Pelargonium plants are a genus of herbaceous and mostly evergreen perennials, shrubs, and succulents. Pelargoniums are native to southern Africa and grow well in desert and mountainous areas. (In South Africa, a species of pelargonium called Pelargonium sidoides is used as an herbal remedy for respiratory infections.) These flowering plants are often grown as houseplants in window boxes and hanging baskets.
I. Appearance and Characteristics
Pelargonium is a genus of flowering plants that includes about 280 species of perennials, succulents, and shrubs, commonly called geraniums, pelargoniums, or storks bills. Geranium is also the botanical name and common name of a separate genus of related plants, also known as cranesbills. Both genera belong to the family Geraniaceae. Carl Linnaeus originally included all the species in one genus, Geranium, and they were later separated into two genera by Charles Louis L’Héritier de Brutelle in 1789.
Pelargonium occurs in a large number of growth forms, including herbaceous annuals, shrubs, subshrubs, stem succulents and geophytes. The erect stems bear five-petaled flowers in umbel-like clusters, which are occasionally branched. Because not all flowers appear simultaneously, but open from the centre outwards, this is a form of inflorescence is referred to as pseudoumbels.
The flower has a single symmetry plane (zygomorphic), which distinguishes it from the Geranium flower, which has radial symmetry (actinomorphic). Thus the lower three (anterior) petals are differentiated from the upper two (posterior) petals. The posterior sepal is fused with the pedicel to form a hypanthium (nectary tube). The nectary tube varies from only a few millimeters, up to several centimeters, and is an important floral characteristic in morphological classification. Stamens vary from 2 to 7, and their number, position relative to staminodes, and curvature are used to identify individual species. There are five stigmata in the style. For the considerable diversity in flower morphology, see figure 1 of Röschenbleck et al. (2014).
Leaves are usually alternate, and palmately lobed or pinnate, often on long stalks, and sometimes with light or dark patterns. The leaves of Pelargonium peltatum (Ivy-leaved Geranium), have a thick cuticle better adapting them for drought tolerance.
Pelargonium is a large genus within the family Geraniaceae, which has a worldwide distribution in temperate to subtropical zones with some 800 mostly herbaceous species. Pelargonium itself is native to southern Africa (including Namibia) and Australia. Southern Africa contains 90% of the genus, with only about 30 species found elsewhere, predominantly the East African rift valley (about 20 species) and southern Australia, including Tasmania. The remaining few species are found in southern Madagascar, Yemen, Iraq, Asia Minor, the north of New Zealand and isolated islands in the south Atlantic Ocean (Saint Helena and Tristan da Cunha) and Socotra in the Indian Ocean.
The centre of diversity is in southwestern South Africa where rainfall is confined to the winter, unlike the rest of the country where rainfall is predominantly in the summer months. Most of the Pelargonium plants cultivated in Europe and North America have their origins in South Africa.
II. How to Grow and Care
Sunlight
Like other garden pelargoniums, scented-leaved geraniums prefer full sun but will tolerate partial shade. In very warm climates, some afternoon shade may be beneficial. Shadier conditions may produce leggy plants that require frequent pinching back to keep the plants full.
Temperature and Humidity
These plants are perennial in tropical climates, so are well-suited for hot, humid conditions. Geraniums also do well in very dry climates. They may survive short periods of light frost but should be brought indoors or discarded when the weather turns cold in winter.
Watering
Scented geraniums are drought tolerant and don’t like sitting in wet soil. Water when the soil feels dry about an inch below the surface. Prolonged periods of dry soil will cause the leaves to turn yellow, then brown and fall off, but the plant will come back again with regular water.
Soil
Soil should be well-draining, but not too rich. As with herbs and other plants grown for their essential oils, rich soil can lessen the strength of the fragrance. Scented geraniums will tolerate most soil pH, but a slightly acidic pH of about 5.8 to 6.3 is ideal.
