BFBI: Milium effusum

In this blog post, Pieter De Frenne (Ghent University) talks about his recently published Biological Flora of the British Isles paper on the perennial grass, Milium effusum…

The choice of our study species was not easy.

It is the year 2007. I have just graduated and started my PhD. I am at a meeting with my supervisors and collaborators of the international research network FLEUR. We are going through a long list of potential forest herbs to study along a climatic gradient between France and northern Scandinavia.

The list of criteria to be met was not short. Our future plant of interest should occur in temperate, boreal and subarctic Europe (our study region), a relatively slow colonizer from ancient into post-agricultural secondary forests (our research topic), a characteristic species and abundant in European forests (that is logical) and, not least, should be easy to grow in potting soil for our experiments (which is even more logical).

We had already selected a forb (Anemone nemorosa) and were searching for another study species of a contrasting growth form. A grass. Important disadvantages were raised about Deschampsia caespitosa, Brachypodium sylvatium, Poa nemoralis and Holcus mollis. After a while, we decided wood millet (Milium effusum) would qualify.


Part of an inflorescence of Milium effusum. The grass often bends towards the ground resulting in the characteristic shape of the panicle.

Milium effusum is a relatively tall grass (up to 1.8 m). It is a common feature of mature woodlands in England and other parts of Europe, and has a wide distribution in the northern hemisphere from eastern North America to Japan. The seeds (botanically speaking, caryopses) are relatively heavy (on average 1 – 2 mg), germinate easily and plants can be simply propagated clonally.

The species has even given its name to an entire association of acidophilous beech and oak forests; in the so-called Milio-Fagetum forests, Milium is a flagship species together with species such as Oxalis acetosella, Luzula pilosa, Maianthemum bifolium, Carex remota, Rubus fruticosus, Convallaria majalis and Anemone nemorosa co-occurring in the understorey.


Example of typical Milio-Fagetum forest (Zoniënwoud, near Brussels) with Milium effusum, Rubus fruticosus, Carex remota and Oxalis acetosella (photo:, Bart Roelandt).

Fast-forward eight years. I am in Greece in March 2015. I am attending another meeting with my former PhD supervisors and the same collaborators from FLEUR. We are brainstorming plans to synthesise all our Milium data collected during the past decade.

We studied wood millet’s seed quality and germination, seedling growth and survival, adult behaviour, reproduction and seed bank. We grew the seeds in potting soil in incubators, planted the species in forests, made it germinate in petri dishes. We weighted thousands of seeds, washed off soil from its roots, scanned leaves and fed plants with nitrogen.

At the meeting in Greece, Annette Kolb (Bremen University) coined the idea to write an account for the Biological Flora of the British Isles. We quickly searched online for the account of wood millet. Fortunately for us, it did not yet exist. Two years later, we are very pleased to see our own account now go to press.


Wood millet in an incubator north of the Arctic circle at the Climate Impacts Research Centre in Abisko, northern Sweden.

Biological Flora of the British Isles is a vastly influential series of manuscripts published in Journal of Ecology. Each manuscript contains, at the time of publication, a state-of-the-art autecological description of plants occurring in the British Isles.

The series was launched at the annual 1940 BES meeting in Oxford. The Second World War actually prompted this decision (see “The Biological Flora of the British Isles: 75 years and blooming” by Tony Davy, BFBI Editor). At the time, it was felt “that the present wartime circumstances, which are unfavourable to long-term investigation and to much field work, may not be so unfavourable to the sorting out of data which have, for the most part, already been collected” (citation from the foreword to the Journal of Ecology, Vol. 29, page 356, printed in August 1941).

The first articles in the series were published on four rushes (Juncus sp.) in volume 29 in 1941. Today, more than 300 species have been described in Biological Flora accounts in almost 5000 journal pages. If these pages were to be printed together in a standard hardcover book, this would result in a book of almost 30 cm thick (or four times the printed trilogy of “The Lord of the Rings”). All species accounts are listed here and are available via JSTOR (before 1999) or Wiley Online Library (after 1999).

Our own addition to the series summarizes facts and data on Milium effusum compiled from 186 books, reports and papers published between as early as 1597 (the oldest source that we cite in our account) and 2016. The paper is now available online and will be included in the next print issue of Journal of Ecology.

Pieter De Frenne, Ghent University, Belgium,


One thought on “BFBI: Milium effusum

  1. Pingback: Volume 105, Issue 3 | Journal of Ecology Blog

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