Wednesday, August 5, 2015

All about Flickweed

Flickweed is common in CP collections, but talking with close friend Jessica about it a few months back, I realised that I really new very little about it. A chance encounter with it the other day gave me an opportunity to read up about it, so here is a summary of what I learned:


Flickweed (Cerastrum hirsuta) is a small herb that is a native of damp areas in western Europe and North Africa. It is also known by many other names, including hairy bittercress, snapweed, shotweed and pepperweed. From a CP perspective, it is an issue because it spreads like wildfire in both bog gardens and potted CP collections.

Cardamine_hirsuta_flower Cardamine_hirsuta_flower_close

Above are some close-ups of the flowers, which are like very tiny, dainty goblets.


Flickweed gets its common name because it produces specialised, elongate seed capsules called a siliques, which are shown above. When the seeds are ripe, the sides of the silique split open if they are touched, explosively launching the seeds over distances of nearly two meters. At right is a close-up of several siliques.

The explosive method of seed dispersal means flickweed can soon establish itself throughout a CP collection. This happened with the first bog garden I had in Queensland. It got in because a few plants were growing nearby the bog. Once it was in, it needed a complete removal of plants and fresh peat to eliminate it. Subsequent bog gardens were all raised, and I think this may have helped by keeping the soil away from plants growing in the garden.

I don’t have flickweed in my collection because I have been very careful to make sure I removed any plants before they made it into the collection, and then kept a constant eye open for seedlings and removed them before they produced flowers. I had hoped that it would be a scourge I would not have to manage due to our cold winters. However, I have started to notice flickweed appearing as a weed of garden beds around Canberra. These pics were taken at CSIRO Black Mountain.

Cardamine_hirsuta_wp_JN  Cardamine_hirsuta_wp_JN2

Once established, flickweed clumps up fast and can also form dense carpets. Attempts to weed it result in more seeds being dispersed. Sadly, it will require a complete and simultaneous removal of media (including from roots of plants) to eliminate it when established in a bog garden, followed by a vigilant watch for stragglers afterwards. It can be easier to eliminate from a potted collection, but be sure to check around the edges of pots and also drainage holes to make sure you get every plant, and keep checking for and remove re-growth as it occurs. Prevention is the best cure, so it pays to remove any flickweed present from new purchases and keep the new plants quarantined to eliminate the possibility of seedlings. Weeding is really only practical to eliminate populations that are just starting out, but be careful not to spread it further if it is in seed. Herbicides do work, but they are impractical in collections.

As for my collection, its still freezing cold here, and I’ve been taking plenty of pics of frosted up plants. They will feature in a separate post sometime over the weekend, along with a bizarre “weed” that came up in Sphagnum moss that I don’t have the heart to kill off. Spring can’t come fast enough!