Manzanita, Arctostaphylos, a Genus Whose Time has Come: Advocating for a Plant

 

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Many Arctostaphylos, like these A. densiflora ‘Howard McMinn’ make admirable landscape plants on xeric sites. This is above Riverplace Marina on the east facing bank of the Willamette in nutrient poor, compacted fill. It shares the site with Compact Oregon Grape and a variety of local dry site natives, Mediterraneans and Californians.

Thirty years ago, when I first moved here to the Portland area from the Central Oregon High Desert country, very few people were growing Manzanita.  Those plants that you did see were local natives that you had to search out, remanent populations of widely scattered stands, in western Oregon, in the Cascades, parts of the Gorge and Siskiyous or on old stabilized dunes above the beach, e.g., near Manzanita.  They were mostly ignored in the trade, barely recognized by anyone other than those in the Northwest native plant societies and hikers who would go out on forays botanizing. When I still lived in Bend, I would occasionally order dry-land native plants, like Cercocarpus, that could be seen in the Ochocos, from Forest Farm in southern Oregon.  My first two horticulture books, other than the many vegetable growing guides I bought from Rodale Press and Steve Solomon’s guide, were the Sunset Western Garden Guide and Arthur Kruckberg’s, “Gardening with Native Plants of the Pacific Northwest”…I went through them over and over again.  In the small space Kruckberg devoted to Manzanita he wrote, in the first paragraph, “Only Arctostaphylos uva-ursi…, A. nevadensis…and possibly A. patula are hardy in colder areas.”  Because I lived in one of these ‘colder areas’ this stayed with me, effecting my view of the genus.  I’ve already posted on A. patula, of it growing in Central Oregon, the eastern slopes of the Cascades and as a specimen outside of our breakfast window in my childhood home.  Other than A. columbiana, a denizen more of the western Cascade slopes and the high ground of the Coast Range, Kruckberg barely mentions the other species and forms…of which there are argued to be between 50 and 100, primarily in California and  southern Oregon.  

In my early years working in the trade here in the Portland area, Kinnickinnick, Arctostaphylos uva-ursi, was used everywhere, and still is.  In fact it has been over used, often planted in single species masses on sites where it quickly thins out and shares space with locally dominant weeds on soils maybe too rich, too moist and incurring too much foot traffic.  People often forget that native plants seen to dominate in situ does not automatically translate to our created landscapes.  Natural sites are the result of thousands of years of selection and the deposition of probably millions of seeds, creeping stems, etc. of local members of the plant community.  They weren’t ‘planted’.  They happen, or not, over time.  They are ideals and cannot necessarily be willfully created by us.  This kind of experience made a lasting impression on me as well.

While working in Parks, as I did over the years, programs developed to re-create native landscapes in an effort to provide better habitat for our dwindling and locally threatened wildlife populations.  This was happening more broadly on public lands as well as on large mitigation projects where property owners were charged with offsetting the damage their development would impose on the landscape.  Riparian areas, wetlands and uplands were all included.  Nurseries began producing the large numbers of the needed native plants for these projects that the industry had previously been producing in much smaller numbers for collectors and homeowners who  were looking for a relatively small number.  The nursery industry stepped up applying their production methods.

Arctostaphylos columbiana was a plant of choice on many of upland projects…and it’s use proved to be a struggle.  While it seemed to be an obvious choice when examining native sites, it was difficult on these created sites to establish and grow on this species.  Nurseries would produce them, crews would plant them and those charged with their maintenance would watch them suffer and decline, sometimes quite rapidly, literally ‘collapsing’.  It proved to be intolerant of summer overhead irrigation the moisture and warm temperatures being ideal for fungal diseases that are fatal to most plants in the genus.  This is the way things stood.

Manzanitas did develop a few champions locally here in Portland.  Sean Hogan, (dedicates a few pages in his wonderful book, Trees for all Seasons: Broadleaved Evergreens for Temperate Climates, to the more garden adapted larger growers while doing the same for many other genera.) with local roots, of Cistus Design Nursery and a little later, Paul Bonine, (read Paul’s article in Pacific Horticulture) from the Eugene area, teaming up with Greg Shepherd to form Xera Plants, worked hard to broaden the palette of plants available  to local NW gardeners while consistently making efforts to increase their use in the industry.  Among these plants have been the iconic Manzanitas almost all of which can only be found on upland sites in a band along our North American west coast.  The majority of this area is botanically known as the California Floristic Province (Floristic Province, Regions and Kingdoms are defined by their shared flora and contain species that are endemic, occurring no where else in the world.) which extends up into southwestern Oregon.  A handful can be found north and east of this region, while only one, A. uva ursi, is more broadly northern circumboreal.  Much work has been done combing through landscapes like Oregon’s Siskiyous to find forms that might prove dependable here in Portland and the lower elevation areas west of the Cascades.  The thinking being that plants from higher elevation southern sites might prove more hardy in more northerly locations.  This has often been proven out for many other genera.

