Source: http://glaucus.org.uk/Violets.htm
Timestamp: 2019-04-18 10:40:33+00:00

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On a afternoon when the sun came out unexpectantly, I quickly spotted my first two Grizzled Skippers of the year on the lower slopes of Mill Hill, now decorated with Dog Violets, but much more sparsely than normal. A Common Bee-fly hovered above the violets and a Carder Bee flitted between the flowers quicker than my camera could focus. There were occasional Sweet Violets as well, but not so many.
On a dull afternoon I made my first cursory visit of the year (after a week of squalls) to Mill Hill, just to the area around the Reservoir. There were Sweet Violets scattered sparsely over the undulating area immediately south of the Reservoir.
These violets were discovered amongst the other Dog Violets on the lower slopes of Mill Hill at the northern end. They differ slightly from most of the Dog Violets because they have longer pointed sepals and their spurs, although white, are tinged with purple. I think they lie within the normal variation of the Dog Violet, Viola riviniana.
Dog Violets had already taken over from Sweet Violets as the dominant violet over the lower slopes of MIll Hill.
Sweet Violets were commonly spread over the lower slopes of MIll Hill, but not abundant and the flowers were a bit bedraggled after the recent rain which left the steps and paths muddy but passable.
On the violet scattered lower slopes of Mill Hill, most of the thousands of violets were rain battered Sweet Violets, but the first Dog Violets appeared in flower.
The lower slopes of Mill Hill hosted the first wild Sweet Violet in flower for 2016. I only saw one, but there could have been more.
Easter brought a spell of weak sunshine. The first Dog Violets flowered on the lower slopes of Mill Hill, with the Sweet Violets much less than in previous years. Green shoots of various herbs appeared through the layer of moss.
Probably Sweet Violet as the stem is usually hairy in Hairy Violet?
Dog Violets were still in flower but there were coming to their end on the lower slopes of Mill Hill. A new violet had appeared with blunt sepals and a purple spur: a few were in flower and others were just budding. The leaves were plain and without hairs. As Sweet Violets had ceased, these were not thought to be them. They could either be a hybrid, an accidentally introduced cultivated stock or may be Hairy Violets? Viola hirta.
Closer examination shows hairy sepals and slightly hairy leaves.
Violet leaves on the lower slopes of Mill Hill. The flowers did not seem to have appeared yet ? Or maybe they have completely disappeared?
Dog Violets were now abundant over the lower slopes of Mill Hill with Sweet Violets still abundant as well.
Hundreds of Sweet Violets were sprinkled over the lower slopes of Mill Hill.
Notably there was a cleistogamic flowering Dog Violet in the south-central area below the path on the lower slopes of Mill Hill.
Notably there was a cleistogamic flowering Sweet Violet at the southern end of the lower slopes of Mill Hill.
On the slope beneath the seat on the southern part of Mill Hill, the first Sweet Violets of the year were seen in flower. There were half a dozen clumps and over a hundred flowers that had not opened fully.
From the middle of March thousands of Sweet Violets appeared and lasted until the first week in April, when they were replaced by Dog Violets which started at the end of March and their last date was not determined because of the poor weather but were present in their thousands in the middle of April.
In the second week in May hundreds of violets with a purple spur, rounded sepals and slightly hairy leaves appeared, with a few white ones. Nearer the end of May violets were noted with a purple spur and pointed sepals and dark green leaves without any noticeable hairs.
Hundreds of violets are present on Mill Hill. One was photographed with pointed sepals and a purple spur and small cupped dark green leaves that were not hairy.
On the lower slopes of Mill Hill, a new spread of violets were present in hundreds. They all had a purple spur and rounded sepals. Because of their different flowering date and a even violet (with a few white specimens) colour, I have tentatively identified these as Hairy Violets, Viola hirta.
On the lower slopes of Mill Hill the Dog Violets predominated with thousands still present. The thousands of Sweet Violets had all faded, which leaves the identity of some of the fresh violets near the bottom of the slope as a bit of a puzzle. One fresh one would have been identified as a Sweet Violet a fortnight ago with a purple spur, rounded sepals and attractive to a handful of the tiny black pollen beetles Meligethes. The second one nearby was even more problematic: it was deep violet in colour but it had a white spur (but maybe it had not coloured up?) and rounded sepals. The leaves were noticeable, medium-sized and cupped, but although very slightly hairy they were mostly smooth. I have tentatively identified the first one as a Hairy Violet.
Hairy Violet ? Hairy Violet ?
