GROWING HEALTHY ROSES By Merylyn Condon
On garden radio there are often calls asking for home recipes for controlling pests and disease as an alternative to using chemicals. One thing has become very clear, and that is that many people shun commercial pesticides, fungicides and the like.
In writing an article for the HSOC bulletin, I originally planned to include a few of the recipes which are often asked for, but on reflection I realised I would need to put those recipes into context, for using such concoctions is less than useless unless you carry out a whole set of sensible gardening practices. It’s a big subject and while many of the homespun recipes are not rose-specific, for this article I’ll concentrate on roses and what you can do to reduce the effects of pests and disease on them.
Here is an easy guide to help you to grow healthy roses, at the same time avoiding the need to resort to ‘the big guns’.
- Buy quality disease-resistant plants, two years old, strong and healthy.
- Avoid bagged roses which already have started to sprout and have spindly, discoloured shoots. They are a waste of time and you will do yourself a favour if you start with healthy stock.
- Irrigation should be planned to keep leaves dry.
- Mulch to retain soil moisture, increase worm and microbe production as well as reduce weeds.
- Make a habit of keeping your secateurs handy, but also clean and sharp!
- Prune off old flowers as they finish, always cutting back to strong stems and healthy shoots, rather than simply twisting off dead flower heads as you walk by.
- Good hygiene is important, so collect fallen diseased leaves to remove the source of spores. Bin rather than compost them.
- Roses that repeatedly show signs of black spot and other fungal problems early in spring are best removed. Again, bin rather compost diseased plants.
- Don’t do your winter pruning too early unless there is no alternative. If you must prune early, prune lightly rather than not at all, so you have something to cut back to if a heavy frost burns new growth. Ideally, prune in late winter using sharp, clean tools and remember to wear tough gloves.
- Better to hold back on all sprays, even the home remedies, as the ‘goodies’ should be encouraged to be there and do their job, feeding on other insects and thus reducing the need for any intervention. You can grow plants to attract beneficial insects. To attract lacewings to counter the effects of aphids, try growing achillea, dill, angelica, anthemis, cosmos, coriander, fennel and tansy, just a few of the plants which will attract lacewings. Ladybirds will keep aphids, mealybug and scale under control if their numbers are allowed to build up, but this will only happen if you leave your sprays in the cupboard.
- Regular checks of the garden for any pests or other problems will enable you to act before the problem becomes insurmountable. Ant activity on trunks of shrubs or trees is often the first indicator of sap sucking insects, although with rose bushes, you will often see the aphids before you see ants. Aphids will be most evident in spring clustering on new rose shoots but you can still find them on whatever remaining new growth they can find just before winter (I’ve even seen them in July, still there after a heavy frost). Gloved fingers are the preferred weapon. Just squash them. If you are encouraging beneficial insects to your garden, hopefully there will not be too many aphids to worry about.
- Powdery mildew on heritage roses usually appears in late spring and as the period immediately after flowering is ideal for pruning spring bloomers, removing disease at that time will help to control the problem.
- Black spot on roses is the bain of most gardeners and most of our roses will have it at some stage. If a plant shows signs of black spot early in the season, then don’t waste time (unless the plant has sentimental value). Get rid of it and replace it with one that is more resistant to black spot.
- Make sure you plant a replacement plant in full sun with plenty of air distribution, for if the problem rose has been overgrown by other plants, another in the same position will soon succumb.
- If you think the siting will be OK, then you’ll need to the existing soil with fresh soil and put the old soil somewhere in the garden where other members of the rose family are not growing.
Silkie Roses, a Victorian rose nursery, uses an organic-based fertilizer with trace elements and for consistent growth, apply that at the rate of one half-handful (¼ cup) per plant every 8 weeks. As part of an ongoing maintenance program, their roses also receive an application of a mix of ‘Natrakelp’ liquid seaweed and ‘Eco Oil’ (horticultural oil concentrate made from canola, eucalyptus and melaleuca plants. Their recipe is 5 litres of water to which 2-4 capfuls Natrakelp liquid seaweed and 1 capful Eco-Oil are added. These ingredients are mixed well and sprayed or poured over leaves to run-off once a month before 10am (or more frequently at critical periods, or if disease or pests become apparent). They assert that the healthier the plant, the greater its natural resistance to disease and pests and tolerance to stress. That makes sense!
Be aware also that companies such as Yates and Organic Crop Protectants Pty Ltd (the originator of Eco products) amongst others, strive to ensure that products offered for use by the home gardener are now much more environmentally friendly than once were offered. Also, look for a black spot spray in the form of a potassium bicarbonate, a commercially produced product which will also offer ease of application, so often valued by busy people.
Finally, for those who prefer not to use commercial products or look for a cheaper alternative, I have a few solutions though there are countless variations to these. One should remember the effects of these recipes are short-lived and re-application will most definitely be necessary, particularly after rain. That said, a quick spray with a bicarb solution might be all that is needed to correct a small problem before it becomes a major headache.
- Rose fungicide: 1 litre water. 1 teaspoon bicarb. soda and a sprinkle of Condy’s Crystals, a dash of detergent and fish emulsion. Spray undiluted every few weeks.
- Alternative fungicidal spray of tomato, camomile and milk: 1 cup fresh tomato leaves and 2 camomile tea bags to 1 litre boiling water. Allow to steep for 1 hour. Strain and dilute with another 1 litre water, then add 1 litre mil. Use immediately. Do not store.
Aphids: use a gloved finger to squash or rub off. If a spray is necessary, use potassium soap (Clensel or Natrasoap), or an horticultural oil spray as an alternative to pyrethrum or another insecticide. Of those insecticides on offer at garden centres, Confidor is a preferred option.