Understanding Geraniums: Pelargoniums vs. Cranesbills
When many gardeners refer to 'geraniums', they are typically thinking of the vibrant, often scented-leafed plants grown for summer bedding and containers. These are botanically known as Pelargoniums. True geraniums, often called hardy geraniums or cranesbills, are a different group of perennial plants that are hardy and reliably return year after year. While both share a common name, their growing habits, care needs, and appearance differ significantly. This article focuses primarily on the popular annual bedding and container types (Pelargoniums) due to their widespread use for immediate colour impact, but we will also touch upon their perennial cousins and what to consider when choosing between them.
The allure of pelargoniums lies in their prolific flowering and diverse forms. From the upright zonal pelargoniums with their characteristic leaf zones and masses of clustered blooms, to the trailing ivy-leaf types perfect for hanging baskets and window boxes, and the unique regal pelargoniums (often called Martha Washington geraniums) with their large, showy flowers, there is a pelargonium for almost any sunny spot. Their ease of cultivation and long flowering season, often from late spring until the first frosts, make them a staple in many British gardens, patios, and balconies. Understanding these distinctions is the first step to selecting the right plant for your gardening ambitions and ensuring its success.
Why the Name Confusion?
The common name 'geranium' stuck for pelargoniums due to historical classification. Early botanists grouped them together, but further study revealed distinct differences in their flower structure and seed pods. True geraniums have elongated, crane's-bill-like seed pods, hence the name 'cranesbill'. Pelargoniums, on the other hand, have shorter, more blunt seed pods. Despite the botanical separation, the common name 'geranium' remains widely used for pelargoniums in horticulture, particularly in the UK. When purchasing plants from a garden centre, look for the botanical name Pelargonium on the label if you specifically want the bedding and container varieties, or Geranium for the hardy perennials.
The choice between these two groups depends on your gardening goals. Are you seeking a season-long display of bright, showy flowers that typically needs replacing annually, or are you after a more permanent, low-maintenance perennial that adds structure and late-season interest to borders? Both offer significant horticultural value, but their application and care diverge. For those aiming for immediate, impactful colour across summer months, pelargoniums are usually the go-to choice. Their versatility in pots, baskets, and borders makes them incredibly popular for adding vibrancy to otherwise dull spaces.
The distinction between Pelargonium and true Geranium plants is crucial for successful garden planning.
Pelargoniums are a fantastic solution for gardeners seeking reliable, abundant blooms throughout the warmer months. Their problem lies in their tender nature; they cannot withstand frost and are usually treated as annuals in cooler climates like the UK, or overwintered indoors. True geraniums, conversely, are robust perennials that establish a permanent place in the garden, offering a different kind of beauty with their more delicate, often intricate flowers and attractive foliage, and are generally more tolerant of varied weather conditions.
Selecting Your Pelargoniums for Maximum Impact
Choosing the right pelargoniums from the vast array available can seem daunting, but understanding the main types and their characteristics will help you select plants that suit your specific needs and growing conditions. The common types of pelargoniums grown in the UK include Zonal, Ivy-leaf, Regal, and Scented-leaf varieties, each offering distinct advantages for different garden settings.
Zonal Pelargoniums: The Bedding Stalwarts
Zonal pelargoniums are perhaps the most recognised type. They are upright plants, typically grown as annuals, known for their dense flower heads, often in vibrant shades of red, pink, white, and orange, and their distinctive 'zone' marking on the leaves, which can be shades of brown, green, or cream. They thrive in full sun and are ideal for filling borders, beds, and larger pots with consistent, colourful displays throughout summer. Their sturdy habit means they stand well without becoming leggy, providing a reliable show.
