The Wild World of Geophytes

Dayllies grace Kit’s garden.


By Kit Flynn and Lise Jenkins

Recently, I was asked to give a presentation on the use of bulbs in the garden. While protesting that I knew very little about bulbs, having grown mostly perennials, I chanced to look around the garden — and was stunned to see how many geophytes I nourished.

In the horticultural world, we use the word “bulb” in two different ways. We employ the word to define the true bulb, which is actually a compression of leaves with roots developing at the basal plate at the bottom. Slice an onion in half and the leaves, i.e., the onion’s layers, are visible. Often, bulbs are covered with a “tunic” — think of the onion’s skin.

The second way we use the term is to refer to “geophytes,” i.e., those perennial plants that either propagate by means of underground buds or have an underground storage organ such as a bulb, corm, tuber, rhizome or tuberous roots. Most “bulb” online sources do not limit themselves to just selling true bulbs but also offer a selection of geophytes.

Why do bulb outlets use the word “bulb” rather than “geophyte?” You will probably agree with me that the former is more of an enticement than the latter, especially since most of us haven’t a clue as to what a geophyte is.

Consequently, online bulb sources can sell some exciting plants other than the ubiquitous daffodils. Corms, consisting of solid stem bases, are flatter than bulbs, but also contain a tunic covering, with roots growing out of a basal plate. Instead of multiplying in the way bulbs do, corms simply wither away, only to be replaced by new corms. Think gladioli, crocuses and crocosmias. This is the reason your garden isn’t overrun with gladioli.

Tubers are thick undergrown stems that lack a basal plate. The potato is a perfect example of a tuber. Tubers also lack the tunic and just get larger; they do not throw off new offshoots. An example of a tuber we use in the garden in the caladium.

Tuberous roots are fleshy mini-tubers that come in a clump. Think about daylilies, dahlias and peonies. They grow like tubers: daylilies simply get larger but don’t spread to form new daylilies. The gardener has to divide them to form additional plants.

Super Ellen

Rhizomes are swollen stems that grow horizontally. Generally, these rhizomes should be planted close to the soil’s surface. These are the plants that may spread and spread and spread. Irises, cannas, and gingers all have rhizomes.

There are some general rules to follow when planting geophytes:

  • Plant in well-draining soil;
  • Generally, plant spring-blooming geophytes in the fall;
  • Generally, plant summer and fall-blooming geophytes in the spring after the first frost.

To plant true bulbs and other geophytes, my advice is to do a quick Google search to determine how to plant them. Different bulbs are planted at different depths.

Peonies need to have their tuberous roots close to the soil’s surface, as otherwise they might refuse to bloom. Considering these plants can reach an age of 25, a peony that refuses to bloom for a quarter of a century probably is not the finest garden enhancement. Move a crinum — a true bulb — or a peony at your risk, as they will sulk for a number of years.

When ordering geophytes, it’s important to know which gardening zone you garden in. Zone 7 can grow some hardy amaryllises and cannas whereas Zone 5 can still grow lilies and peonies.

Many gardeners, when thinking of bulbs, will limit themselves to tulips, daffodils, with a few crocuses thrown in, not realizing that there is a whole new world of geophytes out there, just waiting to inhabit your garden.

Absent from their gardens, Kit and Lise enjoy roaming our region exploring the intersection of horticulture and suburban living. More on Instagram @AbsenteeGardener or email:

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