Before cutting a 'geranium' down to the ground, check its leaves and flowers. In British gardens, the name covers hardy geraniums, also known as cranesbills, and pelargoniums, the colourful bedding and container plants many people call geraniums. They are not pruned in the same way.
Hardy border geraniums often tolerate a dramatic cut after flowering and respond with fresh foliage. Pelargoniums may need deadheading, gentle shaping and frost-free winter care. Mixing up the instructions can mean cutting a tender plant at entirely the wrong time.
Identify a hardy geranium
Hardy geraniums generally form spreading clumps or low mounds in borders. Many have lobed leaves and five-petalled flowers in blue, purple, pink or white. They come back year after year in suitable UK conditions.
Some are vigorous summer flowerers that make untidy foliage after the first big display. Others flower in spring or have naturally compact growth and need less intervention.
Look for a botanical label beginning Geranium. If the name says Pelargonium, skip ahead to the section on bedding geraniums before making any substantial cuts.
When to cut hardy geraniums back
For many summer-flowering hardy geraniums, the RHS recommends cutting the foliage back to near ground level after the main flowering display, commonly in June or July. This is sometimes nicknamed the 'Hampton hack'.
A substantial cut can encourage fresh foliage and, in some cultivars, another flush of flowers. But it should be done after the first major display, not while a healthy plant is still covered in flowers you want to enjoy.
Check the species and growth habit. An early spring-flowering geranium or a naturally evergreen type may need a different, lighter approach.
How to make the hard cut
Move stems aside to find the crown, where new shoots emerge from the base. Use clean secateurs or sturdy garden shears to shorten exhausted flowering and leafy stems down near the ground.
Take care not to slice through fresh young growth already appearing at the base. A shallow, clean cut is better than scraping through the crown and damaging buds.
Gather the trimmings immediately. A heavy wet mat of cut foliage can trap dampness around the regrowth. Discard diseased material appropriately; healthy trimmings can be composted.
Care after cutting a hardy geranium
If the weather is dry, water the plant deeply enough to moisten its root zone. The RHS specifically recommends watering cut-back geranium clumps in dry weather to encourage renewed foliage.
Avoid applying strong fertiliser in a rush. Established hardy geraniums often need little feeding in suitable soil. Mulch around the plants if appropriate, keeping bulky material away from the crown.
Fresh leaves may appear within weeks in favourable conditions. A repeat flowering is possible, not guaranteed. Some varieties produce a tidy new mound of foliage without another full flush of flowers.
Tidy hardy geraniums at the end of the year
Many hardy geraniums naturally die back during autumn or winter. Remove faded stems and leaves when they have finished their job and no longer provide useful shelter.
You can sometimes leave sound debris briefly for wildlife, then tidy before new growth appears in spring. Avoid working saturated borders if doing so will compact the soil.
Do not cut away the crown or dig up the roots simply because the foliage disappears. In a hardy perennial, the growing points remain below or near ground level ready for the following year.
Recognise a pelargonium
Pelargoniums are commonly sold as summer bedding geraniums. They have fleshy stems, rounded or scented leaves and colourful clusters of flowers, and many are frost tender.
Zonal pelargoniums have leaves that may show a darker ring. Ivy-leaved kinds trail from baskets, while scented-leaved forms are grown partly for their aromatic foliage.
Their stems and winter behaviour differ from a hardy cranesbill. Most should be protected from freezing weather rather than cut down to ground level and abandoned in an outdoor border.
Deadhead pelargoniums during summer
For a flowering pelargonium, remove faded flower trusses regularly to keep the plant tidy and encourage continued blooming.
Trace the spent flower stem to its base and remove it without tearing healthy stems. Use clean scissors if the truss does not separate easily.
If the plant is growing unevenly, pinch back suitable new tips to encourage branching. Avoid cutting away every healthy growing point from a small young specimen simply to make a perfect symmetrical ball.
Cut back pelargoniums for overwintering
If you intend to keep pelargoniums for another year, bring them into suitable frost-free conditions before hard frosts. How much to shorten them depends on cultivar, available space and the condition of the stems.
Some RHS cultivar guidance recommends cutting established pelargoniums back when bringing them inside for winter. Other plants are better handled with a more moderate reduction and tidying. Do not treat that as permission to leave a heavily cut plant in freezing outdoor soil.
Remove damaged foliage, inspect for pests and give the plant ventilation and appropriate light. Keep winter watering restrained; cold wet compost can damage the roots.
Shape plants again in spring
As days lengthen, inspect overwintered pelargoniums for healthy buds and fresh growth. Remove dead or weak stems and shorten straggly live growth to encourage a more balanced plant.
Repot if roots are overcrowded or the compost has deteriorated, but avoid jumping to a huge container full of wet mix. Gradually increase light and watering as active growth resumes.
Harden plants off before returning them outside after the last frost. A plant kept indoors all winter can suffer shock if immediately placed in exposed full sun and wind.
What if the plant has gone leggy?
A leggy hardy geranium after its first flowering may simply be ready for the post-flowering cut. A pelargonium reaching sideways from a windowsill may need more light as well as selective trimming.
Take photographs or check labels before making major changes. The word 'leggy' describes a shape, not a single problem with one universal pruning cure.
If stems are soft and blackening, investigate waterlogging or rot before pruning. Healthy tissue should be firm and capable of new growth.
Common mistakes
The biggest is cutting every plant sold as a geranium to the ground in midsummer. It may be suitable for a hardy cranesbill but disastrous for a tender pelargonium without protection or viable regrowth.
The second is cutting the crown itself instead of old stems. Keep an eye out for tiny fresh leaves at soil level.
The third is expecting instant flowering after a hard cut. Give the plant light, moisture and time, and remember that repeat flowering depends on cultivar and conditions.
Pruning becomes straightforward once you know which geranium you've got. Hardy cranesbills and colourful bedding pelargoniums share a common name, but they deserve different treatment.