On Amelanchier / Serviceberries: Their Susceptibility to Rust and Their Use in our Gardens

Sometimes we are drawn to plants by memories and sentiment, plants we have early associations with.  They can regularly appear in our palette, our quiver of plants, that we might choose from.  We all have our preferences, our biases.  Sometimes the mismatch might only be aesthetic other times it can be a problem related to our site conditions.  When we include these plants they may struggle, yet persist in the garden, maybe demonstrating to others their ‘ill-fit’.  When a plant is a poor fit, its inclusion can become a glaring error to others that we are blinded to.  Diseases can present such a problem, diseases that can be problematic in our area, or that our site is simply unfortunate enough to suffer from.  ‘Rust’ diseases,  Gymnosporangium spp., can be an issue here.  In the case of Serviceberries, it can be disfiguring and debilitating.  Several of these species attack Rose Family members, that include the Serviceberries, which seem particularly susceptible, though it doesn’t kill them.  Diseased, stunted and suffering, unwilling to just die and put us both out of our misery, these plants continue.  It is akin to being drawn to the wrong lover or life partner…it’s not going to work out and we simply can’t seem to help ourselves.

The Rust diseases are called such because of the characteristic color of their spore producing bodies. To occur they generally require the presence of members of the Rosaceae and the Cypress Family, which includes the most common host, the Junipers.  This fungus has two stages in its life cycle that are necessary, each requiring its own host plant and conditions.  There are some 36 different species of the Rust organisms in North America.  Susceptibility to them varies between plant species.  Apples, Roses, Pears, Serviceberries, will each succumb, or not, to its Rust species, differently.  In general Rusts over-winter in one form on the evergreens, though they can be perennial on Junipers, and, when temperatures warm in Spring and rains are frequent or humidity heavy, the fungus form telial sori, little tubes growing out from the main body, that swell and turn gelatinous in the wet, producing and releasing spores that move on the wind to the soft new tissues of the susceptible Rosaceae species.  The production of spores can go on for several months into June.

Infection of the Rose host happens after bloom on the Serviceberries and is generally increasingly visible after fruit set.  Here, the bloom period appears free of the infection and the bloom appears unaffected.  Remember that Cypress family host is necessary to infect species of the Rosaceae.  I couldn’t find any info on how close the two must be, but proximity increases the chance of infection.  The disease, on the Rose family host, can be so severe that it can cause complete defoliation of plants, cause their fruit to abort and distort and kill new twig growth…or cause only minor damage varying from year to year.

The Rust goes through similar stages on its Rose family host forming tiny tubes or cups, technically, aecia, perpendicular to the infected tissue, that release spores when mature in June – July when these burst open.   In some cases twigs become infected.  These tend not to lengthen normally, but thicken considerably and may distort.  Heavy infestation of leaves can lead to early leaf drop and add to stress of the trees.

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This shot was taken below Benham Falls a few miles upstream from Dillion and its drop into the canyon. Here the river runs along close to the surface rock.  The lava flow across the river is from the older Newberry flow and the landscape is typical of such conditions.  The soils are deeper on ‘this’ side of the river as well as in the distance where the forest  is taller and more dense.  Benham Falls, above us here, was created by another flow from Lava Butte some 6,000 years ago.

Dillion Falls, on the Deschutes River, is upstream from Bend several miles.  I think the first time I visited it I was 19 driving there with a friend.  I’d been backpacking and camping through Scouts and had been going more on my own and was really starting to notice the plant world around me in the high desert and the forest and alpine areas of the eastern Cascades.  This was the kind of place I gravitated toward with prominent geology, a place of views, of power.  I was drawn to basalt bluffs, ridge tops, canyon rims and ledges that gained a ‘power’ from elevation, the expanses that opened before them or through which water carved its way.  Dillion Falls is a class V rapid, serious expert water that can kill the novice or unwary, on the upper Deschutes River where it tumbles, suddenly dropping 15’ down through basalt then into a ‘roller coaster’ ride down into its canyon which confines it, other than a relatively short section through Bend, until its confluence with the Columbia.  It is Ponderosa Pine country, the Juniper that dominates the dryer high desert yielding to the ‘thirstier’ Pine.  I grew up in the High Desert north and east of here.  Sagebrush, Rabbitbrush, Juniper and, sadly, Cheat Grass.  Here at Dillion the desert has been replaced by Ponderosa Pine, Deer Brush, Green Leaf Manzanita and the ubiquitous, Ribes cereum, due to greater precipitation, though it is still dryish, .  The plants along the river’s edge stand in stark contrast to those spreading out across the basalt, different again than the relatively lush meadows upstream of the Falls, beyond the leading edge of the lava flow.  The soil is very thin here filling in the course cracks and low spots in the fractured basalt laid down here thickly, and more ‘recently’, around 7,000 years ago, by a massive flow of magma through a fissure in the NW flank of the Newberry Volcano, now ‘quiet’, collapsed into a caldera containing East and Paulina Lakes.

