Holly

(Ilex aquifolium)

 
 
Holly Berries, photo: © Jürgen Howaldt (Wikimedia)

What is Holly?

  • Holly is an invasive ‘environmental’ weed of forests, forest margins, riparian areas, disturbed sites, waste areas and gardens in the cooler temperate regions of Australia.
  • Holly does occur in Tasmania, and is a declared weed under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of Holly are prohibited in Tasmania.

How to identify holly?

  • Holly is widely cultivated in Australia as a garden ornamental and hedging plant, with numerous cultivars available, including some without prickly leaves and others with variegated leaves.
  • An upright (erect) much-branched shrub or small tree usually growing up to 10 m, or occasionally a larger tree up to 15 m in height. Holly’s thick and leathery spine tipped leaves have glossy dark green upper surfaces and paler, duller undersides.
  • Small pinkish-white flowers (about 8 mm across) are produced in clusters of three in the leaf forks, with separate male and female flowers borne on separate plants, (‘dioecious’). Rounded berry-like fruit (7-10 mm across) turn bright red as they mature in Autumn, and are mildly poisonous to humans, causing vomiting.
  • The fruit are eaten by birds and other animals which disperse the seeds into bushland, and they may also be spread in dumped garden waste. Plants can also spread laterally by suckering and layering to form dense thickets, replacing native plants and shrubs.
  • Holly is also dispersed intentionally by people, being available in nurseries, garden centres, markets, and in florist shops.
  • For further information or help in identifying holly, contact Biosecurity Tasmania on 03 6165 3777.
Image: Mature holly trees.

Holly in Tasmania

  • Holly (Ilex aquifolium) is native to northern Africa, western and southern Europe, and western Asia, and now naturalised in New Zealand, western USA, Hawaii, and in much of temperate south-eastern Australia, (on the central and southern tablelands of New South Wales, Victoria, Tasmania and south-eastern South Australia).
  • Tolerant of summer drought, modelling indicates very strong year-round suitability to much of Tasmania, with several known naturalised holly populations in parts of the state.

Legal status of holly in your area?

  • The legal responsibilities of landholders and other stakeholders in dealing with holly are laid out in the Statutory Weed Management Plan for Holly.
  • For details regarding distribution of holly, including whether your area falls in an eradication (‘Zone A’ municipality), or containment (‘Zone B’ municipality), refer to the Tables and information provided in Section 12, ‘Management of Holly by municipality’, in the Statutory Weed Management Plan for Holly.

See also
Statutory Management Plan for Holly
Weed Links and Resources

Other useful links
Holly Control: Hobart City Council Bushcare Experience (by Rob Beedham)
Pest Genie
APVMA


Holly Control Guide

Do

  • Plan your control program, this will save time and money in the long-run;
  • Consider the impact of your control methods on off-target species, especially if herbicides are used;
  • Ensure machinery and equipment is washed down between sites or prior to contractors leaving site;
  • Get in early for new infestations, Control of mature trees is more difficult and expensive;
  • Carefully time your use of herbicide for best results (see Herbicides for Holly Control below for more information);
  • Coordinate your control program with neighbouring landholders where your weed problem crosses property boundaries;
  • Revisit and regularly inspect the site and ensure follow-up is undertaken;
  • Use a combination of different control methods; and
  • To reduce re-infestation, restore the disturbed habitat with new plants such as native species, non-invasive garden species, vigorous pasture and/or production crops where suitable.

Don't

  • Don't introduce holly to holly-free areas (e.g. by failing to wash down machinery and equipment between sites);
  • Don't start your control program without first planning your approach;
  • Don't allow holly to flower and set seed before treatment;
  • Don't rely on one attempt at removal - follow-up is essential;
  • Don't rely on just one control method;

Spread of holly

  • Holly berries (with seeds) are readily carried long distances by rivers and streams, in mud and soil carried on road graders and earth moving equipment, farm machinery, vehicles, footwear, and in the digestive tracts of birds and animals.
  • Berries can also be distributed via contaminated agricultural produce, garden waste dumped in bushland and roadsides, or cultivation as an ornamental plant.
  • Germination of root suckers and branches can occur after some soil or vegetation disturbance including cultivation, fire, slashing, herbicide treatment, road-making, pig-digging, etc.
  • Holly can also invade new areas without major disturbance via seed dispersal.

Avoiding the introduction of holly

  • If cultivation must be carried out in infested areas, ensure all equipment is cleaned and checked for holly berries or seeds before moving to un-infested areas. If possible, always work un-infested areas first.
  • Gravel and sand should not be removed from infested quarries and streams.
  • Holly growing along access tracks must be controlled to limit spread of seed. Vehicles, bush walkers and horse riders using infested areas should keep to designated routes to avoid disturbance and spread of seed.

Physical removal

  • Small seedlings can be hand pulled or grubbed when the ground is moist. They are often difficult to pull out due to strong roots. Do not hand pull if all the roots cannot be confidently removed, as they will re-sprout.
  • After clearing always carry out follow up treatments, as holly when left readily regenerates forming dense thickets in moist bushland areas, seriously impacting and threatening native vegetation.

Cultivation

  • Pasture improvement is an effective method of control for arable land infested with holly. Large plants can be mechanically removed, followed by repeated cultivation, cropping and/or pasture establishment and grazing.
  • To reduce re-infestation in bushland, disturbed habitat can be restored with new plants such as native species and/or non-invasive garden plants.

