Trees and Shrubs That Self-sow Excessively

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The Norway maple (Acer platanoides) produces so many seedlings it can easily become a garden pest. Source: www.massaudubon.org.

All plants reproduce. If they didn’t, they’d go extinct! But most do so modestly, producing a plant here and there, just enough to maintain their population. Others, though, do so profusely, becoming an annoyance to gardeners and spreading into the wild far from where they are native. Most such plants are simply called weeds and they tend to be annuals, perennials or biennials. However, there are also trees and shrubs that overdo it and can become invasive due to aggressive self-sowing as well.

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False spirea (Sorbaria sorbifolia) can be highly invasive locally, but tends to spread via suckers rather than seed, so doesn’t get far. Source: Fanghong, Wikimedia Commons

Of course, there are different ways in which a plant can become invasive. Through suckers, for example. Think of false spirea (Sorbaria sorbifolia) or staghorn sumac (Rhus typhina). They certainly get around, but since they sprout from wandering roots, they only tend to be invasive on a very local scale. Woody plants that spread by seed can get much farther. What with birds, squirrels and wind to carry them greater distances, they can really get around.

I, for example, have no Norway maple on my property, nor do any of my immediate neighbors, but there are several further down the street and as a result, I find hundreds of Norway maple seedlings in my gardens every year.

The Ones That Overdo It

What follows is a list of trees and shrubs that have the reputation of being invasive through their seeds, but…

Not all plants on the list will be invasive under all conditions. They’ll only cause problems when the local environment is appropriate to their needs. For example, tamarisk or saltcedar (Tamarix ramosissima) is very invasive in drier climates, but not a problem at all in more humid ones, while Japanese barberry (Berberis thunbergii), which can be terribly invasive in moderate climates, doesn’t produce fertile seed in colder ones and thus is not a problem there.

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Frangula alnus ‘Ron Williams’ Fine Line is a sterile columnar form of the otherwise invasive alder buckthorn (F. alnus). Source: springmeadownursery.com

Also, there are sterile forms of many of the trees and shrubs listed here, such as Frangula alnus ‘Ron Williams’ Fine Line, a sterile form of the otherwise invasive alder buckthorn (F. alnus), while new sterile varieties of Japanese barberry (Berberis thunbergii) and winged euonymus (Euonymus alatus) are either under development or being introduced. If there’s a tree or shrub you like, but it has invasive tendencies, you can often find a sterile or nearly sterile form you can use with impunity.

Mulching Can Help

Fortunately, using a good mulch will prevent most tree and shrub seeds from germinating. They simply can’t germinate through a thick mulch. That said, some trees—especially nut trees—are among the few plants whose extra robust seeds really can germinate through a mulch. Those that are invasive even under 2 inches (5 cm) of mulch are marked with an asterisk (*).

You Choose

I’m not saying do not plant the plants listed here—some are great garden plants!—but forewarned is forearmed!

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Himalayan blackberry (Rubus armeniacus, syn. R. discolor, zone 7) is extremely invasive in some climates, but not hardy enough to be a problem in colder areas. Source: www.nwcb.wa.gov

  1. Alder buckthorn (Frangula alnus, formerly Rhamnus frangula) zone 3
  2. American elm (Ulmus americana) zone 3
  3. Amur honeysuckle (Lonicera maackii) zone 2b
  4. Ash (Fraxinus spp.) zone 2 to 7, according to species
  5. Autumn olive (Elaeagnus umbellata) zone 4
  6. Bird cherry (Prunus padus) zone 2
  7. Black locust (Robinia pseudoacacia) zone 4b
  8. Box elder* (Acer negundo) zone 2
  9. Blackberry (Rubus spp.) zone 2 to 8, according to species
  10. Bramble (Rubus spp.) zone 2 to 8, according to species

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    Renowned for its stunning fall colours, burning bush (Euonymus alatus) can nevertheless be invasive in some areas. Source: www.plantes-shopping.fr

