Mercury Bay Weed as a Lawn Plant

New Zealand Journal of Agriculture, Volume 81, Issue 2, 15 August 1950, Page 109

Mercury Bay Weed as a Lawn Plant

THE perennial Dichondra repens, a member of the convolvulus family, has some merit as an alternative to the better-known lawn grasses. Under the common name of Mercury Bay weed the plant has become quite well known, especially in the northern districts of New Zealand, and numbers of attractive lawns have been established with it. Though lawn grasses are preferable under most conditions, Mercury Bay weed has proved satisfactory on some lawns, where it stands up better to dry conditions than grass. Because some difficulties have been encountered in establishing lawns of Mercury

Bay weed,

W. S. Kemp,

Orchard Instructor, Department of Agri-

culture, Auckland, explains in this article the conditions under which the plant will grow and describes methods of planting and cultivation which have been found successful.

AS can be seen from the photographs Mercury Bay weed is not a grass but a small, low-growing, creeping plant which roots at the nodes and has small kidney-shaped leaves. The foliage is a dark grass green (lighter coloured if the ground is very dry or the plants are unthrifty), and occasionally it turns brownish green for a short time in autumn. Two of the main advantages of Mercury Bay weed are that it remains green throughout comparatively dry summer seasons and that it needs mowing only occasionally. Nevertheless, it requires some water and the lawnmower cannot be dispensed with. On the other hand the weed is unsuitable for tennis lawns because its growth is too slow in re-covering worn patches, the soft, succulent leaves are inclined to be slippery, and the plant juices quickly stain tennis balls a dark green. After a few seasons the original plants sometimes tend to “run out” in patches, which must be replanted carefully to prevent establishment of strong-growing weeds against which Mercury Bay weed cannot compete. Under moist conditions the rapidly extending runners will invade cultivated garden soils in which they quickly become established and where they can be as great a nuisance as many other weeds. However, normal cultivation along the edges of garden plots will deal with that problem. The plants will not thrive in districts subject to severe frost. American reports indicate that- minimum air temperatures of 25 to 26 degrees F. (6 to 7 degrees of frost) are sufficient to cause severe injury, resulting in browning of the leaves, while lower temperatures may kill the plants. Equivalent temperature readings taken at ground level would be several degrees lower. Preparation of Land for Planting Preparation of the section to be planted should be as thorough as for a grass seed-bed. To give the soil time to settle down before planting is done the land should be levelled and dug over at least 6 weeks before, making sure that all weeds are completely buried or that difficult ones like docks are removed. At intervals

up to the time of planting light surface cultivations should be given to destroy weed seedlings as they appear above the ground. A dressing of a fertiliser mixture of 3 parts of sulphate of ammonia and 1 part of superphosphate applied at the rate of loz. per square yard should be worked into the soil just before the final raking and rolling before planting. Except on very acid soils liming is not necessary. Before the plants are set out the land should be given a final light raking and levelling, and should be rolled to consolidate the surface. "Plugs" The lawn is planted up by the unusual method of setting out “plugs” of Mercury Bay weed. The plugs, as shown in the illustration on this page, are Ijin. in diameter and lin. thick, and are planted in holes of the same dimensions. A special tool is used to cut the plugs from a nursery bed or lawn, and the same instrument serves to make

the planting holes. One type of cutter, illustrated on page 111, will take one plug at a time, another kind is made from a cylindrical tube, with the lower cutting end sharpened and an outer collar fitted to regulate the thickness of the plugs. As successive plugs are cut out they push each other up through the cylinder and emerge at the top. For planting a lawn, cutting tools may be hired from some retailers of Mercury Bay weed plants, which are usually sold as plugs. A smaller and less expensive cutter may be purchased, or could easily be made, for planting small areas. Planting the Lawn Mercury Bay weed may be planted at any time of the year, but the best months are from October to January. The plugs are set at varying distances apart (see the illustration on page 111); the closer the planting the sooner will the area be covered by plants. The usual spacings are from 4in. to Bin. between plants, although sometimes plants are placed at 12in. intervals. The governing factor is the amount the planter is prepared to lay out for plants. If plugs are set 4in. apart, four times as many plugs are required than if Bin. spacings are made. At Bin. intervals 20 are needed for each square yard of lawn. Under satisfactory growing conditions a lawn area set with plugs at 4in. intervals will be completely covered within 2 months of planting (see the illustration on page 111). The wider the spacing the longer is the time taken for the plants to cover the area. From a lawn closely planted in October it should be possible to cut plugs for a further area in January. Of course the holes in the lawn must be refilled with soil.

