Pacific Crabapple Project
Native Apple Rootstock Research and Development
With support of the Western Sustainable Agriculture Research and Education (SARE) program, we are excited to announce the launch of an on-farm research project that could hold the promise of new rootstock options for apple production – including options with greater disease resistance, tolerance for wet soils, and climate adaptability! Watch this page for regular updates on this project.
(Photo by Gordon Leppig and Andrea Pickart)
Why We Need a Rootstock Revolution
October 29, 2017
Grafting apple trees onto specific rootstocks for size control, early bearing, and pest and disease resistance has been practiced for hundreds of years. Ultimately this practice was formalized in Europe during the mid-1800s with the selection of specific named (or more accurately, numbered) rootstock cultivars. By the 1970s and 80s apple rootstock development peaked with research programs in new regions including Russia and the United States (notably from the Cornell/USDA research station in Geneva, NY).
Despite this work, today the diversity of commercially available rootstocks remains
extremely limited. Practically speaking, the most widely available options are the Geneva selections, the Malling (England) rootstocks, or the Russian BUD rootstock series. This represents rootstocks selected at only 3 locations, optimized for 3 climates, 3 soil types, and common production challenges found in 3 regions.
While good efforts have been made to evaluate the adaptability of rootstocks beyond the original research stations where they were selected, additional screening usually takes place within regions where the apple industry is already well established (and where previous Geneva, Malling, and Russian rootstocks were already successful). This process does little to expand the range of rootstock options for new regions and new climates.
The result is that aspiring apple growers are often forced to artificially re-create optimal growing conditions for the rootstocks available to them. Irrigation systems, drain tile, even the placement of apple trees on elevated beds are just a few of the common ways farmers modify land to sustain non-locally adapted rootstocks.
We believe this approach is fundamentally flawed. Rather than altering land and water to meet the needs of a crop, an agro-ecological approach should call for planting crops that are already adapted to the local landscape and the local climate. This project was launched as with the intention of developing precisely such an option for the maritime Pacific Northwest.
Six species in the Malus genus are native to North America. In the western United States this includes Malus fusca (the Pacific crabapple), a species that is abundant in maritime climates extending from Alaska to Northern California. Unique among apple species, Malus fusca exhibits a wide-range of adaptability to common maritime site conditions: thriving in hydric and wetland soils (including saltwater estuaries), as well as in heavy clay soils, and poorly drained upland sites. It is considered a keystone native species in both high rainfall climates such as coastal mountain rainforests, and in lowland rainshadow environments such as the Puget Sound ‘banana belt’ where local rainfall averages may total less than 20 inches annually.
For at least two decades a handful of amateur pomologists and backyard orchardists in the Northwest have dabbled with the use of Malus fusca as a rootstock for table apple varieties. Anecdotally, these novelty grafts have been largely successful, apparently thriving even in conditions where traditional apple rootstocks do not, such as wet meadows. Unfortunately there is no actual research demonstrating how widely compatible Malus fusca is with various apple varieties.
Through this project we are establishing a replicated research block of Malus fusca rootstocks, testing more than two dozen apple varieties for grafting compatibility over a three-year period (with additional traits, such as suckering, evaluated in future years).
Continue to watch this page for more project details, updates, and extended information on the ecology of Malus fusca.
Orchard Block Site Preparation Begins
October 30, 2017
We’ve been working diligently at the farm to prep our research block planting area. The first step was some extensive brush hogging and mowing of an abandoned pasture area. In the weeks and months ahead we will be getting the deer fence installed, laying out the rows, and removing the existing vegetation (replacing it with a native grass/forb understory to support beneficial insects, pollinators, broader biodiversity).
Interestingly, there are several wild Malus fusca in the hedgerow around the planting area so we know the species is well adapted to the site. This removes one variable from the study, although we will maintain a control group of non-grafted Malus fusca trees in the orchard block which will allow us to compare the growth potential against the grafted trees.
Site Preparation Continues
December 20, 2017
Our BCS tractor has been putting in lots of hours prepping ground for the new orchard block. We don't have a huge range of implements but have been successful at prepping the site using an Italian-made R2 Rinaldi Stone Burying Plow. The tool is a reverse tiller (the blades spin in counter rotation to the tractor's direction of travel) with a fence of heavy gauge metal bars that separate rocks, vegetation, roots, thatch and other debris from the soil and pushes it all to the bottom of the plow pan -- leaving a smooth fluffy bed of soil that is rolled by the trailing packing wheel. It's definitely not a plow for ongoing use, but so far it has been good for breaking and prepping new ground.
