THE WATER HYACINTH. 
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There are three useful factors which operate to prevent its spread too far— 
1. It is killed by salt water. 
2, It is very susceptible to cold. 
3. It does not live on dry land at all. Sack 
1. It is very intolerant of salt, and soon dies out in the tidal waters of rivers, 
even though masses continue to float down the stream from the fresh water 
above. Salting the plant has been suggested as a method of checking its 
development. P : 
2. Moderate cold checks it, and moderate frost injures or kills it. _ Hence it 
does not flourish much further south than the north coastal rivers in New South 
Wales unless we go inland. 
3. The usual method of clearing away the weed is to drag it out and heap it 
on dry land, where it will soon rot; but on account of the large amount of water 
it contains it will live for some time, and care should be taken to place it where 
it will not be knocked back again into the water by animals, or by heavy rains. 
It is found that a current of about 4 miles an hour is rapid enough to carry 
the growth away. Still the plant is often found growing in the bends of rapidly 
running streams, and in Emigrant Creek, a stream entering the Richmond a few 
miles above its outlet, the Hyacinth is abundant in a rapidly running stream, 
but protected by growths of the giant reed, Arundo phragmites. It is doubtful 
whether floods will eradicate growths like this. ‘ 
It is likely to prove dangerous only in the warmer parts of Victoria, where 
it might become a serious pest in irrigation channels, lakes, and water-courses. 
The spread of the plant should be carefully watched, as it is a fact well proved 
that plants can become acclimatized to the new conditions, more especially with 
respect to temperatures, at which growth will take place. In other parts of the 
world Water Hyacinth has become as great a pest as in Florida and Australia, 
and much attention has been deyoted to various ways of combating it either by 
utilization or destruction. 
It. was introduced into Indo-China twenty years ago, and at first its flowers 
were sold in the streets. It has now become a serious pest, resulting in much 
legislation being passed to secure its destruction. 
Similarly, in Burmah, there is the Water Hyacinth Act, No. 1, 1917, providing 
for the destruction of the plant and all its parts. ; 
In Tonkin its appearance dates from 1902, Cochin China 1904, and in 1906 it 
was unknown in Cambodia, but in five years it had become an insurmountable 
obstacle to navigation, and in 1916 was present in all the smallest water- 
courses, as well as in large central lakes. ‘The natives throw down planks on it 
to cross the water-ways. ‘ 
It also occurs in Java and Japan, and the Federated Malay States. 
The rate at which it grows has been a matter of careful observation, and a 
single root has in a few months covered a space of 600 square metres. 
In addition to blocking navigation along creeks and water-ways there are two 
other aspects worthy of note— 
1. In periods of drought the only green feed and water available are in 
‘these creeks, and the weed soon becomes eaten near the edges. Cattle 
seeking further relief have to descend steep banks, and in stretching 
out to reach the remaining green weed frequently slip in, and, being 
too weak to recover, are drowned if help is not soon forthcoming. 
- ‘Many head of stock are thus annually lost, and in one district. of 
the Clarence River some sixty to seventy head of cattle were drowned 
in one year. 4 “A 
2. On many farms of the North Coast the only supply of water for farm 
stock is obtained from lagoons, creeks, or blind water-courses. When. 
the Hyacinth becomes well-established in these areas the water is 
rendered unfit for drinking purposes. The decomposing plants give 
off most offensive smells, the water becomes inky black and putrid, 
and stock will not touch it. It is in such places as these that the 
weed is often difficult to eradicate, but in the ereeks it can be cleared. 
Attempts at Utilization. 
Many experiments have been carried out in all infested countries to discover 
some profitable way of utilizing the pest. It is not recommended as a manure 
for direct application, as it is very bulky to handle, rots quickly, and does not. 
provide much humus. It has only a very slight and temporary value. 
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