So, early on in their efforts this included species like A. viscida, A. glandulosa and A. hispidula in addition to our local A. columbianaA. patula, that I grew up with, had seemed to be intolerant of growing conditions west of the Cascades.  Still, this group gives us some choices, more when you include the various hybrids of these that naturally occur when populations overlap.  There have been many surprises along the way, particularly plants from much further south that have proven to grow admirably here in the much wetter, and often colder, Willamette Valley.

Several of these species have ranges that overlap and can be found in mixed populations.  Sean has found this to be the case here in the Siskiyous and more locally at places like our own Mt. Hood, where he has found natural hybrids of A. columbiana x A. patula as well as others that in include A. nevadensis, or Pinemat Manzanita.  Not only do these share a mix of physical characteristics, their performance and site requirements do as well, in unexpected if not promising ways, in some cases giving us cause to believe that these hybrids may be better ‘garden’ plants for us here on the West side than either of their ‘parents’ might suggest.  Such hybrid swarms have been found in other mixed populations, and had cuttings collected, stuck and rooted, awaiting testing in the ground.  Sean has been searching for a site large enough to contain and test his babies where they can be monitored over the long term.

I first planted A. densiflora ‘Howard McMinn’ in ’00 on a short steep pitch of poor fill soil next to the lower parking lot at Dunaway Park.  They did too well, relatively quickly outgrowing their space and crowding the sidewalk.  They were squeezed on the other side by the more vigorous Ceanothus thyrsiflorus ‘Victoria’, and thus so limited were, sadly, but necessarily, removed.  I later planted them along the Riverplace Esplanade on the Willamette, further away, again in poor, mineral fill, well above the normal high water level.  While slow, they have proven to be tough growers.  It is interesting to note that the species is close to extinction within its natural territory a few miles west of Santa Rosa, California.  We can view the planting of such plants as a conservation effort.  These are handsome plants of great aesthetic value.  Planting them is not a sacrifice.

It is sad and all too common that Manzanita are still being bulldozed in preparation for the building of more housing across much of their California range.  At some point, our society is going to have to address this issue if we, along with the world, are to survive.  This is an all too common plight for Genus Arctostaphylos as many of its remaining populations are limited to very small areas.  It reminds me of the several hundred Rhododendron species in China many of which are confined to a single, small, remote valley, or ravine, in its southern mountains.

A. patula frequently follow fires and harvesting in forests such as in Oregon’s Lodgepole and Ponderosa areas.  A. columbiana, difficult to establish where we may want it, often fills in acres of exposed land within its normal range.  Foresters consider their removal as necessary to timber production.  Their thicket forming habit threatens to shade out tree seedlings and ‘robs’ young trees of available water and nutrients, or so the thinking goes.  As in much of California some of these area are subject to ‘development’ as well,  particularly around towns and small urban areas like Bend.

Growers like Paul, Greg and Sean have refined their techniques for propagating and growing these on in pots for the trade.  Still there are many of these that will, in Paul’s words, very much remain wild, because of difficulties growing them on to salable size and/or their intolerance of summer irrigation.  Many of these struggle in pots, likely because pot culture requires that they be routinely watered during our warm summer, fungus prone, months, and they die.  Part of this is because customers tend to want larger plants giving them a more full and ‘mature’ landscape immediately.  They, we my friends, are often unwilling to buy small plants.  The reality is that they perform better planted out in the ground establishing more quickly and attaining larger size than a plant purchased in a larger size.  If nurseries could move their stock more quickly, selling smaller pots, there would be more species and selections available.  Many gardeners, especially novices, don’t trust that their ‘babies’ will survive much better if the hose is kept away.  This adds to the difficulty in marketing Manzanitas.

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This A. pajaroense ‘Warren Roberts’ is planted on the bank next to the ramp going to Riverplace Marina on the Willamette. Next to it, by the vented green ‘box’, was an Arbutus menziesii that was established and doing well, untill the irrigation system was inadvertantly turned on. It collapsed quickly. This Manzanita and others nearby, including A. ‘Sunset’, hardly seemed to notice. I wouldn’t recommend the practice. Two Arbutus arizonica also perished.

