Timothy, the Hay Fever Culprit?

Phleum pratense and Phleum bertolonii spikelets © Karen Andrews

The UK has one of the highest world rates of hay fever in its population, rivalled only by Sweden. The summer hay fever is sheer misery for many UK residents. Between 20 and 25% of the UK population suffer. 90-95% of these annual sufferers are allergic to grass pollen. Timothy, Phleum pratense, is generally recognised as one of the main culprits.

Know your Enemy

What does this offending grass look like?

A Case of Mistaken Identity?

Phleum pratense‘s spikelet is often confused with the inflorescence of Alopecurus pratensis, Meadow Foxtail. Hower, the latter grass is one of the first to appear in spring. If you make yourself familiar with its characteristics with a hand lens at that time, you will not be deceived later in the year when Phleum pratense‘s inflorescence appears. It also has a distinctly coarser feel to the touch. I find the first two descriptions used by Dominic Price particularly memorable:

  • A microphone-like inflorescence
  • Double-awned glume with the look of Batman’s headgear or Devil’s horns under a hand lens
  • Blunt ligule
  • Flowering June to August, sometimes persisting into September
  • Spikelets can often be found as dried relics or with chewed appearance at field edges and roadsides later in the year
  • Bulbous base with shallow roots
  • Green in in winter, with tillers in both spring and autumn.

Distinction by Chromosomes

While I was working on my MSc grass project, I found the distinction between Phleum pratense, Timothy and Phleum bertolonii, Smaller Cat’s-tail, particularly confusing. As I discovered both specimens in the same patch of grass on campus, the distinction based on length of the inflorescence seemed to be more a matter of plant variation. Some botanists prefer to describe a subspecies. Cope and Gray advise that Timothy is an extremely variable species with a large number of cultivars introduced for hay or grazing. No single characteristic is considered totally reliable for identification other than the different chromosome numbers: pratense is hexaploid, 2n = 42; bertolonii diploid, 2n = 14). Thus, true species distinction becomes impossible in fieldwork.

Sole Culprit?

It should be stated in Timothy’s defence that grass allergy sufferers may be sensitive to more than one species of grass. They can be allergic to a small number or a much larger range of grasses. The other commonly mentioned culprit is Perennial Rye Grass, Lolium perenne. We can’t be sure how much of the blame should be attributed to the Smaller Cat’s-tail. According to the MetOffice, there are 150 other grasses that cause hay fever. Research is ongoing to identify and isolate the culprits for more informed pollen count warnings.

The grass hay fever season peak is between June and July when grasses release huge amounts dry, dusty pollen to reproduce. This is peak flowering season for Timothy grass. It seems extraordinary to think that Timothy’s pollen grains of between 22-122 micrometers in diameter can cause so much misery. Some poor souls are also allergic to various trees and wind-pollinated weed pollen extending the season of suffering for many more months of the year.

Hay Fever on Increase

Allergy desensitisation treatment is based on Timothy pollen, therefore the effectiveness is somewhat hit and miss. It is expected that 30 million people will suffer with hay fever by 2030. Hay fever often starts in childhood. Sometimes it eases with age, but for many it remains an annual purgatory. Figures show that an increasing number of adults are experiencing hay fever symptoms for the first time. The rise in allergic children is particularly worrisome.

The climate emergency with its hotter, drier summers is making more of the UK population susceptible to pollen allergies. Pollen counts are on the rise for both individual days and the overall number of days exceeding past limits. Summer 2018 was the worst year on record. Pollution appears to exacerbate hay fever sufferers’ symptoms in big cities. Those who suffer with allergic rhinitis are at much greater risk of developing asthma. There are currently 18 million hay fever sufferers in the UK. Hay fever can be a contributory factor in asthma deaths. There are 5.4 million people in the UK with asthma, of whom 1.1 million are children. Hay fever also has an adverse effect on children’s education and exams as they find it difficult to concentrate and sleep in summer months.

Timothy and Farmers

Hay fever sufferers may have cause to detest Timothy Grass, but farmers appreciate it as a good animal feed. It has high nutritional content and digestibility. Grasses barely grow at all when winter temperatures fall below 5ºC. Farmers grow and store grass crops to feed their livestock in the lean winter months. They either store the mown hay dry or wet as silage. Silage forms a major part of the winter diet in the UK. Therefore, much British agricultural land is devoted to its production in spring and summer months.

Timothy and Climate Change

Timothy favours a temperate climate for optimum growth. It has shallow roots and is already noted for being intolerant of trampling. Pollen counts reduce in persistent hot weather. It should also be noted that Timothy may not tolerate the extreme heat of climate change. Digestibility decreases as temperatures increase. The quality yields previously gained and sought from Timothy Grass may drop. Farmers may have to seek alternative grasses and crops for fodder.

Pet Food with Clue to Future?

Timothy Grass is also sold in pet shops for food and bedding material for the small pets. Alfalfa from legumes is available as an alternative feed. It is much richer and denser than Timothy hay. For example, it contains higher levels of protein and calcium. It is suitable for young rabbits, but not for adult rabbits.

The pet shop might therefore suggest an alternative crop for animal fodder under climate change conditions. Alfalfa, Lucerne or Medicago sativa, has been used as an animal fodder since ancient times in warmer climates.

In the meantime, we have to hope that researchers will come up with more answers for hay fever sufferers. Living in a pollen trap under the Mendip Hills, our family solution was always to hop in the car of a summer evening and head for sea air at Brean or Weston-Super-Mare. Unfortunately, that isn’t a feasible option for many city dwelling hay fever sufferers.

References and Further Reading

Copyright Note

Karen does not seek or receive any commercial interest or advantage from this blog. She is not promoting any business venture. She simply loves to share fascinating facts about plants. These pages illustrate her love of plants, botany, biodiversity, gardens and creative expression. There is always so much to learn about plant diversity. This blog is designed as a showcase for photography, commentary on plants and wildlife, gardens and other places visited, horticulture and related topics. Viewpoints are her own, not those of her employer.

© Karen Andrews 2018 onwards. All rights reserved. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Karen Andrews and BotanyKaren.net with appropriate and specific direction to the original content. 

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