covered in weeds
you help us with a weed that is overtaking everything planted on
our bank? It has pink flowers like a sweet pea, climbs to a considerable
height and when you cut it down it just grows away again from the
root system. We've tried spraying it with all kinds of weedkillers
but nothing seems to work.
CHECKED with sweet pea expert Keith Hammett and it sounds like your
problem is caused by the perennial sweet pea Lathyrus latifolius.
It comes from Chile and really shouldn't be called a sweet pea at
all as its flowers, which can be pink, rose or white, have no scent.
The popular scented sweet peas are mostly bred from forms of Lathyrus
odoratus which originate in Italy.
Keith suggests you should
be able to control this weedy variety by cutting them back to the
ground, allowing new growth to reach 30cm or so high, then spraying
it with a glyphosate-based herbicide such as Roundup or Glyphosate.
It will take several weeks for the foliage to die down and for the
next year or two you'll almost certainly have to keep spot-spraying
new growth until the fleshy root system has either absorbed enough
of the spray to kill it or dies of exhaustion.
There will also be seeds
in the soil which will continue to germinate over the next few years
and you'll need to either pull these seedlings out while they're
still small or spot spray them.
When spraying, make sure
you thoroughly cover all foliage but avoid getting it on desirable
Other products you could
try include Activated Amitrole and Escort. Adding a sticking agent
such as Pulse or Sprayfix to the mix helps improve the effectiveness
of these sprays, so check the label and follow the recommendations.
Also perhaps worth a
try is Vigilant which comes as a gel that is applied directly to
the cut stems at the base of the plant immediately after you chop
off the top growth.
Gardener, Issue 177, 2005, Page 30
Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.