Garden Work for May

New Zealand Journal of Agriculture, Volume 98, Issue 4, 15 April 1959, Page 406

Garden Work for May

By

ROSALIE A. CAMPION,

Horticultural Instructor, Department of Agriculture, Wellington

The May holidays are a time when controlled : fires outdoors are popular. If children are encouraged in early years to help with cleaning up and burning

rubbish, the gardening instinct may be fostered and remain for life. This is

an excellent time for the burning, of any diseased plant material and for cleaning up any corners which have not been given attention during the busier, summer months. Grassed areas which have been allowed to seed could be cut off with a scythe or sickle and the rubbish raked off and burnt. Lawns In the milder, northern districts it is not too late to prepare and sow down new lawns. Where frosts are experienced it is better to wait until spring before sowing, as the young seedlings may be checked. Hard frosts, can lift the soil, and the roots of young seedlings, unless well established, will be damaged. Bare patches in old lawns should be “scarified” by raking stiffly to break up the soil, topdressed with new soil if necessary, and reseeded. A satisfactory seed mixture for use on new lawns or for reseeding consists of two parts of Chewings fescue and one part of certified browntop. To obtain a good growth response a fertiliser should be applied and raked in with the seed. On most soils a mixture of three parts of sulphate of ammonia and one part of superphosphate, used at | oz per square yard, has given good results. Blood and bone is an unsatisfactory lawn fertiliser, as it encourages growth of weeds and of fungi which cause open patches in a lawn. Weeds The joints of steps, paths, and drives often harbour difficult weeds and periodical treatment with chemicals will prevent the breaking of asphalt, and other materials when eradication of weeds is attempted. Arsenical weedkillers will kill all plant growth, but care must be taken to keep them out of reach of children and to destroy the containers or bury them deeply. Other useful materials are based on sodium chlorate and borates. A complete weedkiller can also be safely made from two parts of dalapon and one part of amitrol applied at 1 oz to 20 sq. yds. in autumn and again in spring. Mechanical methods are still the best for removing many perennial weeds, from the flower garden. A heavy mulch of sawdust can encourage the weeds to grow into the surface area, where removal is easier. For a more detailed list of weed control methods, in the flower garden, see the November 1957 issue of the “Journal”. Dahlias Except in the mildest areas dahlia, plants should be lifted each year when the frosts have touched them. While, there is sufficient growth to identify them the plants should be rogued and any discarded which may be infected, with virus or which, because of their type, colour, or growth, do not warrant.

a place in the garden. If new plants have not made a very good display, it may be worth giving them a second trial. Tubers should be stored in moderately cool conditions. Chrysanthemums The late-flowering varieties of chrysanthemums will be nearing maturity and some shelter should be provided for the flowers. The plants are very hardy, but bad weather can spoil the flowers, especially of the large exhibition types. After they have been grown for several months it is folly not to cover them with light scrim or plastic at this time. If the plants should suddenly wilt and die, the root area should be checked for waterlogging or the presence of grass grubs, and if these

are not the cause of the trouble, the most probable cause is the verticillium wilt fungus, which inhabits the soil. Where this disease occurs plant debris should be burnt and not composted, It is unwise to grow susceptible plants such as stocks, luculia,. Rhus cotinus, Iceland poppies, or gerberas on this area for three to four years. Such a wide range of plants are affected by this fungus that consideration should be given to sterilising the soil with formalin or vapam. If leaf spotting is troublesome sprays of thiram at 1£ oz to 4 gallons of water should be used. Most insect pests of chrysanthemums are controlled by the application of lindane emulsion at i fl oz to 4 gallons of water, and this can be applied with thiram if necessary. If brown rust pustules are evident, sprays of zineb should be applied. Tomato Spotted Wilt Virus The tomato spotted wilt virus has a wide host range among ornamental

plants. Dahlias and chrysanthemums are two of the most susceptible plants. Diseased plants are usually stunted and have fewer and smaller flowers. On the leaves the usual symptoms are light-coloured ringspots 'or lightcoloured areas composed of a series of wavy lines: The symptoms are often inconspicuous and overlooked, thus remaining a constant source of infection to other susceptible plants such as callas, cinerarias, anemones, primulas, and Iceland poppies. There is no cure for this disease and all infected plants should be burnt. Keeping garden areas clean will destroy alternative weed hosts such as buttercup, black nightshade, and henbane. Nasturtiums, another host, should be carefully examined for symptoms such as wavy leaf edges and mosaic mottling of the leaves. The disease is

spread from plant to plant by small black insects known as thrips, which s h O uld be controlled by spraying with DDT or dieldrin emulsion, Lilies Lily bu lbs should not be lifted for replanting until their new position has been prepared by digging to a depth o 18 n and incorporating any availab organic matter. Plantings should be grouped, the bulbs being placed at their original depth with at least twice their width between them, Most lilies are easily raised from seed) and O r large gardens, especially this is an economical method of obtaining a good display, though it takes several years. The seed should be sown as soon as it is ripe into a soil which drains freely and is rich