Dog Violets were in flower now equalled or exceeded the thousands of Sweet Violets on the lower slopes of Mill Hill. On the Waterworks Road, the Sweet Violets were repeatedly visited by a male Orange-tip Butterfly.
Amongst the thousand of Sweet Violets on the lower slopes of Mill Hill, attracting a few Peacock Butterflies, I also noted the first Dog Violets in flower. The micro-moth Violet Cosmet, Pancalia leuwenhoekella, was spotted on a Sweet Violet flower.
On the Downs-Coastal Link Cyclepath north of Old Shoreham, the only violets noted were several small patches of the white variety of Sweet Violet.
The sunshine came out in the afternoon when I decided to visit Lancing Ring where Sweet Violets, including white variants were in flower under shelter of the trees.
Under a blue sky and weak sunshine (14.6 °C) the Sweet Violets were flowering on Mill Hill, where I saw two Peacock Butterflies (my first two butterflies of the year), one flying across the road at the top of the hill and another one fluttering over the lower slopes.
The first Sweet Violets appeared on the Lancing Ring Nature Reserve.
Violets with purple spurs and rounded sepals (thought to be Sweet Violets) were occasionally seen on the southern end of the lower slopes of Mill Hill, as well a frequent Dog Violets.
A new blooming of violets made their regular appearance in summer but there is a puzzle over which species they are, with pointed sepals (like the Dog Violet) and a whitish-purple spur (with a shape like that of a Sweet Violet). After discussion these have been identified as the Dog Violet, Viola riviniana.
A few Peacock Butterflies visited Dog Violets which were now the dominant species with thousands of plants flowering on the lower slopes of Mill Hill, all mixed up with the remaining Sweet Violets.
The first Dog Violets of the year were seen on the Pixie Path.
Sweet Violets were abundant on the lower slopes of Mill Hill including a few patches of white ones. They were visited by both Peacock and Brimstone Butterflies.
On the still muddy Coastal-Downs Link Cyclepath a small patch of white Sweet Violets were noted.
The first Sweet Violets of the year seen on the verges of the Waterworks Road, Old Shoreham.
Cleistogamic flowers of Sweet Violets and Dog Violets were scattered thinly over the lower slopes of Mill Hill.
Dog Violets were frequently noted in flower on the lower slopes of Mill Hill.
Sweet Violets were occasionally seen on the lower slopes of Mill Hill and they were probably frequent, with at least one Dog Violet noted in flower.
At least two second flowering of Sweet Violets were noted on the lower slopes of Mill Hill.
On a mown garden verge at the top of The Drive, north Shoreham, diminutive Sweet Violets were flowering for the second time this year.
I think I also spotted an isolated Hairy Violet, the first of the year, but the identification is always tricky with these as they look like Sweet Violets.
There were still frequent Dog Violets on the lower slopes of Mill Hill. Their condition was past their best after a week of inclement weather.
Patches of unidentified Violets, Viola, were noted for the first time this year growing in cleared patches of scrub. I was surprised that I had not seen these clumps before on Mill Hill.
These could be the Early Dog Violet, Viola reichenbachiana.
The "tall" flowers, obvious gaps between the petals, dark colour and lack of notch in the spur all suggest Early Dog Violet, Viola reichenbachiana (which is indeed earlier than Common Dog Violet, coming between Sweet and Dog around here). However, I'd like the spur to be dark purple! And it usually grows in or at the edges of woodland not on open hillsides, but of course things might be different in the south.
The latest thinking (which I tend not to agree with) is that these are hybrids, intermediate between Early Dog Violets and Common Dog Violets. The sepals are spade-shaped ending in a point.
On the lower slopes of Mill Hill, Dog Violets were now about equal in prevalancy to the Sweet Violets.
The first Dog Violets of the year were spotted on the Pixie Pathand later some were visited by Peacock Butterflies on the lower slopes of Mill Hill, where the Sweet Violets were still dominant and abundant.
On the lower slopes of Mill Hill there were more Sweet Violets including white specimens. Sweet Violets were present in just a small clump on the steep slope beneath the seat on the southern section of Mill Hill.
A single Sweet Violet was spotted on the lower slopes of Mill Hill.
A Sweet Violet was noted in flower on the lower slopes of Mill Hill.
A Hairy Violet was spotted in a hole on the middle slopes of Mill Hill.
A single violet was noticed with a purple spur the lower slopes of Mill Hill, and this could have been the first Hairy Violet of the year.