We should note that we could just plant the new orchard block in the existing pasture vegetation except for a couple of things: The pasture is heavily invaded with wild rose, snowberry and other shrubs to the point that mowing alone wasn't giving us good control of the competing woody vegetation. We really needed a cleaner slate to give small transplanted apple trees a competitive edge. Second, we want to establish a higher quality/higher diversity understory for the orchard consisting of native grasses and native wildflowers such as camas. The aggressive non-native forage grasses dominating the pasture are a barrier to that goal. With the use of a native rootstock for the apple trees and a native seed mix for revegetating the understory, we hope to have a mostly native plant community with all of the associated benefits to soil health and soil biodiversity.
Scion Wood Selection
January 9, 2018
(Photo by Ed Scheenstra)
With gracious support from our technical advisor Dr. Carol Miles and her technician Ed Scheenstra at Washington State University's Northwest Research and Extension Center, we've been able to secure scion wood for the following varieties: Amere de Berthcourt, Blanc Mollet, De Bouteville, Brown Snout, Brown Thorn, Bulmer’s Norman, Cimetiere, Court Pendu Rose, Dabinett, Domaines, Frequin Rouge, Jouveaux, Medaille D’Or, Mettais, Michelin, Muscadet de Dieppe, Muscat de Bernay, Peau de Vache, Reine des Pommes, Vilberie, and Zabergau Reinette.
Additionally, we are expecting a second batch of scion varieties from Dr. Thomas Chao, the USDA's apple genetic resources horticulturist (sort of a librarian of apple varieties!). Those scion varieties include: Sangre de Toro, Raxao, Blanquina, Teorica, Xuanina, Vedialona, Coloradona, Solarina, De la Riega, Collaos, Perico, Maria Elena, Reineta do Caravia, Repinaldo do Liebana, Pepa, Peil de Sapa, Bedan des Parts, Manchurian, Wickson, Binet Rouge, Calville Blanc, Nehou, Dolgo, Kerry Pippin, and Irish Peach.
In the weeks ahead grafting will begin at a feverish pace when our shipment of 500 rootstocks arrive from the nursery. We are aiming to do 10 or 12 replicated grafts of most varieties, but in some cases limited scion availability will result in fewer grafts of some varieties.
Rootstock Trials – Year 1 Results
December 28, 2018
Somehow we survived a full year of this project. With 2018 behind us, there’s finally some time to process our thoughts, reflect back on the challenges and accomplishments, and to look ahead.
First, it’s worth noting that this project turned out to be a heck of a lot of work. We knew it would be, and yet, there were some unpredicted surprises along the way (aren’t there always):
- Malus fusca is tough wood. This matters when you start grafting hundreds of trees. The scions of domestic apple varieties are soft and cut easily with a grafting knife. The rootstocks on the other hand, especially those with some thick caliper take constant knife sharpening, and a lot of pressure. You cut yourself more, you get blisters, your thumbs get sore. It’s work.
- 2018 was bone dry for us. By our measure, the farm got less than 20 inches of rain this year (22 inches is normal – we’re in a mountain rain shadow). Keeping irrigation water on the trees was a constant task. At the peak of summer we would water for hours, then scratch the soil surface only to see things were still bone dry. Thirsty rabbits chewed through the irrigation lines. Pity the salmon. Pity the planet. We don’t need a hotter, drier climate. In the hedges, the wild Malus fusca trees seemed to be holding on, if there is any reassurance in that.
- Plastic is the new pariah. And rightfully so. Plastic tree guards crack and photodegrade faster than advertised, dropping shards onto the soil, blowing away in the wind. Shockingly, stupid plastic tree guards trap and kill little meadow song sparrows that land on the tree stakes, then fall into the tubes where they can’t spread their wings, and they die. What a stupid waste. There has to be a better solution to deploy on hundreds of trees that doesn’t kill, doesn’t pollute, and keeps the voles from gnawing the trees down to toothpicks. By the way, the voles do gnaw the trees down to toothpicks if you take the guards off. They do it as quickly as in a single night without the tree guards in place, despite an abundance of raptors and coyotes.
As for the grafting results, we’re still waiting to see how some varieties are performing. The “success” of some grafts is a bit more ambiguous in the first year, than one might predict—especially in a dry year where every tree is drought-stressed. That said, we do have some general trends and some specific results already in:
- General trend: Malus fusca likes to sucker. Seeing the tree in the wild, of course, this is obvious. We anticipated a lot of pruning to keep suckers down, and indeed that prediction is proving true. In some of the grafts, the suckers are quite a bit more vigorous and fast growing than the scions -- although there are some exceptions to this (see the comments on French varieties below).