[The upper Deschutes River is having a man induced water crisis that not only effects its ecological value and viability, but the region’s economy as well.  For an interesting article on this and the increasingly common issues surrounding water rights in the western US see this article in Bend Magazine.]

I have an affinity for Ponderosa Pine country.  I can breathe there, their tall trunks, with their thick, platy and fissured bark, punctuating the landscape, each provided with ‘polite’ space between them, unlike much of the Juniper country of the High Desert, that has been crowding its way in, cutting off views, its heavy resinous scent filling the air after thundershowers and the thick Lodgepole Pine forests to the south.  This maybe my favorite ‘landscape’.  And, here beneath them, scattered and intermingled within their roots, is the low brushy Serviceberry, Amelanchier alnifolia, or at least a form of it, that occurs at its driest limit here in Oregon on the edge of the High Desert, seemingly sharing very little with its brothers and sisters in the woods of the Willamette Valley.

I’ve always liked Serviceberry, its single simple white flowers, its sweet little dark blue ‘apples’ so unlike those fruits of the similar appearing Juniper and Oregon Grape, a ‘surprise’ to the tongue.  And, like Manzanita I have been drawn to them, almost genetically.  I put these plants on a shelf for later when I moved to the Willamette Valley seeking them out when I would return to the ‘dry’ side.  I put them on the shelf for awhile.  Just a few years later, on a hike through the low foothills, south of Portland, I rediscovered Amelanchier, this time a thin, tall, rangy shrub in the understory, stretching for sunlight.  I was startled when I discovered that this was the same ‘plant’ I knew from the basalt lava flows and the eastern foothills I was much more familiar with.  I hadn’t noticed them being used much in landscapes on the west/wet side back then and these ‘leggy shrubs didn’t compete well with all of the more ornamental plants i was learning then..  I’d had Kruckeberg’s, Gardening with Native Plants of the Pacific Northwest, since the mid ‘80s, a book I acquired after my Sunset guide and several veggie gardening books, but for some reason it took me awhile to see these as suitable landscape plants.  One of the ‘sins’ of being a local.  I have since learned that this Serviceberry can be found growing in habitat, somewhere in every county in Oregon, from the Columbia River Gorge to the Wallowas south to the Ochocos, Owyhee and Steens country, to the Sikiyous and coast north through the coast range and Willamette foothills.  In fact it can be found across much of North America, though in other regions a few other species can also be found.  Locally, this is our only native species. (For more information on this species, discussing its virtues, history and uses, click here.)

Then, some 20 years ago I bought three ‘Autumn Brilliance’ Serviceberries, an Amelanchier x grandiflora selection.  This one was described as an elegant, small, tree form of the Serviceberry, with larger flowers .  While not the one I remember, this is a hybrid of two eastern species, A. laevis and A. arborea.  It also has the showy characteristic Fall color, at least on the leaves it is able to hang on to into the Fall.

I planted them out in my parking strip before I noticed a problem.  As a clone these are asexually propagated, in this case, grafted.  Their desirable characteristics are assured by grafting these rather than growing them from seed.  Second generation seedlings grown from hybrids can show a very high degree of variability looking and performing like a very different plant.  This wasn’t the surprise for me.  The surprise was that they were grafted on to a Crataegus monogyna rootstock, English Hawthorn, an invasive tree in our region which I have pulled, cut, treated and dug out, over the years by the hundreds!  This is another tree readily consumed by birds that they than ‘spread’.

