higher expected lifespan of the polyethylene weed barrier, Wofford believes the two key raw materials in this type of NO-WATER, NO-WEED flowerbed should have a minimum life of eight to ten years.
Based on previous beds done at similar high rates of polymer-incorporation, Wofford believes that the test bed ground will not have to be broken in successive years. To replant each year a gardener will simply have to brush the old bark aside, locate the holes sliced into the polyethylene, and do the transplants again. Since the bed will be wet from spring snowmelt, only a minimal watering around the actual roots viii be necessary at planting time each year.
If any bed modification (such as, adding more polymer) prove necessary, the DeWitt PRO5 Weed Barrier can be removed, the polymer worked into the bed, and the weed barrier easily replaced.
Fertilizer requirements have not yet been worked out, but the Community Garden bed has been fertilized just once by sprinkling two tablespoons of Miracle-Gro over the bed and allowing the next rain to filter it down into the root system. Based on research at Pennsylvania State University and elsewhere, it is likely that fertilizer inputs can be cut by 50% into such beds because leaching is significantly reduced by the polymer.
Several other variations of the NO-WATER, NO-WEED flowerbed technology are being developed simultaneously.
Using 700 feet of large, polymer-loaded contours on a 7500-foot-elevation mountainside near Peyton, Colorado (35 miles southeast of Castle Rock), Kirk and Blanca Hopkins have planted a commercial raspberry (250 plants). blueberry (50), and blackberry (10) farm. These 310 bushes were planted on April 5, 1992, and all are doing well after four months without any supplemental irrigation. The goal is total reliance on rainfall capture. The biggest problem at the site has been how to cover the contours with DeWitt PRO5 Weed Barrier to cope with the heavy suckering of the raspberries and blackberries.
A second NO-WATER, NO-WEED blueberry planting with 36 plants, using a 4 lbs. per 100 sq. ft. rate of polymer in a bed under DeWitt PRO5 Weed Barrier has been planted by Dale Greenwood in Littleton.
In both of these tests, pH is lowered to acceptable levels through peat moss and/or pine needles – a necessary procedure in Colorado’s alkaline soils. Greenwood’s site is located on flat ground, and will not have the advantage of the hillside runoff at the Peyton site.
Dale Greenwood also has a 1200-square foot vegetable garden with thirty pounds Hydrosource per 1000 square feet, and DeWitt PRO5 Weed Barrier for weed, moisture and erosion control. The polymer rate is probably only 25% of the amount estimated to be needed for exploratory research into NO-WATER gardening, but Greenwood has observed dramatic decreases in watering and weeding requirements.
Another type of flower and vegetable bed is being developed in which rainwater from a house roof is collected by the gutter system and funneled into the plant bed for storage in polymer (incorporated at a high rate). Connie Ellefson, a civil engineer by profession, WPI employee, and co-author of the recently published Xeriscape Gardening (Macmillan Publishing Co., NY) points out that a one-quarter-inch rain on a l,500-square-foot roof captures 227 gallons of water which can be funneled into a polymer-loaded bed.
A number of local homeowners have expressed an interest building variations of such systems. And Wofford comments, “It may even be possible to raise vegetables without traditional tapwater irrigation with such water-capture systems. Rooftop catchment systems can deliver several hundred percent more rain than normally falls into a garden, and the polymer offers, for the first time, long-term, in-ground water storage at economical prices.” Wofford believes that underground storage of rainwater in Hydrosource is available for about $25 per 100 gallons of capacity.
The two major research areas needed to develop the NO-WATER/NO-WEED technology are:
a.) Determination of optimum hydrated polymer-to-soil ratios for various plants to attain maximum growth and/or flower/fruit production.
b.) Determination of evapotranspiration rates for various types of plants in different parts of the country. The water-collection systems must be over-engineered to prevent failures during unusually dry periods of the growing season.
Notes Ellefson, “The NO-WATER, NO-WEED concept of gardening appears to have great promise for areas of the country which can take advantage of frequent summer showers to recharge the water storage system.”
Western Polyacrylamide, Inc.
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Copyright 1992 by Daniel J. Wofford, Jr, and Dale Greenwood.