Chemical control

  • A number of herbicides are registered for use on holly in Tasmania, see Herbicides for Holly Control for more information.
  • Apply herbicide when plants are actively growing, generally spring to early summer, and after the autumn break; however, local experience has found that holly responds well to cut and paint techniques throughout the year. For the most effective control of holly, do not treat during winter as the tree is dormant and will not take up the poison.

  • Cut the shrub off at ground level and paint stump immediately with an undiluted herbicide. This is useful for larger seedlings or small shrubs that are too hard to hand pull. See Herbicides for Holly Control below for more information.
  • Cut stump application is useful where foliar application of herbicide may cause off-target damage, for example in treating holly on riverbanks or amongst desirable shrubs and trees.
  • Larger shrubs and trees can be treated by drilling holes 2-3 cm in the trunk as close to the root as possible, and filling each hole immediately with an undiluted herbicide. The tree will then slowly die and may need to be removed later. This is useful when you do not want to open a hole in the canopy by removing a large tree. Repeat treatments may be required over 12 months. See Herbicides for Holly Control below for more information.
  • Allow regrowth to reach 50 to 100 cm high before herbicide treatment; this ensures enough leaf area to absorb sufficient herbicide to kill the roots.
  • Sprayed bushes should not be removed until full brownout has occurred (at least six months after treatment).

Hobart City Council Bushcare Experience

Holly Control: Hobart City Council Bushcare Experience (by Rob Beedham)

Herbicides for Holly Control

These herbicide recommendations are made subject to the product being registered for that purpose under relevant legislation. It is the user's responsibility to check that registration or an off-label permit covers the proposed use. Always read the herbicide label.

If in doubt, visit the Australian Pesticides and Veterinary Medicines Authority (APVMA) website.

Only herbicides registered for use in pasture and non-cropping situations are listed in the following table. Care must be taken in using herbicides as non-target plants contacted may be harmed. For recommendations in specific crops consult an agronomist.

Wetting agents

Carefully consult the product label for specific directions regarding the use of wetting agents or adjuvants.

Waterways and wetlands

Be careful! Many herbicides can cause damage to waterways and wetlands. Check the herbicide label directions carefully before use near waterways and wetlands. For more information see Guidelines for Safe and Effective Herbicide Use Near Waterways.

Herbicide Brands and Concentrations

Herbicides are referred to by the active chemical ingredient in the following table. The product trade names in this publication are supplied on the understanding that no preference between equivalent products is intended and that the inclusion of a product does not imply endorsement by DPIPWE over any other equivalent product from another manufacturer. Information on available brands containing the herbicide you require should be obtained from a reputable herbicide supplier or the APVMA website.

There may be a number of products with the same active ingredient some with alternate formulations (concentration) registered for control of a weed eg: Glyphosate 360g/L, Glyphosate 450g/L may be registered for use on the same weed. Alternate formulations such as these will have a different application rate. Always check the label.


Foliar spray - spot spray, knapsack application

Herbicide
(active ingredient)
Example of commercial product (concentration of active ingredient) Application rate of commercial product
(With water unless indicated)
Withholding period Comments
Glyphosate** 360 g/L (where product has an aquatic registration)Weedmaster Duo
360 g/L
Roundup Biactive®
360 g/L
10 -13 ml/L plus adjuvant ONLY in accordance with label as requiredNot required when used as directed.In accordance with APVMA permit PER84775.

For spot spraying of regrowth and seedlings.

Do not treat during winter as the tree is dormant and will not take up the poison.
Glyphosate** 540 g/L (where product has an aquatic registration)Roundup Power Max®
540 g/L
7 ml/L plus adjuvant ONLY in accordance with label as requiredNot required when used as directed.
Triclopyr 300 g/L +*Picloram 100 g/L + Aminopyralid 8 g/L*Grazon Extra (300 g/L, 100 g/L, 8 g/L)400 ml/100 LNot required when used as directed. In accordance with APVMA permit PER84775.
Metsulfuron-methyl 600 g/Kg**Associate®, Metsulfuron 600 WG Herbicide10-15 g/ 100 L plus wetting agent ONLY in accordance with label as requiredNot required when used as directed.In accordance with APVMA permit PER84775.

*Note: picloram remains active in soil for extended periods and may leach into groundwater.

Drill and Fill, Cut stump and Basal bark applications

Herbicide
(active ingredient)
Example of commercial product (concentration of active ingredient)Application rate of commercial product
Withholding periodComments
*Picloram (44.7g/L) + aminopyralid (4.7 g/L)Vigilant II®Apply gel undiluted  3- 5 mm thickNot required when used as directed.Cut stump and apply immediately.

Suitable for non-crop situations.
Glyphosate 360 g/L (where product has an aquatic registration)Weedmaster Duo
360 g/L
Roundup Biactive®
360 g/L
UndilutedNot required when used as directed.In accordance with APVMA permit PER84775.

For paint or cut stump techniques.
Triclopyr 600** g/LGarlon TM 6001:60 in dieselNot required when used as directed.

*Note: picloram remains active in soil for extended periods and may leach into groundwater.

**These products are not registered on label for this use in Tasmania and will not be mentioned on products labels, however a permit (number - PER84775) issued by the Australian Pesticides & Veterinary Medicines Authority allows this specific use. If using this method and herbicide you will require a copy of this permit. For further information on permit details visit the APVMA website.

Important Disclaimer
To the extent permitted by law, the Tasmanian Department of Primary Industries, Parks, Water and Environment (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using information or material (in part or in whole) contained on this website.


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