Boraginaceae - Borage family

Above: Viper's-bugloss, Echium vulgare. The inflorescence is a spike with scorpioid cyme side-branches. Cymes are sympodial branching units and scorpioid means that the flowers are borne on the axis on alternating sides. The proximal flowers (those nearest the main spike axis) open first and the others follow in succession. The flowers are pink initially but turn blue as they open and mature. The bract accompanying each flower bud is clearly visible on each cyme. There is a slight asymmetry to the flower, with the stamen filaments arching upwards (adaxially). The floral formula is: K(5) C(5) A(5) G(2) with each of the two fused carpels divided into two, resulting in a four-chambered ovary.

These plants occur on sandy and chalky soils, such as chalk grasslands, sand dunes, cliffs and disturbed ground. The large showy flower spikes attract bees and butterflies to pollinate the plant. This plant has been the subject of much analysis in an attempt to answer questions like: How do pollinators divide their time between the flowers on one spike? What is the optimum number of flowers per spike? How does having more flowers trade off against the risks/benefits of geitonogamy (fertilisation of a flower on a spike by pollen from another flower of the same spike)? These questions are important if we are to understand why some plants have large showy flower spikes with many flowers whilst others have only solitary flowers.

Viper's-bugloss is either biennial or a semelparous (monocarpic) perennial meaning that it reproduces then dies. Setting flowers is not enough to bring about death of the plant, rather it must set seed. This contrasts with iteroparous (polycarpic) perennial plants which can set seed each year.

The nectary is a rounded octagonal disc surrounding the base of the ovary with about 200 to 600 stomata through which the nectar is presumably secreted. The style is covered in long, dense and non-glandular trichomes, whilst the stigma is covered in unicellular papillae (see trichomes) which have stalks expanding into a 'corrugated umbrella'. The corrugations of neighbouring papillae interlock, especially in young flowers. The outer (lower or abaxial) surface of the calyx (fused sepals) bears many non-glandular trichomes formed of one to several cells and up to about 1.4 mm in length and fewer much shorter glandular hairs, each consisting of a stalk with a spherical head formed by a single cell. The function of these structures is presumably to guard the flower against nectar and pollen-stealing insects which do not affect pollination. However, it should be remembered that pointed non-glandular trichomes have been shown to have a sensory function in some plants - detecting walking insects by touch and mobilising the plant's chemical defences in response. It would be interesting to see whether or not the non-glandular calyx trichomes of Echium are tactile sensors. (See the beautiful study by: Weryszko-Chmielewska, E. and M. Chwil, 2008. Micromorphology of glandular structures in Echium vulgare L. flowers. Acta Agrobotanica 61: 25-34. This study is available online.)

Wood Forget-me-not (Myosotis sylvatica)

Above: Forget-Me-Nots, Myosotis, like this Wood Forget-Me-Not (Myosotis sylvatica) with their unmistakable small blue flowers are also members of the borage family.

The rootstock is short or absent and non-branching. The central stem is erect, surrounding stems are decumbent at the base and then ascend upwards. The stem leaves are sessile and elliptical, oblong or lanceolate with short stiff spreading hairs. The lower leaves gradually narrow at the base into a short petiole. The basal radical leaves are up to 15 cm long, the stem leaves up to 5 cm long.

Myosotis

Characteristic of the genus Myosotis, the 5-lobed corolla has a scale or boss at the base of each petal limb. The petals are initially pink but turn blue (or yellow in some species) upon opening. The calyx of 5 sepals is fused into a tube with 5 apical teeth. The flowers are born in scorpioid cymes: the inflorescence axis keeps giving dominance to one of its side-branches - the axis gives off one dominant branch, as its own growth terminates in a flower, which itself branches in a similar fashion, resulting in a compound (sympodial) axis bearing a number of flowers. Such a composite axis made up of branches is called a monochasium (mono- because one branch was given off by each parent axis). In a scorpioid cyme the flower-bearing branches develop on alternating sides, in a zig-zag arrangement. This type of inflorescence is characteristic of many Boraginaceae and sometimes curves or coils downwards like an upside-down scorpion's tail.