Ivy-Leaf Pelargoniums: Trailing Beauties
Characterised by their trailing, cascading stems and ivy-like foliage, ivy-leaf pelargoniums are perfectly suited for hanging baskets, window boxes, and the edges of raised planters or walls. They produce clusters of single or semi-double flowers, often in softer hues like pale pink, lilac, and white, as well as deeper reds and purples. Their trailing habit adds a softer, more romantic dimension to displays, softening hard edges and creating a lush, abundant look. They also appreciate a sunny position.
Regal Pelargoniums: The Showstoppers
Regal pelargoniums, also known as Martha Washington geraniums, are grown for their spectacular, large flowers, often with intricate markings and ruffled edges. While beautiful, they are generally more demanding than zonal or ivy-leaf types, requiring specific conditions to perform their best. They prefer cooler temperatures, good air circulation, and protection from harsh sun and wind. They are often treated as short-lived perennials or conservatory plants rather than purely annual bedding. Their dramatic blooms make them ideal for specimen pots where they can be admired.
Scented-Leaf Pelargoniums: Fragrance and Texture
For an added sensory dimension, scented-leaf pelargoniums are an excellent choice. Their flowers are often less showy, but their foliage releases a delightful fragrance when brushed, ranging from rose, lemon, and mint to spice and apple. Varieties like 'Rozanne' (though this is a true Geranium) or 'Attar of Roses' are popular. They are wonderful for planting in pots near seating areas or pathways where their scent can be enjoyed. They also benefit from full sun and good drainage.
When selecting, consider the plant's habit: upright for beds, trailing for baskets, and focus on flower and leaf colour to complement your existing garden scheme.
The potential problems with pelargoniums often stem from choosing the wrong type for the location or failing to provide adequate sun and drainage. Ensure you select varieties suited to your chosen spot, whether it's a sunny patio, a shady corner (though most pelargoniums prefer sun), or a hanging basket that needs a cascading effect.
Cultivating Success: Planting and Care for Geraniums
Once you have selected your pelargoniums, proper planting and consistent care are key to ensuring a season of vibrant blooms. These plants, while generally forgiving, thrive with a little attention to their basic needs, particularly regarding light, water, and soil.
Planting Your Geraniums
The best time to plant pelargoniums in the UK is after the risk of frost has passed, typically from late May onwards. If you have purchased plants that have been hardened off, they can be planted directly into their final positions. For containers, hanging baskets, or window boxes, use a good quality, peat-free compost that offers excellent drainage. If planting in beds, ensure the soil is well-drained; amend heavy clay soils with grit or compost to improve aeration.
When planting, ensure the root ball is level with the surrounding soil. For containers, leave about 2-3 cm of space at the top for watering. Space plants according to their mature size, usually around 20-30 cm apart, to allow for good air circulation, which helps prevent fungal diseases. Gently firm the soil around the base of each plant.
Watering and Feeding
Pelargoniums prefer to dry out slightly between waterings. Overwatering is a common mistake and can lead to root rot, especially in cooler or damp conditions. Water thoroughly when the top inch of soil feels dry to the touch. For plants in hanging baskets or containers, this may be daily during hot, dry spells. Reduce watering in autumn as the plants' growth slows.
To encourage continuous flowering, feed your pelargoniums regularly. A balanced liquid feed, applied every two to four weeks during the growing season, is ideal. Look for feeds that are lower in nitrogen and higher in potassium, as this promotes flowering rather than leafy growth. Alternatively, you can incorporate a slow-release fertiliser into the compost at planting time, which will provide nutrients over several months.
Deadheading and Pruning
Deadheading – the removal of spent flowers – is crucial for maintaining a continuous bloom. Regularly pinch off or cut the faded flower trusses back to a set of leaves. This encourages the plant to produce more flowers rather than putting energy into seed production. For zonal pelargoniums, you might also want to pinch out the growing tips of young plants to encourage bushier growth and more flower stems.
If plants become leggy or straggly, a light trim can help rejuvenate them. Ivy-leaf types can be trimmed back to encourage a fuller cascade. Ensure any pruning cuts are clean to minimise the risk of disease entry.
