Field Woodrush the Grass Lookalike Weed

L&D FEATURE Field woodrush The grass lookalike weed Dr Terry Mabbett looks at the strange case of the grass that isn’t Broad-leaved plants and coarse ABOVE: Field woodrush fordshire is a small attractive golf straw whether as wild flowers or typically grows in patches grasses are clearly different plainly visible in April due to course laid out on ancient ‘common turf weeds are quite rare in south and easily distinguished a mass of brown flower heads land’ that pre-dates ‘Magna Carta’, Hertfordshire, where chalk seams (panicles). as turf weeds, but suppose and famous as the actual site of a rippling down from the Chilterns you are faced with a weed fifteenth century battle in the ‘Wars to the north provide the overriding that looks like a grass but of the Roses’. The course has its soil influence. Without this peculiar isn’t and colonises turf like own perennial battle with tracts of pocket of wet acid grassland I would broad-leaved weeds though wet acid soil on impoverished land have been forced to travel a long is essentially unaffected by within an otherwise fertile and free distance to find pictures of the field selective herbicides. draining region of the Home Coun- woodrush used to illustrate this Culprit is field woodrush (Luzula ties. article. That said I doubt whether campestris) one of the most stub- The whole area is traversed by ‘rich’ is an adjective the head born and difficult to control weeds brooks and ditches and dotted with greenkeeper at this course would of turf in the United Kingdom. spring fed ponds. Many of the greens use to describe one of the UK’s most Field woodrush exploits impov- become flooded in winter and some difficult to control turf weeds grow- erished soil low in humus and fairways are infested with field ing in perennial abundance in his nutrients and acid in reaction. woodrush. The field woodrush only ‘backyard’ and well outside of its Greenkeepers in northern and becomes obvious in April as large usual range. western regions generally face patches with a chestnut brown hue the biggest and most intractable from the flowers that may persist for Plant profile problems. That said field woodrush several weeks because the ground is will exploit pockets of impoverished too soft for prompt regular mowing. Field woodrush may present a acid turf almost anywhere, even The patches of white flowers that puzzle to all except the dedicated within ‘chalk-flavoured’ alkaline follow in June are heath bedstraw botanist. According to its descrip- soils in south eastern England. (Galium saxatile) another other low tion field woodrush bears long, On the gentle rolling land where pH (acid) indicator species. narrow and tapering leaves north London meets south Hert- Field woodrush and heath bed- sheathed in a loose layered rosette NOVEMBER 2009 GI 25 L&D FEATURE Close up on field woodrush with some usefully placed organic fertilizer (rabbit droppings) Chestnut brown panicles typical of field woodrush After spring mowing field woodrush retreats into the sward to blend in with coarse true grasses White flowers of heath bedstraw appear alongside field woodrush in June confirming acid nature and low fertility of the soil Field woodrush plants showing their tough stolons covered with dead and dying leaf tissue to Golfers may suddenly find themselves in what looks like and feels like a mini-rough in the form a substantial thatch. middle of the fairway 26 GI NOVEMBER 2009 L&D FEATURE around smooth stems bearing is obvious, without getting down ‘Commercial Experience’ is the Golden Key clusters of brown flowers borne Sponsors on ‘all fours’ with a magnifying unofficial industry-used term to on panicles. On this basis Luzula glass. Field woodrush is generally describe ‘insider’ knowledge on campestris sounds remarkably like regarded as a problem for turf in incidental control of field wood- a true grass belonging to the plant the wetter western and northern rush achieved by certain selective family Graminae, but this perennial areas of the country on soils suf- herbicides, though it is not listed monocotyledon actually belongs to fering high leaching, high acidity as controlled on the product label. the Juncaceae or rush family. Field and low fertility. However, this Reasons for absence of field wood- woodrush is one of a dozen or so ‘pseudo’ grass readily invades and rush from product labels in spite of wild Luzula species characterised takes over equivalent soil profiles its high weed status could be many by tufted appearance and dark wherever they occur, as seen by and varied. They are often related to green grass-like leaves, in this case this particular infestation on the scope of field trials (e.g. insufficient fringed with long soft and silky leaf northern fringes of London. number or diversity of sites) or hairs. The shiny chestnut-coloured nature of trials data showing insuf- flowers borne on short spikes