Geraniums impress with their colorful flowers. With the right care – the right cutting, watering, and fertilizing – diseases can be avoided.
Pelargoniums ( Pelargonium, also geraniums) belong to the cranesbill family (Geraniaceae). Most of the approximately 250 game species are native to South Africa but came to Europe as early as the early 16th century. At that time they were wrongly classified in the genus Geranium. However, pelargonium and geranium differ in their flower structure.
Pelargoniums owe their vernacular name as geranium to this taxonomic faux pas. Since its successful arrival in Europe, the geranium has not only been established linguistically, intensive breeding has also resulted in new color variants. The flowers of the numerous varieties shine from May to the first frost in an attractive color spectrum from white to red to purple.
Geraniums are not exactly maintenance-intensive. But for beautiful flowers to appear in large numbers on strong shoots, your geranium needs a lot of fuel in the form of water and regular fertilization. Reaching for scissors also strengthens healthy growth and is essential before wintering the South African beauties. So that you can keep your balcony favorites happy, you will learn everything about watering, fertilizing, cutting, and wintering geraniums in this article.
Water geraniums properly
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Geraniums not only devour nutrients, but they also need a lot of water. Geraniums can indeed dry out without being damaged, but they only bloom particularly profusely if they are regularly watered with rainwater at room temperature. However, care must be taken that the plants are not constantly wet. Therefore, it is better to pour vigorously once than more often with small amounts of water. Do not water again until the soil has dried and avoided waterlogging.
Summary of watering geraniums:
- Water regularly and vigorously
- Avoid waterlogging
Tip: If your geraniums look limp and withered despite sufficient watering, this may be due to root damage caused by waterlogging.
Fertilize geraniums properly
Geraniums are among the heavy eaters. This, combined with frequent pot cultivation, means that you will not be able to avoid fertilization. You should fertilize the hungry plants from the time they are planted until well into October. You can use the following fertilizers for geraniums:
- Compost and horn shavings
- Special flower fertilizers
- Mineral fertilizers such as blue grain
When planting, you can use a slow-release fertilizer such as compost and horn shavings. As a rule, three liters of compost per square meter and a handful of horn shavings are worked into the potting soil. After that, you do not need to fertilize for three to four weeks. Instead of compost or horn shavings, you can also work a primarily organic long-term fertilizer into the soil.
When choosing the right fertilizer for Geraniums, you should make sure that the nitrogen content (recognizable by the “N” of the NPK ratio) should be higher. The phosphate content (P), on the other hand, should be the smallest. Our Gardender organic flower fertilizer is the ideal choice. It consists mainly of organic components. In this way, you not only protect the environment but also supports the microorganisms in the soil, because the nutrients are in complex form and must first be broken down by the soil life.
This means that organic fertilizers also have a natural long-term effect. You only need to fertilize once in the spring and top up now and then. Mineral fertilizers, on the other hand, are added to the irrigation water every one to two weeks. You can read here how exactly you go about fertilizing geraniums – you will also find valuable information on the nutritional needs of the exotic species.
Summary of fertilizing geraniums:
- Use slow-release fertilizers such as compost, horn shavings, or organic fertilizers when planting
- Subsequent fertilization occasionally; mineral fertilizers: every one to two weeks in the irrigation water
- Our recommendation: Use primarily organic fertilizers with a high potassium content and phosphate
Cut geraniums properly
Geraniums are generally very well tolerated when it comes to pruning. Withstanding geraniums, you can create smaller and larger tall trunks or bushes by cutting shapes and let your creativity run free. Those who live creatively on a small footing can be content with clipping off the tips of the new shoots from spring to early summer. This way the plants do not shoot into the herb. The mother plant is stimulated to branch and the clipped shoots are ideal for pulling cuttings. You can find out how this works below.
In weeks with high rainfall, there is an increased risk of rot or mold formation on withered flowers. To avoid this, you should regularly remove (clean) the faded inflorescences by hand. This additionally strengthens the formation of new flowers, because by removing the flowers the seed formation is suppressed and new flowers sprout. It is ideal if you carry out this maintenance measure weekly. With a certain subspecies of the hanging geranium ( Pelargonium peltatum ), cleaning is not necessary because they clean themselves. The varieties ‘Cascade’ or ‘Villetta’ are particularly popular.