Thousands of Dog Violets now dominated the lower slopes of Mill Hill, although hundreds of fading Sweet Violets could still be easily found. The Sweet Violetsunder the Hawthorn scrub by the steps in the north-west scrub part of Mill Hill were still in good condition.
The first Dog Violet of 2009 was seen in flower on the Pixie Path to Mill Hill.
At least three Peacock Butterflies visited the Sweet Violets on the lower slopes of Mill Hill. One characteristic of the violets on this original chalkhill although there were tens of thousands scattered over the main transect area, the leaves were exiguous compared to violets growing in more fertile soil.
Sweet Violets of the white variety in flower in the shade, Lancing College grounds next (north of) the entrance road before the pond.
Sweet Violets were flowering in the clumps in the meadows on Lancing Ring Nature Reserve.
Thousands of Sweet Violets were in flower scattered over the lower slopes of Mill Hill.
There were scores of Sweet Violets seen in flower on the north-south section of the Pixie Path to Mill Hill and scores more on the edge of the grass adjoining the copse at the top of Chanctonbury Drive, south-east of the bridge over the A27 to Mill Hill.
There were the first large handful of Sweet Violets seen in flower on the steep slope beneath the seat on the southern section of Mill Hill. This was earliest date in the year that they have been recorded (in the last five years, since 2004).
A single flower of Sweet Violet was noted are the southern end of the lower slopes of Mill Hill.
A Sweet Violet was noted in flower on the lower slopes of Mill Hill. Its leaves completely lacked any hairs when seen clearly with the naked eye.
The Dog Violets were prevalent, as well as Sweet Violets in thousands scattered over the lower slopes of Mill Hill. They seemed to be in fewer numbers than previous years. The leaves of some of Sweet Violets? on the open slopes were slightly hairy, whereas other were not hairy at all. So these could have been early Hairy Violets?
Thousands of Sweet Violets were in flower and at least one Dog Violet was identified from the the lower slopes of Mill Hill. Clumps of Sweet Violets were seen on the the Pixie Path to Mill Hill.
Hundreds of Sweet Violets were now to be seen flowering on the lower slopes of Mill Hill, with a few clumps on the Pixie Path.
FrequentSweet Violets were now to be seen flowering on the lower slopes and under the thorn in the scrub in the north-west corner of Mill Hill. A clump was also seen on the road verge at the top of The Drive, Shoreham. This area was downs early in the last century.
A handful of Sweet Violets were in flower at the top of the wooded slopes on the southern section of Mill Hill.
Violet leaves were noted as very common amongst the leaves of Horseshoe Vetch, Hippocrepis comosa and in many places on the lower slopes of Mill Hill.
A Dog Violet was seen in flower on the lower slopes of Mill Hill.
A Dog Violet was seen in flower on the Pixie Path.
One Hairy Violet, Viola hirta, was seen on the lower slopes of Mill Hill. There would have been more.
Surprisingly, a fresh crop of hundreds of Dog Violets had appeared on the lower slopes of Mill Hill. All these flowers inspected had very clear all white spurs.
It looked like a few Hairy Violets, Viola hirta,were in flower on the western slope of Lancing Ring, This ID has not been confirmed, but the spur was purple and the sepals rounded.
A few clumps of bright blue-violet Hairy Violets, Viola hirta,were recognised in flower on the steep (45°) slopes near the rabbit warrens at the top of the steep part of the lower slopes (NW of the Reservoir) of Mill Hill on land of about an acre that is exiguous in Horseshoe Vetch, disturbed and deeper soil and many more Violet leaves, all small, but the largest nearer the entrance to the burrows. Identification was by a combination of the purple spurs, the rounded sepals and importantly by the unusual rosette arrangement of the lower leaves (which does not always occur). The leaves were not hairy to the naked eye (an ID problem) but hairs on the stems and a few on the leaves showed up in a close-up photograph.
On the main part of the lower slopes I spotted my first Hairy Violet and later I spotted just the one Dog Violet in flower, identified by its pointed sepals, but it had a white and lilac spur. It was also possible it had hairy leaves, but it was possible that the hairy leaf belonged to another plant? This oddity is illustrated in the photographs above.
PS: Dog Violets were discovered in prime flowering condition on 26 May 2003, so they can be later than normal.
Hairy and Sweet Violets like fertilised and disturbed soil a fraction more than Dog Violets, which will grow on areas without soil but on areas with soil as well.
Hairy Violets only come out in May when Sweet Violets have already ceased for a whole month. Dog Violets follow Sweet Violets but even they usually end in late April.
