Introduction

Himalayan Blackberry or Rubus armeniacus or Rubus bifrons (confusingly, both names seem to be currently accepted) is a well-known invasive species in some areas. Where I grew up on the Sunshine Coast of British Columbia, Canada, it was everywhere. It does less well in the colder interior, but it still does grow there, just much less invasively. As a child, I did not understand that it was invasive and not native. I just loved eating handfuls of the huge juicy, and sweet berries. I would go out picking bucketfuls of berries every summer with my mother and my three brothers. Now I know how invasive it truly is, and somehow the fruits seem a little less sweet to me now. Once established, the removal of Himalayan Blackberry can be very challenging.

Description of Rubus bifrons or Rubus armeniacus

Leaves & Stems of Rubus bifrons or Rubus armeniacus

Rubus bifrons and Rubus armeniacus are members of the Rosaceae family of the Rosales Order of flowering dicots. They are a perennial vine-like trailing shrub that grows 1 – 7 m in length and 0.4 – 1 cm in diameter with arching or creeping stems that are sparse to densely hairy and armed with numerous prickles. They have a large root crown of roots and rhizomes that grow to 0.5 m and sometimes up to 2 m deep.

The leaves are deciduous or sometimes somewhat evergreen and palmately compound with 3 – 5 spreading leaflets. Leaflets are elliptic or ovate to sub-orbiculate and 6 -15 cm long and 4 – 9 cm wide with a rounded or somewhat cordate base. Margins are moderately to coarsely serrated, and the apex is acute to acuminate. The lower surface is whitish to grayish green, while the upper surface is glossy bright green or dark green. There are filiform or linear stipules that are 7 – 15 mm in length. The largest veins have hooked prickles on them.

Flowers & Fruits of Rubus bifrons or Rubus armeniacus

Himalayan Blackberries usually have loose terminal inflorescences that generally extend past their subtending leaves. Sometimes the inflorescences may grow in the leaf axils as well. They are in a thryse with 10-60(-100) flowers in them. Pedicels are covered with prickles, are densely hairy, and may or may not be glandular. Flowers are bisexual with 5 white or pink petals. Petals are not connate (free), are obovate to elliptical and shape, and are 10 – 15 mm long each. It has filiform stamen filaments, and its ovaries are apically hairy.

They produce abundant black fruits that are juicy drupecetums, an aggregation of drupes on a fleshy accessory peduncle. Most people refer to them as ‘berries’. Fruits are globose or almost cylindrical and 1 – 2 cm long with 15 – 50 individual drupelets that strongly adhere to the accessory peduncle. Abundant fertile seeds are produced in their fruits, from 7000 – 13000 seeds per square meter of stems. Seeds can remain viable in the soil for several years.

Similar Species Frequently Confused With

There are native Rubus species throughout North America, but many are smaller plants with smaller or differently shaped and/or colored berries. Some native and introduced Rubus, however, grow to similar sizes but can be differentiated as follows:

• Rubus laciniatus, Cutleaf or Evergreen blackberry, is native to Eurasia and has been fairly widely introduced in North America. It grows in similar habitats to similar sizes with similar fruits but can easily be distinguished by its lacinated or deeply cut leaflets as opposed to the whole serrated leaflets of Himalayan Blackberries.
• Rubus pascuus Chesapeake Blackberry is a native shrub of Kentucky, Virginia, Maryland, Delaware, North Carolina, and South Carolina. It has tighter and shorter inflorescences, is more densely glandular, and its terminal leaflets are erect rather than spreading in Rubus bifrons.
• Rubus pensilvanicus Pennsylvania Blackberry is native throughout eastern Canada and the USA. It usually is a bit smaller than the Himalayan Blackberries, and its very red stems are densely covered in red prickles. It also only ever has white petals on its flowers, and its abaxial leaf sides are hairy but never whitish or grayish-green.
• Rubus ulmifolius Elmleaf or Thornless Blackberry is another European species that has been introduced that superficially looks very similar, but it is only found in California, Oregon, and Nevada. If prickles are not present, they can easily be distinguished by this. However, sometimes it does have prickles, in which case you can differentiate it by its strongly pruinose stems that Himalayan blackberries lack.
• Rubus vestitus European Blackberry is found on the Pacific coast of the US and Canada. It is an armed shrub that is generally smaller than 2 m. It also has narrower inflorescences, nearly round terminal leaflets, and stipitate-glandular hairs lacking in Himalayan Blackberries.

Native Distribution of Rubus bifrons or Rubus armeniacus

There is much debate as to the taxonomic description of this species. Some sources call them all Rubus armeniacus and say these are from Europe. Other sources say that the species are only native to Armenia and Iran. Other sources call this plant Rubus bifrons and say it is widespread in Europe and includes Rubus armeniacus. In either case, whether the same or separate species, they are virtually identical, and both are native to Europe, one more widespread and the other less so.

