Earth Day – Going Underground

When looking at a well-established spring garden, the first new growth usually comes from plants such as crocuses, tulips, violets, and allium; all of them have buried or partially buried swollen parts, which serve as storage of nutrients while the plants are dormant.  These swollen underground structures are generically called bulbs, but in fact, only some may be classified as such.

1) True bulbs are characterized by rings, or layers, that may be seen when sliced in half; these are modified leaves around a short underground stem.  Some examples in my garden right now, are grape hyacinths (photo below, left) and tulips (photo below, right):

And a very clear example of edible bulbs, are onions (photo below, left).  A cross section of a spring onion shows how the swollen layered bulb is already being used by the plant to nurture roots and green tops (photo below, right):

The plant will form new bulbs, called bulbets, the mechanism by which they generally multiply.

2) Corms are swollen underground stems, but do not have modified leaves around, so their inside is solid.  Buds form at the top of the corm and grow into stems and flowers, while growth at the bottom of the corm forms roots and new smaller corms, called cormels.  Some flowering examples are crocuses and water lilies, while edible corms include some exotic-sounding ingredients, but not unusual in Asian cuisine, such as water chestnuts, eddo (photo below, left) and taro (photo below, right):

I do not have any corms in my garden, but I am going to try gladiola this year; I just bought a packet of corms at a nursery (photo below, left).  A cross section of one corm shows the solid interior (photo below, right):

Tubers may be divided into two categories:

3) Stem Tubers are also underground stems, but are not at the base of the plant as corms; they have several buds around their surface (called “eyes”), and each plant may have multiple tubers forming a network.  Potatoes are the best known examples; in my garden, sunchokes have become perennials, as mentioned in previous posts, when I collected a fall harvest (photo below, left), and my recent spring cultivation (photo below, right):

4) Root Tubers, as the name indicates, are swollen roots, and they form all around one central stem, as in the case of yuca (not to be confused with the house plant); supermarket waxed yuca is shown on the photo below, left.  A flowering example in my garden are dahlias, Mexico’s national flower.  I had a very successful dahlia garden last year, and since they need warm weather, I saved some of the crowns (central stem with tubers) indoors (photo below, right): 

I was rather pessimistic about their survival, but I read Chris Mousseau’s post in which he reports success from giving his dahlias a head start in soil indoors, before potting and taking outside, so that is what I will be doing soon.

5) Rhizomes are swollen stems, and grow tops and roots in the same way as corms, but they are elongated and oriented always parallel to the ground surface, propagating in that fashion, often emerging partially.  In my backyard, bearded irises are starting to show some leaves (photo below, left); some rhizomes may be seen, especially in the new growth (photo below, right):

Over the years, I have had nice harvests of baby ginger, light and with a tinge of pink, like the ones from last fall (photo below, left); this spring, some of the re-planted rhizomes are already budding indoors (photo below, right):

6) Finally, specialized taproots – When seed germination takes place, the first structure to sprout is usually a root, called the taproot.  In some plants, the original taproots then diffuse into a system of fibrous roots, while in others, the taproot persists as a central structure.  In some cases, the plants have taproots that have specialized for food storage, such as is the case of beets, parsnips, and carrots.  In the photo below, left, the green top of an overwintered parsnip this spring, and right, a bunch of carrot (taproots) from last summer:

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I am joining Six on Saturday 22/4/2023, hosted by Jim Stephens @ Garden Ruminations.

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I am sharing my post at Cee’s Flower of the Day (FOTD) Challenge for April 22, 2023.

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