Tom Karwin, on gardening · Aug 13, 2026
Gardening with geophytes
We say “bulbs,” but the underground pantry may be a true bulb, corm, tuber, or rhizome. Late summer is when you plan the spring show.
We say “bulbs,” but the underground pantry may be a true bulb, corm, tuber, or rhizome. Late summer is when you plan the spring show.
Geophytes are perennials that keep their reserves underground. Gardeners lump them as “bulbs,” which is fine in the nursery aisle and sloppy in the bed. True bulbs (daffodil, allium) are layered like onions. Corms (gladiolus, crocus, freesia) are solid stems. Tubers (some dahlias, cyclamen) are swollen roots or stems. Rhizomes (iris, fortnight lily) run sideways.
When spring bloomers finish and the leaves start to yellow, that foliage is still feeding the pantry for next year. Do not braid it into submission or cut it green. Wait until it straw-colours, then tidy.
Where they come from, and when to plant
Mediterranean-climate regions — California, the Mediterranean basin, Chile, South Africa, parts of Australia — are rich in geophytes that like a wet winter and a dry summer. South Africa in particular is a centre of bulb diversity that behaves well on the California coast if drainage is honest.
Late summer into autumn is the planning season for spring bloom: order, sort by depth and sun, and get them in the ground so roots can run in cool soil. Plant at the depth the package states; a rule of thumb is two to three times the height of the bulb in loose soil, shallower in heavy clay or for rhizomes that like their backs near the surface.
This week in the garden
Walk the fading spring geophytes and mark clumps that are crowded or blooming less. Those are next year’s divisions. Make a short list of new corms and true bulbs while the gaps are still visible.
Enjoy your garden.
On Gardening columns for home growers. Independent notes on these topics — not affiliated with any newspaper. Timing depends on your climate.