Lex has asked me to talk to you about why and how we replace roses in our garden.
Firstly the “why”. Audits are done every year on the beds in the Tudor Rose. There will always be some that are performing badly, having reached their life span. It is a sad probability that more modern roses have a shorter life span than some of the old favourites. They age quicker and produce less, smaller blooms. Over the past 20+ years we have had a replacement team responsible for selecting those beds which are to be replaced. They present their findings to Council for approval. We try to only replace one bed in each petal each year. We certainly do not want the public to see three or four beds in the same petal, bare for at least two months waiting for replacement. Not good for a display garden open to the public.
Then the team have the responsibility of selecting new roses. Past experience tells us that it is dangerous to rely on descriptions in catalogues. The nurseryman is in the business of selling roses so makes each cultivar sound tremendous, using emotive language and names. Consider the names that came out to commemorate the anniversary of WWI.
Because of this danger, we instituted three beds to trial how each potential rose performs in our soil and climate. Each potential candidate is on trial ( three plants) for two years. Each of you has the opportunity to comment on the roses in these beds (in writing to our secretary, please). Unfortunately these trials can create a problem as the roses we are trialing may not be commercially available when we need them. There are some 5000 new roses created every year. It is a sad fact that 2000 of them are not commercially available the following year due to fashion changes and poor sales.
Coming back to selection of new roses, it is important to remember that we are a display garden, not a garden for growing prize blooms. A lot of prize winning show roses are often not suitable for a display garden. Take for example, Papa Meiland or Peace. Beautiful flower, good perfume – lousy bush, spindly and hard to maintain.
The replacement team has to consider the height, shape and colour of the selections. They have to ensure that the new cultivar is pleasing to the eye, has good foliage, has good perfume, is not going to attack the public by wayward growth and will not colour clash with its potential neighbour. They also have to consider whether the quantities we need for a bed will be commercially available. It is no good selecting a rose only to find that there are only three of them available when we need twenty in two years time. What a task!!
One of those up to the task was Veronica who was a member of the replacement team for many years. She was President of National Rose Society of Australia, was in constant contact with local and overseas breeders and distributors and took notes of potential roses at rose shows. She visited the trial beds at Adelaide over the last four years. She was a source we will miss in our selection process.
For those of you who are unaware, the Australian Rose Trials are the only independent trial of new plant releases for Australia and are conducted over a two year period. The new releases are given a number and grown incognito where they are regularly judged by a team of rosarians under the control of the National Rose Society and the Adelaide Botanic Gardens. Points are given for colour, fragrance, perfume, growth habit, disease resistance, and tolerance to Australian conditions. We have Medal winning roses in our Garden.
Then there was Joan who, for years, was tasked with finding sources for the roses we needed. There are only a handful of rose nurseries in Australia who breed the quantities we need for a bed. Those same rose nurseries are in the business of making money so if a rose is inferior or weak or not selling, it will be tossed out in favour of the next fad.
Talking of fads, it cannot be stressed too much how big an influence Rose Society Shows have on the rose market and our thinking. If a rose doesn’t win prizes, it quickly goes out of favour with the members of the Societies. and this is reflected in sales of that rose.
Graham and Marlene are also dedicated to selecting plants which perform well as park roses. As well as selecting from catalogues, they rely quite heavily on information from the public and our members. If you grow a rose in your garden which yo believe would do well in our garden, let them know.
Coming back to rose selection, one of the criteria is disease resistance. There is no such thing as disease free roses. Some lines of breeding are creating disease resistant plants but even these need the staples to keep them healthy – one bucket of water a week, four feeds throughout the year and five hours of sunshine. Our Parks team provides the water but is restricted in the usage due to the age of the watering facilities – only one section of the Werribee estate can be done at any one time.
