Zonal geraniums were discovered in South Africa and if you have a similar, tropical climate, you can grow them as perennials. Along with zonal geraniums, there are 3 more types of Pelargonium:
- Ivy-Leaf Geranium (Pelargonium peltatum) – As their name implies, these geraniums have a trailing habit and ivy-shaped leaves. The flowers are smaller and less showy than zonal geraniums and the plants are often used as spillers in containers.
- Scented-Leaf Geranium (Pelargonium domesticum) – Scented geraniums get their fragrance from the oil in their leaves. They can mimic all kinds of scents, like lemon, rose, mint, pine, fruits and even chocolate. The flowers tend to be small and often insignificant and the leaf shapes will vary. Besides their ornamental and fragrant appeal, many can also be used in cooking.
- Regal and Angel Geraniums (Pelargonium domesticum) – The Regals, also referred to as Martha Washington geraniums, are full, bushy plants with flowers in unusual colors and patterns. Angels are smaller versions of Regals. They tend to be spring bloomers.
- Leaves: Oval leaves grow on succulent stems. The leaves often have zones of maroon or bronzy-green.
- Flowers: Flowers can be single (5 petals) or double and come in clear white, pink, salmon, orange, red, magenta, lavender and bi-colors.
Common Name:Geranium, Zonal Geranium
- 'Appleblossom Rosebud' - Pom-pom flowers in a pink and white bi-color.
- 'Black Velvet Rose' - Dark, chocolate-brown leaves with only a narrow band of green and bright rose-pink flowers.
- 'Calliope Dark Red' - a cross between zonal and ivy-leaved, with double, dark-red flowers.
- 'Divas Orange Ice' - an F1 hybrid with bi-colored white and soft orange flowers that look like creamsicles.
Every year there are more and more choices. If you find a good source, there are Pelargoniums that are tulip-flowered, cactus-flowered and spiky star-shaped flowers. There are also the fancy-leaved varieties, grown more for their variegated and patterned foliage.
The softer pinks and salmons complement blue and purple flowers and the lavender shades really stand out next to the chartreuse foliage of Huechera or sweet potato vines.
Soil: Zonal geraniums are not terribly fussy about soil pH, but prefer a slightly acid soil of about 5.8 to 6.5
Planting: You can start zonal geraniums from seed, cuttings or transplants. Taking cuttings was the traditional method of propagating geraniums and maintaining favorite varieties. If you choose to take cuttings, make sure you only use healthy, vigorous plants.
Starting Geraniums from Seed: Geranium can easily be started from seed, although the seed is usually for F1 hybrids. Seed geraniums are bred to be disease resistant and to bloom well in the heat of summer.
Start seeds 8 - 10 weeks before your last frost date. They can take up to 2 weeks to germinate and should be kept warm, 70̊ and 75̊F (21̊ - 24̊C), and moist in the process. Scarifying the seed before planting will help aid germination.
Harden off young plants before planting outdoors. They should begin to bloom about a month after being set out.
Maintenance:Zonal geraniums are not heavy feeders, but since they are usually grown in containers, a light feeding with your favorite fertilizer, every 2-4 weeks, will keep them vigorous.
Stressing them slightly by watering only after the soil has dried out completely for a day or two seems to encouraging more profuse blooming. Just don't leave them dry for so long they start dropping leaves and declining.
If you don't live in USDA Zone 9 or higher, your plants will need some winter protection. You can bring them in and grow them as houseplants, in a bright, direct light window. You could take cuttings in mid-summer and bring these smaller plants indoors, or you can over winter your geraniums in their dormant state.
Pests & Problems:For the most part, zonal geraniums are not prone to insect pests, when grown outdoors. Indoors, aphids and whiteflies can become a nuisance.
There are a few fungal and bacterial diseases to look out for, mainly
- Stem or root rot caused by poorly drained soil.
- Gray mold or botrytis, especially in humid or damp weather, which causes grayish fuzz on the leaves and eventually a slimy mush.
Special thanks to the National Garden Bureau which named Pelargonium its 2012 Plant of the Year and provided research for this article.