Fertilizing
Go easy on the fertilizer. Scented geraniums are light feeders, and their scent will be stronger if they are grown on the lean side. Potted plants will need more fertilizer than plants in the ground, however. You can feed potted geraniums every three to four weeks through the spring and summer with an all-purpose fertilizer at half the label’s recommended dilution. Do not fertilize at all during the winter.
Pruning
Occasional pinching and light pruning will make your scented geranium plants more full and bushy. If your plant gets too large, don’t be afraid to prune it back to maintain its shape. Spring is the best time to prune because this will give the plants time to set buds and flowers. But large plants can handle some cutting back during any season. Spent flowers should be deadheaded to stimulate new flower buds.
Propagation
A handful of varieties can be started from seed, but most scented-leaf geraniums are hybrids and will need to be purchased as nursery plants. Small plants are often available in the herb section of nurseries and are usually affordable. You can also easily take root cuttings and make more plants. Here’s how:
- Snip 6-inch long cuttings from growing stems and remove all but the uppermost leaves.
- Dip the cut end of the cutting in rooting hormone, then plant in a small container filled with moist vermiculite.
- Keep the vermiculite moist until a good network of roots develops, then transplant into the garden or into a pot filled with peat-based potting mix.
- Note, however, that if your plant is a trademarked variety (and many are), it is not legal to propagate the plant by any method.
How to Grow from Seed
If you’d like to grow your own scented-leaved geraniums from seed, it’s best to start indoors in December. Spread the seeds across a tray filled with seed-starting medium, and then cover them with soil to a depth of 1/8 inch. Mist the soil to moisten it, but take care not to leave it soggy. Place the tray in a warm, light spot, and mist regularly to keep the soil moist. The seeds typically germinate in around 3 weeks.
Continue to keep the seedlings in a light, warm location, and mist them regularly to prevent the soil from drying out. If necessary, thin the seedlings so each has a clear area around it. Once the danger of frost is past, you can plant the seedlings outside in your garden, either in a pot or in the ground.
Potting and Repotting
Scented-leaved geraniums are generally purchased as small nursery plants but grow quite quickly. Plant them in containers filled with a peat-based potting mix. They make lovely additions to a hanging basket or grow several varieties in one large container. You can also grow each plant in its own separate pot. Whatever you choose, geraniums prefer slightly acidic soil. Full sun generally provides the best flowering, but they will tolerate part shade.
These plants like to be slightly rootbound, so if moving your scented-leaf geranium to a larger pot, only increase the pot size by one inch across and deep. As a general rule, an 8-inch pot is a good size for an average-sized scented-leaf geranium.
Overwintering
While many gardeners treat these tender perennials as annuals, disposing of them once the chill of winter kills them off, some people have success in maintaining their potted scented-leaved geraniums over the winter, generally by bringing them indoors and treating them like a houseplant until the following spring. If you try this, be sure the plant gets plenty of bright light. It may get leggy in too much shade. If that happens, you can prune lightly to create a bushier plant.
Although success varies, you can also place potted geraniums in a cool, dark space for the winter, allowing them to go dormant in the pots. Trim back the plants by one-half and water deeply before storing them. Through the winter, water lightly every so often to prevent the soil from completely drying out. In the spring, bring the potted plants back outside and water deeply. But don’t be surprised if some plants fail to return from dormancy.
Pests and Diseases
Generally, you won’t have much trouble with scented-leaved geraniums, but like any plant, they can have their issues.
Leggy Growth
One of the most common issues with scented-leaved geraniums is leggy growth, meaning long spindly stems without a lot of leaves. This is usually caused by insufficient sunlight. If your plant is in a pot, move it to a location where it will receive at least six hours of sunlight each day. In the hottest areas, morning sun is best to prevent scorch.
Leaves Turning Yellow
There are several reasons why your plant might have yellowing leaves, but one of the most common is overwatering. Scented-leaved geraniums are somewhat drought tolerant, and prefer to go a bit dry between waterings. If your plant starts yellowing, cut back on the water and be sure that the soil is dry at least an inch down from the top before watering again.
