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Pelargoniums, commonly known as geraniums, are a large, diverse group of mostly evergreen and tender plants used as bedding or houseplants. Although pelargoniums are often called geraniums, this is not correct, as the true geraniums are hardy herbaceous plants.
Most pelargonium cultivars are divided to six groups:
Pelargoniums can be grown in borders or containers. In borders or beds, plant in fertile, neutral to alkaline soil. Most prefer full sun. Regal cultivars prefer partial shade and zonal cultivars will tolerate some shade.
For indoor or outdoor container cultivation use well drained soil-less multipurpose compost or soil-based compost such as John Innes No 2.
If growing indoors or under glass grow in full light shaded from scorching midday sun.
Water moderately during the growing season from spring to summer, avoid the compost becoming too wet and provide good ventilation. Apply a balanced liquid fertiliser according to the application 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. Water only sparingly in winter. Many will continue flowering if kept at 7-10°C (45-50°F).
Pelargoniums are usually grown as annuals, but with a little care, they can be carried through the winter using one of the methods described below:
This method is useful where there are large numbers of plants to overwinter; it suits soft-stemmed pelargoniums that cannot be kept in a semi-dormant state as per method 3.
This method is useful where there are only small numbers of plants to overwinter and space in the glasshouse or conservatory to keep them.
This method is only suitable for varieties with tough woody stems, but is useful where there are large numbers of plants to overwinter.
Many pelargoniums are naturally bushy. They can be pinched back in spring or early summer to encourage further branching. Tall, vigorously growing cultivars can be trained on canes to form a pillar. Young plants of trailing ivy-leaved cultivars are best pruned back to promote branching.
Deadhead plants regularly to promote flowering.
If kept actively growing all year round, the majority of pelargoniums can be renovated by hard pruning in spring. Those that are overwintered in a semi-dormant state (method 3) have already been cut back in autumn and should not need further pruning.
Zonal F1 and F2 (bedding type) pelargoniums and species pelargoniums can be propagated by seed. Sow in late winter and grow on in a protected environment such as a heated greenhouse.
Many bedding type pelargoniums are sold as plug plants from mail order suppliers.
Pelargoniums can also be propagated by taking softwood cuttings from spring to autumn.
Pelargoniums are easy to grow, but there are a few things worth watching out for:
Begonias: houseplantsBegonias: outdoorsContainer maintenanceContainers: planting upContainers: summer selectionFuchsiaPelargonium rustThe Pelargonium and Geranium Society
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