Trying to sell plants that die when treated like other ‘normal’ garden plants can make it more difficult to sell them.  Nurseries cannot afford to dedicate their space and efforts to growing product that doesn’t sell.  One strategy then is to promote only those plants with some tolerance to summer irrigation eliminating most species and cultivars.  Another would be to sell all Manzanitas as locally intolerant of summer irrigation.  Many of us tend to ‘lump’ plants of a particular genus together and initially treat them all the same.  This is not always safe to do.  I killed several Salvia species by treating them as if they were mediterranean finding out only belatedly that some come from summer wet areas.

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The partners in crime in the Manzanita plot at NWES. From left, myself, Mark Wilson, Eric Van Dyke and John Long (Steve Morgan behind the lens). Courtesy Steve Morgan

More recently, Neil Bell, down at the North Willamette Experiment Station (NWES), took a road trip, along with Xera’s Paul Bonine, to a variety of nurseries and California Botanical Gardens bringing back plant material and then added more of Sean Hogan’s selections to total 75 species and cultivars to plant out in the ground as a test.  If you visit the NWES site you will immediately notice the relative flatness of the land and test plots.  No slope, no raised beds equals no surface runoff.  The soil is Latourelle Loam, a common type in the Willamette Valley, nutrient rich and relatively fine textured, much like the soil across much of inner SE Portland where I live.  On a recent visit on a cool, rainy February morning, myself and a group of Manzanita-philes walked the test plot.  It had been planted out in fall of 2011.  There were significant blanks where plants had died.  The remaining plants displayed a vigor  that, in several cases, was startling to us given the soil conditions and their location here so far north from their native homes.

Many of you with some history of perusing catalogs for Arctostaphylos will be a little surprised at the soil conditions these plants were grown in at NWES.  Most descriptions emphasize drainage, as in good or excellent, not what comes to mind with Willamette Valley Latourelle loam.  Bell was doing a ‘real world’ test knowing that most gardeners, are not going to amend their soil with significant grit, berm it or replace it.  They are going to simply plant them.  His test then would ‘favor’ the toughest plants.  What we are finding on other sites as well is that many Manzanita are tougher than we thought when it comes to soil conditions, as long as we remember to strictly limit or eliminate the summer watering of plants.  One will also notice at NWES that no gravel mulch was used, a practice often recommended to reduce splashing by winter rains.  The impact of rain drops on bare soil dislodges and carries soil particles and fungal spores into the air and onto the leaves, often resulting in fungal spotting of the foliage which, in some cases, can go beyond an aesthetic issue to compromising the health and vigor of the plant.

From a NWES document explaining the initial planting:

Four plants of each cultivar or selection were planted in a completely randomized design with plants separated within the row by 5’. Plants were hand-watered at planting and were then overhead watered until reliable rainfall began in October. After this time, no further supplemental water or fertilizer was applied to the planting. In addition, fungicides, insecticides or other pesticides were not used at any time to control diseases or pests, and no pruning was done to the plants. The goal is to assess landscape performance in a “low-input” system.

From a NWES document presenting the evaluations after a 2013 significant cold event.table_Arctostaphylos_damage copy

Unlike the previous two winters, which had seen very mild conditions which had caused no visible damage to the various cultivars in the evaluation, the weather turned sharply cold in western Oregon in early December, 2013. Low temperatures at the North Willamette Research and Extension Center in Aurora dropped to 10°F on Dec 8th and 11°F on December 9th.  Prior to this there had been numerous nights in late November where temperatures dropped into the high to mid-twenties  and given this, and the occurrence of the two cold nights in the middle of the dormant period, as well as the fact that the plants were now well-established, it provided a legitimate opportunity to assess comparative hardiness of the cultivars in the evaluation. A visual estimate of damage to the plants was done on January 17th, 2014, 5 weeks after the cold event. Weather during the period after the cold event had been fairly mild, which allowed for good symptom development. Plants were evaluated on a 1-5 scale, with 1 equaling no damage; 2 equaling minor foliar discoloration or damage; 3 equaling leaf or stem injury to outer 30% of the canopy; 4 equaling leaf or stem damage to outer 60% of the canopy; and 5 equaling damage to the leaves or stems on the entire plant.

