Watsonia meriana var. bulbillifera

(Watsonia, Bugle Lily)

Sir William Watson (1715 - 1787), the British botanist after whom Watsonia is named, would quite possibly be very disappointed with the activities of his namesake species on Australian turf.

Watsonia meriana var. bulbillifera is a problem plant in all States and Territories, except the Northern Territory. Legislation does apply in South Australia and Victoria, but it is still permitted entry to Australia.

Like many invasive plants, this one started off as a common garden ornamental, and while it is certainly an attractive plant, once it gets out of the garden it just rockets along.

Watsonia is a member of the Iridaceae Family, along with Iris. It grows from corms (these are like bulbs but are actually short, swollen underground plant stems), and each season one to three new corms will form above and beside the old one.

That's not its only reproductive ability. It also forms stem bulbils. These are corms that develop as clusters of 4-12 on the lower part of the flower spike. There can be as many as 50 or more bulbils, from the size of rice grains to a large marble, on each flowering stem.

Watsonia can also reproduce by seed but seed capsules are rarely produced. Not that this plant needs to produce seed. The corms and bulbils alone do a great job. The stem bulbils mature rapidly after flowering, and are released very readily once mature. (Not only that, but bulbils will still develop and mature on flower stems that have been cut and are sitting in a vase of water!)

Description

Watsonia produces long strappy leaves that are quite rigid. These start growing from the corm during winter. From October to December, tall flower spikes are produced. They can be 20 - 40cm long with about 10-15 individual flowers on each spike.

Flowers are tubular and curved, and they can be found in orange to red, rarely pink or purple.

The plant dies down after flowering. The underground corms are about 4-8cm in diameter and have a tunic of netted fibres. They tend to be close to the soil surface.

Control

Slashing and mowing only serves to spread the plant further if the stem bulbils have formed, as this will see them jettisoned far and wide.

Slashing stems down to about 10-15cm, before the bulbils form, prevents stem regrowth and will reduce the vigour of the below-ground corms.

Ideally plants should be dug up, taking particular care to remove all the corms. Excavation around plants needs to be done carefully to avoid spreading corms. Bag and dispose of in the garbage.

Herbicide can be effective but the trick is to spray or wipe individual plants' leaves and stems as they emerge but before they lengthen. It will take a few seasons of constant attention before plants are eradicated - there is a lot of stored energy in those corms that needs to be exhausted.

When removal is not immediately possible the spread of the plant can be limited by cutting and removing the corm-laden stems during summer, before corms mature.

This plant can be confused with Crocosma x crocosmiiflora (Montbretia), and Chasmanthe floribunda (African cornflag) as well as other introduced Watsonia species. They are all invasive species, but this particular Watsonia is the only one that produces stem bulbils.

Information sources:

Blood, K., 2001, Environmental Weeds - A field guide for SE Australia, published by CH Jerram Science Publishers.
Muyt, A., 2001, Bush Invaders of South-East Australia, published by RG and FJ Richardson.
Images by Elaine Shallue, SGA (copyright)

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