FERTILISING ROSES IN NOVEMBER
The roses have just completed their October marathon and it is time to power them up for the next show in December.
Monthly fertilising, from September to April helps the roses to flower for 10 months of the year and grow strongly, which makes them more heat and drought tolerant.
It is easy to spot hungry roses; the leaves are light green, the bushes don’t grow or flower well and are easily affected by black spot, even after spraying.
The simplest way to give roses what they need is to follow the recommended dose, worked out by the fertiliser manufacturers who have based the dosage on the nutritional requirements of the rose.
Giving double the amount of fertiliser won’t make a rose grow faster but will, more likely, burn its leaves and may even kill the rose.
For instance, Vigorosa 5:1:5 (25) contains the right mix of nitrogen, phosphorus, and potassium as well as Epsom Salts, Lime and micro elements for flowering, root and shoot development. It also contains humic acids, which play a very important role in improving the soil structure and water retention capacity.
The recommended dosage is 30 grams per rose bush, 15 grams for miniatures or newly established roses and 60 grams for large climbers and. Each Vigorosa bucket contains a 30 g measuring cup. For best results feed every 4 to 6 weeks, depending on how hungry your plants are.
Many gardeners just give Epsom salts but that only supplies a single micro-element and there is the danger of over-dosing on Epsom salts. However, if the soil tends to be too alkaline, watering with Epsom Salts will acidify it.
Gardeners also wonder about the effectiveness of foliar feeds. A rose feeds best through its “feet” so one should never replace the granular fertiliser like Vigorosa with a foliar feed.
However foliar food such as soluble Phostrogen rose food and tonic can be added to your spray every two weeks. It is in a chelate form, which means it is immediately absorbed and available to the leaves and stems. The calcium and potash strengthen the cells, making the blooms better and longer lasting.
Chlorosis, which is indicated by yellowish leaves and pronounced green veins, is caused by the roots being unable to draw iron out of the soil. Soil compaction and poor aeration is usually the cause of it. A sprinkling of 50 g of LAN around each bush may help and digging in coarse compost.
There are some simple do’s and don’ts when applying fertiliser.
- Do not place small heaps of fertiliser around the base of the rose, especially the stems of standard roses. This is too concentrated and could burn the leaves on a rose.
- The best way to apply fertiliser is to sprinkle it over or around the bush, to fall on top of the mulch. Shake or wash off any powder that did not roll off leaves. Fertiliser granules that stick to wet leaves will burn the leaves. If there has been rain, rather wait until the leaves dry out before fertilising.
- After fertilising, water deeply so that the fertiliser goes down to the roots. Not watering enough could result in fertiliser burn.
- Fertiliser burn is quite easy to recognise. In severe cases the stems become black with brittle black-brown leaves.
- Do not fertilise roses that have lost their leaves. This would set the rose back even further or kill it. Without leaves the fertiliser cannot be converted by the process of photosynthesis.
Wait until new growth appears on the upper parts of a denuded bush. Then break out the tips of the new red shoots. This will force the bush to start sprouting on the bare lower part. Once the new shoots have sprouted a small dose of fertiliser can be given- about a teaspoon per bush.