How to plant and grow pelargonium

What you need to know about pelargonium

Name: Zonal geranium, geranium (Pelargonium x hortorum) and ivy-leafed geranium, trailing geranium (Pelargonium peltatum).

Plant type: Evergreen perennial, moderately short lived.

Height/size: Variable, around 50 x 50cm.

Climate: Tropical, sub-tropical, warm temperate, sheltered areas in cool temperate zones.

Soil: Free-draining, light (clay free) soil or premium potting mix.

Position: Full sun.

Flowering: Much of the year, depending on variety.

Feeding: Quality controlled-release fertiliser at recommended intervals. Liquid feed regularly.

Watering: Water lightly when dry. Considered dry hard

Appearance and characteristics

With flower colours that range from simple whites to flamboyant, near fluoro-oranges and reds, pelargoniums are loved by gardeners around the globe. Little wonder, considering that given the right conditions they are extremely hardy and reliable, and even a first-time plant parent can achieve awesome results.

Many keen gardeners often wonder what the difference is between geraniums and pelargoniums. The common names of pelargoniums are actually misnomers, as while pelargoniums are closely related to true geraniums they are their own genus. Pelargoniums take their botanic name from the Greek word for stork, pelargós, as their seed capsule is said to resemble the bill of a stork. The true geraniums are Geranium species, and the name is derived from the Greek geranos, meaning a crane, due to their seed capsule being similar in shape to the bill of a crane.

The Genus Pelargonium is a very large one with around 300 recognised species although only two, and their hybrids, are commonly grown by home gardeners – the zonal and the ivy-leafed ‘geraniums’ – both native to Southern Africa.

Zonal geraniums (Pelargonium x hortorum varieties) are the ones most commonly seen in nurseries. They have a mounded, stocky form about 30-40cm in size. Their leaves are roughly circular to heart or kidney shaped, undulating, notched on the edges and are held on long stems. Leaves are slightly furry, somewhat thick, and are marked with lines or stripes into ‘zones’. The leaf colour ranges from green to patterned and many are fragrant when crushed. The flowers are held on long stems in an umbel, a flowerhead with an umbrella-like shape, well above the foliage. There are simple flowers, where the petals lay flat, and the more fancy ruffled doubles with masses of petals.

The colours range from clean whites, delicate to candy pinks, red, scarlet and vibrant orange, some colours so intense they border on fluoro! Many flowers will often have striping near the base in contrasting colours.

Ivy-leafed geraniums (Pelargonium peltatum cultivars) are those colourful flowers seen tumbling out of planter boxes in pictures of Mediterranean balconies. As the name implies the leaves are shaped like an ivy leaf, 6-10cm across with five to seven lobes held on stems roughly the same length as the leaf is large. The leaves tend to be deep green, sometimes with patterns, and are also slightly glossy and quite thick and fleshy. The flowers are held on long stems in an umbel form and feature five petals, the upper two being larger. They have 5-10 flowers per head. Colours range from white and pink to red and scarlet with some being a mauvish-purple. They have a trailing habit and will cascade from pots and baskets or trail over walls in the garden.
Many have distinctly knobbly joints on the stems. 

Uses for pelargoniums

Zonal geraniums: Garden planting where they’ll form a neat mound, pots and tubs, and hanging baskets.

Ivy-leafed geraniums: Plant to cascade down retaining or rockery walls, pots and tubs, or hanging baskets. 

How to plant and grow pelargoniums

Pelargoniums are considered moderately short-lived perennials. Under ideal circumstances they will continue to perform for three or more years. They are often treated as a very long-season annual, especially in zones with frost. 

Planting tips

• Select a full-sun position for best performance.

• Choose pots with excellent drainage – terracotta is perfect – and use a quality potting mix.

• In the garden, plant directly into free-draining soil without the need for improvement.

How to prune pelargoniums

• Remove spent flowers to encourage new blooms.

• Prune lightly after main flowering to maintain desired form and encourage bushiness.

• Although not essential, occasional applications of a flowering formulation liquid fertiliser will boost flowering.

• Feed with a quality controlled-release fertiliser after main flowering.

Watering pelargoniums

• Once established, water only when quite dry. Avoid watering foliage and flowers as a precaution against fungal problems.

• Only water lightly, don’t drench. In pots or the garden they need to avoid being even temporarily waterlogged. 

How to propagate pelargonium cuttings

Cuttings of 8-10cm in length, that include a couple of leaf nodes, will strike readily in propagating mix virtually year-round but are best taken in late spring or early autumn. Keep cuttings in a warm location as they establish.

Diseases and pests

• May be prone to fungal diseases on foliage and flowers but these problems can generally be avoided through watering the soil, not the plants, and through avoiding over-watering or waterlogging.

• Sap-sucking insects such as aphids and mealy bugs may be a problem. These are easily treated with pyrethrum-based sprays or horticultural oils.

Keep in mind...

• Wear gloves and a mask when handling mulch, compost and potting mix and also when pruning, along with long sleeves, as the leaves and sap of some plants can be a skin irritant and cause allergic reactions.

• If using products to deal with pests, diseases or weeds, always read the label, follow the instructions carefully and wear suitable protective equipment.

• Store garden chemicals and products out of reach of children and pets. 

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