and Silver Key Hard on herbicides ficient control for field woodrush Sponsors developing into three-seeded fruits to ‘pass the test’ and appear on the stand-out en masse in spring, the Selective action of early hor- product label. only time of the year it becomes monal-type herbicides like 2,4-D clearly apparent from a distance. and MCPA and later mecoprop was Cultural control based on the superior adherence Profile as a turf weed of spray to the bigger and rougher Golfers have been known to com- leaf-surface targets of broad-leaved plain about patches of massed flower Despite being called ‘woodrush’ dicotyledonous weeds, compared and seed heads of field woodrush in Luzula campestris is strictly a plant with the narrower and smoother spring, when golf balls land in what of open aspect grassy places like leaves of true grasses. This surface- looks and feels like a mini unofficial golf course fairways. That said the based selectively is supplemented rough slap bang in the middle of ‘woody’ component of the name by anatomical (inner structure) and the fairway. But such complaints This article comes to could equally well refer to the tough you courtesy of the physiological (metabolism) differ- are generally few and far between fibrous nature of its stems and BIGGA Learning and ences between grasses and broad- because regular mowing should Development Fund. leaves which may tear and bruise leaved weeds and responsible for prevent massed appearance of Thankyou to all our key even when cut with sharp and well sponsors differential herbicide translocation flower heads. That complaints occur set mower blades. rates and varying vulnerability of at all just re-confirms the common Field woodrush is easy to over- target sites in the plants’ metabo- close association of field woodrush look especially outside its flowering lisms. with poorly drained acid ground period when the narrow flat leaves Field woodrush appears to resist that cannot be mown promptly and blend in with coarse grasses like selective herbicide action on both regularly during wet springs. Yorkshire fog (Holcus lanatus) along counts. Plants are morphologically Cultural control is only realistic the fairway. Mowing scythes off the similar to true grasses with narrow way of managing severe field panicles allowing the remaining leaves, and in this case covered with woodrush infestations, by feeding vegetative parts to melt back in the long prominent white hairs that fairways adequately to boost fertil- sward. But field woodrush will not can only further impede herbicide ity and thicken swards. And by go away because tough creeping action. The monocotyledonous investing in high quality lime-based stems called stolons continue to lineage shared by Graminae and products to reduce acidity and spread relentlessly across the Juncaceae make field woodrush create conditions less to the liking surface of the ground rooting at the close in form and structure to true of field woodrush, without alter- nodes. The stolons are sheathed grasses, which is responsible for ing composition of the turf grass with a thick layer of dead and dying the generally low susceptibility of population. Or else ignore the weed leaves which collectively produce Luzula to selective herbicides. and reap some benefit from having an extremely dense thatch on Clear-cut differences between fewer casting worms on the surface the fairway where patches of field dicotyledonous broad-leaved plants of an inherently high acid soil. Any woodrush occur. (e.g. common daisy – Bellis peren- recommendations for physical Similarity to true grasses in mor- nis) and monocotyledonous true removal of field woodrush should phology (shape and form), anatomy grasses is the very basis of selective be approached with care because (tissue structure) and physiology herbicide action. However, any dif- cut pieces of stolon can root to form (metabolism) is why field woodrush ferences such as they are between new infestations. is such a troublesome weed and turf grasses and field woodrush Field woodrush is also called almost impossible to control even appear insufficient for its commer- sweep’s brush after shape of the with modern selective herbicides. cial control by selective herbicides flower spikes but this not a weed Being a weed of impoverished acid approved for use in managed turf. that is easily swept away. However, soils it is unlikely to occur in the Field woodrush is recognised as weeds are just green plants in the well-managed and nutrient rich one of the most difficult to control wrong place at the wrong time and professional turf of greens or tees weeds of managed turf. Some con- in other sectors Luzula species are constructed on well-structured and trol is known to occur during rou- valued as ground cover plants espe- free draining substrates. tine application of newer and more cially for poor moist soils.

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