How to grow pelargoniums

Choosing pelargoniums

Pelargoniums (often called ‘tender geraniums’) are bright, cheerful summer-flowering plants. If you are looking for a show-stopping bedding plant, a drought-tolerant hanging basket plant or something new for the windowsill or conservatory, pelargoniums make a great choice. There’s plenty to choose from so here are some pointers on which to grow.

Summer colour

There are three main types of pelargonium that are popular for summer-long colour:

• Zonal: Grow this pelargonium for bedding displays or in containers on a sunny patio. Many have attractive foliage with purple or maroon markings in zones on the leaves, hence the name. Plants are upright and bushy with succulent stems and offer clusters of single or
  A type of flower that has extra petals, often having a fuller appearance. Plants with double flowers are often considered more ornamental and showy than those with single flowers, though they are generally not as good for wildlife, having little or no pollen. Some plants naturally produce double flowers, while others may be bred for this trait. Examples of plants with double flowers include roses, sunflowers, dahlias, and zinnias.

  double flowers in red, salmon, pink or white
• Regal: Another popular type of pelargonium that flower slightly earlier than the Zonal. Plant up several in pots to brighten an outside space or enjoy them indoors. Their ruffled flowers are some of the showiest offered in shades of mauve, pink, purple or white
• Angel: Similar to Regal pelargoniums, Angel types are compacter and bushier. Darker markings on the upper petals give the flowers a pansy-like look. They make an excellent choice for pots indoors or out

Trailing habit

Known as Ivy-leaved pelargoniums (because of the shape of their leaves), grow these trailing types in hanging baskets or containers so that their stiff fleshy leaves tumble down the sides. You can pick from a wide range of flower colours and anticipate a long flowering display, still blooming long after most summer baskets have finished.

Scented-leaves

Aromatic when their leaves and stems are rubbed, Scented-leaved pelargoniums deliver in smell what they sometimes lack in flower power. As well as being scented, the leaves are often attractively lobed, toothed or variegated. Perfect for a greenhouse or conservatory, or in pots on a sunny patio where the heat brings out the best of the volatile oils. There are many different scents to choose from so be warned, it can be addictive to start a collection. Unique pelargoniums also have scented or pungent foliage but usually showier flowers than Scented-leaved types.

Buying

Many bedding type pelargoniums are sold as

Seedlings or young plants grown singly in small modules, with the advantage that they can be transplanted with minimal root disturbance. Bedding plants and young veg plants are often sold as plug plants of various sizes, with smaller ones requiring more aftercare. They usually need to be potted up and grown on indoors until large enough to plant outside.

Nurseries specialising in pelargoniums are the best place to go to for the widest range, especially of particular forms such as the Scented-leaved or Regal pelargoniums. Search for them with the RHS Find a Plant tool.

When to plant

Wait until frosts have past if you are growing your pelargonium in a bedding scheme or standing pots outdoors for the summer. This is not usually before the end of May in most parts of the UK (and early to mid June in Scotland). Also, it’s important to take a couple of weeks to harden off your plants, a way of acclimatising them to outdoor living.

Remove all packaging straight away from newly arrived plug plants and pot them up either into cell trays or individual pots. Grow these on in a bright, warm (7-21°C/45-70°F) place until ready to plant out. If you have overwintered container-grown plants which you plan to keep in pots, repot them in spring.

Where to plant

Grow pelargoniums in borders or containers. In borders or beds, plant in fertile, neutral to alkaline soil. Most flower best in full sun. However, Regal cultivars prefer partial shade and Zonal cultivars will tolerate some shade.

When growing in containers, either indoors or out, use peat-free multipurpose compost or soil-based compost such as John Innes No. 2. The lighter-weight multipurpose is ideal for hanging baskets. Position your indoor, conservatory or greenhouse pelargonium in full light but shade them from scorching midday sun.

How to plant

See our guide on bedding plants if you are planting your pelargoniums out into the border.

Or check out our container planting page for pelargoniums in pots.

Watering and feeding

Pelargoniums are not thirsty plants so water moderately from spring to summer, taking care that the compost doesn’t become too wet. Open windows or vents in a conservatory or greenhouse in summer to be sure of good air flow. Water only sparingly in winter, so that the compost has time to dry between waterings.