The graft was good.  In 20 years it has not failed.  Though for 20 years I’ve had to annually remove suckers from the rootstock that would otherwise eventually out compete and out grow my Serviceberry if I left them uncut.  This upset me.  I ended up tearing one out years ago.  Another I gave to a neighbor who planted it in their sloping front yard.  For several years they dutifully removed   the competing suckers, but that was awhile ago now.  It’s a Hawthorn bush today crowding out the Serviceberry.  Unfortunately this happens all too often when ‘scion’ wood is grafted on to a different rootstock.  Too often the rootstock retains its propensity to sucker and novice or indifferent gardeners end up with the rootstock dominating the scion.  This is most noticeable when they are in bloom.  It is very common to see Cherries and Dogwoods here with contrasting flower colors at least until the grafted scion is completely shaded out.

IMG_7932My remaining tree still occupies the space outside my dining room window where it consistently blooms late March to April every Spring, quite spectacularly in fact, and then begins to to exhibit an infection of Rust on the leaves and fruit, every year, spreading in our cool wet spring weather, often heavily coating the new shoot growth as well causing it to contort.  Some years, some portion of the fruit escapes the infection.  Other years most of the fruit is infected and much of it aborts dropping prematurely.  I have no plants from the Cypress family in my garden, they are however, in my immediate neighborhood. (There is an poorly maintained planting of a Tam Junipers about a block away)

I did an informal survey of the Cypress family members in a two block radius of my garden and found the following: Arbor-Vitae – 3 hedges within one block; another 5 within 1 1/2 blocks; 4 more within 2 blocks.  Western Red Cedar – 2 within one block; 2 within two blocks; Boulevard Cypress – 1 at 1 a 1/2 blocks; Junipers – 2 within 1/2 block; Blue Cypress – 1 at 1 1/2 half blocks away; Weeping Alaska Cedar – 1 at 1 1/2 blocks; Chamaecyparis spp. 1 at 1 1/2 blocks and 1 at 2 blocks away; Incense Cedar 1 at 1 1/2 blocks and 1 at 2 blocks.  I did not count the number of plants in each hedge or grouping and I did not inspect them for the fungus.  I did not find a definitive list of which Cypress family species host particular Rust species.  Some or most of these may not be a suitable host plants.  Still, in a 2 block radius there are 25 ‘potential’ sources for the disease!

Spores are typically individual cells and are much smaller than seeds.  A single fungus ‘body’ of some species can produce upwards of a ‘trillion’ spores!  Studies have found that as many as 99% of spores travel under 100 yards or so though they have also been found to travel many miles.  So a rough rule of thumb would be that both hosts would need to be within 100 yards of each other, keeping in mind predominant wind directions during sporulation and the height of the infection and their ability to be carried on the breeze.  When airborne they can potentially travel for miles.  One infected Juniper can then spread the pathogen over a very wide area, but it must land on a suitable host to continue the cycle, Cupressaceae to Rosaceae and back!

The tree is still here, because we can sit inside and watch the birds descend on it to feed, and, if we are lucky, this will include the Cedar Waxwings, though it has been awhile since I’ve seen any.  The suckers remain consistent though and the Rust contorted new shoot growth piles itself up atop the straight trunk much as it was in the nursery row.  The tree has gained very little height.  It looks squashed.  And, this is why I’m writing of it, even though it is in a fairly open location, on the street with no other trees crowding it, so, relatively good light and air circulation, it still suffers badly from Rust.

‘Autumn Brilliance’ is not alone among Serviceberries here suffering this disease.  At least seven different Gymnosporangium spp. can attack the Serviceberries.  The infection can be very common amongst the entire genus.  In a relatively open mixed woodland setting within a larger landscape, it is probably no big deal, especially when there are no infected alternate hosts in the area, but in a prominent location in a smaller landscape? infection is hard to ignore.  Most poor or non-performer plants in my home garden don’t last long, yet this one still remains.  It does so for the reasons I’ve already mentioned, attachments, its spring bloom and the fact that it is a very good wildlife plant, providing food for native songbirds.

