Geranium vs Pelargonium: True Geraniums vs Zonal Pelargoniums
Most garden center “geraniums” are actually pelargoniums — tender South African plants that die at first frost. True geraniums are hardy perennials in zones 3–9. Here is how to tell them apart and which to grow.
Walk into any garden center in spring and you will find benches loaded with “geraniums” — vivid red, coral, and pink flowers on compact mounded plants destined for containers, window boxes, and bedding schemes. Almost none of them are geraniums in any botanical sense. They are pelargoniums: tender plants from southern Africa that share the common name but differ from true geraniums in cold hardiness, flower structure, and every practical growing decision that follows from those two facts.
The mix-up has survived for nearly two centuries because pelargoniums arrived in European nurseries before botanists formally separated them, and the word “geranium” was already in common use. For gardeners the distinction is not pedantic. True geraniums (Geranium spp.) are hardy perennials that return every year across most of the US. Zonal pelargoniums (Pelargonium × hortorum) are tender perennials that die at first hard frost unless brought inside. They share a family — Geraniaceae — but not a genus, and their care needs reflect that split.
Quick Comparison: Geranium vs Pelargonium
| Feature | Hardy Geranium (Geranium spp.) | Zonal Pelargonium (Pelargonium × hortorum) |
|---|---|---|
| Mature size | 6–24 in tall, spreading to 36 in | 12–24 in tall, upright and compact |
| Light | Full sun to part shade | Full sun (min. 6 hrs); poor in shade |
| Water | Low to moderate; drought-tolerant once established | Moderate; dislikes waterlogged soil |
| Difficulty | Easy — very low maintenance once established | Easy; needs deadheading and frost protection |
| USDA zones (perennial) | Zones 3–9 depending on species | Zones 10–11 only; annual elsewhere |
| Average cost | $5–12 per plant | $3–8 per plant (bedding pack) |
The Naming Confusion: How It Started
Both genera belong to Geraniaceae, the cranesbill family, and for most of the 17th and 18th centuries everything in that family was classified under Geranium. The formal split came in 1789, when French botanist Charles L’Héritier de Brutelle recognized Pelargonium as a separate genus based on differences in flower symmetry and a distinctive nectar tube absent from true geraniums. As the Missouri Botanical Garden notes, the confusion between the two genera persists in common usage simply because nurseries had already established “geranium” as the trade name for pelargoniums long before the botanical distinction reached everyday gardeners [1].
European collectors had been importing pelargoniums from the Cape of Good Hope since the early 1600s. By the time the taxonomic split was formalized, “geranium” was the word customers recognized and the word nurseries used to sell them. The trade name proved impossible to change. Today virtually every mass-market bedding “geranium” in the US is a pelargonium, and the confusion is so deeply entrenched that many seed catalogs list both names side by side to avoid losing customers who know only one of them.
The practical consequence is that a search for “geranium care” will return results for two biologically distinct plants with different hardiness, different flower structure, and different propagation methods. Knowing which one you are growing is the first step to giving it the right care.
How to Tell Them Apart at a Glance
The most reliable identifier is flower symmetry. Geranium flowers have five nearly identical petals arranged evenly around a central point — if you draw any line through the center of the flower, both halves will mirror each other. This radially symmetrical (actinomorphic) structure is consistent across the entire genus and every species.
Pelargonium flowers are bilaterally symmetrical (zygomorphic): the two upper petals are visibly larger and typically marked with darker veins or contrasting color, while the three lower petals are smaller and differently shaped. Only one line of symmetry exists — down the vertical axis. This bilateral arrangement is the single most diagnostic difference between the genera, present in every pelargonium species, and was the primary basis for L’Héritier’s separation of them in 1789.
Two secondary identifiers are useful in the garden:
- Zonal leaf markings: Many zonal pelargoniums show a darker horseshoe-shaped band across the upper surface of each rounded leaf. Not every cultivar displays strong markings, but when the “zone” is visible it confirms the plant is a pelargonium.
