Tuberous Geranium Plants: How To Grow A Tuberous Cranesbill Flower

Tuberous Geranium Plants: How To Grow A Tuberous Cranesbill Flower

By: Mary H. Dyer, Credentialed Garden Writer

What are tuberous geranium plants? And, what is a tuberouscranesbill? How are they different from the familiar geranium we all know andlove? Keep reading to find out.

About Tuberous Geranium Plants

The familiar scented geraniumsare actually not true geraniums;they are pelargoniums. Tuberous geraniums, also known as hardygeraniums, wild geraniums, or cranesbill, are their slightly wild cousins.

The pelargoniums growing in a container on your patio areannuals, while tuberous geranium plants are perennials. Although the two plantsare related, they are very different. For starters, tuberous geranium plantsvary substantially from pelargonium in color, shape and blooming habits.

As the name implies, tuberous geranium plants spread viaunderground tubers. In spring, clumps of rosy lavender blooms marked with darkpurple veins rise on wiry stems above lacy-looking foliage. Seedpods thatappear at the end of the season look like crane’s beaks, thus the name“cranesbill.”

Planting Tuberous Geraniums

Suitable for growing in USDA plant hardiness zones 5 through9, tuberous geranium plants may look delicate, but they’re actually very tough.The pretty woodland plants are also easy to grow. Here’s how:

  • Choose a planting location carefully. Tuberous cranesbill flowers can be rambunctious, so be sure they have room to spread.
  • These plants tolerate nearly any soil, but they perform best in moderately fertile, well-drained soil – much like conditions in their natural environment.
  • Full sun is okay, but a little shade or dappled sunlight is best, especially if you live in a climate with hot summers.
  • Plant tubers about 4 inches (10 cm.) deep in in spring or fall. Water well after planting. Tuberous geranium plants are drought tolerant once established.
  • Remove wilted blooms (deadhead) to extend the blooming period.
  • Tuberous geraniums are cold hardy, but a generous layer of mulch such as compost, chopped leaves or fine bark will protect the roots during the winter.

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Start Indoors For Best Blooms

In zones 2-8, Begonias do best when given a head start indoors so they can develop before being transplanted or moved outside. Start Begonias 8-12 weeks before the last frost in your area.

To help Begonia tubers warm up from their winter dormancy, place in a warm location (about 70°F) with indirect sunlight, preferably an east, west, or south facing window. If you don’t have good natural light, grow lamps can provide the necessary light for growth. Water slightly every few days, or when the soil has dried out. Water around the edges of your tuber, but not directly on it: avoid overwatering or soggy soil, as water can pool in the tuber’s hollow dip and cause rot.

To increase humidity, you can cover pots loosely with a clear plastic bag. Expect to see growth in 3-6 weeks’ time, depending upon your overall growing conditions. (Note: In zones 2-8, if you do not start Begonia tubers ahead of time indoors, you may only see minimal blooms late in the season.)

The photo shows a sprouted begonia tuber. The top side of the tuber has a hollow dip, and the bottom is rounded with roots. Plant with the round side down. The hollow dip is the top, and sometimes it will already be sprouting buds. If the buds are coming up, try not to bump or break them, and carefully place the tuber in the ground.

Oregon gardeners, here’s your March guide to planting and planning

March is the time to divide hosta, along with daylilies and mums. Marcia Westcott Peck

With the arrival of a few sunny days in Oregon, gardeners are eager to get to work as we look ahead to spring and summer bounty. But what do you need to do now? The Oregon State University Extension Service offers monthly planners for gardeners. In March, it’s time to plan your vegetable garden and monitor soil temperatures, just to get started.

Below, find more timely advice on garden chores, fertilizing, pest control, and more from OSU Extension. These tips are not necessarily applicable to all areas of Oregon. For more information, contact your local Extension office.

Oregon State University Extension Service encourages sustainable gardening practices.

Practice preventive pest management rather than reactive pest control. Identify and monitor problems before acting, and opt for the least toxic approach. Conserve the predators and the parasitoids that feed on insect pests.

MSU Extension Gardening in Michigan

Summer blooming bulbs, rhizomes, tubers and corms that are planted in spring and early summer are avoided by deer.