Those of us who garden here and watch the seasonal cycles of our local weather will note that the pattern that was described above is typical for our area: mild then getting slammed for a week or so between mid November and early December, followed by mild until another week of cold between Christmas time and a week or so into January followed by mild for the remaining winter.  Historically, yes, we can have other cold periods, but we’re talking ‘normal’ here.  Anyone more interested in this should read Paul Bonine’s Xera Blog.  His writing on the topic is concise and his interpretation, for the non-meteorologically inclined, I found very helpful.

It would be good to see a more recent evaluation because there appeared to be a few surprises, to us, that looked relatively vigorous, particularly A. rainbowensis and A. refugioensis, which in the evaluation suffered significant damage, yet looked surprisingly good to us on our visit.   A. refugioensis calls home the coastal facing mountains just north of Santa Barbara, and A. rainbowensis, from Agua Tibia Mountain west to the Santa Margarita Mountains in San Diego county.  The performance of such plants suggest an adaptability that goes well beyond what one might expect.  My own experience growing A. viscida ‘Sweet Adinah’, a selection from the Siskiyou Mtns. of a species that extends down to the south end of the Sierra Nevada and A. rudis, that scored a 3.0, from a mesa and coastal hills around Santa Maria and Solvang, A bakeri ‘Louis Edmonds’, the species of which comes from the coastal mountains just west of Santa Rosa, all further corroborate the idea that this genus contains much promise as landscape plants in our area, as long as their specific soil conditions are kept in mind, specifically low organic content and an avoidance of summer irrigation.

It is also interesting to note on the performance evaluations that there are several hybrids that out perform either one of the parents, their performance and durability exceeding either hybrid parent.  The separate parents, A. patula and A. columbiana,  in these selections and hybrids can combine into plants with unique genetic expression in these forms that give them a ‘durability’ that allows them to perform for us in the valley.

Other plants like A. pajaroensis ‘Warren Roberts’, a selection from a species restricted to the Pajaro Valley near Monterey Bay, is an amazingly tough and beautiful selection here.  This plant has proven out for me where I’ve planted it in downtown Portland and at my home.  Other selections are available including A. p. ‘Myrtle Wolf’ which is purportedly more cold hardy.  It makes me wonder if the many small scattered enclaves of Manzanita in California have been trapped on receding ‘islands’ in a ‘sea’ of rising heat and drought, a fate they seem to share with many species native to the Madera Sky Islands in southern Arizona and northern Mexico, where species are slowly ‘climbing’ the mountains to find the cooler temperatures and moisture, while literally running out of real estate as they climb.  Some ecologist worry that it won’t be long before species are lost from these scattered mountaintops and the whole region.  Between this and the devastation of continuing development the future would seem dim across many of these species’ home ranges.

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A. hookeri ‘Ken Taylor’ 19580, I think this is what we decided this one was (most had their labels missing). The specie’s natural range is limited to the hills east of Monterrey Bay around Prunedale toward Salinas (my birth town). It earned a 2.0 rating and here is very clean showing some weed smothering density.

Brought here to western Oregon these plants may find new life.  The shrinking California gene pools and the narrow genetic material within the selections we have may work against their long term survival here.  A wide gene pool assures a healthy population.  Planting these out in our landscapes where they grow on undisturbed over the longer term locally offers these plants some hope for their continuation.  In a mixed planting of Manzanitas, their promiscuous nature and their proclivity to cross, may, in the long run help assure that the genus survives.  What ‘testing’ that has been done indicates that many of these may be stellar performers in many of our very urbanized landscapes as well as worthy of trying out on larger ‘reveg’ sites.  They are uniquely and may be, fortunately for us, well adapted to xeric sites, a particularly promising characteristic as we look ahead to both a warming climate and a relative scarcity of water as our own population and demand for it increases.

Growers like Cistus and Xera, while they love these plants, are businesses…they can’t afford to dedicate a lot of time and space to plants that won’t perform for their customers and clients.  Some of these will make it into their production schedules only in small numbers for collectors.  For the most part they need to dedicate their efforts to the plants that are proven, that can survive the mostly kindly ministrations of their customers and home gardeners, whether the plants ‘want’ them or not, so they look to the toughest plants and press for willing customers to test others out across a variety of sites.  This is what is ultimately needed now so that we can define the growing parameters for each species, hybrid and cultivar.  Customers want assurances that a plant will not only survive, but will do well! and we can’t know that until we get more of these out into the landscape.

Further testing in the ground around the region by aficionados, designers, landscape contractors and interested institutions, on sites presenting conditions different than those at NWES, will help us all in determining the ‘range’ across which the genus, its species, hybrids and selections can be successful.  Different soils, slopes and aspects, different plant communities, cultural practices, if monitored, will move this effort along.  Random planting without monitoring, sharing of results and discussion will keep us where we are knowledge-wise, with a promising group of plants their potentials unrealized.