Habitat Types Where Himalayan Blackberry is Found

Himalayan Blackberry grows in both wetland and upland environments. While it grows abundantly in riparian areas, it does not invade the permanently wet soils of the wetlands though it will tolerate temporary flooding of up to 40 days. It will even tolerate occasional flooding of brackish water. It grows best at low elevations but can grow up to 1200 and occasionally 1800 m above sea level.

Himalayan Blackberries prefer moist, nutrient-rich loam but do not require it. They can also be found growing in soils with a wide range of textures, fertilities, and pH from acid to alkaline. It prefers sunny sites but easily grows in part shade as well.

Human Uses of Himalayan Blackberry

Himalayan Blackberries are widely used as food. They are eaten fresh as berries or frozen or canned for winter use in pies, cakes, jams, jellies, and wines.

Blackberry roots and berries are often used to treat diarrhea, fluid retention, gout, diabetes, gout, and inflammation. It is sometimes used to prevent heart disease and cancer. It makes a good rinse for irritation of the mouth and throat.

They are planted along fences and trellises to create impenetrable barriers to keep people and animals out of an area.

Distribution of Rubus armeniacus, Rubus bifrons in North America

The Himalayan Blackberry species were first brought to North America as a food crop in 1885 for its abundant berries.

In Canada, Rubus bifrons has been recorded in British Columbia, Ontario, Quebec, and Nova Scotia. Canadensys does not distinguish between the two species and uses only Rubus bifrons stating that Rubus armeniacus is a synonym.

In the USA, the Himalayan Blackberry is reported as two separate species. USDA states that Rubus bifrons is only found in the eastern part of the country in Oklahoma, Texas, Missouri, Arkansas, Louisiana, Kentucky, Tennessee, Mississippi, Alabama, Georgia, South Carolina, North Carolina, Maryland, Virginia, Washington DC, Pennsylvania, New Jersey, New York, Connecticut, Rhode Island, and Massachusetts.

USDA states that Rubus armeniacus is more widespread in the west and scattered in the east. It is found in Washington, Oregon, California, Idaho, Montana, Nevada, Arizona, Colorado, New Mexico, Missouri, Arkansas, Illinois, Kentucky, Tennessee, Alabama, Ohio, Virginia, Delaware, Pennsylvania, New Jersey, and Massachusetts.

In Mexico, Rubus bifrons so far has been reported in Veracruz and Oaxaca. Rubus armeniacus has been reported in Baja California (norte), Puebla, Mexico State, Jalisco, and Chiapas.

Himalayan Blackberries have now been introduced on every continent except Antarctica.

How Himalayan Blackberry Spreads

It is primarily spread long-distance by deliberate human introductions planting it in their gardens. It quickly escapes from cultivation due to its aggressive growth.

Short-distance dispersal occurs through birds and animals which eat the abundant fruit and then spread the seeds around in their feces. Humans also spread the fruits by picking them, eating them and dropping them, etc. They also spread vegetatively through their root crown and rhizomes and by rooting at nodes on their stems that come into contact with soil.

Habitats at Risk of Invasion in North America

Himalayan Blackberries are considered particularly invasive on the west coast of North America in low-elevation riparian, deciduous, and conifer forests as well as grasslands. It is heavily invasive in riparian communities in that area. It invades the same types of areas in the east but may be less invasive there due to the other aggressive native and non-native vines that are abundant in that region.

Himalayan Blackberry will not invade permanently wet soils or high-elevation montane forests. It will grow in middle-elevation montane forests but not very well. It will also not grow in most arid areas due to lack of moisture unless it is in a riparian zone with perennial access to water.

Impacts of Invasion

In North America, the Himalayan Blackberry is considered the most invasive nonnative shrub on the western coast from British Columbia, Canada, south to California, USA. They are aggressively spreading shrubs that quickly scramble over and smother all other vegetation in their path, excluding tall trees, as they cannot climb as high as English Ivy, for example. However, it can quickly smother and kill all young trees in its path. It is highly competitive for light, space, and nutrients. Due to its aggressive growth, it quickly out-competes native vegetation.

It replaces the more bio-diverse native shrubs and herbs that would have otherwise grown there, creating complete monocultures if the conditions are suitable for them. This out-competes our native vegetation, reducing biodiversity and even causing local extirpation of species. It also forms dense thickets in riparian areas that impede movement and access to water by humans and animals alike.

Himalayan Blackberry is also an agricultural and range land weed that replaces crop and forage lands quickly if left unchecked. Himalayan Blackberry and Scotch Broom are the two most abundant agricultural and range land weeds, causing an estimated $85 million in losses annually.

The abundant dead canes they produce are also a significant fire risk when they die and become brittle as they burn easily.

