22 MAY 2019 GARDENING AUSTRALIA
ROSES
other unproductive canes to encourage new flower growth
from healthy stems. You don’t need a perfect, vase-shaped bush
but should instead focus on having a plant with healthy stems.
PESTS & DISEASES
Humidity is usually the instigator of fungal disease, which is the
most common concern of rose growers everywhere. There are
organic recipes for spraying roses to prevent fungal infection, and
these may also be used as spot treatments. Accepting marks on
leaves and flowers may also be part of the process of enjoying
roses, if you prefer not to routinely spray. A small infection on
a disease-resistant rose will be of little concern. After all, why
is a mark on a rose any worse than soot on gardenia leaves?
If your rose is one that is more prone to disease and it takes
over, the plant may be at risk and should be treated. It’s best to
choose roses that are known to perform well in humid climates,
and to replace one that is constantly sick with a better performer.
Black spot is the most common condition that you will come
across, and it will have already infected the leaves for several
days before you notice it. The fungal spores activate when the
leaf surface is continuously wet for about seven hours, so avoid
watering the leaves in the late afternoon or evening during cooler
months. In summer and spring, this is not a problem, as leaves
dry quickly. Removing affected leaves as they appear reduces
its spread by getting rid of spores from within the garden. Don’t
compost these leaves, as spores thrive in compost conditions.
Another common disease in humid areas is powdery mildew.
This is usually a symptom of poor air circulation, which creates
the ideal environment for it, so avoid shady spots and dense
plantings when creating your garden. Powdery mildew is most
often seen in early spring and early autumn, when cool mornings
with high humidity provide perfect conditions for this disease to
flourish. You can wipe the leaves with a wet cloth to remove the
mildew, or use an organic contact spray to inhibit the spores.
While insect attack may occur on your roses, nature is there
to assist you. Companion planting can help to attract beneficial
insects to your roses. Ladybirds, hoverflies, lacewings, rose
aphid parasitic wasps, dragonflies and damsel flies, as well
as insectivorous birds, spiders and microbats, all work to help
eliminate aphids and other pest insects. If these are left alone,
without any interference, nature will take its course and your
aphid infestation should disappear within a couple of weeks.
Healthy roses are more disease resistant, so grow them in
full sun to give them the best opportunity to thrive. Don’t plant
CLOCKWISE
FROM TOP
The lightly fragrant
Hybrid Tea Rose ‘Elina’
produces abundant
flowers in all climates;
some of the proceeds
from Brisbane-bred
Hybrid Tea rose ‘Lady
Endo’, with its long stem
and intense perfume,
help to fund research
into endometriosis; an
old-fashioned favourite,
‘Monsieur Tillier’ has
medium-sized flowers
with a fresh, herbaceous
fragrance; the delicate,
softly tinted blooms of
‘Seduction’ belie its
reputation as one of the
toughest Floribundas.