Care of roses begins by choosing the habitat of the rose bush.
Roses prefer a sunny, warm, but not drafty environment. The habitat
requirements ensure that the leaves can quickly dry off after
rainfall and thus decrease fungal infestations. Excessively warm
habitats can result in foliage burn. In addition, red spider mites
like dry weather conditions and can damage roses if present in
large quantities. Roses prefer profound and sandy/loamy soil.
Roses are deep-root plants; their roots quickly grow one meter
or more down into the ground. If they run into an impenetrable
barrier (e.g., concentrated building rubble), they tend to grow
crookedly.
When roses are planted in a location where there were previously
roses, the phenomenon of soil fatigue can occur. The causes of
soil fatigue are as yet unknown, but roses do not thrive in such
locations.
The Most Important Care Activities for Roses
The care given to roses depends greatly on the resistance of
roses against pests and diseases. Even the very best of care cannot
improve an incorrectly selected habitat.
Every rose will become diseased if planted in the wrong habitat.
The closer roses are together, the more sensitive they will be.
Infestations of fungal diseases vary from year to year. During
rainy summers, black spot can occur more intensively, while mildew
occurs during warm muggy summers. Even roses that are regarded
as robust cannot defend themselves against new strains of pathogens
after several decades. Roses should therefore be strengthened
through various cultivation measures, such as choosing the correct
habitat and type of rose, correct fertilization, and good care.
If they are to provide enjoyment for a long time to come, roses,
especially tea rose hybrids, Polyantha and Floribunda roses, must
be protected from diseases and pests. As soon as the branches
have attained a length of 10 to 20 cm, the plants must be sprayed
or pollenized against fungal diseases (black spot, rust, powdery
or downy mildew). Spraying against disease must be repeated regularly
every 10 to 14 days.
Roses have a high need for nutrients. Roses that are not sufficiently
cared for become susceptible to fungal disease, do not bloom abundantly,
and sprout weak shoots.
The first fertilization of the year should be done at the end
of March or beginning of April. Rose fertilizer should be evenly
distributed. The last fertilization of the year should be done
at the latest at the end of June. You should not fertilize roses
later than that.
The damage and consequences of nutrient deficiency differs from
nutrient to nutrient.
Roses urgently need nitrogen when sprouting shoots in the spring.
If there is a nitrogen deficiency, light green leaves appear;
an excess of nitrogen promotes the formation of weak, aqueous
shoots that are susceptible to diseases and pests and are also
sensitive to frost in the winter. Therefore, nitrogen administration
in the fall should be as small as possible.
The phosphorous need is not great for roses, as good garden soils
contain sufficient amounts. However, when there is a phosphorous
deficiency, it is characterized by small, blue-green leaves that
are reddish brown in color on the underside.
Auch Kalium-Mangel ist auf guten Gartenböden eher selten.
Kalium ist nötig um die Ausreifung der öfter blühenden
Rosen zu fördern. Bei Kalium-Mangel entwickelt sich das Laub
schlecht und es treten dunkelgrüne oder braun-graue Flecken
am Blattrand auf.
Calcium regulates the pH value of the soil. When soil calcification
is necessary, this should take place in the fall or winter, several
weeks before planting. Lime has an enormous influence on the soil;
too much of it leaches it, and too little holds iron in the soil.
Iron deficiency is characterized by yellow discoloration of leaves
(chlorosis). It is mostly the young leaves that become yellow,
and only the veins remain green. The entire plant becomes stunted.
However, iron is important for the formation of chlorophyll. Therefore,
roses must be sufficiently watered during dry weather conditions.
For tea rose hybrids, Polyantha, Floribunda,
miniature, and long-stemmed roses, it is sufficient to shorten
the branches in the fall. For shrub, ground cover, and climbing
roses, no pruning is necessary in the fall.
Final pruning should be done between the end of February and the
end of March. Then the branches should be pruned 3 to 4 bud eyes,
depending on the branch strength. Weak, thin, and dead branches
should be entirely removed.
