Valley of Flowers: Himalayan balsam (Impatiens glandulifera)

As you make your grand entry into the Valley of Flowers, you may find it dappled in a prominent shade of pink. The pretty hue is, in part, due to the Himalayan balsam, a plant nicknamed “kiss-me-on-the-mountain” due to its origin in the Himalayas. The hooded shape of this flower has sprung up another nickname – policeman’s helmet. You will find these beauties blooming in abundance throughout the Valley of Flowers, which has the Pushpawati river flowing through it.

The Pushpawati river has an interesting story of its own. The milky waters of this river originate from the Tipra Glacier in Garhwal. Legend has it that the Pushpawati river (“Pushpa” means flower) was named so by the Pandavas in the epic Mahabharata after they saw flowers floating down the river.

The Himalayan balsam plant was introduced into the UK as an ornamental garden plant in 1839. Since then, it has grown into an invasive weed there, competing with the native species for the goodies on offer. There are a couple of reasons for its extraordinary success outside its native range; let’s check them out.

The first reason would be the copious amounts of nectar produced by these flowers, leading to them being called a “nectar factory.” In fact, each flower of this plant is known to produce 0.5 mg of sugar per hour, while those of native species produce less than 0.1 mg per hour. Additionally, these flowers produce nectar at a time when other nectar-rich flowers are not to be found. No wonder that the Himalayan balsam quickly became the go-to refill station for bumble bees, honey bees and wasps!

The pretty pink flowers are a textbook example of functional design. They hold copious amounts of nectar, but store it in a not-so-accessible place. The bee has to actually climb in to the helmet-shaped part of the flower to gain access to the goodies. This particular act of the bees has earned the flower yet another nickname – Bee bums – and the picture below will tell you why!

Now, why would the flower produce lots of nectar for the bees, and then restrict easy access? Let’s take a look at the above picture again. While the bee is busy feeding inside the flower on the left, closely observe the flower on the right? Can you see tiny pink appendages hanging from the ceiling of the flower, like chandeliers, with white/cream trimmings? Those are the stamens, or the male reproductive parts of the flower. They produce pollen, which is showered on the bees while they are busy feasting on nectar. When the happy, satisfied bee finally emerges from the flower, it is covered in a white pixie dust of pollen (check out the picture below). In fact, so profuse is the pollen shower that the emerging bee is forced to clean its eyes before heading out to another flower, and yet another drink. The whole process ensures that the pollen stuck on its backside is transferred to the next flower, where the stigma (female reproductive part) is waiting, ready to complete the process of pollination. The Himalayan balsam plants have chartered out the bee courier service as an effective way of transferring pollen from one flower to another, with the copious nectar being a small price to pay for excellent service!

The second reason for the plant’s success at flourishing outside its native range is the manner of seed dispersal. If the Himalayan balsam is a master at ensuring pollination, it also makes sure that the resulting seeds have their best shot (literally) at survival. The ripe seed pods eject their seeds by an interesting mechanism known as “explosive dehiscence.” Much like the build-up to an earthquake, the pressure inside the seed pod gradually increases as it ripens, reaching a breaking point when fully ripe. At this stage, even a tiny disturbance can trigger an explosion along lines of weakness in the pod, shooting seeds to distances up to 7 meters. For comparison’s sake, this distance almost approaches the Olympics long jump record!

The highly efficient survival mechanisms of this plant enabled it to quickly become invasive after it was brought in to the UK. Ironically, when the plant was first introduced, it was marketed as an exciting plaything for children under the name “Mr Noisy’s exploding plant”. The takeaway point – the decision to introduce a non-native plant in a region where it may become invasive is no child’s play!

P.S.: Thanks to Belur Ashok for this image (Fig 2) of Pushpawati river on Flickr shared under the terms of license cc-by-2.0

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