Deer-resistant iris and allium planted together. The plants in the foreground (Nepeta sp. and Salvia sp.) also have deer resistance from their strong scents and fuzzy leaves. Photo by Sarah Rautio, MSU Extension.

Whitetail deer are common in most environments where we live. While there are many smart ways to deter deer, two connected ways are to plant a variety of plants that deer avoid and to transition from a simple landscape design with “buffet-style” offerings to a more complicated and large-scale design that “buffers” the damage. Here we focus on one specific group of plants: summer blooming bulbs, rhizomes, tubers and corms that are planted in spring and early summer for summer display. In an upcoming article, we will focus on deer-resistant bulbs to plant in the fall for the following spring.

Bulbs, rhizomes, tubers and corms fall into a biological category called geophytes. Many summer blooming geophytes can be purchased two ways: dormant form (e.g., bulbs in mesh bags) or actively growing plants in pots. In fact, some of us may not even realize we are purchasing a geophyte when we chose one of them as a container plant!

Here are some summer geophytes that deer avoid along with some buffer style design ideas.


Commonly known as flowering onions, there are hundreds of species of alliums in the world, some of which can be grown as perennials in the Midwest. Alliums bulbs generally need to be planted in the fall, but it is increasingly more common to find some narrow leaved perennial-like species grown in pots. Deer dislike allium because they have a strong pungent scent and taste.

Summer perennial allium interplanted with deer-resistant ornamental grass. Photo by Sarah Rautio, MSU Extension.


Deer avoid both the German and Japanese versions of iris because these plants have tough (German) or grass-like (Japanese) leaves, two qualities that deer dislike. German varieties withstand dry sandier soils and Japanese ones favor wetter richer soils therefore, there is an iris for everyone! Iris look stunning planted en masse with other plants, especially ones that bloom at the same time. Irises are rhizomes and are very easy to grow and reproduce.


Commonly known as Poker Plants or Desert Candles, these rhizomes produce narrow grass-like foliage much like ornamental grasses. Deer dislike grass-like blades due to their sharp edges. Originally from Africa, Kniphofia grows in mountain ranges in its native habitat and can therefore survive some cooler temperatures here in Michigan (USDA Zones 5 and 6).

Red hot pokers intermixed with other prairie-like perennials and annuals within a large flower bed. Photo by Sarah Rautio, MSU Extension.


Quite tricky to grow for a beginner, eremus (foxtail lilies or Desert Candles) are majestic if you happen to have the perfect soil conditions they need. These plants are not very well-known in the U.S. but enormously popular in England. They are native from Eastern Europe to China and hardy in USDA Zones 5-7. They are generally unreliable in Michigan because they are very susceptible to root rot in the winter from wet soils and need to be planted in very well-drained soil. Their grass-like foliage gives them their deer resistance, but test a small amount out first before investing in a larger planting given their pickiness.

Foxtail Lilies can grow to be 3 feet tall and have interesting serpentine-like tuberous roots. Photo by Sarah Rautio, MSU Extension.


Peonies are perennials that are sold both as dormant tuberous roots and as potted plants. The leathery leaves of peonies make them deer-resistant, albeit a small risk to the flowers. Nonetheless, it is no surprise they have endured on their own in the middle of yards adjacent to open farmland areas of Michigan where deer and harsh winter winds are common. Many gardeners are also surprised at the variety of cultivars and 33 species of this plant, many of which thrive in cold growing zones (as low as USDA Zone 3). A diverse collection peaks in bloom in June at Matthaei Gardens in Ann Arbor, Michigan.

Many varieties of peonies tolerate very cold climates. A young boy admires a peony in Oulu, Finland, not far from the Arctic Circle. Photo by Sarah Rautio, MSU Extension.


Similarly to peonies, there is a reason why gladioli historically withstood deer damage in the unfenced gardens of farming communities. Deer do not like their rough, grass-like leaves – in fact, “glads” are sometimes called “sword lilies,” and if there is any fear of the deer picking off the flowers, gardeners typically harvest bloom stalks prior to emergence for longer vase life anyhow. Other less known varieties of gladiolus have looser blooms (e.g. G. callianthus). These looser forms, and even the traditional varieties, can be left to flower in beds with other deer resistant perennials. The 300 species of gladioli originate from warmer climates than the growing zones in Michigan, so their corms need to be lifted and stored for the winter.