Climbing roses that bloom only once
Biennial, wilted branches and weak new shoots should be entirely
removed.
Climbing roses that
bloom often
Just thin out; remove the oldest and any weak branches. Shorten
any lateral branches on the leader branch by 2 to 3 bud eyes,
depending on the branch strength. Remove weak lateral branches.
Bush roses that bloom only once
Just thin out. Remove old wood that is no longer capable of blooming.
Leave the fruit.
Bush roses that bloom often
Thin out, shorten strong new shoots by about 1/3. Cut back lateral
branches by about 2 to 3 bud eyes.
Ground cover roses
These should only be thinned out and lightly pruned.
In the summer, all wild shoots should be removed from roses, i.e.,
dug out and torn away (do not cut).
Blossom Pruning
For tea rose hybrids, Polyantha, Floribunda, miniature, long-stemmed,
and often-blooming climbing and bush roses, always cut off blossoms
after they have wilted in the summer (with 2 leaves).
After the growth period, the roots
have penetrated the ground so deeply, that the roses can supply
themselves with water. Only during periods of dry weather in the
summer should you water roses (in the morning). The leaves and
blooms must always remain dry, however (to prevent risk of fungal
infection).
Bei den Rosen sollte der Fuss des Rosenstockes und die aufgehenden
Pflanzenteile geschützt werden. Die Rosenrabatten werden
mit Tannenästen so abgedeckt, dass die Rosen vor der Wintersonne
geschützt sind. Die Stammrosen werden entweder mit Tannästen
oder mit Stroh eingepackt. In sehr kalten Lagen sollte der Rosenstock
am Fuss etwa 20-30 cm mit Kompost angehäuft werden. So verhindern
wir, dass die Rosen zurück frieren.
Starting in August, dark purple, star-shaped spots appear on
the surface of the leaves. The leaves then quickly become yellow
and fall off. The disease first occurs on leaves that are close
to the ground, but it soon afflicts the entire plant. This fungus
thrives in moistness and occurs primarily during wet summers.
Afflicted roses are often leafless starting in August, so that
the plant is forced to sprout new, stronger shoots. This takes
a lot of energy, and the branches cannot properly mature before
winter sets in.
Prevention
Select robust and resistant rose types. Choose the roses’
habitat so that the leaves are able to dry quickly after rainfall.
Never water leaves from above. Immediately collect and destroy
afflicted leaves, because they spread the fungus.
Powdery mildew occurs early in the summer during warm humid weather
conditions. It afflicts the leaves, stems, thorns, and partially
also the petals and fruits. A white, flour-like film develops
on the surface. In severe infections, the underside of the leaves
can also be affected. The consequences are growth problems and
atrophy of the afflicted aerial parts, which die off in extreme
cases.
Vorbeugung
Select robust and resistant rose types. Choose the roses’
habitat so that the leaves are able to dry quickly after rainfall.
Never water leaves from above. The roses must be given potassium-rich
fertilizers.
Downy mildew is also characterized by a white film, but it develops
on the underside of the leaves. Dark spots appear on the surface
of the leaves. The infection first afflicts young leaves and spreads
from top to bottom. The leaves wilt and fall off.
Prevention
Destroy the afflicted leaves. Plant the roses in habitats where
their leaves can dry quickly. The roses must be given potassium-rich
fertilizers.
Yellow or red spots appear on the leaf surface; the underside
of the leaves have rust-colored dots, which later become black.
A habitat that is too loamy as well as humid weather conditions
promote this type of fungal disease. If this disease occurs several
years in a row, the rose can be very weakened.
Prevention
Destroy the afflicted leaves. Plant the roses in habitats where
their leaves can dry quickly.
Small, grayish brown spots with a black edge appear on the leaves.
There is a black dot in the middle of the spot. A severe infection
can cause the leaves to fall off. These spots are caused by a
fungus that overwinters on leaves that have fallen off, but infects
young leaves via spores in the spring. The fungus occurs primarily
in damp locations or when the leaves have been unable to dry off
for a long period of time.
