Wednesday, August 4, 2010

Weed-travelled Weed


If you happen to be standing in a farm gateway and detect a whiff of pineapple scent in the air, this is where it will most probably be coming from - the rayless mayweed, also more aptly named pineapple weed, Matricaria discoidea. No one is quite certain where it originally came from or how it arrived in Britain but it probably came here from the North-West United States, and it may have reached there from North-East Asia, where it also grows. Since it first appeared here, in North Wales in 1871, it has spread to every part of the UK.


Pineapple weed thrives in compacted soils that few other plants will tolerate and is often found in farm gateways - and almost anywhere where soil is compacted by the weight of vehicles. Sir Edward Salisbury, the late Director of the Royal Botanic garden at Kew and author of the the New Naturalist classic 'Weeds and Alien's (1961) attributed pineapple weed's success to two factors - aside from its tolerance of soil conditions that deter competitors. One was its prolific seed output. Salisbury was a meticulous measurer of weeds' reproductive potential and calculated that, on average, the plants produce about 7000 seeds, 93% of which germinated. He found one exceptional plant that produced an estimated 70,000 seeds. The second factor was the motor car. Pineapple weed didn't really begin to spread far and wide until widespread ownership of cars with treaded tyres carried the seeds in mud over long distances; pineapple weed is a botanical hitch-hiker.

6 comments:

  1. We also have it in the Eastern US... though not in my forested area. I've often wondered about its origins.

    ReplyDelete
  2. It reminds me of the much seeding 'Congress weed' Parthenium, which arrived in India in the 1970's from the U.S.A and is now rampant all over India

    ReplyDelete
  3. Fascinating facts Phil.
    A plant that seems to be seen everywhere I visit.

    ReplyDelete
  4. Greetings Valerianna, some plants are incredible travellers, aren't they?

    ReplyDelete
  5. Hi lotusleaf, I think both plants are in the same family, so I guess that may be one reason why they share the same invasive tendencies...

    ReplyDelete
  6. Hi Keith, I suppose it must still be on its world tour .... probably in most western European countries too..

    ReplyDelete