Polygala serpyllifolia

Milkwort Family [Polygalaceae]

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looks like 5

Photo: © RWD
The flowers of Heath Milkwort have slightly less variation in length (4.5 to 6mm for Heath, as opposed to 4 to 7mm for Common Milkwort)
Note the stems, which are square in places. Milkworts can have round, angular or square stems in various locations.

It is not mentioned in books that the leaves of Heath Milkwort are narrower than those on Common Milkwort, but maybe this is NOT an identifying feature?

Photo: © RWD
Heath Milkwort can be a deeper-blue than Common Milkwort, as here

Photo: © RWD
Heath Milkwort, with usually 3 to 10 flowers per spike, has far fewer flowers than Common Milkwort which usually has between 10 and 40 flowers.

Photo: © RWD
The stem is square in places here (but may be round or angular elsewhere). [Note that the stem shape is NOT a diagnostic characteristic].

Photo: © RWD
It is hard to count flowers when some are fully open and others not; there might be 9 flowers here on one stem (there is another on a shorter stem bottom left which shouldn't be counted). The fact that veins are visible on the petals is not a sole reason to think this specimen is Common Milkwort; [the veins on Heath Milkwort are less anastomosin], but it may be... However, the possibility that there might be more than 10 potential flowers would make it more likely that this specimen is probably Common Milkwort.

Photo: © RWD
With possibly only 8 flowers and with many absent leaves (shown by the presence of stumps on the stem where leaves have dropped off) makes this more likely to be Heath Milkwort (despite some network of veins on some petals).

Photo: © RWD
With only 4 flowers this has to be Heath Milkwort (although the leaves are still theoretically not opposite anywhere, they do become pretty close to being opposite in the centre...)

Photo: © RWD
In Heath Milkwort the outer 3 sepals are usually acuminate (pointed - as here) at the tip [whereas in Common Milkwort they are usually obtuse (bluntish)]. So despite the near-opposite leaves this is indeed Heath Milkwort, rather than Heath Robinson :-)


 Mutations Menu

16th June 2009, Great Orme, Llandudno, N. Wales. Photo: © RWD
This specimen exhibits proliferation, a mutation where the flowers are totally abnormal in both shape, size and their number. This specimen is not necessarily Heath Milkwort; it could be Common Milkwort, your Author cannot tell - the number of flowers is irrelevant to identification here. It was found near the similarly deep-blue specimens from the Great Orme above, so is assumed to be the same species, Heath Milkwort.

Proliferation usually occurs as a result of damage to the plant in its early stages, but there can be many other causes.

No relation to : Sea Milkwort (Glaux maritima), Milk Thistle (Silybum marianum), Purple Milk Vetch (Astragalus danicus), Lesser Milk-vetch (Astragalus odoratus), Alpine Milk-vetch (Astragalus alpinus), Milky Bellflower (Campanula lactiflora), Milk-parsley (Thyselium palustre), Cambridge Milk-parsley (Selinum carvifolia), nor with any of the ~30 other plants with 'Heath' in the common name such as Heath Dog-violet (Viola canina), Heath Groundsel (Senecio sylvaticus), Heath Pearlwort (Sagina subulata), Heath Wood-rush (Luzula multiflora), Heath Lobelia (Lobelia urens, Heath Rush (uncus squarrosus), Heath Fragrant-Orchid (Gymnadenia borealis), Heath Cudweed (Gnaphalium sylvaticum), Prickly Heath (Gaultheria mucronata), Heath Bedstraw (Galium saxatile), Sea Heath (Frankenia laevis), Cross-Leaved Heath (Erica tetralix), Darley Dale Heath (Erica × darleyensis) nor with Heather (Calluna vulgaris) etc. [plants with similar names belonging to differing families].

Usefully, this species of Milkwort does not hybridise with other Milkworts unlike the other three, Common Milkwort, Chalk Milkwort and Dwarf Milkwort.

Many similarities to : other Milkworts (Polygala species)

  • LENGTH OF PLANTS: Common Milkwort up to 30cm, erect or scrambling. Heath Milkwort up to 25cm scrambling to procumbent. Chalk Milkwort erect to ascending to 20cm. Dwarf Milkwort erect to ascending up to 10cm [16cm occasionally].
  • LEAF ARRANGEMENT: Common Milkwort has leaves which are all alternate on the stem and do not form a basal rosette (as they do in Dwarf Milkwort). Chalk Milkwort produces an irregular false rosette of blunter leaves near the base (but stem bade leafless).
  • LEAF SIZE DISTRIBUTION: Both Common Milkwort and Heath Milkwort have stem leaves which get smaller down the stem. [Whereas the leaves on both Chalk Milkwort and the very rare Dwarf Milkwort get larger lower down]
  • NUMBER OF FLOWERS: Common Milkwort usually has more than 10 flowers (10 to 40 per spike) in its main stalk (any side branches may have fewer). [Whereas Heath Milkwort usually has less than 10 flowers (3 to 10) - but on Heath Milkwort, they can drop off leaving just the stump on the stem]. Chalk Milkwort has 6 to 20 per spike. Dwarf Milkwort 7 to 30 on main spike.
  • COLOUR OF FLOWERS: The flowers of Common Milkwort can be shades of blue, purple, pink or white (as can those of Heath Milkwort). [The flowers of Chalk Milkwort are usually gentian blue and only rarely are they pink or white. The flowers of Dwarf Milkwort vary depending upon location: in the North they are blue or pink but in the South they are blue or greyish-white.]
  • SIZE OF FLOWERS: Common Milkwort 4 to 7mm. Heath Milkwort 4.5 to 6mm. Chalk Milkwort 3 to 6mm. Dwarf Milkwort 2 to 5.5mm.
  • VEINS ON PETALS: Common Milkwort has well-branched anastomising veins [which other milkworts lack (apart from the slight chance that Chalk Milkwortt occasionally may have sparingly anastomosing veins)]. Anastomosing means that the veins get more numerous towards the edge and moreover often curl back and intercept each other making an increasingly denser network the nearer the edge (see petals near the centre)
  • HABITAT: Common Milkwort chalk or limey or acidic grassland, heathland and sand dunes. Heath Milkwort acid grassland or heathland. Chalk Milkwort and Dwarf Milkwort chalk or limestone grassland.
  • RARITY: Common Milkwort and Heath Milkwort fairly common. Chalk Milkwort a slightly rare [R]. Dwarf Milkwort a very rare [RRR]

It is native and occurs frequently throughout most of Britain on acid grassland or heath (missing out on the sand-dunes and calcareous grassland which Common Milkwort also enjoys).

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Polygala serpyllifolia

Milkwort Family [Polygalaceae]