Background
In l979 Watsonia control commenced in the Darling Range community of Darlington. At the time, Darlington was 'riddled' with Watsonia. Most creeks, much public reserve land, many road verges, and much private property was mildly to severely infested. This was not unique to Darlington of course, and this situation exists today in many other hills settlements and throughout much of the south-west.
Today Darlington generally presents a Watsonia-free face to the visitor, and even many who live here don't see Watsonias. For those who observe more closely there are still plants here and there, and a few notable infestations either well contained on private property or in more recently controlled areas at the margins.
Today
On round numbers the control area is now about l0 sq.km/ very roughly 3 x 3 km south of the Great Eastern Highway, north of the Helena River valley, east of Boya and west of Glen Forrest. This area contains a great variety of reserved land 'managed' variously by the Ministry for Planning, CALM, DOLA or Shire of Mundaring, and of course private residential or semi- rural land, road reserves, and an ex rail reserve.
The topography is typical Darling Scarp with steep slopes, deep valleys, granite outcrops and laterite upland. A great variety of natural vegetation inhabits this land and ranges from near pristine to severely degraded. Watsonia is kept under total control within this area each year with a resource of about 300 man-hours, an average of 2 hrs per day between the beginning of August and the end of December. About l0 litres of Roundup, a few pairs of rubber gloves and a good deal of sweat is expended during this period. A couple of 5l pressure sprayers, a small sponge wiper, a pair of one-handed shears and a bag or two complete the equipment line-up. An ordinary small sedan and lots of leg-work is used for access.
Early Years
In the early years of the program not much was known (by anyone) about Watsonia control. Effort was concentrated on grubbing out, publicity, street parties and a "Wattie Weedend'" each spring. Roundup had not become available and some early spraying was done with DPA. There was so much Watsonia to target in central areas that working deep into the larger reserves was not considered. Slowly experience was gained and lessons learnt, but the big breakthrough towards long term success was in the realisation of what "control" really meant. Control Control is the total prevention of reproduction within the area concerned, along with prevention of re-introduction from outside that area. If this is coupled with the progressive destruction each season of some of the remaining plants, particularly the larger, older ones capable of reproducing, eventually elimination will result.
These fundamentals apply to any weed control of course, but Watsonia has several features which make it unusually amenable. These are its seasonal growth, the well defined and clearly visible flowering of only the larger and older plants, and following that its well packaged seed containers with a clearly defined "spill time".Control
Control is the total prevention of reproduction within the area concerned, along with prevention of re-introduction from outside that area. If this is coupled with the progressive destruction each season of some of the remaining plants, particularly the larger, older ones capable of reproducing, eventually elimination will result.
These fundamentals apply to any weed control of course, but Watsonia has several features which make it unusually amenable. These are its seasonal growth, the well defined and clearly visible flowering of only the larger and older plants, and following that its well packaged seed containers with a clearly defined "spill time".
Fundamentals
Once these fundamentals are understood the control technique becomes obvious.
Rule 1: Each season try and destroy all those plants that flower. If some non-flowering plants can also be destroyed, that's a bonus.
Rule 2: In late spring/early summer after flowering has finished but before seed has dropped, check all control areas and cut off, remove and destroy any remaining stems containing maturing seed.
This maintenance can take perhaps 8-10 years in the very worst cases, and that leads to :
Rule 3: Be consistent, determined and thorough in the long term application of Rules l and 2 For don' t bother to start. One of the more common Watsonia species (W. bulbillifera) has bulbils (baby or daughter corms) clustered on the stems, rather than seeds in pods. This species is much easier to control than the true seeding type, and can usually be close to eliminated from an area in 3-4 yrs. One of the worst is the less common small seeding type Watsonia marginata.
Conclusions
There are many other aspects to effective Watsonia control such as the interaction with fire, (controlled and uncontrolled burns), the specifics of plant destruction, choice of control area, timing of work and of course regeneration of native species and interaction with other weeds. But hopefully this article introduces a sound underlying basis for control and gives some idea of what can be achieved and the resources involved. I am encouraged by feedback that other people are now starting to verify the success of those methods and principles.
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