State of Milkweed Seedstock Availability for Monarch Habitat Restoration

April 30, 2014By

A Preliminary Assessment

By: Gary Nabhan, Chip Taylor, Bonnie Harper-Lore, Laura L. Jackson, Eric Mader, Mark Fishbein, Sarina Jepson, Laura Lopez Hoffman and John Anderson 

 

Monarch Butterfly Laying Eggs on Milkweed

Monarch Butterfly Laying Eggs on Milkweed

 

According to several widely-cited refereed journal articles, monarch butterfly populations may have declined precipitously over the last decade due to a number of man-made and natural factors:

a.) dramatic reduction in milkweed densities on a hundred million or more acres of row crop farmlands due to intensified glyphosate use in weed management practices;
b.) fragmentation, degradation or conversion of wild lands habitat due to urban expansion, drought, water scarcity and climate change;
c.) conversion of 24 million acres from perennial vegetation to crops lands in the 5 years following the implementation of the ethanol mandate at the end of 2007 (including 11.2 million acres previously enrolled in the conservation reserve program);
d.) erratic weather during the last three breeding seasons; and
e.) continued degradation of the overwintering sites due to logging, climatic disruptions and poorly regulated tourism.

Whatever the drivers of the 90% monarch decline have been, our immediate goal is to restore habitats essential for monarch breeding and overwintering that may aid in at least an eight-fold population recovery over the next decade or less. These habitats will also benefit other pollinators, especially honeybees and native bees. To achieve such goals, we need

1) a target area of suitable, accessible habitat in the summer breeding grounds in the upper Midwest (Corn Belt) where most monarchs migrating to Mexico begin their lives;
2) access to and collaboration with private and public land managers who wish to cooperate on restoration of wildlife habitat for monarchs and other pollinators;
3) adequate supplies of the twenty most easily propagated milkweed species that monarchs use from that region;
4) matching of the most ecologically-appropriate provenance or ecotype of seed to the site;
5) seeding rate recommendations to establish ten to twenty milkweeds per acre amidst a mix of native wildflowers for forage and native perennial grasses for cover.
6) in highly managed public species, transplanting of 60-80 milkweed “plugs” into suitable conditions for survival at costs of $1.50 to $6.00 per plug;
7) protracted attention and extended funding for subsequent management of mowing, reduction or suspension of herbicides, tillage for control of herbicide-tolerant weeds, etc., so as not to diminish these recruited populations.
8) Training for CRP, highway, railroad and transmission line maintenance crews.

Our tentative assumption is that would take a minimum of 500 milkweed seeds sown per acre to be sufficient to establish a population of 10 to 20 milkweeds per acre to hold monarch populations through their periods of breeding, egg laying and metamorphosis period. These would be integrated into a seed mix with 30-40 native species – and if 50% of the mix would be perennial grasses, the cost per acre, now well above $350/acre, could potentially come down to $100 or less.

There are about 4000 seeds in an ounce or pure live seed for an easily propagated species like Asclepias syriaca, with a pound of seed being sufficient for sowing 128 acres. At that rate, our initiative would need a minimum of 3900 pounds of a species like Asclepias syriaca for milkweed and monarch recovery on 500,000 acres and a minimum of 7800 pounds for 1,000,000 acres.. Currently, Asclepias syriaca and A. tuberosa seed wholesales between $70 and $80 per pound, and retails at $160 to $300 per pound. With increased production that retail cost can probably be reduced to $140, and bulk seed purchased on a consistent basis could be produced by large scale operations in the native seed industry on a consignment basis with good provenance for each lot for as low as $60 a pound.

Assuming that a minimum of 7800 pounds of milkweeds seeds for pollinator seed mixes will eventually be needed annually just for conservation reserve lands, the annual cost of the milkweed seed alone (not including the other species in the seed mix) would be at least $1.2 million. Further, if the seed costs per acre are kept at $100-150, the overall costs of seeds alone would be $100-150 million for a million acres. The Tallgrass Prairie Center in Iowa, however, reminds us that true restoration costs, from seedbed preparation, mowing and maintenance, will be up above $500 per acre.

There are several sources of milkweed propagation material to ramp up habitat restoration to the even the million acre level (7800 pounds) within a matter of two to three years. Monarch Watch calculations suggest that we will need to be planting and establishing 5 to 10 million milkweeds a year just to keep up with current annual habitat losses that have not yet been curbed. Dr. Chip Taylor, the Monarch Watch Director, projects that the continuing annual loss of habitat due to be in excess of 1 million acres per year including only 1) conversion of CRP lands to croplands, and 2) exurban development converting croplands to housing developments.

 

Monarch Butterfly

 

It follows that to keep the monarch population from declining further, it will be necessary to focus first on offsetting these annual losses. If restoring milkweeds over a million acres per year is the goal, the question then becomes; what will be required to do so? What seed resources do we need, not only of milkweeds but of grasses and other nectar producing forbs. To get a sense of the capacity issues we need focus first on the availability of seeds of milkweeds and the possibility of scaling up the seed production capacity to meet the needs of such a program.

1. The dozens of large-scale commercial native seed companies already growing milkweeds across the United States—especially in the Upper Midwest (Corn Belt) where monarch summer breeding occurs.. This robust industry has decades of experience growing milkweeds and other forbs to support CRP clients and other Farm Bill conservation program participants.

An initial inquiry of just six of these native seed companies (for nursery and garden shop trade. For milkweed seed oil, and for CRP land seeding) revealed the following annual milkweed seed harvest volumes (for all milkweed species they grow):

a. 500 – 1,000 lbs/year from a Wisconsin producer
b. 400 – 600 lbs/year from an Indiana producer
c. Roughly 1,500 lbs/year from a Pennsylvania producer, and
d. Roughly 3,000 lbs/year from an Iowa producer.
e. Roughly 6000 lbs/year from a California producer, which currently has 18,000 to 20,000 lbs of seed in stock;
f. Roughly 2,700 lbs/year from a New York and Michigan producer, with over 6,500 lbs of seed currently in stock.

