History & Introduction

Orange candleflower (Arum italicum) is a herbaceous perennial, a member of the Araceae family, and a native of Asia, Europe, and North Africa. It has been introduced in parts of the United States. It was originally introduced and planted as an ornamental ground cover in the horticultural trade, in several parts of the United States. It is now considered invasive in some parts of the US, especially in the state of Washington, because it is difficult to control, spreads rapidly, creates a dense monoculture, is resistant to many herbicides, and, like other invasive species, threatens native plant diversity and damages wildlife habitat. In LIISMA, research-grade observations of the plant have been reported in Suffolk County, Brooklyn and Staten Island. 

The plant may be found in forests, urban areas, riparian zones, and wetlands. When this species takes over our forests and stream banks, it causes increased erosion, slope instability, and water quality problems.  Human health is also a concern, as all parts of orange candleflower are poisonous.  Contact with this plant can cause skin irritation; eating any part of the plant can be fatal. All parts of this plant are poisonous to humans and wildlife. (Portland Environmental Services, 2014)

Identification & Biology

Orange candleflower is a stemless woodland species that typically grows 12-18″ tall. It resembles our native Jack-in-the-Pulpit (Arisaema tryphyllum), with the main difference being the bloom description, as the native Jack-in-the-Pulpit has a greenish purple bloom, and orange candleflower has a yellowish-green to creamy-white bloom. Each flower of orange candleflower consists of an erect, finger-like spadix covered with minute, creamy white flowers and a large, sheath-like, light green spathe which subtends and partially envelops the spadix like a hood. Flowers are produced in the spring. 

The arrowhead-shaped, long-petioled, glossy grayish-green leaves with pale green midribs are 8-12″ long. After bloom time in spring, the leaves and spathe die back, leaving only the thick spadix which develops attractive, bright orange-red berries in summer. New leaves emerge in autumn and remain evergreen in warm winter climates but die back in cold winter climates where they emerge again in early spring. All parts of this plant are toxic to humans and wildlife, as contact with this plant can cause skin irritation, and  eating any part of the plant can be fatal. This perennial plant spreads by seed and small underground, rhizomatous corms (like bulbs). The plant spreads easily through soil disturbance and human planting, while seeds can be distributed widely by birds who love to feed on the plant’s berries.

Damage and Concern

Orange candleflower is currently spreading on the West Coast (Washington, Oregon and California) but also has been reported in the eastern U.S., and is a Tier 3 species in the LIISMA region. Orange candleflower forms a dense groundcover that shades out other plants. Riparian habitats are particularly susceptible to invasion. Orange candleflower also has the ability to survive harsh winters, giving it another advantage against some native vegetation. It is recommended to wear gloves when handling this plant, to prevent dermatitis-like symptoms from occurring. There are currently no effective ways to eradicate the plant once established, and it is unresponsive to many herbicides. 

Management & Control 

Mechanical Removal: If it is possible to do so without damaging other nearby plants, remove the entire plant (including the bulbs and all the tubers) with a shovel and bag and dispose of it as landfilled waste. Since arum resprouts from root fragments, it is critical that you dig up the entire root network. It may take several years of repeated mechanical removal to eradicate arum from an area. If digging up the plants is not possible for you, prevent the spread of this species by cutting back and bagging the seed clusters in late summer. 

Chemical: Most chemical treatments are not very effective at killing arum on their own. While they can kill arum foliage, they do not consistently damage the tubers, which can continue to detach and spread even after treatment. Repeated treatments that involve alternating different herbicides or using a tank mixture has a greater chance at successfully eradicating arum. Remember to follow all directions on the pesticide label before application or to consult with a professional pesticide applicator.

Monitoring & Reporting

LIISMA is currently monitoring orange candleflower as part of our Early Detection and Rapid Response program. As reports of the species are collected, LIISMA is dedicated to delineating and managing any early emerging infestations of the species before they become widespread. Orange candleflower is currently a Tier 3 species on Long Island, prioritized for early detection and containment. 

Your reports matter to us– report the species to iMapinvasives as soon as you detect it. 

Citations 

Portland Environmental Services. (2014, April 4). Italian arum (Orange Candleflower). City Green Blog RSS. Retrieved February 21, 2023, from https://www.portlandoregon.gov/bes/article/486580#:~:text=Human%20health%20is%20also%20a,the%20plant%20can%20be%20fatal%20

Washington Civic Engagement. (n.d.). Italian Arum. Document center • cowlitz county, WA • civicengage. Retrieved February 21, 2023, from https://www.co.cowlitz.wa.us/DocumentCenter

Washington State. (n.d.). Italian Arum. Washington State Noxious Weed Control Board. Retrieved February 21, 2023, from https://www.nwcb.wa.gov/pdfs/ItalianArum_Brochure.pdfWashington. (n.d.). Italian arum. Washington State Noxious Weed Control Board. Retrieved February 21, 2023, from https://www.nwcb.wa.gov/weeds/italian-arum