There is a little confusion surrounding pelargoniums since, though they are often called 'geraniums', these are a completely distinct plant to the true, hardy herbaceous geraniums. Pelargoniums is the correct term for a wide range of mostly evergreen and tender plants used as house plants or for bedding plants in parks and gardens. Pelargoniums are a popular greenhouse plant and a polytunnel can also be used to great effect to grow a range of these attractive flowers.
There are six main types of pelargonium: regal, angel, ivy-leaved, zonal, scented-leaved and unique. Be sure to choose the right cultivar for your needs and wants and remember that some, in particular those with larger blooms, are best grown from small container plants or cuttings rather than from seed.
Most pelargoniums will prefer a site in full sun and the extra protection from wind and extra warmth provided by a polytunnel can be beneficial, especially if there is not a sunny windowsill inside your home available to grow flowers on. It is best to grow pelargoniums in a bright spot but out of direct sunlight.
Water pelargoniums moderately and consistently during the active growing season in the spring and summer. It is important, however, to avoid getting the growing medium too wet and it is also important to ensure good ventilation. Stop watering before the first frosts threaten and water only very sparingly in the winter months.
A general purpose organic fertiliser can be applied in the spring, though once flowers form, it is important to change to a high potash fertiliser such as a comfrey tea – such as would be used on tomato plants.
Pelargoniums can be overwintered using several different methods. You can overwinter varieties with tough, woody stems, softwood cuttings can also be taken in the late summer and overwintered before potting up in the spring. You can also overwinter many varieties indoors, under glass or in a heated polytunnel. Many will bloom over the winter and throughout the year if kept at a temperature above 7-10 degrees Celsius.
Pelargoniums are usually used as a house plant rather than cut for use in displays, this means that they can give good value and a pleasant display for much if not all of the year. However, these plants also make for lovely cut flowers, which are used in a variety of different floral displays.