Dear Helen: I’m not sure whether I managed my hanging basket begonias properly as they began dying down. When about half the stems had detached and fallen over, I brought the baskets into the shelter of a house wall, under a very broad roof overhang. I did not know whether to cut off or pull away the remaining attached stems, so I left them to fall away on their own. What should I do now with the baskets and tubers to keep them safe from frost over the winter? B.L.
This question arrives in my mail every autumn. You did precisely the best thing in allowing the stems to fall away on their own. Breaking them off prematurely can damage a tuber’s growth ring. Keeping the plants growing for as long as possible also helps to ensure development of the most fully nourished tubers possible.
If space is available, the baskets holding the tubers can be placed in a frost-free storage place, ideally at temperatures between 4 and 10 C. It is more usual to carefully unearth the tubers for more space-efficient winter storage. Keep their labels with them for clear identification at spring planting time.
I brush excess planting mix off the tubers and store them single-layered in shallow boxes with a light covering of vermiculite or peat. Vermiculite works best for me.
Check on the tubers a few times over the winter. Any sign of shrivelling indicates a need to spray-mist the storage medium lightly. It can also indicate that they need cooler storage temperatures. Avoid over-dampening the medium, which can cause mould.
Start the tubers back into growth indoors again in late winter, when pink nubs of growth appear on the tuber tops. Early March is the timing I aim for.
Dear Helen: I missed out on planting a winter cover crop. For next year, is buckwheat a good choice?
P.G.
Buckwheat is frost tender, not suitable for fall planting. It’s a wonderful soil builder for planting from spring through mid-August. It germinates and grows quickly. The succulent growth, chopped down and dug under, decomposes quickly as well.
Dear Helen: I’ve come to understand that there are different categories of plants classed under the terms “flower bulb” and “bulb” in general. Do you consider it necessary to understand these category names and the differences among them?
C.B.
Except for inquisitive home gardeners who want to know exactly how their different plants develop, I suppose it’s not necessary. I expect many grow perfectly lovely gardens without knowing details of the different structures that produce the tulips, dahlias, bearded irises and crocuses in their gardens.
For the inquiring minds, here’s a brief roster of categories commonly gathered under the term “bulb” or “flowering bulb.”
True bulbs consist of layers of fleshy scales, which are modified leaves, wrapped around a central growth bud and attached to a base plate from which roots grow. Most have a dry, papery, protective covering. Examples: Onion tulip, Narcissus (daffodil), lily, Hippeastrum (indoor amaryllis). Some, like our Christmas amaryllis plants and Narcissus, develop offset bulbs at the base of the parent bulb.
Corms usually have a similar conical or a flattened shape and papery (or fibrous) covering as well as a base plate, but the body of a corm is a solid mass of storage tissue. A corm is an annual structure that shrivels away as the plant grows. At the same time, it develops a new corm or corms on top of or beside the old one. Gladiolus, crocus, freesia.
Tubers are solid, swollen food storage structures with no base plate or papery or fibrous covering. Roots grow from most of a tuber surface. The shape is variable. Above-ground growth is generated from buds, or “eyes.” Most expand as the plant grows. Potato, tuberous begonia, anemone, cyclamen, Eranthis (winter aconite).
Tuberous roots are sometimes classified also as tubers or tuberous-like roots. They consist of swollen storage structures that are modified roots, borne in clusters from crowns located at the base of old stems. Dahlia, Clivia, Ranunculus, Alstroemeria (Peruvian lily).
Rhizomes are thickened, nutrient-filled stems that grow horizontally and spread outwards partly or entirely below the soil surface. They produce points of growth at intervals. The main point of growth is at the tip of the rhizome. Bearded iris, calla lily, canna lily, Convallaria (lily of the valley).
