Lawn troubles

My turf seems to dry out very quickly. What can I do to keep it going in long, dry spells when the use of garden hoses is prohibited?

Grasses are difficult to kill and although the lawn may go very brown it will usually recover from even the worst British drought. If you must not water the lawn, it helps to raise the height of cut when mowing and to let the cuttings remain on the lawn. Compost is also useful – a light dressing will act as a mulch during the drought and heavier dressings each autumn will build up the moisture-holding capacity of the top soil.

What is the best way to drain a lawn which tends to hold water?

The trouble may be caused by impermeable top-soil. In that case monthly aeration with solid-tine aerators and/or hollow-tine forking at say, 3-year intervals to help excess water through the soil may do the trick. If sub-surface drainage proves necessary, a soakaway constructed in the lowest corner should help. The soakaway might be a metre or yard cube filled with stones, topped with gravel and/or coarse sand, and finished off with top soil and turf. If this is not sufficient a diagonal land drain could be laid 600 mm (2 ft) deep to empty into the soakaway. Only rarely is it necessary to install a full herringbone system of drains, and there could be difficulty in obtaining a suitable outfall for such a system.

My cylinder-type mower produces an uneven cut-in the bands across the lawn there are variations in grass length. What is the explanation?

The cause may be the mower or the lawn. The cutting height should be checked at various parts of the mower’s bottom (fixed) blade. It may need to be adjusted to ensure an even height of cut right across the blade. The trouble may. On the other hand, arise from the lawn. If it is cut across a slope the weight of the machine can result in a shorter cut at the lower side, especially if the surface is soft.

Part of my lawn is so short of light owing to nearby trees that it is very difficult to keep grass on it. What can I do about this?

If you must have a lawn under trees, let the grass grow quite long – up to 50-75 mm (2-3 in) – because this helps all lawn grasses to survive. Some people sow wood meadow-grass (Poa nemoralis) for its shade-tolerance, but unfortunately it does not tolerate any mowing at all. Shortage of light may not be the only cause of trouble. The combination of shade and drip can keep the surface over-moist for long periods, while in dry weather tree roots compete for nutrients, and for moisture, too. Possible action might therefore include tree-root pruning, aeration, extra watering in dry weather, and even applying a little extra fertiliser.

In my fine lawn there are patches of a soft, broad-leaved grass which I am told is Yorkshire fog. Can anything be done about it?

Yorkshire fog (Holcus lanatus) is the commonest and most noticeable invader of lawns. On utility lawns it probably does not matter much, but it looks bad in a fine lawn. Unfortunately there are, as yet, no selective grasskillers. If the patches are small and few, hand weeding or replacing them with good turf is the best answer. The alternative is regular, severe scarification of individual patches of the unwanted grass using a garden knife to cut into the surface at close intervals in one direction and then across the cuts in other directions before collecting up the debris. If you persevere with this treatment you should at the very least thin out the Yorkshire fog, and so make it much less conspicuous.

How do I get rid of yellow suckling clover patches?

This weed has proved difficult to eliminate but it is moderately susceptible to proprietary weedkillers containing the chemicals ioxynil and mecoprop. Even with these, repeated applications (at month intervals) may be necessary. A few other problem weeds, hitherto difficult to kill, respond to similar treatment.

Can I treat my lawn with selective weedkiller during the winter?

The selective weedkillers used on lawns contain plant-growth regulators. These are absorbed mainly through the leaves and are distributed throughout the plant, causing growth inhibition or modification. The process of distribution works best when the weeds are actively growing. In winter, when there is little growth, distribution is sluggish at best, so the effects of the weedkillers will be greatly reduced.

Apart from that, the calm, dry days necessary for spraying weedkillers are much rarer in winter than in the rest of the year.

How can I prevent moss invading my lawn?

Good lawn management to produce a healthy vigorous sward is the best defence against moss. The conditions that encourage moss include: wetness; dryness (for instance on bumps or ridges where the grass becomes weak); cutting too dose; poor surface smoothness leading to ‘scalping’ (slicing off the surface of bumps) when the grass is mowed; a soft spongy sward with a thick fibrous layer; low fertility (caused by, for instance, deficiency of lime or plant food, or a shortage of top soil); compaction of the top soil (giving poor aeration and drainage); constant shade.

The shaded part of my lawn has developed a slippery surface scum varying in colour from green or blue-green to black. Is there an easy method of getting rid of it?