Consistent deadheading is the single most effective way to prolong the flowering season of your pelargoniums.
Overwintering Pelargoniums
While often treated as annuals, pelargoniums can be overwintered to provide plants for the following year. In autumn, before the first hard frost, carefully dig up plants or take cuttings. If overwintering whole plants, prune them back by about a third and pot them into fresh compost. Store them in a frost-free, bright location, such as a cool greenhouse, conservatory, or even a bright windowsill, and water sparingly. They will likely look rather straggly but will respond to warmer conditions and increased watering in spring.
Taking cuttings is a more reliable method for many. Take 7-10 cm cuttings in late summer, remove the lower leaves, and insert them into pots of well-drained compost. Keep them moist and in a warm place until rooted, then pot them on and overwinter as described above.
Troubleshooting Common Geranium Problems
Even with careful cultivation, pelargoniums can sometimes encounter problems. Understanding the common issues and their causes will help you address them promptly and keep your plants healthy and floriferous.
Fungal Diseases: Botrytis and Downy Mildew
Botrytis (grey mould) often appears as fuzzy grey patches on leaves, stems, and flowers, particularly in damp, humid conditions or when plants are overcrowded. Downy mildew presents as yellow spots on the upper leaf surface with purplish-grey mould on the underside. Both thrive in poor air circulation. Prevention is key: ensure good spacing, water at the base of the plant rather than overhead, and remove any dead or diseased material immediately. If a plant is severely affected, it may be best to discard it to prevent spread.
Pests: Aphids and Whitefly
Aphids can sometimes infest young shoots and flower buds, causing distortion and weakening the plant. Whitefly can be a problem, especially on plants overwintered indoors. Regularly inspect your plants for signs of pests. Small infestations of aphids can often be washed off with a strong jet of water or wiped away. For more persistent problems, consider using an insecticidal soap or a suitable biological control. Encouraging beneficial insects in your garden can also help.
Leaf Discolouration and Flowering Issues
Yellowing leaves can be a sign of overwatering, poor drainage, or nutrient deficiency. If the soil is consistently wet, reduce watering frequency and check drainage. If the soil is dry and leaves are yellowing, a dose of liquid feed might be beneficial. If plants are not flowering well, ensure they are receiving adequate sunlight and are being deadheaded regularly. Lack of phosphorus and potassium in the feed can also inhibit flowering; switch to a bloom-boosting fertiliser.
Ensure plants have good air circulation and avoid overhead watering to minimise the risk of fungal diseases.
Leggy growth, where plants become tall and sparse with few flowers, is often due to insufficient light, overfeeding with nitrogen, or a lack of regular pinching out when the plants were younger. Pruning back leggy plants can encourage new, bushier growth, but they will need adequate light to flower well subsequently. Remember that different types of pelargoniums have different growth habits; compare the plant's behaviour to its expected type.
Exploring Alternatives to Pelargoniums
While pelargoniums offer reliable colour, gardeners looking for different aesthetics, varying care requirements, or a more sustainable approach might consider alternative flowering plants. Exploring these options can introduce new textures, colours, and ecological benefits to your garden spaces.
Hardy Geraniums (Cranesbills)
As mentioned, true geraniums (cranesbills) are excellent perennial alternatives. They are hardy, long-lived, and offer a wide range of flower shapes and colours, from delicate blues and purples to vibrant pinks and whites. Varieties like Geranium Rozanne are renowned for their exceptionally long flowering period. They generally prefer well-drained soil and can tolerate a range of light conditions, from full sun to partial shade, depending on the variety. While their flowers might be less showy than some pelargoniums, their reliability and perennial nature make them a valuable addition to borders and ground cover.
Begonias
For partially shaded areas where pelargoniums might struggle, tuberous and fibrous-rooted begonias offer spectacular blooms. They come in a wide array of colours and forms, from ruffled, camellia-like flowers to elegant, trailing varieties. Begonias thrive in moist, well-drained soil and appreciate protection from harsh midday sun. They are often treated as annuals in the UK but provide a lush, tropical feel.