Both this hybrid and the parent species would seem to do better back east in their native range.  The Missouri Botanical Garden says that it suffers few problems there, but its performance has not translated here in the landscape.  It is also important to note that in some states laws have been passed requiring the removal of the most common alternate hosts from important apple growing areas, another member of Rosaceae.  A. alnifolia, our native, has fewer foliar problems on the east-side of its range in Oregon, this could be because of colder drier spring weather.  Gymnosporangium spp. requires moisture/wet, to support the development of the infectious spores.  A. alnifolia also occurs in the Columbia Gorge, at least in the eastern portion, on Dog Mountain and at Catherine Creek, they seem healthy enough growing with vigor, often with the smaller Garry Oaks common there and with conifers as well, if the canopy is open, growing smaller than the Willamette Valley populations I’ve seen.  In the Gorge I see it typically growing along the forest edge.  In some sections of the meadow on Dog Mountain is a squat form of Juniper and while I didn’t tromp all around to investigate, and please don’t, the Serviceberries up there appeared free of Rust though I haven’t been up there after bloom when infection tends to start showing.  Any plant will have areas within its normal range where it does more poorly than it does in others.  Plants like people and animals become susceptible to various infections when their overall state of health is sub-par.  This may be the case with Serviceberries and Rust.

Amelanchier alnifolia occurs somewhere in all of Washington and Oregon’s counties.   Adapted and native plants can still be susceptible and effected by local common diseases.  This may not be a big deal for many, but for those of us with higher performance and aesthetic expectations of our plants, it can be an issue.  https://www.wnps.org/blog/plant-profile-serviceberry/

There are seven species that cause a fungal Rust infection on Amelanchier alnifolia.  Check out the PNW Handbook.  All of these must alternate between hosts to complete their cycle, a requirement easily met in an urban area.  Depending on the Rust species there are specific Junipers and Cedars that must be available to serve as alternate hosts.  If they are absent, then there will be no infection of your Serviceberries.  In an urban area their inclusion in the local landscape can be problematic and out of your control.  I doubt if your neighbors would appreciate your cutting their host plants down.  In a forested or woods situation, without the appropriate host Junipers or Cedars, your plants should be free of Rust.  On the other hand does the presence of these Junipers and/or Cedars alone mean automatically that your Serviceberries will be infected, the fungus must be present.

On a late April walk through downtown I visited Tanner Springs Park at the north end of the rapidly redeveloped Pearl District.  Here, several years ago, when the Park was in its early years, I planted 3 tree form Autumn Brilliance Serviceberries and a loose group of Amelanchier alnifolia ‘Regents’, a dwarf form, in a difficult soil mix I have written of previously.  One of the Autumn Brilliance is no longer there, I’m not sure why, but all of the other plants are doing reasonably well, the A.a. ‘Regents’, perhaps smaller than you might expect, but performing well and…at least when I looked, free of Rust.  I suspect this is due to the absence of the necessary Juniper and Cedars in the area. (There are also some larger A. alnifolia shrubs planted on the embankment above the railroad tracks along the northeast side of The Fields about 3 blocks north and are ‘clean’ as well.)

I returned to these two Parks, Tanner Springs and The Fields, in the first of June…and found Rust.  Turns out I was wrong.  Alternate hosts must be available.  All of the plants were infected though the extent of the infection was more limited than at my home.  It varied from plant to plant but infection was probably in the 10-30% range on the leaves and there was also infection of new shoot growth.  It would be interesting to do a survey of the Portland area to see if anyone’s plants are free of Rust this year and if this was a particularly bad year, but I don’t have the time or resources to do it myself other than maybe informally on FaceBook.  Odds are that if you plant any of the Serviceberries here in the Portland area you will face the challenge of Rust.  It may be possible to limit its spread with the used of fungicides, but remember these three things about fungicides: 1, they are prophylactic, they must be in place on plants surfaces to prevent infection, 2, they can be ‘washed’ off relatively easily in rainy weather, which we can have on a daily basis in Spring, and 3, the spores are released over a long period during spring, into June at least.  At any point if your plants are unprotected they can be infected and once infected, that tissue will remain so.  Airborne fungal disease are problematic this way in the Pacific Northwest.  If the host plants are available, these diseases are difficult to control.

Sometimes we want a plant that just won’t perform as we might like.  There’s nothing wrong with Serviceberries.  I have a fondness for them, but I wouldn’t recommend them here anymore in most urban situations.  They have a very nice spring flower show, produce tasty fruit that the birds also love, with very nice Fall color, and, as a small tree or shrub, fit into small gardens and help step the landscape down to more human scale from a stand of Doug Fir or any other large trees, but before we plant them we should understand their requirements before we set ourselves up for disappointment.  Rust is not just a cosmetic problem, it can stunt and deform new growth, when out of control.  We all have plants that we have a soft spot for.  The challenge is to recognize this so they do not become a handicap.  Know your plants and your site.

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