(A minority of sources, however, describe the inflorescence as a raceme, which is generally defined as a single axis or monopodium bearing flowers on short stalks and looking at the mature inflorescence the difference is not obvious, only a study of development can certainly distinguish these two types and a raceme can be more generally defined as an axis bearing flowers on short stalks, as is the case here.).

In Myosotis sylvatica there are often numerous slender stems up to 20 to 60 cm tall (1 to 2 feet). The plant occurs in woods and is biennial or occasionally perennial. A very similar form of Myosotis arvensis is said to grow in the same habitat and the two are very easily confused.

The calyx is covered in a few long adpressed hairs (adpressed = lying more-or-less parallel to the surface) and many incurved hooked hairs.

Close-up views, click images for full-size.

Field Forget-me-not (Myosotis arvensis)

To be sure, distinguishing between Myosotis sylvatica and Myosotis arvensis on morphological grounds is not easy. There are differences in the fruit (nucules) - those of M. arvensis being black and less keeled than the brown fruit of M. sylvatica but in the absence of fruit to examine it gets harder. This is compounded by the fact that M. arvensis var. umbrosa grows in shady woods and there has been confusion between this and M. sylvatica. In the past botanists questioned whether they were even separate species. Some differences between the two are:

• The leaves of arvensis are narrower and more parallel-sided than those of sylvatica.
• The corolla tube is as long as or shorter than the calyx segments, such that the petal limbs emerge in a cup-shape whereas in sylvatica the corolla tube is longer than the calyx segments such that the petal limbs stand clear of the sepals and hence appearing more like a flattened disc (except where they are so close together they can not open fully).
• In M. sylvatica the style is more than half the length of the calyx, compared to less than half the length in M. arvensis.
• However, perhaps the most obvious difference, and the one used here is that the corolla in arvensis is normally about 3 mm in diameter (up to 5mm) whilst in sylvatica it is about 8 mm across. Thus, the flowers in M. arvensis are usually strikingly smaller.

Myosotis arvensis occurs in many parts of the world (see: http://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:118914-1) and is found in the British Isles on cultivated fields, waste places and especially on sandy or gravelly soils; with var. umbrosa apparently occurring in shady woods along with Myosotis sylvatica (further study might be illuminating here).

The stems of Myosotis arvensis reach 25 to 45 cm in height. The stems and leaves are often thickly covered in stiff hairs.The calyx has a few long adpressed hairs and many hooked hairs, as in M. sylvatica but the hooked hairs are said to be more numerous in M. arvensis.

Hound's-tongue (Cynoglossum officinale)

Hound's-Tongue occurs naturally across much of Europe and northwestern Asia and has been introduced into North America (see: http://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:115233-1). This species is described as a monocarpic perennial that usually flowers in the second year (i.e. is usually biennial) but may flower in a later year (as is the case with Myosotis sylvatica and Myosotis arvensis as many biennials are not strictly so). the plant usually dies once it flowers, but may survive to flower again the following year.

The stem leaves are crowded and strap-shaped or lanceolate (lance-head shaped); the upper leaves lack stalks and their basal lobes may partially encircle the stem (they are semi-amplexicaul) but the lower stem leaves have short stalks.The baslamost radical leaves are lanceolate or elliptical and their bases attenuate into long petioles.

The shoots and leaves are covered in soft silky hairs and generally present on both sides of the leaves to give a grey-green leaf color, but in var. subglabrum the leaves are more-or-less hairless and shiny on their upper surfaces. The variety seen here is the usual hairy var. officinale.

Cynoglossum officinale is found in waste places, along the borders of fields and roadsides and on sandy hills near the shore.

