Bulbs, Tubers, Corms or Rhizomes?

Iris

By now we have spread the compost we make here by composting prunings, lawn clippings and leaves, back onto the beds in order to suppress weeds, retain moisture and nourish the soil. Most of the herbaceous plants have died back and been cut down, so when we do need to walk over the beds to prune or tidy leaves we have to be careful not to tread on the emerging bulbs.

Amongst the earliest arrivals are Winter aconites (Eranthis hyemalis), Spring Snowflakes (Leucojum vernum ), Snowdrops (Galanthus nivalis) and Crocuses (Crocus sp.), but which of these are bulbs, which are corms, and while we are at it, for that matter, what is a corm?

Bulbs, tubers, corms and rhizomes are all essential food storage organs that plants utilise in order to keep a temporary or long term store of starchy energy.

Bulbs – are created underground and formed from layered leaves. Spring Snowflakes and Snowdrops are both examples of bulbs.

Tubers – are normally also underground and are a swollen section of a stem or a root. Lords-and-ladies (Arum maculatum) is an example of a tuberous plant and, familiar within the gardens, it spreads readily through the more informal woodland areas.

Corms – are created underground and formed from the stem. Crocuses are in fact corms although you may not immediately realise this from the bag of bulb-like plants you may purchase from the garden centre.

Rhizomes – are swollen stems growing on or near the soil surface. Iris’ are a good example of a plant with rhizomes, and these storage organs actually benefit from growing on the surface of the soil as this enables them to absorb warmth from the sunlight.

If you would like to see more of these interesting plants feel free to come and explore the gardens. The gardeners are always happy to point you in the right direction.