The description is typical of an invasion by algae, and the affected area is probably very damp because of the shade and possibly of the soil conditions. If you can get rid of the surface moisture by aeration and alleviation of the shade, and then apply a little fertiliser to promote vigorous growth, the algae will probably disappear. It may help to water in a solution of sulphate of iron at the rate of 50 g in 8 litre/4 m2 (1-1/2 oz in 1-1/2 gallon/4 sq yd) or by using a dichlorophen-based moss killer.

How can I eliminate moss?

There are several proprietary moss killers based on dichlorophen or chloroxuron. It is better to treat the whole lawn rather than just the obvious patches, although this is expensive. Somewhat cheaper, if perhaps not so effective, are the products based on lawn sand. Before treating the moss, however, try and find out why it is there: unless the cause is removed, moss will return even after using moss killer.

Patches on my lawn become discoloured when the ground starts drying, and then stay yellowish no matter how much water is applied. How can I deal with this?

Such patches are often found on raised parts of the lawn, where water just runs off the surface. Alternatively or additionally, there may be a shortage of good soil below them. Sometimes ‘droughty’ patches are caused by the presence of tree roots, in which case root pruning or even removal of the offending tree is the answer. There are, however, dry patches which, it is believed, are due to a fungus (possibly no longer present) which has produced material that effectively waterproofs the soil.

In any case, once soil has completely dried out it can be very difficult to wet. Spiking or forking helps to let water in, and it may also be beneficial to use a wetting agent because very dry soil often repels water. Some people use a mild (bleach-free) washing-up liquid suitably diluted as a wetting agent, following this immediately with a thorough sprinkling of plain water. There are also several proprietary soil penetrants.

What is the cause of brown patches on my lawn and how can I get rid of them?

Brown patches are due to a variety of causes including:

(1) scorch by chemicals (including fertiliser);

(2) scorch from animal urine;

(3) drought;

(4) spilt oil or petrol;

(5) fusarium patch disease.

The remedy depends on the cause. The immediate answer to the first three and possibly to the fourth is to apply plenty of water for a time and ultimately to over-seed any bare patches. With petrol or oil damage, it may be necessary to excavate contaminated earth and replace it before reseeding. The first four causes are unlikely to spread. Fusarium, however, can spread rapidly and cause extensive damage, so immediate treatment is necessary.

Numerous brown patches, 75-100 mm (3-4 in) across, have suddenly appeared on my lawn. They seem to start as small yellowish spots, which get larger and browner, or reddish brown, finally turning dark brown. The grass appears to be dead in the middle of some of the patches. What’s the trouble?

It sounds very much as if you have an attack of fusarium patch disease, which typically occurs during mild, moist weather in spring and autumn although it can come at other times when weather conditions suit it. The matter is urgent but perhaps you can get positive identification from local parks staff before treating the whole lawn with the relevant fungicide. The fungicide, of course, will not bring the dead grass to life, so some re-seeding or re-turfing may also prove necessary.

Some years ago I successfully treated an attack of fusarium patch with a mercurial fungicide. I now have a fresh outbreak of the disease, but mercury fungicides seem to be unavailable.

EEC regulations ban the use of these fungicides (mercury compounds are very poisonous). Readily available, however, are a number of excellent proprietary fungicides based on organic chemicals, some of them quite new. They are usually produced for application with added water by means of a suitable sprayer or with a watering can fitted with a fine rose or dribble bar.

My lawn, consisting mainly of fine grasses, is producing small yellowish tufts of grass above the surface. Can this be cured?

Your lawn seems to be affected by yellow tuft disease, which attacks fine bent grass. This is not a common disease and its cause is not fully understood. It may be due to physiological disturbance started by injury of some kind, and it is sometimes associated with wet surface conditions which can be helped by aeration. Scarification, employed in conjunction with mowing, eliminates the tufts.

My old-established lawn, cut regularly at about 6mm (l/4 in), has developed sunken patches about 150mm (6 in) across. How should I deal with them?

There is probably a pronounced layer of fibrous material (mat or thatch) at the surface, and the likely cause of the trouble is a fungus attacking the fibre. This fungus feeds on the accumulated fibre, breaking it down and so producing the depressions. Killing the fungus is difficult; it may be worth trying close forking of the areas, and then applying a turf fungicide at double the normal rate, followed by clean water to wash it well in. Often such fungal attacks die out of their own accord, and the patches neither grow big nor spread. In such cases all that is necessary is smoothing out the depressions with sandy compost. Sometimes, however, patches of replacement turf may be needed.

