The above plant looks pretty nice, right? The flowers appear from June to October and are attractively shaped,coming in subtle hues of pink, purple and off-white with striking golden markings on the inside of the central section. What if I told you that it also has a sweet, delicate fragrance and that bees absolutely love it? Sounds like the sort of plant you might like in your own garden maybe? OK, what if I next told you that its common name was Himalayan Balsam?
That might still not mean anything to a lot of people. In fact when I was shown this statuesque annual by our then Assistant Head Gardener about 3 years ago when I first started training in horticulture, I wasn’t aware of its significance at all. It just looked like another charming addition to the plants at Chartwell! Himalayan Balsam is actually a major problem weed that grows quickly and spreads at an alarming rate, smothering most other vegetation as it goes.
It was first introduced into the UK in 1839 from the Himalayas to Kew Gardens as a potential new ornamental plant for our greenhouses and gardens. Giant Hogweed and Japanese Knotweed (two other notable invasive weeds) were also introduced around the same time and all three were advertised as being able to quickly establish within an area! Little did we know then that it would go on to become such an unwanted native, particularly thriving on scrub land and alongside water. As well as its speedy growth pattern, it can tolerate low light levels which allows it to get a head start on any other plants around it and then continue to shade out them, before also out-competing them for water and nutrients as well as light, eventually killing them off.
The thing that I found most fascinating about this plant when I was first introduced to it was not the flowers or the scent or even the thuggishness. No, it was the exploding seed pods. In fact, I’m a tad ashamed to say that I squealed like a little girl when I touched one of those pods only for it unravel and burst apart instantly! It was almost like it was alive! I played a similar trick with some friends of mine a few weekends ago when we came across some Himalayan Balsam while on a walk. My strapping 6 foot plus mate physically jumped backwards as the pod did its party piece for him!
Each plant can grow up to 3m in height and potentially produce up to 800 seeds. These seeds can be thrown up to 7m away from the plant as a result of these erupting seed pods. This is how the plant spreads so quickly. The seeds are also able to remain viable for long periods of time and when cast into a moving stream or river, can be transported even further away.
As part of my National Trust Careership course I was tasked with creating a small wild flower meadow near our compost zone at Chartwell. Unfortunately we spotted recently that some Himalayan Balsam had snuck its way in (although I must admit I briefly enjoyed the extra colour that it brought to the patch!). Luckily there wasn’t a huge amount so I was able to pull it up quite easily. For such a large plant, its roots are relatively insignificant as shown below:
We will burn the removed plants the next time we have a bonfire and make sure that none of it enters our compost system. For more serious outbreaks, chemical control might be the only option however. Himalayan Balsam can be fought with a weedkiller based on Glyphocate for instance. This is a non-selective systemic chemical that is applied to the foliage of a plant. Although it becomes inactive on contact with the soil, care must be taken not to expose the foliage of any neighbouring ornamentals to the spray.
Some interesting common names for Impatiens grandulifera include Policeman’s Helmet, Bobby Tops, Copper Tops, Gnome’s Hatstand and Kiss-me-on-the-mountain! You can also apparently make a decent curry from the seeds! The recipe can be found here. I haven’t tried it myself but if anyone out there gives it a go, please let me know what its like!
In other news, I’m pleased to announce that Horticulture Week have started running stories from this here very blog on their website! Horticulture Week is the industry trade magazine and premier website for professionals working within all areas of the UK’s vibrant horticulture industry. Both the magazine and the website are read by thousands of readers every day. You can have a look at their version of all things Chartwell here.
I look forward to seeing you all in the gardens at Chartwell soon, where I promise you won’t see any Himalayan Balsam while you’re here…