The last time in the year the geraniums are cut back in September / beginning of October before they are moved to their winter quarters. The long, unwooded shoots are shortened to about ten centimeters, leaving two to three knots per shoot. In addition, all leaves are removed. After a successful wintering, the spring pruning takes place at the beginning of budding (around the beginning of February). Since geraniums bloom on the new shoot, radical pruning leads to a particularly large number of flowering shoots.
Summary of how to cut geraniums:
- In summer: Occasionally shorten the shoot tips for a better growth habit
- Weekly: Clean up dead flowers to minimize the risk of mold and rot
- Beginning of February and September / October: radical pruning
Tip: If you leave out one or more main shoots when pruning hanging geraniums and only cut back the branching side shoots in spring, you can keep them as climbing plants.
Unfortunately, geraniums do not survive the frosty winters outside of their sunny African homeland. So that you can still enjoy your geraniums for years to come, they have to be moved to their protected winter quarters before the first frost. This is ideally a dark, cool room such as a basement. Your geraniums will stay there until spring after the following preparation:
- Carefully dig up the geranium
- Gently knock the soil from the roots
- Cut back as mentioned above
- Cover the roots in a pot or bag with sand and potting soil
- Place the geranium in the winter quarters
It is only poured in such a way that the root ball does not dry out completely. There is no fertilization at all during hibernation.
The most important geranium diseases at a glance
With the right site conditions and proper care, geraniums are free-flowering plants. The following pests or diseases can nonetheless occur.
Geranium rust in geraniums
The susceptibility to geranium rust is particularly increased when the leaves are wet. You can recognize an infestation by the fact that the leaves turn yellow to brownish and pustules sometimes appear on the underside of the leaves. Spots or rings are visible on the upper side of the leaf and spread rapidly. Since geranium rust is contagious, you should remove the affected leaves as soon as possible and dispose of them in the event of an initial infestation. You can also support the plant with a plant tonic and should absolutely avoid watering the plant from above. The geranium should also be protected from rain.
Botrytis in geraniums
The so-called botrytis (also called gray mold) is a common fungal disease. Similar to geranium rust, there is an increased susceptibility in wet and cold weather. If your geranium has rotten spots with a gray coating of spores, it is most likely affected. Then you should first remove infected parts of the plant and, in principle, keep the plant drier. Spraying bio-active agents with field stalks and oats provides additional strengthening.
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Aphids on geraniums
Aphids also often target geraniums. An infestation often occurs in winter quarters when the plant is dark and does not grow much. By sucking the aphids, the geranium leaves curl and make the infestation recognizable. If this is the first aphid infestation, rinse the geranium thoroughly with water. If they occur more frequently, you can also fight the aphids with soapy water.
Spider mites in geraniums
While gray mold and geranium rust usually occur in wet weather, geraniums can be attacked by spider mites in dry, warm weather. The infestation can be recognized by silvery dots on the upper side of the leaf and webs on the underside of the leaf. In most cases, it is sufficient to spray the geranium with water and treat it with a plant tonic.
Whitefly on geraniums
Geraniums are particularly susceptible to attack by white flies in warm, sheltered locations and winter quarters. The pests settle on the underside of the leaves and cause yellow spots on the leaves by sucking. Affected leaves then dry up and fall off. To combat it, you should remove infested leaves and, if the infestation is low, attach yellow panels. Parasitic wasps are well suited for natural control by beneficial insects.
Summary of the most important geranium diseases:
- With geranium rust, the leaves turn yellow to brownish; partially pustules appear on the underside of the leaf; spots or rings are visible on the upper side of the leaf and spread rapidly; contagious
- If botrytis or gray mold is infested, rot areas with a gray layer of spores appear
- Aphid infestation can be recognized by the wavy leaves
- Spider mites leave silvery dots on the upper side of the leaf and webs on the underside of the leaf
- White flies settle on the underside of the leaves and cause yellow spots on the leaves by sucking; affected leaves dry up and fall off
This special article also tells you what to do if your geraniums have yellow leaves.