Similarly, the Parks team arrange for contractors to spray the garden for diseases, but at $1300 per spray, cannot afford to do this as regularly as we would like. Wouldn’t it be lovely if we had roses that didn’t get diseases? We must always be mindful of the valuable input and assistance by Parks people in helping us to maintain the garden, in spite of the financial restrictions imposed on them.
Let me give you a very irreverent look at our two most common fungal diseases, and some means of overcoming them, strictly according to Wal.
Black Spot:- A fungal disease which is spread by spores and affects the leaves of susceptible plants, leaving black spots which slowly cover the whole leaf, turning it brown and usually causing it to drop off. In very heavy infestation the bush can be defoliated. All treatment must be done when the foliage is just starting to appear and should continue every week. By the time you notice the black spots appearing on the leaves of your favourite bush, it is usually too late to do anything about it. You can remove the affected leaves; you can pick up every leaf that has dropped to the ground (University of San Diego has produced “evidence” that the spores die when the leaf dies on the ground); you can spend a fortune on the most poisonous fungicides available (and most commercial products are); you can rip out the bush and select a cultivar that is black spot resistant; or you can use Wal’s magic mix, described later.
On a different note, I have been reading up on the dreaded black spot. There are literally libraries of information on this disease. The most interesting thing that I found in several references was that pathogenic fungi, such as blackspot, are genetically variable and multiply rapidly so that they are capable of evolving new strains or races. For example the Houston Rose Society quotes “The slightest mutation of the fungus impedes the effectiveness of the fungicide treatment by camouflaging the product’s target. Fingicides with single-site modes of action are Rose Pride (Funginex) and Green Light Systemic Fungicide.
Genetic mutation of fungi is more common than we think. There are 54 known variations of blackspot fungus in North America and these variations or “races” of the disease are frequently geographically specific. Roses resistant to one race of blackspot fungus may prove susceptible to other races of the disease.”
For this reason, many of the “experts” recommend changing the nature of your spray every time. For example one Canadian rosarian states “spray every week with alternative fungicides having as active ingredients triforine and chlorothalonil; these substances have different properties which because of this prevent the fungus developing resistance.” He goes on to say that he believes that the air remains polluted by blackspot spores.
It is known that the spores splatter for incredible distances when hit by a drop of water, hence the old wives’ tale about not watering the foliage.
Powder Mildew:- Usually first noticed on the leaves as a white powdery film, it can quickly spread along the stems and will affect the flowers, particularly the new buds. It is spread by spores, usually in high humidity conditions. It is one of the reasons why old wives advise never to use overhead watering, at sundown. I don’t quite know what you do if it rains at that time. Some cultivars are more susceptible to powder mildew than others. The longer term volunteers will remember Cream Dream, which only lasted one season. Such cultivars were planted at the end of grapevine rows. When the cultivar showed signs of powder mildew, the vintner knew it was time to spray his vines.
Fungal Disease Spray Cure:- I believe that any spraying regime should be effective on four levels; safety to the environment; safety to one’s self; low cost; and effective. The following mix for the home garden has been trialled for many years, and if used regularly (Forgive me, for I don’t), will meet all the requirements mentioned. Those who have used it regularly claim that they have a complete absence of fungal diseases even in seasons when this problem was fairly prevalent. The principle behind the spray is to coat the leaves so that the spores cannot attach themselves to the leaf.
During the growing season from September to April, every seven to ten days, mix the following brew and spray all the foliage, front and back, stems and near ground of your roses. Use no other fungicide.
In five litres of water, stirred well (I use a Hill’s 5 litre pressure sprayer)
3 teaspoons of sodium bicarbonate
30 mls canola based or water soluble oil
3 mls cheap washing up detergent
Another cheap method for the home garden is to take ½ litre of full cream milk, mix with 5 litres of water and spray for all you are worth. Not very practical for our garden?
In addition, about once a month, give each plant about 5 mls of potassium nitrate to give good strong vegetative (leaf) growth, but be aware that this may well be to the detriment of a good floral display.
Wal J 7th March 2018