  11. Burning bush (Euonymus alatus) zone 5
  12. Butterfly bush (Buddleia davidii) zone 6b
  13. Chinese elm (Ulmus pumila) zone 2
  14. Chokecherry (Prunus virginiana) zone 2b
  15. Common buckthorn (Rhamnus cathartica) zone 2
  16. Dog rose (Rosa canina) zone 4
  17. European birch (Betula pendula) zone 3
  18. European privet (Ligustrum vulgare) zone 4
  19. Guelder-rose (Viburnum opulus) zone 3
  20. Horse chestnut* (Aesculus hippocastanum) zone 4b
  21. Japanese barberry (Berberis thunbergii) zone 4
  22. Morrow’s honeysuckle (Lonicera morrowii) zone 4
  23. Mountain ash (Sorbus spp.) Zone 3
  24. Multiflora rose (Rosa multiflora) zone 5b
  25. Norway maple* (Acer platanoides) zone 4b
  26. Norway spruce (Picea abies) zone 2b
  27. Pin cherry (Prunus pensylvanica) zone 2

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    Common buckthorn (Rhamnus cathartica) is very invasive in most temperate climates. Source: nyc.books.plantsofsuburbia.com

  28. Plane (Platanus spp.) zone 5 to 9, according to species
  29. Raspberry (Rubus idaeus) zone 3
  30. Redleaf rose (Rosa glauca, formerly R. rubrifolia) zone 2
  31. Rose of Sharon (Hibiscus syriacus) zone 6b
  32. Rowan tree (Sorbus spp.) Zone 3
  33. Rugosa rose (Rosa rugosa) zone 3
  34. Russian olive (Elaeagnus angustifolia) zone 2b
  35. Saltcedar (Tamarix spp.) zone 5 to 9, according to species
  36. Scots pine, (Pinus sylvestris) zone 2b
  37. Sea buckthorn (Hippophae rhamnoides) zone 2b
  38. Siberian elm (Ulmus pumila) zone 2
  39. Siberian peashrub (Caragana arborescens) zone 2
  40. Silver maple* (Acer saccharinum) zone 2
  41. Small-leaved lime* (Tilia cordata) zone 3
  42. Sugar maple* (Acer saccharum) zone 4
  43. Tamarisk (Tamarix spp.) Zone 5 to 9, according to species

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    Tatarian honeysuckle (Lonicera tatarica) can be quite invasive in temperate climates. Source: www.florafinder.com

  44. Tatarian honeysuckle (Lonicera tatarica) zone 4
  45. Tree of heaven (Ailanthus altissima) zone 6b
  46. Walnut* (Juglans spp.) Zones 4b to 8, according to species
  47. Wayfaring tree (Viburnum lantana) zone 2b
  48. Winged euonymus (Euonymus alata) zone 5

Trees and Shrubs that Get Around

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A typical suckering shrub: multiple stems, each with its own roots.

Most trees produce only a single trunk over their entire life. The average shrub, too, produces all its branches from a single base. But there are exceptions to this rule, woody plants that send out suckers (basal shoots) from creeping roots, stolons, or rhizomes. Sometimes these sprout near the mother plant, but other times they can be a good distance away. And suckering trees and shrubs do tend to get out of hand over time. Sometimes these plants sucker only under specific conditions, such as when their roots are damaged by hoeing or when the mother plant is under stress. Others, on the other hand, sucker happily under just about any condition!

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The false spirea (Sorbaria sorbifolia) is an example of a widely grown and attractive shrub… whose suckers do tend to get out of hand!

You can turn this disadvantage into an advantage in areas prone to erosion because suckering trees and shrubs create a complex mass of rhizomes, stolons and roots that holds the soil in place. Laidback gardeners can also benefit from their tendency to wander by letting them fill in empty spaces in the garden. A single shrub that covers a large area means a lot less planting… and a lot less expense! Also, most suckers are not just shoots, they are rooted plants: you can easily dig them up and replant them elsewhere, which gives you plenty of free green material for future plantatings! But no matter where you plant suckering plants, and even if you appreciate their ability to proliferate, you still need to know how to stop them. They won’t be able to escape, for example, if they are surrounded by a terrace or trapped between the wall of the house and a walkway. And cities often use them as low-cost fillers for traffic medians: no way they’ll find their way of that kind of barrier.

