Agapanthus praecox is a rhizomatous, perennial herb. Its leaves are robust, strap-like and evergreen and there are 6 - 20 leaves per individual plant. The leaves grow in dense clumps from bulb up to 60 cm high. The composite inflorescences are large and round, made up of tubular flowers. These are either coloured white or light blue. Inflorescences can grow up to 1.2 m in summer. (ARC 2009; FloraBase 2010; Notten 2004; Weeds of Blue Mountains Bushland 2010). \n

Known subspecies of Agapanthus praecox include A. praecox ssp. minimus, A. praecox ssp. orientalis and A. praecox ssp. praecox. Subspecies readily hybridise, especially when grown in close proximity. In the Auckland region of New Zealand, the sale, propogation, planting and distribution of A. praecox is prohibited. However the miniature variety and culativars, along with A. praecox ssp. orientalis are allowed, despite being weedy (ARC 2009; ReportageEnviro 2010; Notten 2004; USDA, ARS 2007; Weeds of Blue Mountains Bushland 2010).

The leaves, sap and rhizomes of A. praecox are highly toxic to humans and may cause ulceration of the mouth, skin rashes and burning sensations. Especially toxic to children. A. praecox appears on the FDA Poisonous Plant Database. (Barr 2001; DPI Vic 2008b).

Ornamental, medicinal (FloraBase 2010).

Agapanthus praecox can grow almost anywhere and survives well in poor soil (FloraBase 2010). Adequate water is required in spring and summer. Preferred conditions for A. praecox growth include sun and semi-shade (ARC 2009), and soil that is well-drained, rich, and with plenty of organic matter (FloraBase 2010). Leaves are robust, and the plant is tolerant of frost (ARC 2009), hot and cold, wind, salt and heavy damage (Weedbusters 2010). Rhizomes and seeds are tolerant to sea immersion (Weedbusters 2010). A. praecox is easy to grow and it does well even in the poorest of soils, but it must receive some water in summer. To perform at its best, give it rich, well-drained soil with ample compost (decayed organic matter) and plenty of water in spring and summer. It prefers full sun. All the evergreen agapanthus are best lifted and divided every four years or so to ensure flowering. A. praecox will tolerate light frost, but is hardy only in the milder parts of the Northern Hemisphere, like the southwest of England and in the Mediterranean (Notten 2004)

Agapanthus praecox is a prolific seeder and primarily reproduces by seed. Reproduction also occurs via rhizomes. Seeds are produced in late summer into autumn, are small, black and shiny and are produced in a three sided capsule. Seed dispersal is effective, via wind, water, garden waste and contaminated soil. A. praecox germinates densely. (FloraBase 2010; Weedbusters 2010; Weeds of Blue Mountains Bushland 2010).

Agapanthus praecox can form very dense clumps and pure stands, which exclude all other vegetation. This can lead to suppression of growth of native species, and can result in massive biodiversity loss. The root network is very dense, and can also exclude native species. The roots can crack concrete, causing problems for walkways and roads. Growth on roadways can cause clogging of drains leading to flooding, which can damage roads. (DPI Vic 2008b; NPPA 2008; Weedbusters 2008).

A Risk Assessment of Acacia farnesiana for Hawai‘i and other Pacific islands was prepared by Dr. Curtis Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service. The alien plant screening system is derived from Pheloung et al. (1999) with minor modifications for use in Pacific islands (Daehler et al. 2004). The result is a score of 14 and a recommendation of: \"Likely to cause significant ecological or economic harm in Hawai‘i and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawai‘i and/or other parts of the world.\" Agapanthus praecox can be controlled using mechnical techniques alone, or in conjunction with chemical methods. Scattered plants should be dug out, and corms and root fragments disposed of carefully (refuse transfer station or dry and burn). Another alternative is to crown the plant, and apply herbicide immediately after. While A. praecox doesn't respond well to most herbicides, this cut-and-paint method has been found to be effective. As plants often resprout and the seed bank can lead to reinfestation, follow up treatments are necessary. (PIER 2010; Weeds of Blue Mountains Bushland 2010; Weedbusters 2010).