ESTABLISHING MERCURY BAY WEED IN A LAWN

The actual planting is very simple. For the first row of plants a garden line is stretched along a few inches from one edge of the prepared land. The plug cutter, is used to cut out planting holes at the chosen intervals along the line. Then the plugs are slipped into the neatly fitting holes and are pressed down with one foot. Planting is continued by moving the line across the area and setting out plugs in successive rows in the same manner. When a section has been planted the new lawn should be carefully watered and should be rolled as soon as possible to consolidate the plugs and the surface of the soil. Where it is desired to convert a large area of grass lawn to Mercury Bay weed the practice illustrated on page 112 has sometimes been adopted. Although it has the disadvantage that a longer period is required to make the desired change, it is a cheaper method. The procedure adopted is as follows: After the number of plugs to be purchased has been decided the area which they will cover is prepared in the normal manner and the plugs set out. New sections are added as plugs become available from previously planted areas. The small centre plot shown in the illustration on page 112 was planted first and the surrounding area was planted later. Care of Lawn after Planting During the period taken by the plants to cover the soil completely, systematic, ruthless suppression of weeds must be the first consideration. Weeds are sure to appear in the spaces between the growing plants, but they must not be allowed to remain there. The worst offenders are clovers, coarse grasses, and the übiquitous flat or broad-leaved weeds. . Mercury Bay weed cannot grow either over or under such intruders ; and therefore cannot grow into the compact and

even lawn which is always the aim, unless the weeds are removed before they grow large. For the first few weeks weeding can be done most quickly with a sharp narrow-bladed hoe, but when the lawn plants creep further over the bare spaces the hoe must be discarded and weeding of the reduced areas must be done with a smaller implement, such as a hand trowel or an old knife. Once the Mercury Bay weed has grown into a compact mat over the whole plot weeds will have little chance of becoming established. However, odd ones will come through even the best-kept lawns and, as in grass

lawns, they must be destroyed or they will eventually spoil the whole effect of neatness which is so much desired. Moss, which sometimes encroaches upon grass lawns, will also invade Mercury Bay weed lawns. It seldom gains a hold in a healthy lawn, but is inclined to appear in moist, shady places, especially if the lawn plants are weak. Careful weeding and an application of nitrogenous fertiliser will usually remedy this fault, but moss is rarely troublesome in a well-kept lawn which, with adequate supplies of fertiliser, is able to retain its supremacy over the slower-growing mosses. Feeding the Lawn In common with lawn grasses Mercury Bay weed needs applications of fertilisers to enable it to thrive and compete successfully against weed competition. Unfortunately there is no selective mixture which can be suggested to give this lawn plant an advantage over all undesirable plants, nor is it immune from a certain amount of foliage scorch due to applications of fertilisers, although it recovers its green appearance quickly. A recommended fertiliser mixture is 3 parts of sulphate of ammonia to 1 part of superphosphate, applied at intervals of 3 months (preferably in dull or showery weather to reduce scorching) at the rate of loz. to a square yard of lawn. The nitrogen content of this mixture, together with the fact that Mercury Bay weed needs little or no lime, tends to reduce competition from clovers. Removing Weeds . t If a compact growth of Mercury Bay weed is maintained, very few flat weeds will grow in the lawn, but grasses are more difficult to keep out. The coarser grasses and odd : flat weeds which usually- grow in. tufts can be destroyed by hand weeding. Finer grasses cannot be eradicated, but are not strong enough to crowd out the Mercury Bay weed, and do not adversely affect the appearance, of the

MERCURY BAY WEED AS A LAWN PLANT

lawn. They do, however, make more frequent mowing necessary if they become strongly established. Fortunately, the finer grasses do not have much chance of growing in a dense mat of Mercury Bay weeds, and will not be troublesome if the ground is carefully prepared before planting time. Mowing A well-kept lawn of Mercury Bay weed needs very little mowing, but should be cut occasionally to keep the surface neat and level. Growth is

very slow between the end of March and early September and the lawn may require no mowing in those months. During the warmer months, especially if rainfall is plentiful, growth is comparatively rapid, with the inevitable result that the lawnmower will have to be used five or six times during that period. Although this plant thrives in rather dry, sunny situations, and remains green through fairly long dry spells, an occasional watering may be necessary to maintain its bright and fresh appearance.

Renovation of Old Lawns After a few years there may be signs of the plants “running out” in patches. Usually these patches will show first where the original plugs were set, the younger growth remaining healthy. Replanting the weak patches with plugs from healthy parts of the lawn will remedy the fault. Mixed Lawns Some very successful mixed lawns of Mercury Bay weed and good lawn ‘grasses are to be seen in the Auckland district. Most of these have been grass lawns in which plugs have been set without disturbing the grass. If this type of lawn is desired, the best time to set the plugs is late spring or early summer as soon as spring growth of the lawn grasses slows down in the drier and hotter weather. The Mercury Bay weed then has several months in which to become firmly established before the autumn flush of growth gives the grasses another temporary period of supremacy before the semi-dormant winter period. Mixed lawns need about the same amount of mowing as do grass lawns, but they remain much greener during the dry summer months. For those who value lawn clippings the mixed lawn has the advantage that it provides a supply of this material. Mercury Bay weed will not dispose of all the problems and work associated with garden lawns, but. given the attention it merits, it will, in the warmer parts of New Zealand, give year-round greenness under conditions too dry for the usual lawn grasses. Reference “Construction, Renovation and Care of the Bowling Green," by E. Bruce Levy. .