The shape and the size of the Violet leaves seem more influenced by the habitat than the species. They are larger in more fertile areas and can be very small and hard to find with Dog Violets.
The butterflies were visiting Dog Violets and many of the Grizzled Skippers were seen on this small plant.
Dog Violets were now in ascendancy with thousands on the lower slopes of Mill Hill, but white Sweet Violets were still very frequent.
Dog Violets on the lower slopes of Mill Hill were seen in flower for the first time this year. The thousands of violets over Mill Hill were a mixture of Sweet Violets and Dog Violets.
There were thousands of battered Sweet Violets on the lower slopes of Mill Hill with white specimens which were in a better condition. They were visited by tiny black flies.
There were scores of Sweet Violets scattered thinly over the lower slopes of Mill Hill, but nothing else of note on the first available day when the path down to the lower slopes had not been too muddy to use.
On the verges and open front gardens of the old chalkhill near the top of Chanctonbury Drive (SE of the bridge to Mill Hill), swathes of Lesser Celandine and Sweet Violets were flowering. More Sweet Violets were in flower (over a hundred) on the steep slope beneath the seat on the southern section of Mill Hill. There were a handful seen on the lower slopes of Mill Hill as well.
There were three Sweet Violets still seen in flower on the steep slope beneath the seat on the southern section of Mill Hill.
TwoDog Violets were seen in flower on the lower slopes of Mill Hill. They were seen separately between the middle section and the northern end.
At the northern end of the lower slopes of Mill Hill, I noticed a frequency of Violet (Dog &/or Sweet) leaves.
On the lower slopes of Mill Hill, there were a handful of both flowering Dog Violets and Hairy (or Sweet) Violets were seen in passing and their leaves and sepal colour were both clearly different.
I spotted one autumn Dog Violet on the lower slopes of Mill Hill in the early afternoon. Its leaves were noticeable.
I think the above flower was Hairy Violet on the lower slopes of Mill Hill.
A few Sweet Violets still flowered under the shade of the Hawthorn on Mill Hill, but it was mostly Dog Violets in the open.
Dog Violets had now replaced the Sweet Violets*, notably on the lower slopes of Mill Hill where the first of the micro-moths Pancalia were seen amongst the exiguous leaves of the violets on the bank. (* None were noted, although I did not search for them.) I have a note that the larvae of Pancalia feed on Hairy Violets. The one seen definitely was noted amongst the leaves of Dog Violets.
Amongst the plants noted first in flower today were Dog Violets on the lower slopes of Mill Hill. But it was a remaining Sweet Violet that attracted a Peacock Butterfly.
About one in a thousand of the Sweet Violets on the the lower slopes of Mill Hill were white in colour. About 20 of the white ones were actually seen on the lower slopes in the Force 5 breeze gusting to Gale Force 7.
Spring is imminent. There were Sweet Violets in flower one the slope by the most southerly seat on the southern section of the upper part of Mill Hill. These violets have large leaves and only the first of the flowers have just appeared. Then there were several hundreds of Sweet Violets spread widely over the lower slopes of Mill Hill. These latter hundreds on the barren (not fertile) soil had their usual exiguous leaves and some were pale violet and a handful had white flowers. No violets were observed in the scrub near the steps. This area has been partially cleared of vegetation for some reason.
This Sweet Violet from the slope just beneath the seat on the southern part of Mill Hill was the typical colour of over 90% of the violets seen. The patch of Sweet Violets beneath the seat on the southern part of Mill Hill have much larger leaves than the violets on the open chalk herbland. A white flowered Sweet Violet from the lower slopes of Mill Hill. Most of the violets scatterred thinly over the lower slopes were the strong violet colour shown on the far left. A pale Sweet Violet flower from the lower slopes of Mill Hill. Notice the small leaves showing on this plant and on the lower slopes of Mill Hill, the leaves are always small.
The first Sweet Violets began to open in a clearing of the woodland under Common Ash trees on Lancing Clump. These qualify as the first wild flowers* of the year.
There was absolutely not the remotest sign of the Sweet Violet clump flowering on the southern slopes of Mill Hill.
*There is always the possibility that the Sweet Violets on Lancing Ring are escaped garden plants or planted from cultivated stock. They look slightly different from the wild plants on the low fertility Mill Hill slopes and flower a month earlier.
Hairy Violet was confirmed in flower on the lower slopes of Mill Hill, by the sepals and hairy leaves. The spur was purple. The image is for identification clarity.