Prevention
Collect and destroy all leaves afflicted by the disease. For new
plantings, select a habitat that is not too damp and do not space
the plants too close to each other.
In wet summers, this fungus attacks primarily buds and blooms,
but young shoots as well. Spots are formed on the pedals and buds
cannot open, exhibit brown spots, become covered with mousy gray
mildew, and rot. Gray mildew is caused by a fungus that overwinters
on aerial parts that have died off. Due to wind and sprinklers,
spores can be present in the air during the entire vegetation
period. The roses then become infected during damp, rainy, and
dreary weather.
Prevention
Select well-ventilated habitats where roses can dry off quickly.
Cut off and destroy affected aerial parts. Do not water the plants
from above and do not use single nitrogen fertilizer.
The leaves and blooms have a sallow tint to them. The surface
of the leaves is sprinkled with whitish yellow dots. In severe
infestations, the afflicted aerial parts are covered with a cobweb.
You can see reddish mites through a magnifying glass. Starting
in May, the red spider mite can occur in large quantities during
hot, dry weather.
Prevention
Red spider mites appear primarily during hot, dry weather. This
fact should be considered when choosing the rose habitat. Collect
and destroy afflicted leaves.
Damage is often seen on young shoots and leaves. They have growth
problems or grow crookedly, and in severe cases can even die.
Aphids do not damage the roses through their suction activity,
but rather with their excrement. This honeydew sticks to the leaves,
and it is on this sugary cover that black spot fungus likes to
settle, which then damages the leaves even more. Aphids appear
in large quantities primarily between April and May and can become
bothersome.
Prevention
Protect roses from water deficiency and too much nitrogen fertilizer.
Promote beneficial organisms such as ladybirds, common green lacewings,
and flower flies.
The leaf roller is only about 3-4 mm in length and has a black
body. The female lays eggs on the leaf edges of the roses between
May and the beginning of June. The leaves become “rolled
under.” Small larvae develop inside the roll leaves, which
protects them and renders them invisible for a long time. The
damage the plants by chewing holes in leaves and through skeletonization.
Prevention
Regular use of pesticides. Promote beneficial organisms such as
Ichneumon flies.
Swellings (galls) up to the size of a tennis ball can appear
that look like they are covered with moss. The are greenish, yellowish,
or reddish in color. The larvae of the gall wasps settle in these
rose apples, which are divided into chambers . Gall wasps lay
their eggs in early summer in young leaf buds, where new galls
(swellings) develop due to the wasps’ excrement. Wild roses
are especially affected.
Prevention
Remove and destroy affected aerial parts. In this state, combating
the pest is virtually useless.
The leaf surface is sprinkled with whitish dots. Numerous yellowish
white to greenish larvae and mature insects with long wings sit
on the underside of the leaves. They flee the rosebush if you
touch it. The insects damage the roses by sucking (feeding) on
them on the underside of leaves.
Prevention
Select the correct habitat (not too hot or dry).
Affected young shoots wilt and dry out. Often, you can see a
drill hole in the branches with a flour-like stem. Inside the
sprout, a white larva that can reach up to 15 mm in length will
eat through the stem. Larvae either eat their way up or down.
For cane borers that eat their way up, a leaf wasp lays its eggs
from April to May in the leaf stalk. The larva eats its way upwards
up to 10 cm.
For cane borers that eat their way down, a leaf wasp lays its
eggs from April to May in the soft leaf bud. The larva eats its
way down inside the shoot about 4 to 5 cm, after which the shoot
wilts and dies.
To be on the safe side, you should split the shoot at the wilted
location. If you see a burrow with small caterpillars, then you
have rose cane borers.
Prevention
Cut off affected shoots up into the healthy wood and destroy the
shoots. Prevent over-fertilization. Soft shoots are especially
susceptible to attack.