A familiar (Grandiflora hybrid) and less-familiar (Gladiolus callianthus) variety of Gladiolus.


Also called Lily of the Nile, this is a unique bulb to many. Its large blue flowers have a similar look as allium, but it differs from allium because it blooms later in the summer, has smaller species diversity (only six to 10 species, plus some hybrids), and gets its deer resistance from its leathery leaves rather than a strong scent.

Agapanthus grown in a container in front of a greenhouse. Photo by Sarah Rautio, MSU Extension.


Not all begonias are deer-resistant, but those with fuzzy stems/leaves or waxy/leathery leaves tend to be. Begonias have rhizomatous or tuberous stems and tremendous species and cultivar diversity, both in numbers (1,800 species worldwide) and in plant form.

Rex Begonias have rhizomatous stems, fuzzy leaves and stunning foliage. Waxy-leaved begonias (e.g., bedding) have tuberous stems, waxy leaves and are grown more for their flowers than leaves. The large leaf wax begonias (e.g., angel wing begonia) have the most deer resistance because deer can still pluck smaller wax begonias right out of the ground (taste test), even if they do not want to eat them. Except for the hardy begonia, Begonia grandis, which can only be grown in USDA Zone 6 or higher, begonias in Michigan are grown as annuals in summer or overwintered indoors as houseplants.

A close-up of plant hairs on a Rex Begonia demonstrates a classic deer resistant feature that some plants have: fuzzy leaves. Photo by Sarah Rautio, MSU Extension. Color and form diversity across many cultivars of Rex Begonia. Photo by Sarah Rautio, MSU Extension.


Commonly called Elephant Ears, this is a diverse group of tuberous rooted plants from the Araceae plant family with large leaves and often brilliant colors. Elephant ears originate from warm regions and can only be grown as annuals in Michigan. Their deer resistance is likely connected to a toxin they produce called oxalate/oxalic acid. This toxin is also present in other plants of the Araceae family, such as perennial skunk cabbage, and in perennial rhubarb (Rheum sp.), both of which are deer resistant. Imagine a garden full of elephant ears, skunk cabbage and rhubarb—wow!

One of the more brilliant varieties of Caladium sp.

More deer-resistant geophytes:

  • Blazing Star (Liatris punctate or the Michigan native Liatris spicata) – Not quite as deer resistant as other bulbs, this corm still has some resistance, especially if interplanted with other deer resistant plants that complement it, like Echinacea.
  • Bleeding heart (Dicentra ) – A common perennial that is sold in both dormant form (in bags) and active form (in pots). All species and cultivars of bleeding heart have very high deer resistance.
  • Canna lilies (Canna) – Their leathery leaves and often large size make them deer resistant. Their rhizomes need to be lifted in most areas of Michigan in the fall—allow the foliage to die back before cutting the tops off for storage.
  • Crocosmia/Montbretia – These corms produce plants with orange/red flowers on tall stems and grass-like foliage ‘Luicifer’ is hardy to USDA Zone 5, but most of these are only suitable down to Zone 6.
  • Cranesbill (Geranium tuberosum) – A tuberous rooted perennial in the geranium family, these wild versions of geraniums are deer resistant due to their fuzzy stems and leaves.
  • Fumewort (Corydalis solida) – Often sold in pots in early spring, this is a woodland plant.
  • Winter aconite (Eranthis hyemalis) – A less familiar bulb that belongs to a more familiar plant family, the Ranunculaceae (buttercups). It is sometimes sold as a potted plant, producing yellow flowers on a low-growing plant.
  • Wood sorrel (Oxalis adenophylla) – Another unfamiliar plant from the more familiar genus Oxalis (shamrocks). It is mostly sold as a plant in containers rather than in its dormant corm form.

This article was published by Michigan State University Extension. For more information, visit To have a digest of information delivered straight to your email inbox, visit To contact an expert in your area, visit, or call 888-MSUE4MI (888-678-3464).

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