I would hope that the NWES would continue growing on these plants and even testing more of them as well as other drought tolerant members of this region that we have previously avoided or ignored.  Parks and other public entities are well positioned in our Cities to promote their use more widely by the public if they start using these plants on many of the thousands of acres of land that they hold collectively.  Just as important is the need for garden designers and landscape architects to educate themselves and begin getting these plants into their projects, because it is highly ‘unlikely’ that their clients will be demanding them given their relative ignorance, an ignorance that goes well beyond that of ours in the trade.

These plants have a place in our landscapes here in Portland, the Willamette Valley, and north in the Maritime Pacific Northwest, given the disruption that almost all sites have suffered, the upending of topsoil, the loss of organic content resultant from the stripping off of vegetation and native plant communities and the common use of mineral, lower nutrient, fill soils, across our cut and filled landscapes.  As our climate continues to warm, changing our weather/precipitation patterns, our need for durable xeric plants and landscapes will only increase.  Manzanitas deserve a place in our landscapes today!

Book Resources:

Field Guide to Manzanitas: California, North America and Mexico; Michael Kauffmann, Tom Parker and Michael Vasey, photographs by Jeff Bisbee; Backcountry Press 2015.

Gardening with Native Plants of the Pacific Northwest; Arthur Kruckeberg, University of Washington Press 1982. (Obviously mine is an old edition. The newer includes more plants?)

The Jepson Manual: Vascular Plants of California, 2nd Ed., University of California Press, 2012.  For the more serious plants person.

Manzanitas of California, Phillip Wells.  The most comprehensive work available on manzanita and recommended by Sean Hogan.  This was published in limited numbers and must be sought out.

Native Treasures: Gardening with Plants from California; Nevin Smith, University of California Press 2006.

Trees for all Seasons: Broadleaved Evergreens for Temperate Climates; Sean Hogan, Timber Press 2008.

See also an earlier positing I made on A. patula!

Additional on line ‘Pacific Horticulture’ articles: ‘Manzanita’ by Paula Panich, January 2008; ‘Vine Hill Manzanita’ by Phillip Van Soelen, January 2004; ‘The Northwest Plant Evaluation Program: Identifying Good Plants for Pacific Northwest Gardens’ by Neil Bell, Summer 2014.

Sources:

For those of you who are unfamiliar with the website, ‘Plant Lust’, it is an on-line ‘catalog’ of catalogs, often including many photos of the listed plants, not all of them currently available, from, as of this writing, 78 specialty nurseries. The descriptions are from the nurseries themselves, so a little research on your part may be necessary as many of these are regional growers from elsewhere…meaning that everything isn’t hardy here and their growing conditions may vary from yours.  Many of the Arctostaphylos listed here in are numbered or named selections from specific locales of the same species, with different growing conditions, elevations or forms.

Oregon

Cistus Nursery, 22711 NW Gillihan Road, Portland, OR 97231,(Sauvie Island), Portland; has an extensive catalog offering plants for retail on site as well as doing on line sales.

Forest Farm, in business for over 40 years, now does on-line mail order sales from their site in southern Oregon.

Xera Plants is a wholesale grower with a retail shop at: 1114 SE Clay St. Portland, OR 97214, whose on-line catalog is both informative and fun to read.

Washington

Desert Northwest, in Sequin, WA is a mail order nursery with a good selection of Arctostaphylos and a wide assortment of xeric plants amenable to the Maritime Pacific Northwest.

Far Reaches Farm in Port Townsend, WA.  While their Arctostaphylos listing is not large they are another must see nursery.  Check out their on-line catalog.

California

As my target audience are those living in the Pacific Northwest, I’m not including a list of all of the nurseries that produce and sell these plants there.  There are many!  And, anyone attempting to ‘naturalize’ their own landscape in California, the center of diversity for this genus should seek them out!

 

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2 thoughts on “Manzanita, Arctostaphylos, a Genus Whose Time has Come: Advocating for a Plant

  1. Loree

    “Planting them is not a sacrifice”… well said! Excellent article, and I’m not just saying that because of the plant lust mention. I continue to be pleased with the number of Manzanita I see growing around NE Portand when I go for walks. Hopefully the tide is turning and people will be demanding them, err, buying them and making the work that Sean, Paul, Greg and Mr. Bell have been doing pay off.

    Like

    Reply

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