Geranium or Pelargonium: planting cultivation care and flowering

Undisputed flowering plants, geraniums and pelargoniums do wonders in the ground or in a planter depending on the case. They bloom from May until frost, but they are two different genera, and it is important to differentiate them because some are hardy while others do not support frost. Let us see in a nutshell what is the difference between gender Geranium and the kind Pelargonium before turning to the planting and maintenance of these annual or perennial plants which brighten flowerbeds, terraces and balconies with their pretty plain or variegated foliage and their abundant flowering in many colours.

Do not confuse Geranium and Pelargonium

Unlike botanists, home gardeners don’t always distinguish between geraniums and pelargoniums. For example, the cultivar that is commonly called Geranium lierre is a horticultural Pelargonium just like the Geranium zonale from the Pelargonium zonale. Similarly, Geranium rosat is a generic term also designating a plant of the genus Pelargonium. To make matters worse, wild species of the genus Geranium are not Pelargoniums. We can still find a common point between all these plants: they belong to the family of Geraniaceae.

It can be noted that the genus Pelargonium can be divided into three groups:

  • Pelargonium zonale,
  • Pelargonium peltatum,
  • Large-flowered pelargonium.

To find your way around, here are some distinctive criteria between the two genres.

  • Plants of the genus Geranium : for most of them, geraniums are perennials rustic who can live outside in the winter. They have 10 fertile stamens. The shape and size of all of their petals are absolutely similar. Note the absence ofhypanthium. The seed capsule of Geraniums resembles a crane beak (Geranium in Greek).
  • Plants of the genus Pelargonium : not offering no frost resistance, they do not survive outside in our winter climates. They are therefore grown as annuals. The number of fertile stamens is less than 10. The petals are of different shape and size, namely 3 lower petals and 2 upper petals, but this distinctive sign is not visible on many hybrids. On the other hand, we note the presence of a hypanthium. As for the Pelargonium seed capsule, it looks like a stork beak (Pelaragonium in Greek).

For the most curious, note that we are talking abouthypanthium (or hypanthe) when the corolla, androecium and calyx – i.e. the whorls – are fused with the floral receptacle, so that the ovaries of the plant end up in a sort of urn.

Plant Geranium and Pelargonium

The best planting time is spring. For a culture in pot, we choose a container with a pierced bottom which can be covered with clay pebbles to promote drainage. If you plan to plant several plants in a planter, it is necessary to space them 25 cm from each other.

The perennial geraniums are also planted in the spring and grown indifferently in a jar or in the ground. They find their place in perennial beds, borders, rock gardens and pots. Care must be taken not to bury the collar. It should be flush with the ground surface.

Once planting is complete, watering should be generous enough to promote rooting.

Growing Geranium and Pelargonium

Geraniums prefer exposures semi-shaded while pelargoniums like to be placed under the sun because they need warmth. Beware, however, of south-facing situations which can be very hot in the middle of summer. As far as the soil is concerned, geraniums prefer compact, well-fertilized, cool soils without excess humidity, and pelargoniums do best in light, humus-rich and non-compact soil.

As we have seen, Geraniums are planted either in pots or in the ground, whereas it is highly preferable to settle for a pot culture for Pelargoniums.

Caring for geraniums and pelargoniums

All of these plants are very easy to grow.


If the rains are infrequent, it is necessary to water geraniums and pelargoniums regularly throughout the flowering period. It is important that the soil of the beds and the substrate of the planters can retain a sufficient level of humidity. We therefore avoid their drying out throughout the summer. Be careful though, you have to be light-handed with geraniums because they hate excess water.

Watering at the end of the evening is perfect because it allows the plants to take advantage of the coolness during summer nights that are sometimes a little too hot. However, avoid wetting the foliage.


A contribution oforganic fertilizer during spring stimulates flowering. For plants in pots or planters, we recommend addingliquid fertilizer every 10 to 15 days, to be diluted in the irrigation water.

Wintering the Pelargonium

It is possible to keep pelargoniums from one year to the next provided that they have been planted in pots and that they are returned before the first frosts. They are wintered in a ventilated, cool room, where the temperature is between 7 and 14°C, after having lowered them to 15 cm. Of course, all flowers should be removed. It is then necessary to stop watering them until the end of February. When vegetation resumes, watering can resume very moderately, but the pelargoniums should only be taken out when the temperatures are sufficiently mild. Beware of late frosts in certain regions!

Mulch perennial geraniums

Installing a mulch at the foot of a perennial Geranium planted in a bed or a rockery helps protect its roots against the harshness of winter. A good layer of dead leaves quite suitable.

Pests and diseases

Geraniums are little affected by pest attacks while pelargoniums can be colonized by pests. aphidsthem thrips and the aleurodes. A black soap treatment kills aphids, while thrips and whiteflies require elderberry leaf decoction sprays.

Geranium and Pelargonium fear excess humidity, which is responsible for cryptogamic diseases. The most common in these plants is rust due to fungus Puccinia pelargonii-zonalis. More or less yellowish spots form on the foliage and are followed by pustules. Necrosis sometimes affects the stems. The disease is prevented by spacing the plants sufficiently apart, avoiding wetting the leaves and overwintering the pelargoniums in a sufficiently ventilated room. To eradicate rust, all you need to do is use a specific treatment, preferably organic.

Other fungal diseases due to a confined and humid environment are likely to appear such as Botrytis (gray rot) which can be treated with Bordeaux mixture. As for thePelargonium ivy edema which causes blisters, it is treated with a specific product that can be obtained in garden centres.

Flowering of Geranium and Pelargonium

To take advantage of a very long flowering time, it is essential to cut the faded flowers as you go, whether for Geranium or Pelargonium. Thus these plants quickly produce other flower buds which follow one another without interruption and the absence of faded flowers is still preferable to preserve the aesthetic appearance of the beds and window boxes.

By regularly distributing fertilizer, these plants bloom profuselyand varieties with drooping branches (P. peltatum) form real waterfalls of flowers. You can also trellis them easily because they are flexible, in order to direct them according to your inspiration. But whatever the choice of the varieties of geraniums or pelargoniums, one obtains against some good care a spectacular effect For many months.

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