The root is a thick and fleshy taproot with a black rind. In the first year it produces a tuft/rosette of radical leaves on long stalks with leaf blades up to 30 cm long. In the second year it usually flowers, producing a flowering shoot up to 30 to 100 cm tall with branches in the upper part and then usually dies but sometimes survives to flower again the following year. The inflorescence is sometimes described as a raceme (a single main monopodial axis bearing flowers on short stalks) but is I think the characteristic sympodial cyme of Boraginaceae (described for Myosotis). The end of the stem bears a pair of inflorescences and also single inflorescences at the apices of its branches. The plant has a characteristic smell of mice which does not seem to be used by pollinating bees to find the plant, though it may help to distinguish its type. The flowers produce copious nectar.

The fruit (nutlets or nucules) have a prominent margin and are covered by hooked spines, presumably to aid dispersal by animals.

Above and below: nucules of Cynoglossum officinale. Note that this infructescence (fruiting shoot) has bracts but it is reported that sometimes the inflorescence lacks bracts in this species.

Green Alkanet (Pentaglottis sempervirens)

Pentaglottis semeprvirens (= Anchusa sempervirens) or green Alkanet (Evergreen Alkanet, Evergreen Bugloss) is native to western Europe and occurs in roadsides and hedges in the British Isles where it is not clear whether it is is native to some parts of the British isles but has certainly been introduced to many parts. It is generally considered non-native to the British isles, but Syme (1867 in English botany vol. 7) thought it might be native to western England.

The stem reaches 30 to 60 cm in height and has no leafy branches. The basalmost radical or rosette leaves persist and have winged petioles and leaf blades up to 12 cm long or so. The stem leaves are ovate, tapering to a pointed tip (they are acuminate) and have entire margins. The uppermost stem leaves are more-or-less stalkless and the basal lobes of the leaf run down the stem slightly (they are slightly decurrent). The bracts (leaves subtending flowers) are ovate or lanceolate and stalkless. There is a pair of large bracts at the base of the inflorescences which occur in pairs.

Above: a white flowered form.

The 5 white scales, one at the base of the limb of each petal, are said to be finely hairy (but I have not looked that closely at them). The plant as a whole is softly hairy.Typical of Boraginaceae the flowers are pinkish in bud but soon turn blue upon opening.

Above: a beefly foraging for nectar by hovering in flight, rather like a humming-bird! The scales that narrow the opening to the throat of the flower ensure that any sizeable insect must have a narrow proboscis of the right length to reach the nectar and its proboscis will likely contact the anthers around the style as it forces its way through the narrow opening.

Each nucule has a scale-like appendage at its base on the inner side (I wonder if this is an elaiosome?).

Close-up views - click images for full-size.

Borage (Borago officinalis)

The Boraginaceae generally have strikingly beautiful flowers and Borago officinalis or Borage, is no exception. The flowers of Borage have an exquisite form. The five sepals, united at their base, form a calyx with five parts which converge (but do not fuse) around the fruit. The five petals lack an obvious corolla tube and are more-or-less rotate (disc-shaped). Five scales, one at the base of each petals, close the throat of the flower and the anthers come together to surround the style. This arrangement must  ensure that that a pollinator probing for nectar will contact the anthers with its proboscis. The anthers are purplish-black and converge and each bears a hornlike appendage on the back which is about as long as the anther.

Borago officinalis isan annual / biennial (dying once it flowers). The basal most radical leaves and the lower stem leaves are oval with long winged petioles (leaf stalks). The blades of the radical leaves are up to 18 cm long. The middle stem leaves are oblong and either have short petioles or sessile with basal lobes. The upper stem leaves are more lanceolate. The succulent stem reaches 2 to 60 cm in height and may be branched.

The flowers are borne on a scorpioid raceme. The hairs are prickly and are borne on tubercles. the pedicels droop when fruiting and the nucules are about 4 mm long and black with a rough texture and a white pulvinus at the base.

The flowers of Borage were once used in salads and, along with the leaves, are reported to have a joy-inducing effect and the welsh used to refer to it as the 'Herb of Gladness' and Syme (1867, in English Botany vol. 7) quotes Burton (Anatomy of Melancholy) who asserted it was the nepenthes of Homer.

Article updated:

9 June 2015
24 July 2016
12 June 2018
30 July 2020
13 Sept 2021
14 May 2022