FIELD GARLICS AND WILD ORCHIDS AT WINDMILL HILL 1981 TO 2002

Terry Knight

The Reserve

Windmill Hill is a Site of Special Scientific Interest situated in south-east Worcestershire in the parish of North and Middle Littleton at grid reference SP 070472. It consists of a half mile long west facing escarpment of the Rhaetic and Mercian Mudstone beds with a base rich topsoil. The bottom 20 to 25 metres is now mature hawthorn scrub with some ash Fraxinus excelsior and field maple Acer campestre. Above this is grassland, generally about 60 metres in width, dominated by tor-grass Brachypodium pinnatum.

Management

The site was formerly grazed but for forty years or more prior to 1979 it was managed only by irregular burning of the grass. This was insufficient to prevent invasion of scrub and allowed what was originally the bottom hedge to expand into the present belt of mature hawthorns. It probably also accounts for the dominance of tor-grass. When the Worcestershire Wildlife Trust purchased the site for a nature reserve in 1979 its first priority was to reintroduce grazing to slow down scrub invasion and to try to control the tor-grass. Most of the grassland has now been fenced to give five end-to-end paddocks. Three of these were first grazed in 1982, a fourth in 1993 and the fifth remains ungrazed at present. Sheep have been used for grazing up to now, usually in the winter and spring, but in eight of the twenty two seasons there was no appreciable grazing. Experiments were carried out in 1998 and 1999 on three sets of small sample plots of grassland. One of these was in a species poor / tor-grass dominant area, the second in a herb rich / tor-grass scarce area and the third in an intermediate area. The plots in each set were subjected to various degrees of 'hand grazing' over the two seasons. From the results of this it was decided to increase the severity of grazing in the paddocks between autumn and spring where this was practical. Despite this, hawthorn continues to invade the paddocks, at a substantial rate at the bottom, and requires to be removed by hand on a four or five year rotation. Some smallish areas of more permanent scrub exist in the ungrazed paddock.

Recording

Out of interest, in 1973 and 1974 most of the field garlics Allium oleraceum and wild orchids were mapped. The wild orchids included bee Ophrys apifera, common spotted Dactylorhiza fuchsii, greater butterfly Platanthera chlorantha, pyramidal Anacamptis pyramidalis and twayblade Listera ovata. When the site became a nature reserve in 1979 it was decided to try to map all six as thoroughly as possible each year. All are perennial monocotyledons and have their growing point below ground and hence protected from grazing although the leaves and inflorescences are vulnerable. Each species occurs in modest numbers and is not too difficult to find, particularly when in bud or flower, making mapping not too onerous a task. The coverage has been fairly good but in some years the reserve was grazed in the summer making mapping impractical. Over recent years rabbit grazing in the summer has extended further into the paddocks. This has probably slightly reduced the number of orchids spotted, particularly in the centre paddock. In a few other years time available, and occasionally enthusiasm, was insufficient to provide full coverage. Where only partial coverage was achieved an adjustment has been made in some cases to estimate the likely yearly total. The results from 1981 have been used as this is the year prior to the introduction of grazing. These are given in Table 1.

	Actual number			Adjusted number			Split
	Field garlic	Bee Orchid	Other orchids	Field Garlic	Bee Orchid	Other Orchid	Other un-grazed	Other grazed
Year
1981	22	132	204	22	132	204	43	161
1982	11	151	147	11	151	193	53	140
1983		97	233	25	97	291	104	187
1984			98	25	88	175	36	139
1985	111	79	174	111	79	232	26	206
1986		18	402	30	18	457	84	373
1987	5		122	5	62	265	28	237
1988	190	106	861	190	106	861	158	703
1989	152	98	366	152	98	402	92	310
1990	569	86	191	569	86	191	101	90
1991	36	73	243	36	73	328	22	306
1992	18	27	285	18	27	452	11	441
1993	140	68	572	140	68	572	113	459
1994	75	5	199	75	5	362	54	308
1995	398	32	487	398	32	694	113	481
1996	5	1	172	5	1	344	48	296
1997		4	188	100	4	272	35	237
1998	45	8	305	45	8	693	83	610
1999	89	22	492	89	22	541	35	506
2000		10	440	150	10	440	42	398
2001	564	6	906	564	6	906	82	824
2002	1025	4	847	1025	4	847	50	797

