How to Grow True Perennial Geraniums

How to Grow Hardy, Perennial Geraniums

Geranium 'Rozanne'
Geranium 'Rozanne' blooms just about non-stop, well into fall. Photo: © Marie Iannotti

Overview and Description:

The term geranium can be confusing. The first geranium most gardeners encounter is not a geranium at all, but Pelargonium, a relative of the perennial geranium being profiled here. True or hardy or perennial geraniums belong to the genus Geranium. You will sometimes see them referred to as cranesbill geraniums, because their seed pods do somewhat resemble a crane’s bill. The foliage is often toothed and remains attractive.

The flowers float on top of the plant, in shades of white, pink, magenta, purples and blues.

There is a great deal of variety in the geranium genus, but most of the commonly grown varieties are low growing, dense, carpet-like plants with flower stalks that poke and weave through neighboring plants. The leaves may be rounded, but more often they are serrated or lobed and quite attractive.

The flowers are small (1") and cupped shaped, attracting plenty of butterflies and bees. Thin stems hold the flowers above the foliage. And they are deer resistant, too.

See more on the variety of true geraniums in the photo gallery "Growing Hardy Geraniums".

Botanical Name:

Geranium species

Common Name(s):

True Geranium, Hardy Geranium, Perennial Geranium, Cranesbill Geranium

USDA Hardiness Zones:

There is some variance in hardiness among the different types of geraniums, but most are perennial in USDA Hardiness Zones 4 - 8.

Mature Size:

Most true geraniums are low growing, from 3 inches tall to about 2 ft. tall. The flowers are held above the foliage, which gives them most of their height. Perennial geraniums can spread 2 - 4 ft. by rhizomes, but they are not aggressive and can be kept in check by periodic dividing.

Exposure:

For the best flowering and most vigorous plants, site them in full sun to partial shade.

If grown in hot, full sun, provide regular water.

Bloom Period:

A few perennial geraniums bloom just once, usually early in the season. Most will start blooming in mid-summer and repeat bloom sporadically throughout the growing season. Newer varieties, like 'Rozanne', bloom non-stop all summer.

Design Sugestions:

Geraniums are wonderful when allowed to spill over edges and rock walls. They are traditionally planted under roses, to camouflage rose knees and complement the roses in color. But they look equally good paired with contrasting textures, like spiky iris or billowy astilbe.

Look for some of the newer hybrids, if you want season-long bloom. 'Rozanne' was the first fuss-free, profuse bloomer, and it has been used to breed more stunners such as: 'Azure Rush’, with lighter blue flowers, and 'Lilac Ice’, which has more white in the flowers against brilliant green foliage.

Suggested Varieties:

  • Geranium endressii 'Wargrave Pink' - The most commonly grown geranium. Salmon pink flowers. 18-24" tall. Zones 3-8
  • 'Rozanne' - A violet blue hybrid that flowers almost non-stop throughout summer. 18-24" tall. Zones 5-8.
  • 'Ann Folkard' - One of the earliest blooming geraniums, with magenta flowers that repeat bloom throughout the season. Trailing habit. 6-8" tall. Zones 5-9.
  • 'Double Jewel' - Double-white petals with a lilac center. It’s short and perfect for containers. 10" tall. Zones 4-8
  • Geranium oxonianum 'Southcombe Double' - Double, pure pink blooms that resemble fluffy asters. 10" tall. Zones 4-8

How to Grow Perennial Geraniums:

Most cransbill geraniums can be started from seed, however the newer hybrids are sterile and must be purchased as plants.

Geraniums prefer full sun and a well-drained, moderately rich soil. They can handle partial shade, but become more prone to mildew if kept damp.

Geraniums are not particular about soil pH, but a neutral to slightly acid soil is ideal. (5.8 - 7.0)

Maintenance:

Geraniums require little care, once established. The plants can get a bit scraggly after blooming and deadheading is difficult with so many wispy stems. Shearing the plants back to basal growth will improve their look and encourage reblooming. The plants fill back in within weeks. The exception is Geranium macrorrhizum, which is easily deadheaded and needs no shearing.

Most species of Geranium live longer if divided every 3-5 years. You can divide more frequently, to keep them from spreading. But once you see the center dying out, it is definitely time to divide.

Pests and Problems:

Slugs may attack young geranium plants. Mildew and rust can infest foliage, especially in partial shade and/or humid climates. Shearing back and disposing of the infected leaves will help.