- Leaf texture: True geranium leaves are deeply lobed or dissected, often with a soft hairy texture. Pelargonium leaves are rounder, slightly velvety, and frequently aromatic when crushed.
Hardy Geraniums: Care and Uses
Hardy geraniums are among the most reliable low-maintenance perennials available to US gardeners. Established plants return every spring in USDA zones 3–9 depending on species, require no winter protection in most climates, and gradually expand to fill borders and suppress weeds without becoming invasive. The RHS describes the genus as one of the most garden-worthy groups of perennials, with species suited to nearly every growing condition from full sun prairie edges to dry shade under trees [4].
Light and soil: Most species perform well in full sun to part shade. Unlike pelargoniums, true geraniums are genuinely shade-tolerant — Geranium macrorrhizum and G. nodosum are among the few perennials that bloom reliably under deciduous trees in dry shade, a notoriously difficult spot to fill. They prefer well-drained to moderately fertile soil and are notably drought-tolerant once their root systems are established in the second season.
Pruning: After the main flush of bloom — usually May through July depending on species — cut the entire clump back by about half with garden shears. This removes spent flower stems, tidies any yellowing foliage, and often triggers a second flush of bloom in late summer. Some cultivars, notably ‘Rozanne’ and G. ‘Orion’, bloom almost continuously from late spring through first frost without any deadheading.
Best cultivars for US gardens:
- Geranium ‘Rozanne’ (zones 5–8): The single most widely planted hardy geranium in US gardens. Violet-blue flowers with a white eye; blooms from late May through October without deadheading; spreads to 24–30 inches and trails attractively over path edges.
- Geranium × magnificum (zones 4–8): Bold violet-purple flowers in early summer; large bold foliage turns rich red and orange in autumn; clump-forming and easy to divide.
- Geranium sanguineum ‘Album’ (zones 4–9): Low spreading ground cover with white flowers over a long season; tolerates dry shade once established; one of the best options for slopes and bank stabilization.
- Geranium macrorrhizum (zones 3–8): Semi-evergreen with aromatic foliage; very drought-tolerant; spreads readily to form a weed-suppressing mat; excellent for difficult dry spots under shrubs.
Hardy geraniums are a cornerstone of the best perennials that come back every year — once planted in suitable conditions, a healthy clump will outlast most annuals in the same bed by decades. They also integrate naturally into cottage garden plantings, where their soft flower form and spreading habit blend seamlessly with roses, salvias, and ornamental grasses.
Zonal Pelargoniums: Care and Uses
Zonal pelargoniums are the bedding plants that define summer containers, patio pots, and window boxes across most of the US. Their tight rounded flower heads — technically umbels — hold their display from late spring until first frost and perform exceptionally well in the heat that would exhaust many flowering annuals by July. The University of Florida IFAS Extension notes they are among the most heat- and drought-tolerant flowering plants for summer containers in warm climates [2].
Hardiness and overwintering: Pelargoniums are native to the winter-dry, summer-warm climate of South Africa’s Western Cape. They evolved for frost-free conditions and are killed or severely damaged by temperatures below 28–30°F. In USDA zones 10–11 they function as true perennials and can grow into substantial shrubby plants over several years. Everywhere else — the vast majority of the US — they are treated as annuals or overwintered indoors.
To carry plants through winter: take 3–4 inch non-flowering stem cuttings in late August or early September before the first threat of frost. Remove lower leaves, allow the cut end to callous for an hour in open air, then insert into free-draining gritty compost. Rooting takes 3–4 weeks on a bright windowsill at 65–70°F. Overwinter the rooted cuttings in a cool but frost-free room (a heated garage, enclosed porch, or south-facing windowsill at 45–55°F) and repot into fresh compost in early spring. Plants from late-summer cuttings typically reach flowering size by May or June the following year.
Conditions: Pelargoniums require full sun for maximum flowering. Unlike true geraniums, they do not tolerate shade — plants in less than 5–6 hours of direct sun produce sparse flowers and leggy growth. They prefer well-drained soil and are more tolerant of summer heat and drought than of overwatering; in containers, waterlogged compost is the single most common cause of pelargonium failure. The RHS recommends allowing the top inch of compost to dry between waterings and ensuring containers have drainage holes [3].