The Pancalia micro-moths were very frequently (50+) seen on Daisies and as they were very small, most were overlooked and they were expected to be common (100+) over the Shoreham Bank.
Dog Violets were in poor condition after the rain and these appeared to be the only violets in flower on the Shoreham Bank.
Grizzled Skippers 11+ were the most distinctive butterfly on the lower slopes of Mill Hill, courting in pairs and nectaring on Dog Violets and the early Horseshoe Vetch only.
The second photograph shows the micro-moths 899 Pancalia leuwenhoekella.
The larvae of this moth feed on the roots, stem and leaves of the Hairy Violet,Viola hirta.
Although the Hairy Violet is present on the Shoreham bank, the other violets, Sweet Violet and Dog Violet are usually more prevalent.
records Pancalia latreillella feeding on all species of violets.
On Mill Hill and its approaches, Sweet Violets were fading and Dog Violets were appearing.
The first dozen Dog Violets were in flower on the the Pixie Path to Mill Hill, but on the lower slopes of Mill Hill the Sweet Violet was still the dominant flower with tens of thousands including white specimens forming a carpet of violet in places. No Dog Violets were identified (yet this year) on Mill Hill. Violets were absent from the grazing areas in the adjoining field to the north.
The white spur and pointed sepals leave no question about the identification.
The Sweet Violets over all of the slopes and amongst the scrub of Mill Hill numbered tens of thousands, mostly violet in colour, but also white ones. In the grass the leaves were small but they were larger in sheltered positions under the Hawthorn.
There were even more Sweet Violets over the grass on the top of Mill Hill, in the cleared scrub areas and under the scrub in shelter. In the open the leaves were absent (could not be discerned easily) or small and without hairs. In the shade the leaves were larger. A few white bunches occurred as well.
Violets from the meadows of Lancing Ring.
It is difficult to distinguish between the Sweet Violet and the Hairy Violet.
The hairiness of the leaves indicates Hairy Violet, but this is not a sure identification feature. These are down as Sweet Violets.
There were thousands of Sweet Violets growing on the slopes of Mill Hill. A single Small Tortoiseshell Butterfly visited one of them for a second on the lower slopes.
It was characteristic of these violets on the lower slopes that the leaves were dimunitive, almost invisible and hard to discover. When just one was discovered, they lacked the hairs of the Hairy Violets. Almost all the flowers were the same shade of violet without any markings or patterns found in Dog Violets. A few violets had central patches of white. Two white violets were seen at the northern end of the lower slopes. Collectively, these violetsproduced a faint perfume (or appeared to: it is difficult to be sure).
There were a handful of Sweet Violets in flower on the lower slopes of Mill Hill.
There were a dozen Sweet Violets flowering in a clump on the northern garden edge of the twitten to Buckingham Park from Ravensbourne Avenue, Shoreham. These could be nursery grown specimens.
A Sweet Violet was flowering in the twitten to Buckingham Park from Ravensbourne Avenue, Shoreham.
The Sweet Violets are in flower on Lancing Ring.
A handful of Sweet Violets in flower in the same place as earlier in the month was the only wildlife observation of limited interest on Mill Hill.
On the steep bank by the first seat from the south on the southern part of Mill Hill, there is a continuous patch of violets which I thought before were Sweet Violets, but now I am not so sure of my identification. There were three battered flowers to be seen, and the edge of these leaves were all hairy, like the Hairy Violets seen on the lower slopes.
These are Sweet Violets because the leaf is rounded rather than pointed.
These all violet plants were almost identical to the ones seen a fortnight before on the lower slopes. The sepals are green but this is not thought to be distinctive. The major difference is that these violets are in a large clump.
There were a handful of violets in flower on the lower slopes of Mill Hill. As always there was a problem identifying them between Sweet Violets and Hairy Violets.
A few Dog Violets were in flower on the lower slopes of Mill Hill out of their normal spring season. Identification was confirmed by their pointed leaves and sepals.
Hairy Violets (originally thought to be Sweet Violets) were in flower on the middle slopes in the area I have christened the Triangle, near the path at the furthest part down the slope (west) where it carves through the Horseshoe Vetch and Bird's Foot Trefoil. These were plants of the short turf, scarcely rising to 40 mm (estimated) in height.
The main expanse of Sweet Violets, by the first seat on the southern bit of the upper slopes, have not had a second flowering this year.
Violets were in flower with one example on the lower slopes of Mill Hill and another cluster beneath the ridge near the rabbit warren where a mushroom was growing.