in organic matter. If a space cannot be set aside as a seedbed in the garden, the seed can be sown in boxes of seed compost. The seed should be dusted with thiram fungicide before it is sown, and where slugs or snails are prevalent suitable baits should be set out. The seed can be covered with a J in. layer of sand and sawdust. Lilium regale and L. formosanum are two varieties which quickly develop leaves after sowing, but the popular L. auratum may not show leaves until a year later. Roses and Black Spot This season has brought with it a general infection of black spot fungus on roses which have not received sufficient preventive sprays of fungicide. This fungus causes purplish or black spots on the leaves and sometimes on the stems and weakens the plants. The disease is carried over from year to year on diseased plant material, generally the leaves which fall to the ground. All infected rose leaves should be picked up as they fall and burnt to help prevent trouble next season. . If rambler roses have not already been pruned, this should be done now by the removal of all branches which flowered last season. This will allow the sunlight to mature the young growths, which can now be tied into place for flowering next season. Caterpillars A number of shrubby plants are disfigured each year by the activities of the leaf-roller caterpillar, which feeds on the foliage and makes a resting place between two leaves, which it webs together. Camellias, boronias, correa, grevillea, pittosporum, and rhododendron are some of the many plants affected and should be sprayed with arsenate of lead or malathion if they are troubled. DDT is rarely effective against this pest. Another curious caterpillar which shelters in a tough brown elongated bag is the young stage of the bag or case moth. These moths are capable of rapidly defoliating such plants as Cupressus macrocarpa, Pinus radiata, and manuka. Where warranted sprays of arsenate of lead or DDT can be used for control. Border Preparations Deep digging of beds encourages the development of good roots and helps the winter rains to penetrate. Even if the border is not being completely overhauled this season, it should be lightly forked to assist aeration. At all times pieces of glass or broken china should be removed as they are forked to the surface. This may prevent an accident in future. The border should receive a light dressing of lime as it is dug, and bearded iris can now be given an annual dressing at 3 oz per square yard.

Iris innominata can now be divided and planted out. This delightful species flowers for a long period in spring and can be planted out in average soil in sunny positions. Ixia and Nerine bowdeni can still be planted in sunny borders. In cooler areas Solomon’s seal and lily of the valley are useful plants which can be planted now. Planting out The planting out of spring-flowering plants such as wallflowers, myosotis, aubretia, primroses, polyanthus, bellis, winter pansies, and violas should be completed as soon as possible. With this month begins the planting period for trees and shrubs. Much of this material is now being sold while in flower in pots, and as the roots are not greatly disturbed when planted from a pot, the planting season has been extended. When the plant is taken from the pot the soil may be broken slightly so that the roots merge with planting soil. Pots should be well watered on the day before planting.

Use of Cold Frame A garden frame is substantially a large box which has a glass lid facing to the sun. It is known as a “cold frame”, as though it is often used for propagation, it has no internal heating apparatus and is generally used outdoors. At this time of the year such a frame can be used to give additional protection from frost to many plants including boxed and roofed geranium cuttings and seedlings of biennials, stocks, sweet peas, carnations, and other plants which are to be set out in spring. The . frame can be used to store half-hardy plants such as irisene, fibrous begonias, cuphea, agathea, and double-flowering lobelia to give them shelter over the winter months. Dahlia tubers and chrysanthemum stools can be placed in sawdust in the frame' for storage or the frame could be used for rooting of cuttings as mentioned last month. The hardwood cuttings should be placed in a gritty medium. The frame should be watered according to the requirements of the

plants which it holds. On fine days the frame can be opened up by 10 a.m., but it should be closed in the mid afternoon to prevent loss of heat. On dull and cold days it should be opened an inch or two only for ventilation. If heavy frosts are expected, a covering of scrim placed on top of the glass will prevent the frost from penetrating. Plants in Glasshouses Under glass young bushes of fuchsias, geraniums, and cherry pie can be pinched back to train them into bushy plants. Pinching plants back entails the removal of the growing point down to a node below which it is hoped a number of shoots will develop. Old bushes of these plants should have a restricted water supply so that they may have a resting period. Seed of cyclamen for next year’s flowers and of chaubard and marguerite carnations, pansies, and violas for spring planting can now be sown. A pinch of fungicide such as thiram should be shaken in each packet of seed to aid germination. Cyclamen plants which are coming into flower should be given a light, airy position under conditions which are not too warm. When watering care should be taken that water does not accumulate in the top of the corm and encourage rotting. General In light warm soil outdoors seed of larkspur, godetia, clarkia, nigella, and antirrhinums can still be sown. Selfsown seedlings and plants from earlier sowings can be thinned out or transplanted to other positions. Cinerarias should be inspected regularly for the presence of the woolly-bear caterpillar. If numbers are few, hand picking is the easiest way of control, but if this is not practicable, dust or sprays of DDT should be used. Layering of plants can be continued this month and any plants which were layered last year and have developed roots can be severed from the parent plant. Under good conditions they could be transplanted immediately, but it is generally better to wait until early spring to transplant them. Preparation for the planting of trees and shrubs should be continued. Where compost is available it should be incorporated into the future root area, and allowed to settle down before planting. Compost now in the bins should be turned and mixed as the bins become full. Material given its second turning now should be in good condition for using in spring. Trees and shrubs especially should be examined closely for the presence of insect pests such as scales, mealy bugs, or thrips and sprays should be applied as required.