Pelargoniums, commonly known as “geraniums”, are very ornamental perennial plants producing lots of extremely colourful flowers for months on end. Some start to flower in spring, but mainly from early June to the first severe frosts of autumn. If grown indoors they can flower all year round.
They are not cold and frost hardy, so shouldn’t be confused with the very closely related true hardy Geranium – or cranesbills – which are perennials grown outdoors all year round.
They are used to provide colourful displays in beds and borders, hanging baskets and all manner of containers, plus indoors and in conservatories and greenhouses.
They are so popular that pelargoniums have their own national society – The Pelargonium & Geranium Society – plus local clubs and societies.
How to grow pelargoniums
Pelargoniums are generally drought and heat tolerant, but are killed by cold temperatures and hard frosts, so should be brought into a protected environment in autumn. They can flower year round if kept at 10-13C (50-55F) or above.
The vast majority of pelargoniums need a position in full sun or at least very good light.
Regal pelargoniums prefer light shade and zonal pelargoniums will tolerate a little light shade.
When growing indoors, provide some shade from scorching midday sun.
To flower profusely, they need a fertile, moist but well-drained soil.
When growing in containers, make sure you use a good multi-purpose compost or one with added John Innes.
There are 6 different main types of pelargoniums, also some types also contain sub-divisions.
Zonal pelargoniums These are the bushy, upright “bedding” pelargoniums with large, single or double flowers, which are planted out in beds and borders or grown outside in containers. Zonal refers to the dark markings on their leaves, many of which are highly attractive and ornamental.
Ivy-leaved pelargoniums These are the trailing varieties, with fleshy leaves and single or double flowers in a range of colours, used in hanging baskets or for edging containers.
Regal pelargoniums These produce single, rarely double, flowers generally in shades of pink or purple or white on larger, bushier plants. They are usually grown outdoors in containers or for indoor displays.
Angel pelargoniums These are similar to regal pelargoniums, but are smaller, more compact and bushy.
Scented-leaved pelargoniums As their name suggests, these are mainly grown for their highly scented leaves, although they also produce attractive small, single flowers. The leaves may also be variegated and/or distinctly lobed or toothed.
Unique pelargoniums Any other pelargonium that doesn’t fall into any other category.
There are several nurseries that specialise in pelargoniums. Visit their websites to see the wide range available, with images to help you select which ones to buy.
F1 and F2 varieties of zonal pelargoniums and species pelargoniums can be grown from seed.
Sow seeds from mid-January to the end of March in pots or trays of moist seed sowing compost and cover with fine layer of compost or vermiculite. Place in a propagator or warm place, and keep at a constant temperature of 20-25C (68-77F).
When seedlings are large enough to handle, transplant them into 7.5-9cm (3-3.5in) pots and grow on at around 10C (50F).
Harden them off by gradually acclimatising them to outdoor conditions for 10-14 days and plant out after thel risk of frost, 30cm (12in) apart.
Plant out pelargoniums in May/June after the danger of frost has passed.
Dig a good sized hole, big enough to easily accommodate the rootball. Add a layer of organic matter – such as compost or planting compost – to the base of the hole and fork it in.
Place the rootball in the planting hole and adjust the planting depth so that it is planted at the same depth as it was originally growing and the top of the rootball is level with the soil surface.
Mix in more organic matter with the excavated soil and fill in the planting hole. Water in well, apply a granular general feed over the soil around the tree and add a 5-7.5cm (2-3in) deep mulch of well-rotted garden compost or bark chippings around the root area to conserve soil moisture and help keep down weeds.
Suggested planting locations and garden types
Flower borders and beds, patios, containers, city & courtyard gardens, cottage & informal gardens.
How to care for pelargoniums
Although generally drought tolerant, pelargoniums growing in the ground may need a thorough watering once a week or so, especially during prolonged dry periods.
In containers, water more regularly, especially in summer, to keep the compost evenly moist but not overly wet or waterlogged. Do not allow the plants to sit in water.
During late autumn and winter, water sparingly – plants may need less frequent watering depending on the temperature and growing conditions.
Feed with a balanced liquid plant food every 10-14 days in spring. When flowers start to form, switch to a high potassium feed throughout summer and when plants are in flower.
To keep plants flowering profusely, deadhead them regularly to remove the faded flowers, by tracing the flower stem to where it joins the main plant and carefully snapping it off.
Young pelargonium plants can be pinched back in spring or early summer to encourage branching and so produce more flowers.
Half-hardy bush and trailing fuchsias should be lifted from the ground in autumn, before temperatures drop below 5C (41F), and overwintered in a frost-free place.
First tidy them up by removing all dead, dying, damaged or diseased growth, and cut them back by around half, or more if necessary, to keep them compact. Then pot them up in pots just big enough to accommodate their rootball and some extra potting compost around the outside. Then put them in a cool greenhouse, conservatory or similar well-lit place.
They can also be overwintered in a frost-free shed or garage, providing they have become dormant and dropped all their leaves.
You can also overwinter plants as young cuttings, taken in late summer. If you leave it until autumn, the cuttings may not be large enough to come through the winter successfully.
Choose strong, healthy young growth that isn’t flowering. If you can’t find suitable shoots, cut back hard one or two at the back of the plants to encourage strong regrowth.
Take cuttings 7.5-10cm (3-4in) long, cutting below a leaf joint, or node. Remove the leaves from the lower two-thirds of the stem and insert in pots of moist seed and cutting compost. Place in a well-ventilated propagator and place somewhere warm, but out of direct sunlight to root.
Cuttings can also be taken in spring to propagate pelargoniums and make more plants of your favourite varieties.