Geranium or Pelargonium: planting, growing, caring for and flowering

Undisputed flowering plants, geraniums and pelargoniums work wonders in the ground or in a planter as the case may be. 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 cannot stand frost. Let’s see in a few words what is the difference between the genre Geranium and the kind Pelargonium before turning to the planting and maintenance of these annuals or perennials which brighten up beds, terraces and balconies with their pretty plain or variegated foliage and their abundant flowering in many colors.

Do not confuse Geranium and Pelargonium

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

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

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

For the more curious, note that we are talking abouthypanthium (Where hypanthus) when the corolla, androecium and calyx – that is, the whorls – are fused with the floral receptacle, so that the ovaries of the plant end up in a kind of urn.

Plant Geranium and Pelargonium

The best time to plant is spring. For a container culture, we choose a container with a pierced bottom that can be covered with clay balls 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 spring and cultivated indifferently pot Where in the ground. They find their place in perennial beds, borders, rockeries and pots. Care must be taken not to bury the collar. It must be flush with the surface of the ground.

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

Growing Geranium and Pelargonium

Geraniums prefer exhibitions half-shaded while pelargoniums appreciate being placed under the sun because they need heat. However, beware 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-fertile, cool soils without excess humidity, and pelargoniums mainly thrive in light, humus-bearing and non-compacted soil.

As we have seen, Geranium is either installed in a pot or in the ground, whereas it is highly preferable to be satisfied with a pot culture for Pelargonium.

Maintain 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 maintain a sufficient level of humidity. We therefore prevent them from drying out throughout the beautiful season. Be careful, however, you must have a light hand 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 the summer nights that are sometimes a little too hot. However, we avoid wetting the foliage.


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

Wintering Pelargonium

Pelargoniums can be stored from one year to the next as long as they have been planted in pots and are returned before the first frosts. They are overwintered in a ventilated, cool room, where the temperature is between 7 and 14 ° C, after having brought them down to 15 cm. Of course, all flowers should be removed. Then stop watering them until the end of February. When vegetation resumes, watering can resume very moderately but the pelargoniums should not be taken out until the temperatures are sufficiently mild. Beware of late frosts in some regions!

Mulch perennial geraniums

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

Parasites and diseases

Geraniums are little affected by parasite attacks while pelargoniums can be colonized by aphids, the thrips and the whiteflies. 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 fungal diseases. Most frequent in these plants is rust due to the 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 sufficiently spacing the plants, by avoiding wetting the leaves and by wintering the pelargoniums in a sufficiently ventilated room. To eradicate rust, it suffices to resort to a specific treatment, preferably organic.

Other fungal diseases due to a confined and humid environment are likely to emerge such as Botrytis (gray rot) that 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 centers.

Flowering of Geranium and Pelargonium

To enjoy a very long flowering period, it is essential to cut the faded flowers as they 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 flower beds and balconies.

By regularly distributing fertilizer, these plants bloom in profusion, and varieties with drooping branches (P. peltatum) form real waterfalls of flowers. You can also train 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.