How to manage invasive sumach trees & root suckers

How to get rid of invasive sumach tree suckers

The Stag’s Horn sumac (Rhus typhina) was a highly popular ornamental tree grown for its branching habit and large ash-like leaves on velvety branches. The foliage, which colours to fiery red in autumn, and produces brown conical fruiting heads make it look wonderful. 

If you have one you’ve probably discovered that it’s entirely unsuitable for small gardens because it suckers. It can even sucker from neighbouring gardens.

If you cut a sumach tree down it can go into overdrive and travel under the lawn in your garden - and those of others nearby, no doubt.

In its native habitat, eastern North-America and Canada, it grows on poor soil so has to ramble in order to find nutrients. On richer soil, such as London clay, it forms a small tree and then continues to ramble helped by milder British winters.

To get rid of of the sumach suckers keep chopping the suckers out and weaken any re-growth with a systemic weedkiller, such as Round Up. Within five or six years the problem should go away, but it’s going to be a long and tedious process. It helps to paint on Round Up gel when the foliage is very young and vulnerable (at 5 - 6 leaves or less). Wrap and bury the treated sumach suckers in plastic bags, or old rubber gloves to protect other plants.

If you can find out where they are coming from, it’s worth putting paving slabs vertically to stop them because they are shallow-rooted.

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Other invasive plants

Plants that behave perfectly well in their natural environment and climate, can become thugs when grown elsewhere. A very few of these are labelled invasive aliens and Britain has roughly twenty of them that create real problems. Most were planted by gardeners for their ornamental charms. However don’t feel too guilty. Gardeners have planted hundreds of species from other countries and only a small percentage have proved truly invasive. The sumac is not listed as invasive: it’s just a problem.

Giant Hogweed (Heracleum mantegazzianum)

Originally from South East Russia and Georgia, can reach 20ft here. It’s often found close to water courses, having escaped from gardens after its introduction in the late 19th century. The sap causes the skin to blister when exposed to sunlight. It’s a schedule 9 plant, so it an offence to grow it in the wild, although it is widespread.  

Japanese Knotweed (Fallopia japonica)

Opinions differ widely as to whether this is a problem or not. However it is almost impossible to eradicate, pushing up through concrete with a root system that can be seven miles in length.  It’s estimated that £150m a year is spent on control and clearing and there’s now a pilot scheme to introduce a Japanese insect as a control. The results are not out as yet, but could the insect become more of a threat? Wait and see.

Hottentot Fig (Carpobrotus edulis)

As the name suggests this South African plant, seem mostly on seaside cliffs in warm places, is edible. Introduced into gardens as early as the 17th century, but not recorded in the wild until 1886, it is smothering local flora. This is also a Schedule 9 plant.

Rhododendron ponticum

This has carpeted woodland areas, but now that has been found to be a Phytopthora ramorum host (a fungal disease also called Sudden Oak Death) so it is being cleared from whole areas because it affects ornamental trees including introduced and native species. The leaf litter releases phenolic compounds  which can also affect water quality in adjacent watercourses. It is of no use to British insect life. It was planted to shelter game birds, because it provides dense cover.

Himalayan Balsam (Impatiens glandulifera)

This is a stately annual with pink flowers, which tends to colonise riverbanks and damp places. The tall, hollow stems are topped with pink flowers. The seedpods explode, scattering seeds over a wide area.  It’s extremely difficult to eradicate, partly because it often grows near watercourses so cannot be chemically treated.

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Five banned water plants - from March 2014

Alien water plants have also proved problematic. They are smothering our waterways, killing fish and other creatures as they go.  The brittle sedum-like little plant, the New Zealand Pygmy Weed or Crassula helmsii, is very aggressive in Britain for instance.  It’s displaced our native flora as well as clogging waterways and sewage treatment plants.  

For many years this was sold in garden centres along with Floating Pennywort (Hydrocotyle ranunculoides), a native of South and North America. It is one of five aquatic plants which are being banned from sale in the UK from April 2014. If you have a pond you may already be nurturing an invasive alien, prompted into aggressive growth by our climate yet perfectly well behaved at home. It must be disposed off carefully and the DEFRA website will give advice. Don’t add it to your compost heap!

The five banned plants

1. New Zealand Pygmy Weed - Crassula helmsyii - (1911)
2. Parrot’s feather - Myriophyllum aquaticum, M.brasiliense, M. proserpinacoides (1878)
3. Water Primrose from Uruguay - Ludwigia uruguayensis or Ludwigia peploides
4. Water Fern from Tropical America - Azolla filiculoides
5. Floating Pennywort - Hydrocotyle ranunculoides  (1980)

For more information, visit Plant Life.

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