Table 1. Number of plants per year

Field Garlics

This is a species of dry grassy banks and although the inforescence consists of flowers and bulbils it rarely produces seed. New plants therefore usually arise from the bulbils falling to the ground and propagating. This is probably assisted on the reserve by the ground shrinking significantly in the summer to produce substantial cracks for bulbils to fall into. They are usually scattered but groups of closely spaced plants do occur in places from time to time. Few records are made from the flatter upper half of the site, most come from the steepest slopes just below the middle path with others on some of the somewhat less steep slopes below. Unfortunately, this makes recording a bit more difficult. As the grass in most places on the reserve is reasonably long in the late spring and summer it is only practical to record around mid July when the inflorescence is well developed. Consequently only flowering plants have been recorded. In scattered locations groups of 25 to 100 flowers come up spontaneously or over a period of one or two years and then disappear just as quickly. A group may then have a similar resurgence and decline in the same spot a few years later. Whether this sporadic appearance applies to the plants themselves or just the flowers is not known.

From Table 1 it can be seen that the numbers vary considerably from year to year. The maximum number recorded was 1025 in 2002. A graph of the adjusted numbers is given in Figure 1. From this, the trend line indicates an annual increase in numbers over the 22 seasons of 12% with derived figures of 18 in 1981 and 200 in 2002. However, as the results are so variable this needs to be treated with a bit of caution. The numbers occurring in the ungrazed paddock are too small to draw any comparison between it and the grazed paddocks other than the numbers appear to be less and the increase small or non-existent.

Bee Orchids

The plants have occurred in three main colonies at the top of the reserve with an occasional plant elsewhere. They tend to be fairly short-lived wintergreen perennials and are normally self-pollinating. Numbers vary considerably from year to year as can be seen from Table 1. Basal leaves first appear in October and continue to appear up to April when they begin to shrivel and die off. Stem leaves and the inflorescence develop in May and June with flowering in July and seed dispersal in August by which time all leaves have shrivelled. Seed is abundant but very light and easily transported away from the reserve by the wind. Where the grass is short they are best recorded in April when the basal leaves are most developed but in long grass it is necessary to wait until the flowers appear. As the main leaves are at their best only in the winter and early spring then this species is likely to be more affected by winter grazing than the other five species. A detailed study carried out between 1975 and 1983 found that, when ungrazed, individual plants could survive at least seven years and flower up to four times.

The adjusted plant numbers recorded each year are plotted in Figure 2. This indicates an annual decline rate of 18% with derived figures of 197 in 1981 and 5 in 2002. No plants have been found in the ungrazed paddock since 1973 so no comparison can be made between grazed and ungrazed paddocks.

Detailed recording of the flowers from 1975 to 1983 showed much variation in lip pattern. Lang (2001) illustrated the basic flower type together with eight recognised variations. None of these recognised variations has been found on the reserve even though up to two-thirds of the flowering plants in a colony had at least one flower in which the lip was significantly different to the basic flower type. Occasionally an abnormal flower has been found. In 1979 one flower was found with the lower half of the left-hand sepal joined to the right-hand half of the lip with the left-hand petal missing. Three flowers on separate plants had abnormal petals in 1981. In one the left-hand petal was replaced by an additional inward facing column with viscidia. The other two had petals deformed such that the petal base resembled the base of a column with viscidia, but the petal apex was almost normal except for ending in three blunt points. One of the two had both petals deformed this way and the other just the left-hand one. All three had normal lips. The degree of variation in flowers of the colonies may indicate that the plants were subject to some sort of stress other than grazing which has contributed to their decline.

Other Orchids

Of the four other orchids only pyramidal is wintergreen. It is usually found in the upper half of the reserve. Like the bee orchid its main leaves start to appear in October and are all above ground by April. However, they are less likely to shrivel in the spring but usually last well into the summer making this species likely to be less affected by winter grazing than the bee orchid. It flowers in July and like the other orchids produces an abundance of light- weight seed that is easily transported away by the wind. As its leaves are very grass-like it is only practical to record it when it is in bud or flowering. The leaves of the other three orchids appear in early May and so are not affected by winter grazing. They flower in June and can be found anywhere in the paddocks although common spotted and twayblade seem to prefer the bottom half. Recording of these three can usually be carried out any time from when the main leaves have emerged until the end of flowering. An attempt has been made to identify individual plants of these species to check for longevity. The record for the site of one isolated plant of each is given in Table 3. This seems to indicate that common spotted survives for at least 14 years, greater butterfly at least 9 but possibly 19 years, pyramidal and twayblade probably at least 13 years.

	Common Spotted		Greater Butterfly Orchid		Pyramidal Orchid		Twayblade
Ref No	19I		63H		71J		56G
Year
1981	a	u	a	u	a	u	P	u
1982