Petunias
Petunias, especially the modern trailing varieties like Supertunias or Wave petunias, can rival pelargoniums for sheer flower power and suitability for hanging baskets and containers. They bloom profusely in full sun and come in an astonishing range of colours and patterns. While they can be thirsty and hungry plants, their vibrant displays are hard to beat.
Fuchsias
Fuchsias are a classic choice for hanging baskets and containers, particularly in areas that receive some shade. Their unique, pendulous flowers are incredibly attractive to pollinators. They offer a more delicate, sophisticated look than the bold blooms of many pelargoniums and come in a vast range of colours and growth habits, from compact bushes to vigorous trailers.
Nasturtiums
Nasturtiums are wonderfully easy to grow from seed, either directly sown or started indoors. They offer cheerful, peppery-scented flowers in shades of orange, yellow, red, and cream, along with attractive, lily-pad-like foliage. Both trailing and bush varieties are available, and they are excellent for filling gaps, tumbling over walls, or attracting beneficial insects. They prefer poorer soils, which encourages more flowers than leaf growth.
Consider the light conditions and your desired aesthetic when choosing between pelargoniums and their alternatives.
Other flowering plants that provide colour and interest throughout the summer include marigolds, cosmos plants, and even sunflowers if space allows. Each offers a unique contribution to the garden's palette and ecosystem, providing gardeners with ample choices beyond the ubiquitous geranium (pelargonium).
Maximising Your Geranium Display Year After Year
Achieving a stunning, long-lasting display with pelargoniums involves not just annual planting but also thoughtful planning for subsequent seasons. By mastering overwintering techniques, propagating new plants, and understanding their role in garden design, you can ensure a continuous supply of these colourful performers.
Overwintering Strategies
As discussed, overwintering pelargoniums is a rewarding way to save on annual costs and maintain beloved specimens. The key is providing frost-free conditions with sufficient light. A dormant, cool environment (around 5-10°C) is ideal for saving energy, but they will need enough light to prevent etiolation. Check regularly for pests and diseases, and water only enough to prevent the soil from drying out completely. Spring is when the magic happens: gradually increase watering, move them to a warmer spot, and prune them back to encourage fresh growth. You'll be surprised how quickly they bounce back.
Propagation Through Cuttings
Taking cuttings from mature plants in late summer or early autumn is a highly effective method for propagation. This ensures you have healthy, vigorous young plants for the following year. Select healthy, non-flowering shoots, cut them to about 7-10 cm, remove the lower leaves, and dip the cut end in rooting hormone if desired. Insert them into pots filled with a free-draining compost mix, water gently, and place them in a warm, well-lit location, ideally in a propagator or covered with a plastic bag to maintain humidity. Once rooted, they can be potted on and overwintered as described previously. This process allows you to experiment with new colours or maintain favourites.
Integrating Geraniums into Garden Design
Pelargoniums are incredibly versatile. For a bold, immediate impact, mass-plant them in beds or large containers. Use zonal types for upright structure and dense colour blocks, and trailing ivy-leaf varieties to soften edges or spill from hanging baskets and window boxes. Combining different colours and types can create dynamic displays. Consider pairing them with complementary plants; for instance, silver-leafed varieties offer a striking contrast to bright blooms, or use them to fill gaps left by early-flowering bulbs.
For a continuous bloom, regularly deadhead and feed your pelargoniums throughout the growing season.
When planning for the next year, think about succession planting. While pelargoniums are at their peak, consider what will follow them, or what can be planted alongside them. Hardy geraniums, for example, can provide structure and colour in early summer and again in autumn, bridging the gap before or after the main pelargonium season. By planning ahead and employing simple propagation techniques, you can enjoy the vibrant beauty of geraniums (pelargoniums) in your garden season after season.