Your pelargoniums will respond well to feeding so apply a balanced liquid fertiliser according to the instructions on the packet, every 10-14 days in spring. Once flowers start to form, switch to a high potassium fertiliser such as tomato feed, feeding fortnightly throughout the rest of summer. Many will continue flowering if kept at 7-10°C (45-50°F), but reduce feeding to once a month in autumn and winter and stop feeding completely if you have dried your plants off in winter (see below).

Overwintering

You can simply grow your pelargoniums as annuals, pulling them out and adding them to the compost heap at the end of the year. But since pelargoniums are perennial plants you might like to save them for another year, especially if you have grown a type or colour you are particularly fond of. To have a go, try one of the methods described below:

Method 1: Overwintering by taking cuttings

This method works well if you have large numbers of plants to overwinter, especially if they are the soft-stemmed pelargoniums such as Zonal types. It is more reliable than keeping them in a semi-dormant state as described in method 3 but takes a little forward planning.

• In late summer, take softwood cuttings (you can discard the old woody plants at the end of the season)
• Once the cuttings have rooted, overwinter them in trays of compost kept on a well-lit indoor windowsill
• Water the trays only sparingly in winter, allowing the compost to dry out between waterings
• Start feeding in late winter, giving a balanced liquid fertiliser every seven to 10 days according to the instructions on the packet
• Pinch out the shoot tips in late winter to encourage bushy growth
• Pot up the rooted cuttings into individual 9cm (3½in) pots in mid-spring
• Harden off and place or plant outside once the risk of frost has passed

Method 2: Overwintering in containers under glass

Opt for this method when you only have a small numbers of plants to overwinter. You can either keep plants in active growth or cut them back to be more dormant, depending on how much space there is in the glasshouse or conservatory (plants with bushy stems and leaves will obviously need more space than those cut back).

• Bring container-grown plants under cover and lift and pot those growing in the soil before the first autumn frosts. Use John Innes No. 1 potting compost. If you do not have enough space to keep the plants at their full size, cut them back to 10cm (4in). This will also discourage soft growth
• Keep the plants in their pots over winter, in a light, airy, frost-free position
• Check those in active growth at least once a week and water if there are signs of drying. Plants which were cut back require barely any water at all until growth resumes in spring. Open windows or vents on mild days in the glasshouse or conservatory to reduce rotting off
• Re-pot into John Innes No. 2 potting or peat-free multipurpose compost in mid-spring
• Harden off and place or plant outside once the risk of frost has passed

This method is the least reliable and only suitable for varieties with tough woody stems, but is worth trying if you have large numbers of plants to overwinter.

• Before the first frosts, lift plants from the ground or pot and shake off excess soil or compost from the roots
• Lay the plants in crates or on a bench in a frost-free place to allow the foliage and stems to dry off and then wrap the plants in newspaper or hang them upside down from the shed or garage roof (which must also be frost-free)
• Inspect the plants in early spring. Those which show signs of growth can be kept. First soak their roots in water for a few hours before potting them up and cutting back all stems to about 10cm (4in). Water sparingly and place somewhere warm and bright such as a greenhouse
• Harden off and place or plant outside once the risk of frost has passed

Many pelargoniums are naturally bushy. But pinch back the tips of shoots, including those of young trailing ivy-leaved cultivars, in spring or early summer to encourage further branching. Train tall, strong-growing cultivars on canes to form a pillar.

Deadhead plants regularly to promote flowering.

If you have somewhere bright in winter, such as a conservatory, and are overwintering your pelargoniums in containers (see Overwintering method 2 above) then either cut back hard in autumn or, if keeping your plants actively growing all year round, give them a hard prune in spring, ready for the new season of growth.

Seed

Zonal F₁ and F₂ (bedding type) pelargoniums and species pelargoniums, such as Pelargonium odoratissimum, can be propagated by seed. Sow in late winter and grow on in a protected environment such as a heated greenhouse.

Cuttings

Pelargoniums can also be propagated by taking softwood cuttings from spring to autumn.

• Poor air circulation and damp conditions favour diseases such as grey mould and rust
• Pelargoniums can suffer from viruses transmitted by sap sucking insects such as thrips, or on pruning or propagating tools including knives or secateurs
• Roots of container grown plants are prone to vine weevil larvae damage
• They can also suffer from leafhopper, root mealybug and whitefly
• Dense clusters of distorted leafy shoots, often close to ground level, are leafy gall