These appear to be Hairy Violets (originally thought to be Sweet Violets). These violets are actually emerging through patches of Horseshoe Vetch.
At least half a dozen Hairy Violet plants were discovered on the lower slopes of Mill Hill, the hairs clearly seen on the leaves and the blunt sepals and blue spur enabling the identification with relative ease and confidence after being viewed through a magnifying lens.
There appeared to be at least one Hairy Violet, Viola hirta, with blunt sepals and hairy leaves. This was seen 10 metres or so north of the Tor Grass near the unruly hedgerow/scrub that separates the lower slopes from the pasture below.
The leaves of the Hairy Violet are more pointed than the Sweet Violet. Hairs are also present on the upper surfaces of the leaves; there are not many and these seem to appear later in spring.
In the north of the vetch trail near the Cowslips there were a few Dog Violets missing their spurs, but with long thin and narrow pointed sepals. At least one looked like the photograph of 15 December 2003. Violets have zygomorphic flowers.
A further check on the violets of Mill Hill revealed that the violets on the upper slopes (the Triangle) and the scrub in the north-west were all Sweet Violets, and the violets on the lower slopes (from April onwards) were almost all Dog Violets. The violets do not seem to be eaten by rabbits.
Their flowering period could be short. The violets out in the sunshine five days ago were now diminished and battered by the rain of the last few days.
The Dog Violets, Viola riviniana, on the parched lower slopes of Mill Hill were a bit more showy in the sunshine, but the wild downland plants are always diminutive. The height of each plant was no more than 45 mm and usually less. The leaves seem to be concave on the open chalk slopes. On the upper slopes, the violets are past their best or overgrown. In the scrub the violets grow higher up to an estimated height of 150 mm.
Late March to the end of May. One record from December.
Further observations would help. Some chalkhills are known to contain only or mostly the Hairy Violet, Viola hirta (sepals).
These violets grow higher, up to a height of 130 mm.
Subsequently, a doubts have crept in because of the pointed nature of the leaves, but the lack of hairs indicate Sweet Violets found in Shoreham town.
All these violets are actually quite easy to differentiate when in flower, if you look at the sepals.
Viola riviniana & V. reichenbachiana (pic) and V. canina (Heath Dog Violet) & V. lactea have pointy sepals - > V. hirta & V. odorata have sepals with rounded ends.
V. reichenbachiana & V. riviniana are very similar when in leaf, however V. reichenbachiana is mainly found in ancient woodland & ancient woodland relicts on base rich soil, V. riviniana is much more catholic in habitat choice, being found in woods, on coastal heaths, lawns etc.
V. odorata comes in range of colours, and usually grows in disturbed shady places. White violets are nearly always V. odorata. V. odorata has leaves which are hairy on the underside, and often forms obvious clumps.
V. hirta is "always" purple, and has leaves hairy on each surface, and grows as single rosettes, it always occurs in ancient grasslands often on chalk, but sometimes in neutral grasslands.
V. canina and V. lactea (Pale Dog Violet) are similar, with "pointy" sepals. They have quite specific habitat requirements, and are both "rare". The leaf shape differs from both V. riviniana/reichenbachiana and V. odorata/hirta. V.canina is wedgewood blue with a yellow/green spur, and is quite distinctive.
Sweet Violet flowers smell sweet (the others are scentless) flower colour very variable, often covers large areas.
Sweet Violet, Viola odorata, and Hairy Violet both have less pointed sepals, hairy leaf stalks and spherical seed pods (the others are triangular and pointed).
Viola reichenbachiana prefers clay to acid substrates and has a short blue spur. Dog Violets Viola reichenbachiana and Viola riviniana have different flower shapes, but it's a bit subtle.
Sweet Violets in purple are scattered with hundreds of plants over the sheltered bits of Mill Hill, mostly violetin colour but in the Triangle area of the middle slopes all white flowers were present. This is a very common wild flower. The identification is being made principally because of the white flower, although the flowering time was considered. The spur seems to confirm that these are Sweet Violets.
The Sweet Violets at the top of the wooded slopes on the southern section of Mill Hill looked battered by the gales and hail of the last two days. By 20 April 2004 these flowers were not visible.
On the path down to the lower slopes of Mill Hill, I saw one solitary small Violet flower. This species is almost certainly a Sweet Violet (opinion changed 2012), with a short (not visible or non-existent) spur. The distinguishing marks on the sepals (cf. calyx) cannot be distinguished in this only photograph.
Violets produce small cleistogamic (i.e. flowers that fertilize without opening) flowers late in the season.

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