Deadheading: Snap off spent flower heads at the base of each stalk as they fade. Pelargoniums do not self-clean — neglected dead heads build up, reduce flowering, and harbor Botrytis (gray mold) in wet weather. In a dry summer a once-weekly pass is usually sufficient; in a wet season check every few days.
Scented pelargoniums: The genus includes a remarkable range of aromatic-leaved varieties used in cooking, perfumery, and as companion plants. Pelargonium graveolens (rose-scented), P. crispum (lemon-scented), and P. tomentosum (peppermint) are the most widely grown. Several scented pelargoniums appear in our roundup of plants that repel mosquitoes for their essential oil content, which does provide measurable short-term deterrence when the foliage is disturbed.
Which One to Grow?
Choose a hardy geranium if:
- You want a perennial that returns every year without lifting or overwintering
- You have part shade, dry shade, or a cottage border to fill with low-maintenance color
- You are in USDA zones 3–8 and want reliable flower coverage without annual replanting
- You need a spreading ground cover that suppresses weeds once established
Choose a zonal pelargonium if:
- You want maximum color impact in containers, window boxes, or patio pots through summer
- You have full sun and need a plant that holds its display through summer heat
- You are happy to replant each year or willing to take cuttings in late summer
- You want the option of scented foliage for the patio or for use in the kitchen
If you have space for both: plant a hardy geranium such as ‘Rozanne’ as a perennial ground layer in a border and use zonal pelargoniums in containers at the front. The two plants do not compete, their seasonal overlap is near-complete (May through October in most US climates), and the contrast between the geranium’s informal spreading habit and the pelargonium’s upright rounded form makes a pleasing composition that looks intentional rather than accidental.
Frequently Asked Questions
Is a geranium the same as a pelargonium?
No. Both belong to the family Geraniaceae but are different genera with distinct flower structure and cold hardiness. Geranium are hardy perennials; Pelargonium are tender perennials from South Africa, frost-sensitive in most of the US. The shared common name dates from 17th-century European nurseries, before the taxonomic split in 1789, and has never been corrected in everyday usage.
Can pelargoniums survive winter outdoors in the US?
Only in USDA zones 10–11 (parts of Southern California, South Florida, and Hawaii). In zone 9 and below, pelargoniums are killed by hard frost. To carry plants over winter in colder climates, take stem cuttings in late August, root them indoors on a warm windowsill, and overwinter the young plants in a cool frost-free room. Alternatively, pot the parent plant before frost, cut it back by half, and keep it in a heated garage or enclosed porch (above 28°F minimum) until spring.
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→ View My Garden CalendarWhich is better for containers — geraniums or pelargoniums?
Pelargoniums are the standard container choice: compact, upright, heat-tolerant, and available in a wide range of colors from deep red through coral, salmon, and white. For a perennial that works in a large container and returns each year, hardy geranium ‘Rozanne’ in a 12-inch or wider pot performs well in zones 5–8 — it will trail over the rim attractively and bloom from May through frost without deadheading.
How do I tell a geranium flower from a pelargonium flower?
Look at the petals. A true geranium flower has five nearly identical petals arranged with radial (360-degree) symmetry — any line through the center produces matching halves. A pelargonium flower has two larger upper petals, often more heavily marked, and three smaller lower petals — bilateral symmetry with only one axis of balance. This difference is visible at a glance on an open flower and is consistent across all species in both genera.
Sources
- Missouri Botanical Garden. Geraniums vs. Pelargoniums. Missouri Botanical Garden Gardener’s Guide.
- University of Florida IFAS Extension. Geraniums (Pelargonium spp.). Gardening Solutions, Institute of Food and Agricultural Sciences.
- Royal Horticultural Society. Pelargonium. RHS Plant Finder.
- Royal Horticultural Society. Geranium. RHS Plant Finder.