Leaves Falling Off
It’s normal for a plant to lose aging leaves, but if your scented-leaved geranium starts dropping even newer leaves—especially if the leaves are yellowed or mushy—then once again, overwatering is the likeliest explanation. Once a plant is actively losing leaves, it is sometimes hard to save it, as the roots are beginning to rot. However, by cutting back on water, replacing some of the soggy soil with fresh soil, and trimming away any blackened or mushy roots, you can sometimes rescue your plant.
How to Get s to Bloom
While grown primarily for their fragrance, scented-leaved geraniums do produce pretty flowers in late spring through the summer. Generally, as long as your plant is receiving enough sunlight and water, you’ll be rewarded with a flush of small blossoms in pink, white, or red, depending on the variety. To keep the flowers coming, deadheads spent blooms by pinching or snipping them off the plant. Perhaps surprisingly, the flowers don’t have a fragrance; these plants are only scented by the oils in their leaves.
III. Types of Pelargoniums
There are many different types of pelargonium plants, and they are most often distinguished by their different types of leaves.
- Zonal: Zonal pelargoniums—often erroneously called zonal geraniums—have round patterns on the inside of the leaves and produce vividly colored flowers. They are often used as bedding plants.
- Ivy-leaved: Ivy-leaved pelargoniums have trailing growth similar to ivy and will grow along fences and walls. The leaves are waxy and the flowers can come in many different colors.
- Fancy-leaved: Fancy-leaved pelargoniums have wide, variegated leaves with serrated edges.
- Regal: Regal pelargoniums are shrubby plants with rounded or lobed leaves and dark purple or red flowers that typically have solid coloration with no zoning or variegation. Angel pelargoniums are a popular choice in this category.
- Scented-leaved: Scented-leaved pelargoniums—also erroneously called scented geraniums—have leaves that emit a strong scent when touched. The modern cultivars have a wide range of smells like peppermint and lemon, and the leaves are often used for potpourri or perfume.
IV. Uses and Benefits
- Ornamental uses
Pelargoniums rank as one of the highest number of potted flowering plants sold and also in terms of wholesale value.
- Scented leaf pelargoniums
Other than being grown for their beauty, species such as P. graveolens are important in the perfume industry and are cultivated and distilled for their scents. Although scented pelargoniums exist which have smells of citrus, mint, pine, spices or various fruits, the varieties with rose scents are most commercially important. Pelargonium distillates and absolutes, commonly known as “scented geranium oil” are sometimes used to supplement or adulterate expensive rose oils. The oils of the scented pelargoniums contain citronellol, geraniol, eugenol, alpha-pinene and many other compounds. The edible leaves and flowers are also used as a flavoring in desserts, cakes, jellies and teas.
Scented-leaved pelargoniums can be used to flavor jellies, cakes, butters, ice cream, iced tea and other dishes, The rose-, lemon- and peppermint-scents are most commonly used. Also used are those with hints of peach, cinnamon and orange. Commonly used lemon-scented culinary species include P. crispum and P. citronellum. Rose-scenteds include P. graveolens and members of the P. graveolens cultivar group. Other species and cultivars with culinary use include the lime-scented P. ‘Lime’, the lemon balm-scented P. ‘Lemon Balm’, the strawberry-lemon-scented P. ‘Lady Scarborough’ and the peppermint-scented P. tomentosum. Scented leaf pelargoniums have also been historically used as toilet paper by fishermen in remote places, such as the Minquiers.
- Medicinal uses
In herbal medicine, Pelargonium has been used for intestinal problems, wounds and respiratory ailments, but Pelargonium species have also been used for fevers, kidney complaints and other conditions. Geranium (Pelargonium) oil is considered a relaxant in aromatherapy, and in recent years, respiratory/cold remedies made from P. sidoides and P. reniforme have been sold in Europe and the United States. P. sidoides along with Echinacea is used for bronchitis. P. odoratissimum is used for its astringent, tonic and antiseptic effects. It is used internally for debility, gastroenteritis, and hemorrhage and externally for skin complaints, injuries, and neuralgia and throat infections. The essential oil is used in aromatherapy.
