Feeding, Manuring and Mulching Roses
Most amateurs under-feed rather than over-feed their roses. Never hesitate to give a ‘fillip’ to any rose bush which is at any time reluctant to make fresh growth. It is often said that aphids and other pests thrive on the soft, sappy shoots produced by the heavy use of mineral (artificial) fertilizers, but heavy infestations are by no means confined to such growth. It is quite safe to use artificial fertilizers on newly planted roses.
The main elements concerned with plant growth are nitrogen, phosphorus, potash and, to a lesser extent, magnesium. Roses rarely suffer from nitrogen deficiency, which can be recognized by pale green leaves and weak growth, but use a nitrogen fertilizer where growth is backward.
Typical signs of phosphorus deficiency are bronze or purplish markings on the foliage, as well as fewer, smaller blooms. Apply bone meal at about 3 oz. per sq. yd. This is an excellent slow-acting corrective. On heavy or acid soils use basic slag instead, at 6 oz. per sq. yd.; this is not leached out by rain.
Shortage of available potash is more evident on light, sandy. It causes rose trees to develop a scorched appearance, with browning round the edges of the leaves. To counteract it apply sulphate of potash at about 3 oz. per sq. yd. or wood ashes at 6 oz. per sq. yd.
Roses grown on light, sandy soil sometimes show symptoms of magnesium deficiency during periods of prolonged wet weather, when magnesium tends to be leached out of the soil. Signs usually appear on the older leaves, which exhibit purple or yellow discolorations between the veins, starting at the bottom of the tree and progressing upward. Apply magnesium sulphate (Epsom salts), using ½ to l lb. per 10 gal. of water.
These usually contain nitrogen, phosphorus and potash in varying proportions, and often magnesium as well. The proportions required by roses are not vital and almost any proprietary fertilizer will give good results if applied according to the maker’s instructions. Do not apply during a drought unless the roses are watered regularly afterwards. Spread fertilizer solutions between the bushes, so that they can be washed in by the rain and reach the feeding rootlets which are concentrated away from the base of the stems.
All artificial fertilizers should be regarded as complementary to organic materials like rotted farmyard manure and: if used exclusively or to excess, they may tend to exhaust the soil.
The spraying of foliage with liquid feed instead of applying the feed to the roots has recently achieved some popularity among rose growers. It is not an alternative to conventional feeding methods, if only because considerably more applications would be needed during the growing season. Young foliage seems to take up nutrients more readily than older leaves. Temporary nutrient deficiencies — of magnesium and iron, for instance — can be corrected, as they appear, by foliar feeding, but concrete recommendations for more general feeding cannot yet be made. Experiment by trying one of the proprietary foliar feeds now available, taking care to follow the manufacturer’s instructions.
Do not spread compost or old farmyard manure round rose trees in winter since this keeps the ground cold and wet. A good way to use it is as a summer mulch to conserve moisture. If the mulching of roses is unsuccessful it is because the mulch has been carelessly applied. Timing is important. Wait until mid-May when the soil is rapidly warming up. Remove all traces ofand thoroughly wet the soil immediately before mulching. Spread the manure loosely, to permit free circulation of air, and about 3 in. in depth. Leave it undisturbed until early October, then work it into the top 2 or 3 in. of soil.
Suitable materials for mulching are well-rotted farmyard manure, leaf mould, well-rotted compost, hop manure, bark fibre, damp peat, vermiculite or lawn mowings. Keep lawn mowings very loose and no deeper than ½ in. as they tend to pack down tightly and may introduce weeds.