- General trend: the pear grafts are all generally not looking great. We knew these were likely a long-shot and indeed, most of them are unhappy and the scions are clearly not thriving.
- More surprising, most of the crab varieties are also not thriving: Dolgo, Manchurian, and a few others. One might think these fellow Pacific rim crabapples might find a compatible match with Malus fusca? Not so. The success rates are low for us.
- The Spanish varieties are struggling. It’s hard to know why. The grafts don’t appear to be failures, but the scions are definitely not vigorous.
- Which leaves us with the French. Generally these varieties are doing great. Potentially the similarity in climate between our farm and Normandy is giving these varieties an advantage. Growth rates of the scion are typically vigorous (outgrowing the rootstock suckers), and the plants generally look exceptional.
So there’s a snapshot update of our 2018 grafting trials. In the year ahead we’ll post a full analysis of grafting success by variety. In the meantime, we’ll be expanding the orchard with more rootstocks, getting them in place for future grafting.
Thanks to the fellow orchardists who have reached out to compare notes. If you have experience with this great native tree, please connect with us and thanks for reading!
Photo directly above: Excellent 1-year scion growth on Bulmer's Norman, a French variety now widely grown in England!
Rootstock Trials – Year 2 Results!
December 18, 2019
Whew! Somehow we made it through our second year of orcharding with this excellent experiment.
A big thank you goes out to Western SARE which provided grant funding for this effort, and an additional thank you for the generous support of technical advisor, Dr. Carol Miles of Washington State University Department of Horticulture.
Here is an update of our findings, lessons-learned, and recommendations to anyone else interested in trying this:
Evaluating for two-year survivorship and successful graft-callousing, the following results were observed:
- Approximately 1/3 of the rootstocks failed, likely due to poor root structure and excessive root pruning (due to variable bare root quality of nursery stock), and due to a poor tolerance on the part of the Pacific crab for root disturbance and drying.
- Overall, Pacific crab produced successful grafts with 86% of the scion varieties.
- Varieties with a greater than 70% grafting success rate included: Bulmer’s Norman, Domaines, Frequin Rouge, Vilibrie, Dabinette, Blanquina, Bedan des Parts, Brown Snout, Ashmead’s Kernal, Normannischen Ciderbirne, Sangre de Toro, Nehou, Brown Thorn, and Amere de Berthencourt.
- Varieties with a greater than 50 to 70% grafting success rate included: De la Riega, Butt Pear, Muscat de Bernay, Zabereau Reinette, Barland Pear, Reine des Pommes, Thorn Pear, Cimitere, Raxao, Kerry Pippin, Pepa, Rieneta do Caravia, and Collaos.
- Varieties with a less than 50% grafting success rate included: Wickson Crab, Repinaldo do Liebana, Calville Blanc, Teorica, Perico, Court Pendu Rose, Medaille D’Or, Peil de Sapa, Hendre Huffcap Pear, Michelin, Coloradano, Manchurian Crab, Barnet Pear, Vedialona, Yellow Huffcap Pear, Peau de Vache, Blanc Mollet, Muscadet de Dieppe, Xuanina, De Bouteville, Mettais, and Jouveaux.
- Varieties with no grafting success rate included: Irish Peach, Binet Rouge, Maria Elena, Solarina, Dolgo Crab, Red Pear, Old Field Pear, and Taynton Squash Pear.
Based upon our observations, Pacific crab is initially compatible as a rootstock for most apple and pear varieties. Limited success, or failures with some varieties in this trial is likely representative of too few replicates of some varieties, and variable rootstock quality -- with some varieties being grafted onto rootstock batches of low quality.
Recommendations and Future Questions
Based upon our initial findings, the use of Pacific crab has the potential to:
- Provide a viable apple rootstock for wet and poorly drained locations in the Maritime Northwest, including eliminating the need to drain wet farm fields for crop production;
- Provide a fully fire blight-resistant rootstock – Malus fusca has documented polygenic resistance to fire blight;
- Foster a more ‘native’ and ecologically appropriate crop system, potentially supporting native soil biodiversity;
Despite these potential benefits, additional questions remain for future evaluation, including the longevity of grafting compatibility, dwarfing potential, bearing age of grafted trees, and consistency of these traits among a wild plant population.
Based on our findings we make the following initial recommendations on the use of Pacific crab as a rootstock plant:
- Due to potential root drying and disturbance sensitivity (as a wetland plant), container-grown nursery stock should be used over bare-root plants where available.
- Grafting should be conducted in the orchard (as opposed to bench grafting), after the rootstock plant has been successfully established.