Potential Benefits of Invasion

Himalayan blackberries are widely eaten by bears, foxes, coyotes, squirrels, raccoons, deer, birds, slugs, and countless other native species. Most native ungulates prefer to browse the leaves, but some (white-tailed deer, for example) have been observed browsing the fruits. Leafcutter ants and leafhopper butterfly larvae also feed on the leaves. It is the preferred larval host plant for leafhopper butterflies. Pollen and nectar are also used by native bees, honey bees, and hummingbirds.

In addition, a multitude of small animals and birds use the blackberry thickets for cover, nesting, roosting, etc. The impenetrable thickets of thorns provide them protection from predators.

All of these animals, however, would have fed on the native Salmonberries, Thimbleberries, or other native species displaced by the invasive Rubus bifrons, however. The dependence of wildlife on the berries creates an additional challenge to the control or removal of the Himalayan Blackberries. Check out the control methods below for more information.

Methods to Remove Himalayan Blackberry

As always, prevention is the preferred method of control. It, like most invasive species, is still widely sold online and in many local garden stores. Do not buy or transport any Himalayan Blackberry. Do not plant it in your yard.

If you see them being sold online or in your local garden stores, please inform them of their invasive status and ask them to do their part and cease selling them. Ask them to instead sell more native species as ecologically friendly garden alternatives to invasive species.

Instead, buy suitable native Rubus species. There are multiple native blackberries and raspberries that are even more delicious and are just as easy to grow as invasive blackberries. Native Rubus species provide additional biodiversity and wildlife values as well.

In fact, due to wildlife values, this makes the removal of Himalayan Blackberry more challenging. Because native wildlife now depends on this non-native species, when you remove a large patch, it should be done in stages. Clear one-third or one-quarter of the patch (depending on the size).

Once cleared and few sprouts keep coming back, then it should be replanted with a variety of native salmonberries, thimbleberries, or other native shrubs that would have originally fed the wildlife in your area.

Research what species are native to your area to find suitable replacements. Then tackle the next fraction of the patch until you have replaced the invasive blackberry with a more biodiverse native selection.

Ongoing monitoring will, of course, be needed to ensure it does not return and overtake your planted native species. See the Integrated Management section below.

In public and natural areas minimizing disturbance and replanting disturbed areas as quickly as possible are the best prevention strategies for reducing the chance of invasion by Himalayan Blackberry or any other invasive species.

Physical Control of Himalayan Blackberry

Once already established, however, physical control is always the most effective means. Physical control is labor-intensive and time-consuming, but it usually causes the least amount of environmental damage.

The best time to remove Himalayan Blackberry is early in the spring, before or later during flowering but before the fruit has set to avoid further spreading the seeds.

Physical methods to remove Himalayan blackberries generally involve cutting, hoeing, digging, and burning. Often a combination of methods is used. Always wear gloves when handling the canes, as the prickles are very tough and sharp and will easily pierce the skin.

Young plants can be pulled by hand.

Mature plants require the cutting of the canes with cutters or loppers and then removing the rootstock.

Burning is also an effective method to remove the above-ground growth, but as with cutting, the rootstock will need to be dealt with as well. A single cutting back of the above-ground growth, however, if not followed with additional treatments, will actually increase the density of the thicket when it regrows. It must be followed with additional treatments and ongoing monitoring.

If the rootstock is not removed, it will grow back quite vigorously. One method is to repeatedly cut it back or burn it multiple times over multiple years until the roots are starved by the lack of above-ground growth.

Rootstocks can also be dug out with a shovel or a weed puller, but they are very tough, and this is only suitable in small patches.

If you have only a small patch to deal with and root digging is too labor-intensive, you could also cover the entire area with a black tarp for at least two growing seasons to solarize it. This is much less labor-intensive than returning repeatedly, but again this only works on small patches.

Note that it is virtually impossible to remove all of the rootstocks due to the size and depth that the roots spread to. Removing as much as you can is critical to success. However, it must be followed by ongoing monitoring over several years to ensure all new sprouts are destroyed.

Disposal of the Shrubs Once Removed

If you have live stems or plants that have seeds on them, they must either be burned in a hot enough fire or solarized. The fire must be hot enough to destroy the seeds. If you are not allowed fires in your area, then you will have to solarize them.

To solarize, put the shrubs under a thick black tarp or into thick black garbage bags and leave them in the full sun for a good 8 – 10 weeks at least to be sure that all seeds are no longer viable. Some sources suggest less time for polarization, but in my experience, differential heat throughout the bag/tarped area as well as variations in sunlight intensity, can result in the survival of at least some seeds if done for a shorter duration. Take them to your local dump once done and inform them that they are invasive species so that they are disposed of appropriately.