I am worried that the toadstools on my lawn may be poisonous. How can I get rid of them?

Toadstools usually arise from fungi in the topsoil which may be treated with fungicide.

How can I control the fairy rings in my lawn?

Treatment depends on the type of fairy ring. In one type the rings show up as dark green ribbons or circles of grass on which puff balls or mushrooms may appear. Any of several different kinds of fungus may be responsible for them, and since their effect is so small most people tolerate the ring. Another type has no visible effect on the grass but is revealed as rings of toadstools which can easily be swept or mown off. Both types can sometimes be controlled by watering in a turf fungicide after sprinkling; no special fungicides are available.

The worst types are those which appear as two concentric dark green rings with a brown or bare zone between them. They may be quite small (less than a dinner plate in diameter) or very large indeed (some have been observed to stretch over several fields). Tan-coloured toadstools are produced from the white mycelium which can be found in the top soil. The only reliable treatment is to dig out all the affected turf and earth completely and replace it with clean soil, after sterilising the dug area with formaldehyde solution.

My lawn looks very poor this summer. Overall it has a brownish appearance with something of a mottled effect. The ‘mottles’ have peculiar bleached but rather brownish appearance, and some of the individual grass leaves are pink and red. What is the cause?

This is almost certainly due to corticium disease; although disfiguring, it only rarely kills the grass. Before taking any action, however, try to get positive identification of the trouble by a member of your local parks staff. If indeed it is corticium, a light dressing of sulphate of ammonia to the whole lawn of about 9-18 g/m2 (1/4- 1/2 oz/sq yd), diluted with sand or compost and watered in if the weather remains dry, should cause the grass to grow away from the disease satisfactorily. Only rarely is corticium serious enough to require treatment with a fungicide.

On damp days in spring and autumn my lawn becomes covered with earthworm casts. I would like to get rid of them but am told that worms are beneficial. What should I do?

There are many species of earthworm but not all of them make casts. Earthworms are useful for mixing and aerating soil, but those which cast cause trouble by making the surface muddy and uneven and by encouraging weeds – their casts make particularly good seed beds for weeds.

Earthworm activity is encouraged if cuttings are left on the turf and by the use of alkaline or organic fertiliser dressings. Improved management, especially removing cuttings and brushing away the casts in dry conditions, help to alleviate the problem.

It is, however, sometimes necessary to use more drastic means. The main wormkillers used by groundsmen are based on chlordane (highly poisonous) or carbaryl (much less poisonous). A fairly safe but messy treatment involves the use of permanganate of potash. Watering this in at the rate of 17 g in 5.41/m2 (1/2 oz in 1 gal/sq yd) brings the worms to the surface, where they can be swept up. Treatment against worms is carried out when they are working at the surface in spring and autumn (preferably the latter). Proprietary products have recently appeared which claim to combine good disease control with selective worm control, and these hold out hope for better worm control in the future.

I suspect that my lawn is affected by some kind of grub. Is there an appropriate mechanical or chemical treatment?

Lawns are seldom attacked by pests. I suggest that you excavate a few holes to see what you can find. You should certainly avoid using pesticides unless they are absolutely necessary. The most common grub to attack turf is probably the leatherjacket, which is the larva of the crane fly (daddy-long-legs).

Sporadic outbreaks of trouble from this source occur on golf courses but seldom, if ever, on lawns. If the presence of leather jackets is established, treat the lawn with a suitable soil insecticide.

On the continent of Europe and occasionally in southern England cockchafer grubs cause damage and require eradicating with a soil insecticide.

Mole hills keep appearing in my lawn (and elsewhere in the garden). How can I stop this? The farmer next door does not bother much about those in his field bordering my garden.

As long as there are moles next door there will be reinvasion of your lawn. You may be able to use traps, handling them with old gloves to minimise human odour, and placing them in the main mole run. It pays to enquire for a local mole catcher -there is usually one somewhere near, although they are getting increasingly rare. You may also be able to get help from the local Pest Officer.

Moles need a constant supply of earthworms for food and you can reduce their activities on your lawn by killing off the worms with suitable wormkiller . Do not, however, try killing the moles by placing worms treated with high toxic strychnine in the runs. Gassing with proprietary products or with exhaust pipe fumes from the car is usually impracticable and rarely successful.

18. November 2013 by admin
Categories: Featured Articles | Tags: , , , , , , | Comments Off on Lawn troubles

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