Himalayan / Indian Balsam Dispersal

[Netuser60]

We are currently busy with controlling Himalayan Balsam (Impatiens glandulifera) and was wondering about all the alternative ways its seeds may be dispersed. It seems that usually the seeds are simply catapulted from the capsules and then are carried mainly by wind or water to new sites.

However, we've been coming across single plants that are well uphill of any watercourse in amongst dense bracken, in an area that doesn't have livestock or any human traffic. Is there any evidence that the seeds are spread by other means such as rodents or birds ??

Thanks !

[davidbr]

I've never heard the seeds are eaten by birds, but they certainly spread on the feet of animals (and humans, of course). In Bristol, Himalayan Balsam often turns up on areas of bare, recently cleared soil, not necessarily by a watercourse, so the seeds seem to be able to remain dormant & viable for quite a time.

It's often characteristic of dumped soil-heaps, so human activity seems to be the main means of spread down here. Personally it's one of my favourite plants and, in my local urban patch, does little harm; there are several areas I know of with extensive stands, a beautiful sight at this time of year in the kind of damp, shady habitat where little else can thrive.

[Netuser60]

I suppose there is a slight chance it may have been moved into the bracken area on the feet of rabbits or hares, or possibly caught in the wool of a stray sheep. I wonder if anyone can confirm that it is eaten by rats or mice which may cache the seeds away from the plant?

Here it is spreading very aggressively across species-rich commons. Initially no-one was concerned but now it has enveloped over 5 acres at one site alone in the space of about 20 years. I was clearing some yesterday and uncovering Ragged Robin and Marsh orchids from beneath its shade.

It may be a lost cause at some sites but one worry is that it is so nectar-rich that it tempts many pollinators away from other wildflowers which then fail to set seed.

[andyv]

I am concerned about HB on a SSSI next to my house. I control the patch outside my fence line by pulling and Natural England are happy to let me do as much of this as I want. The SSSI is a quite extensive wetland which floods about 3 times a year, and the HB appears on the edges but not the centre which tends to be wetter for longer.

I have a few observations to make. Firstly, we had a flood in April about 3 years back and the HB seedlings were much less that year.

Secondly I've just come back from a holiday touring Holland, northern Germany and Denmark. Surprisingly HB does not seem to be a problem in those areas, well not from what I observed, but someone may know otherwise. I did find a few isolated plants in Holland and Germany but these were only in shady woodland, so they seem to be getting outcompeted in sunny areas.

Much more common was Impatiens parviflora, the small balsam. This is also an alien species but doesn't seem to be swamping out other species like HB does in Britain.

I wondered if anybody has worked out why HB is so much less prominent on the continent.