Chemical Control of Himalayan Blackberry

Chemical applications are almost never an ideal method of control for any invasive species. That is because chemical alteration of the environment often makes the environment more suitable for invasive species than native species. Furthermore, it is often difficult to keep the chemical control method contained so that it does not directly affect any native species that are there during the application process itself. As a result, plots where chemical control is used usually show a decrease in species richness. On the other hand, in plots where only physical control is used, species riches significantly increase.

Furthermore, there are no chemical control methods that effectively target only Rubus bifrons or Rubus armeniacus. And due to the nature of Himalayan Blackberry, multiple applications are always needed over multiple years, further degrading the local environment.

Chemical control is not recommended.

Biological Control of Himalayan Blackberry

Biological control involves the use of a predator, herbivore, disease, or some other agent to control an invasive species once it is established in the environment. The problem with biological control is that the agent used must be entirely specific to only the target organism before releasing it into the environment. This is often difficult to determine since the agent of control is also not native to the environment and could behave differently when released there. Take the example of the mongoose and the rat. The mongoose was released in Hawaii in the late 1800s to help control the rat. To this day, there are still rats in Hawaii, but the mongoose has helped to decimate many native bird populations.

Biological control methods are extremely risky and should only be carried out by professionals after years of rigorous study. The use of biological control methods can never be used alone. They must be part of an integrated pest management approach. This is because the control agent would need to effectively destroy over 99% of plants, roots, and seeds to actually control the Himalayan Blackberry on their own. Results this high have never been achieved in the field.

However, using biological control in conjunction with physical control and ongoing monitoring can be very effective at times. However, in North America, so far, there are no biological control methods in terms of insects, fungi, or other pathogens that have been approved. This is because they all put our abundant list of native Rubus species at risk as well.

Using Goats to Remove Himalayan Blackberries

The only recommended biological control method at this time is grazing by domestic goats. Domestic goats are aggressive and non-selective browsers. They will literally eat anything. To use goats, the patch should be penned in, and then the goats left there to graze for 3 years. They will eventually destroy all the above-ground growth and then eat the new sprouts as they come up.

This can be sped up by an entire year by first removing the above-ground growth and then allowing the goats to eat the sprouts as they come up.

This can then be followed with rootstock removal for any stubborn plants that may remain, or simply leave the goats in the area for another year until you see no more sprouts.

At this time, they can be moved to another patch, and that patch can be replanted with native vegetation and a monitoring program implemented to be sure they do not sprout again.

Integrated Pest Management & Ongoing Monitoring

Integrated management is always the best approach. In its simplest and least impactful form this involves physical removal methods, possibly biological control methods, replanting, and ongoing monitoring. Integrated management is required because the area needs to be monitored for returning sprouts or seedlings otherwise, all the hard work done in removal could be wasted if the invasive species is allowed to regrow.

Replanting With Native Species is Crucial

In all cases of Himalayan Blackberry removal, the site will need to be replanted once the majority of the infestation has been dealt with. This is because the bare soil will allow the seed bank of Himalayan Blackberry in the soil to germinate and re-invade the patch they were removed from. Or it will allow the invasion by other nonnative species, which all favor disturbed sites.

A replanting program should already be planned and ready to implement in the 2nd to 4th year upon removal of the Himalayan Blackberry, depending on the speed and success of the removal method.

A variety of native species that are ideally seeds from the local environment to ensure local ecotypes should be planted. If local seeds cannot be gathered or started in time, then purchasing native plants from a reputable nursery specializing in local native species is a good alternative. This must then be followed by ongoing monitoring.

Ongoing Monitoring is Essential

In all cases of invasive Himalayan Blackberry removal, ongoing monitoring is absolutely essential.

Multiple visits should be made in the first two years to ensure that any surviving individuals, their sprouts, and their seedlings are removed so that the population is not able to recover.

Then yearly monitoring after that for at least five years to ensure that none return. This is required whether the area is replanted or not. Himalayan Blackberry is aggressive and prolific and will out-compete planted vegetation if yearly monitoring is not put in place to remove young plants before they have a chance to become established.

References and Resources

CABI on Rubus armeniacus https://www.cabi.org/isc/datasheet/116780

Canadensys Plant Search https://data.canadensys.net/vascan/search

Dictionary of Botanical Terms – Lyrae’s Nature Blog Dictionary of Botanical Terms

Eflora Plants of North America http://www.efloras.org/browse.aspx?flora_id=1

Fire Effects Information System on Himalayan Blackberry https://www.fs.fed.us/database/feis/plants/shrub/rubspp/all.html

iNaturalist Plant Search https://www.inaturalist.org/home

Rubus armeniacus fruits picture from Wikipedia By Daderot – Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=21796138

USDA Plants Database https://plants.sc.egov.usda.gov/home

Wikipedia Himalayan Blackberry https://en.wikipedia.org/wiki/Rubus_armeniacus

Willis, Lyrae (Unpublished).  Plant Families of North America.

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