Collectively this 14,000 to 15,000 pound-weight of milkweed seed yield per year represents between 700,000,000 and 820,000,000 seeds annually produced by just these six companies. This volume should be more than sufficient for seeding CRP lands the next few years, if there are funds to purchase the milkweed seeds.

Mix it with native grass and bee forage seeds and pay restorationists to prepare, sow and maintain lands earmarked for habitat recovery. All of these companies further expressed the motivation and capacity to double or triple this seed production if market demand existed. Because these six companies are only a sample of the larger seed industry (see below) it should be recognized that annual milkweed seed production by this industry — and to a lesser degree transplant production– is potentially very large. In fact, each producer surveyed further made the point that these volumes currently meet market demand at their respective cost-of-production price points. They note that if there were more demand at the existing price, they could increase production and bring the price down through greater economies of scale.

The other obvious seed sources are as follows:

2. Seeds of Success, an interagency native seed collection program, is managed by BLM in collaboration with other federal agencies and partners. There are a total of 70 collections of 23 Asclepias species that were made between 2002 and 2013. Seeds of Success materials are being used for habitat restoration and could be available for use in monarch habitat restoration projects, especially on public lands managed by the BLM and Forest Service; however, SOS collecting teams get right of first refusal to use this seed overage.

3. Monarch Joint Venture-funded milkweed seed propagation projects, such as 8-9 pounds of seed grown out at the Tallgrass Prairie Center for distribution to Iowa Department of Transportation and other public lands managers.

4. Monarch Watch collaborations with private nurseries that provide 60,000 milkweed plugs for transplanting this year. Twenty pounds of swamp milkweed seeds have also been produced in collaboration with NRCS in Manhattan, KS. Several other groups affiliated with MonarchWatch, like Southwest Monarch Study, contract for plugs produced on consignment and guide the distribution of those plugs produced by contract nurseries such as Borderlands Restoration in Arizona.

5. Xerces Society collaborations with S & S Seed’s Hedgerow Farms, Native American Seed Company, etc that have produced seeds for sowing and establishment of a projected 1.75 million plants on tens of thousands of acres since 2010.

6. Ninety-seven or more commercial nurseries in 27 states listed on Monarch Watch’s Milkweed Market that sell transplantable milkweeds directly to (primarily urban) customers. These partially provide stock for the many Monarch Waystations being monitored by citizen scientists. We should seek out further collaboration with other nurserymen associated with AmericanHort, the January 2014 consolidation of the American Nursery & Landscape Association and OFA—The Association of Horticultural Professionals. They likely produce at least 250,000 to 300,000 transplantable milkweeds for retail sale at this point in time.

7. At least 67 private seed companies, some of which are associated with the American Seed Trade Association, which distribute seeds of at least 20 species of milkweeds now listed on the Xerces Society on-line Milkweed Seed Finder.

8. Botanical gardens and arboreta such as Chicago Botanical Garden which will distribute 10,000 milkweed seedlings for free to its members during National Pollinator Month in June, and which are coordinated through the American Public Gardens Association.

It is clear that there is considerable capacity to wield among these many potential partners, and their immensely talented and skilled horticulturists. There are also challenges. Milkweed seed is relatively expensive compared to native grasses and most other wildflowers which serve as effective bee forages, as noted above. However, depending on species and conditions, seed sowing survival rates to seedlings in the wild is far less than 0.5% and may be more like .01% to .005% to mature (second year) seed-bearing plants.

For transplant production, seed germination and establishment rates are much higher (around 80-94% for some lots of pure live seed), but vary significantly depending on species, and many other factors (seed age, storage conditions, etc.). In greenhouse plug production we have extremely high germination and establishment rates). Greenhouse production of milkweed plugs for transplanting can run anywhere from $1.50 to $5.00 per plant. And a study of the difficult-to-propagate purple milkweed (A. purpurascens) transplant success in Wisconsin that indicated of 21 plants surviving transplant shock, that only one third of them survived to the end of the second season, while five seedlings were recruited from the transplant’s seed bank over the same two years. However, Hedgerows Farms has recently had excellent success with seed production of purple milkweed and other, more difficult species. Reintroduction (for the recovery of monarchs, not necessarily for milkweed conservation per se) should therefore focus on the species with the best success for cultivation and transplantation.

The challenge will be to motivate these diverse sectors into a collective and complementary effort among private, non-profit and government players to achieve success over the long haul, not just for a year or two. We recommend the following strategies:

1. Have the USDA Farm Service Agency and NRCS include milkweed seed in all recommended seed mix recommendations for lands receiving funds for habitat recovery on CRP and EQIP project lands.
2. Provide nurseries and seed companies longer-term contracts to produce milkweeds.
3. Have corporate partners from the ag industry provide financial incentives for farmers in their networks to plant milkweeds in seed mixes within those on-farm habitats not immediately adjacent to row crops managed with glyphosate herbicides.
4. Where farmers are willing, include milkweeds in conservation filter strips planting adjacent to row crops where rotational crop and frequent tillage curb competition with crops themselves.
5. Encourage federal, state and private managers of highway roadsides, railroad, pipeline and transmission line rights-of way to include milkweed seeds in their seed mixes, and better time targeted mowing or herbicide use.
6. Build in support not only for seeding, but for maintenance and monitoring.

 

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Compiled by www.makewayformonarchs.org: a milkweed-butterfly recovery alliance of farmers, nurserymen, non-profits, universities, corporate partners, and faith-based communities. Contact gpnabhan@email.arizona.edu

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