EVENTS

Members Reports and Photos

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SATURDAY 3rd AUGUST 2013

Plant Identification: Asteraceae & Umbelliferae, 3rd August 2013.

Leaders: Gerry Sharkey (Asteracea) and Declan Doogue (Umbelliferae)

Report: Pat Lenihan

Members from Donegal and Mayo were among the thirteen participants that ensured a “full house” at the Praeger Centre for this holiday-weekend workshop.

Gerry began by clarifying the potentially confusing structure of the Asteraceae (Compositae). He pointed out that they have a distinct inflorescence (capitulum) which consists of many individual flowers (florets) that is often mistaken for a single flower.  In place of sepals, the base of the inflorescence has bracts (phyllaries), which can be brightly coloured or have a dry and membranous texture (scarious). In addition, they can have spines, different shapes, and arrangements.

Florets are attached to a shared base (receptacle) and have five petals that are fused at their lower ends to form tubes (corolla tubes). They may also be small scales (chaff) between the florets. The calyx of each floret, if present, forms a structure of feathery hairs (pappus) on top of the ovary which aids seed dispersal. 

A typical inflorescence consists of a central ring of tubular florets surrounded by an outer ring of ligulate florets. The former look like toothed-tubes due to their protruding petal tips and are bisexual i.e. having male and female parts. Ligulate florets have a strap-like structure (ligule) attached to the outer side of their much smaller fused corolla tubes which gives them a petal-like appearance. Ligulate florets lack stamens (unisexual) or, more rarely, lack both carpals and stamens (sterile). Some plants have only tubular or ligulate florets.

The best know members of the Asteraceae are Dandelions (Taraxacum species), yellow flowers with soft stems which exude a white latex. The family also includes a wide variety of other well known plants from different genera and many of these were on display such as Cirsium arvense and C. palustris, which usually have purple heads that sometimes are white; the beautiful, calcicole Carlina vulgaris; and Centaurea nigra with technical features similar to Cirsium species but with a black head that becomes brown and harder as the season progresses.

Other species from the genera Sonchus, Achillea, Senecio, Hypochoeris, Mycelium, Lapsana, and Pulicaria were also examined, their habitats described, and their salient features discussed. Gerry stressed that is was important to use a combination of features (floret/pappus types, leaves, bracts, chaff) for identification purposes. He did not consider the  use of keys to be of value in separating genera.

The Umbelliferae (Apiaceae), commonly known as the carrot family, consist of many vegetables and herbs such as carrots, parsnips, parsley, fennel, and celery. However, other members of the family are very poisonous. Declan explained that Smyrnium olusatrum and Aegopodium podagraria and other species were introduced in medieval times and formaly cultivated. Many of these have persisted in the wild and are found in the vicinity of monastic ruins and sites of older habitations.  Members of the Apiaceae thrive on nutrient rich habitats with the result that they are becoming larger and more prevalent due to the increased use of agricultural fertilizers.

The defining characteristic of the family is the inflorescence, an umbel, which is made up of short flower stalks arising from a common point, like umbrella ribs, to form a flower head that can be flat or almost spherical. Umbels are usually compound, the stalks of the partial umbels, which can be subtended by bracteoles, meeting in a point to form the general umbel which in turn can be subtended by bracts.

For identification purposes, the presence or absence of bracts/bracteoles is an important feature. If bracts are present their structure may be significant. Similarly, fruits are often the key to separating species as they can be ribbed/smooth, covered with prickles/spines, and flat or curved. Other diagnostic features include flower colour, leaf size/shape, odour, and habitat.

Both Smyrnium olusatrum and Foeniculum vulgare have yellow flowers: the former species has oval toothed leaves with fruits that appear like an “upturned boat”, whereas the latter has very finely divided leaves and smells like aniseed. Pastinaca sativa has yellow flowers and is similar in size to F. vulgare but its leaves are large and pinnate.

Angelica sylvestris  and Apium nodiflorum both occur in wet habitats. However, A. sylvestris has a large terminal flower head tinged by purple and leaf stalks inflated at the base. In contrast, A. nodiflorum has flowers that form in its nodes. Oenanthe lachenalii, characterized by its long narrow leaves, is also associated with fresh water but in locations where water passes down to salt marsh vegetation. 

Both Conium maculatum  and Aethusa cynapium are poisonous but can be distinguished easily because C. maculatum has stems with purple spots and orbicular fruits, whereas A. cynapium has bracteoles that point downwards.

Pimpinella saxifraga is characterized by having a few narrow upper leaves and many larger basal leaves that are similar to those of Sanguisorba minor. The other burnet, Pimpinella major, has a more Western distribution and large coarse leaves. 

Heracleum spondylium is one of the commonest white flowered species found in hedgerows: Tortilis japonica occupies a similar habitat but is pink flowered and much smaller.

Anthriscus sylvatica has delicate, fern-like leaves, flowers throughout the Spring, and can be identified later in the year by its long fruits. In contrast, Aegopodium podagraria has leaves that are divided into three’s, flowers for less than a week, and has small, ovoid fruits.

Participants, under the leader’s expert tuition, improved their identification skills by comparing and contrasting  the wide variety of the species described above which were made available for study.

             

     

        

     

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