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A bucket or pot whose bottom has been removed will control almost any suckering shrub… but won’t be big enough for many trees.

You can also plant them inside a barrier, such as a big pot or plastic bucket whose bottom has been removed (necessary for proper drainage).

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Anti-rhizome barrier.

Or install an anti-rhizome barrier, also called a bamboo barrier, a sort of semi-rigid plastic film of about 2 feet (60 cm) in height that can be inserted into ground around the plantation. (This product is widely available in Europe and in parts of the United States, but I know only of one source in Canada: Canada’s Bamboo World).

List of Suckering Trees and Shrubs

Here are some temperate climate shrubs and trees that tend to sucker, at least under certain conditions.

  1. American Beech (Fagus grandifolia) Zone 3
  2. Balsam poplar (Populus balsamifera) Zone 2
  3. Blackberry (Rubus) Zone 5
  4. Black locust (Robinia pseudoacacia) zone 4b
  5. Bramble (Rubus) Zones 3 to 7
  6. Buffaloberry (Shepherdia) Zone 2
  7. Bush honeysuckle (Diervillea) Zones 3-5
  8. Chokeberry (Aronia) Zone 4
  9. Chokecherry (Prunus virginaniana) zone 2b
  10. Cliff Green (Paxistima canbyi) zone 4b
  11. Common buckthorn (Rhamnus cathartica) Zone 2
  12. Common dogwood (Cornus sanguinea) Zone 3
  13. Common lilac (Syringa vulgaris) zone 2b
  14. Devil’s walkingstick (Aralia spinosa) Zone 6
  15. European Aspen (Populus tremula) Zone 2
  16. False spirea (Sorbaria sorbifolia) Zone 2
  17. Fragrant currant (Ribes odoratum) Zone 2
  18. Fragrant sumac (Rhus aromatica) Zone 3
  19. Gray dogwood (Cornus racemosa) Zone 2
  20. Hazel (Corylus) Zones 3-6
  21. Japanese angelica tree (Aralia elata) zone 5b
  22. Lombardy poplar (Populus nigra ‘Italica’) Zone 4
  23. Oregon Grape (Mahonia aquifolia) Zone 5
  24. Pin cherry (Prunus pennsylvanica) Zone 2
  25. Raspberry (Rubus idaeus) Zone 3
  26. Red osier dogwood (Cornus sericea, syn. stolonifera) Zone 2
  27. Rugosa rose (Rosa rugosa, some cultivars)  Zone 3
  28. Running serviceberry (Amelanchier stolonifera) Zone 3
  29. Russian olive (Elaeagnus angustifolia) zone 2b
  30. Sea buckthorn (Hippophae rhamnoides) zone 2b
  31. Shadblow serviceberry (Amelanchier canadensis) Zone 4
  32. Siberian dogwood (Cornus alba) Zone 2
  33. Silverberry (Elaeagnus) Zones 1b to 7
  34. Smooth hydrangea (Hydrangea arborescens) Zone 3
  35. Snowberry (Symphoricarpos) zone 3
  36. Staghorn sumac (Rhus typhina and glabra) Zone 3
  37. Sweet fern (Comptonia peregrina) Zone 2
  38. Sweet Gale (Myrica gale) Zone 2
  39. Tree of heaven (Ailanthus altissima) area 6b
  40. Trembling aspen (Populus tremuloides) Zone 2
  41. White poplar (Populus alba) Zone 4
  42. Wild Rose (Rosa, many species) zones 2 to 5
  43. Yellowroot (Xanthorhiza simplicissima) Zone 4