Bittercress

An unwanted plant is making its mark all over my garden. It’s called bittercress and I first spotted it around two years ago in a small shaded area of the front garden. I didn’t pay much attention to it at first but then when seed pods started to pop on the long stems emanating from the rosette of ground hugging leaves, I knew I had a problem.

Bittercress

I’m still unclear which type of bittercress I have but it really doesn’t matter. The names are different but the growth habit of the plants are the same.  The two types I have narrowed it down to are Hairy Bittercress (Cardamine hirsute) and Wavy Bittercress (C. flexuosa) but it’s difficult to single them out.

Bittercress may be small and short-lived but its ability to produce and disperse large amounts of seed makes it an exacerbating weed. They are often introduced unwittingly on the compost of container plants from garden centres and planted in the ground unnoticed. I really don’t know where mine came from but it’s incidental really as these plants are everywhere and the seeds can jump huge distances when the pods pop and even further if they latch onto a prevailing wind. I am finding that it’s not just the seeds that are a problem, each leaf ridge has the capacity to root so if I don’t pull up every last piece of the plant it will come back again.

What is bittercress?

Hairy bittercres is an annual species, common throughout Ireland and the British Isles, particularly on bare ground, path-sides, and on walls. If you do see them in containers when buying plants make sure they don’t have seed heads and that you pull all of the roots out as they can regrow. These are the smaller of the two types growing just a few centimetres

Wavy bittercress is a biennial or perennial plant, common in moist shady places, such as by streams, throughout the Ireland and the British Isles. It may occasionally be troublesome in gardens, usually in moist or poorly drained soils.   These can grow strongly to reach around 50cm (18in) in height in damp conditions but is usually shorter in gardens.

Appearance

They are related to the pretty cuckoo flower (Cardamine pratense), but bittercress is a much drabber plant with small unnoticeable white flowers and pinnate leaves. The arrangement of flowers and seed heads is typical of members of the mustard family (Brassicaceae).

As the plants are frost hardy they can survive the winter and will flower as temperatures rise in early spring, producing several generations in a season. I am finding the bittercress self-set in pots in the tunnel are growing far faster than anything else and will set seed probably before anything else has produced a flower.

Non-chemical control

I wouldn’t be tempted to use chemicals against these plants as they love to set seed in bare patches of ground and chemical control loves making bare patches. So I’ll opt for the more labour intensive methods.

Cultural control is more successful if applied before the weed has had time to set seed. Where infestations of bittercress are light, fork out before the weed sets seed. Among ornamentals or vegetable crops, careful hoeing or hand weeding is the only practical means of destroying either weed. If, however, they have been allowed to seed, they may remain a recurring problem for some time.

On borders or bare soil, deep mulch (15cm (6in)) of organic matter such as garden compost or bark should help suppress the weed.  They are small and don’t really do too much damage in established gardens but I really wouldn’t like to be selling any plants to customers that have either the plant or the seed in the pots so for now every plant leaving my tunnel will be getting a change of soil and a root wash just to be sure.

Runner Up

Runner up to the bittercress for “Most invasive” plant in the garden has to be the tomatoes. Every chamomile plug I have has at least one tomato growing in it. I’d say I have a few thousand to tease out over the coming weeks. They do come out of the soil well though and it’s very relaxing to extract them from the soil and because the root is one long tap, it doesn’t damage the other plants.