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Autumn-flowering Crocus

November 4, 2021
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Crocus is a genus of spring and autumn-flowering corms, related to other members of the Iris family. Many species come from different environments in Europe and Asia.

There are actually more autumn than spring-flowering Crocus species, although a lot fewer selected cultivars. Quite a few are hard to come by, and not that easy to grow outside without glass protection in most British gardens. In fact, it is not difficult to narrow down the choice of those that you may expect to thrive without protection. By far the easiest and most often seen are various forms of C. speciosus. All are good and easy to grow, even thriving in grass. Other species worth trying outside, include Crocus goulimyi, C. kotschyanus, C. longiflorus and C. niveus. Crocuses mostly require full sun and good drainage. The exception being the exquisite Crocus banaticus, whose natural home is in the deciduous forests and moist hillside meadows of Romania. Not surprisingly, it requires a site where the soil does not dry out, and will stand light to moderate shade.

Crocus banaticus

Crocus banaticus

Placement and planting

You can buy these easy autumn flowering crocuses as dry bulbs from garden centres and specialist bulb suppliers from mid-summer onwards. Plant them immediately, in drifts or clumps, in sunny positions in the alpine garden or front of a border. If planting in grass the best technique is to peel the turf off, prick the soil below over with a fork, scatter the bulbs then replace the turf. Nothing more is required than perhaps to scatter some general fertiliser pellets among the developing foliage in spring. And remember if you grow them in grass, not to cut until the tips of the leaves have started to brown off.

The main reason why some of the scarcer species that are available from specialist bulb dealers are are not seen more often, is that they are more vulnerable to wind and rain which bow down or break off the flowers at ground level.

 

Autumn flowering Crocus speciosus

Crocus speciosus

Growing autumn-flowering Crocus in pots

All crocuses will do very well in pots of well drained, gritty, loam-based compost. I have found that they don’t do well in composts based on peat or peat-substitute organic materials. I keep my pots in a well ventilated frame for most of the year, bringing them into the house or alpine house for their brief period of glory. They are kept just moist through the summer by standing the pots on damp sand. Then, simulating the situation in their homelands around the Mediterranean region, I water thoroughly in early autumn to start them into growth. They are then watered as and when they need it until the foliage begins to die back.

 

Crocus goulimyi ex Agia Sofia exhibited by Anne Vale

Crocus banaticus 'Snowdrift' a Farrer medal plant exhibited by Alan Furness

Propagation

Crocuses are generally profligate in producing offset corms as well as replacements for those produced the previous season. Offsets will generally reach flowering size in two to three years. These are genetically identical to their parent corm. Which is useful if you want to increase your stock of a particular cultivar. Or perhaps a variant that turns up from seed in your garden.

If happy, autumn crocuses will also increase freely from seed, to the point where you may need to divide them. This is most easily done when the top growth is dying down. The corms may then be sorted into sizes and replanted so as to ensure a succession of flowering size individuals.

Given this fecundity it is unlikely that you will need or wish to raise new corms of the commoner species from seed. If you do, the procedures are the same as already described for colchicums.

 

seeds and capsule

Crocus capsule and seeds

Pests and diseases

One possible problem in establishing colonies of autumn-flowering crocus plants is predation by small mammals, chiefly in Britain mice and grey squirrels. If you feel that this is a significant risk in your garden, encase the corms in fine-mesh wire netting baskets.

I have occasionally had problems with aphids attacking crocuses in pots, but never a far as I am aware in the garden. Otherwise I have found them to be remarkably free from invertebrate pests, and diseases.

John Good

John Good

Our author is a retired research forest ecologist and Emeritus Professor of Environmental Forestry at Bangor University. Throughout his life, John has been interested in all aspects of the observation and cultivation of plants. Alpines and woodlanders were always of particular appeal. He has called North Wales his home for more than 40 years. John and his wife, Pam, have developed and enjoyed their current hillside garden overlooking the sea for the last 27 years.

He joined the AGS over five decades ago. During this time John has served as AGS Director of Publications, Assistant Editor of our journal and as judge at our shows. After years of serving on the RHS Joint Rock Garden Plant Committee, he is now a friend.

John has travelled and lectured widely on alpines and written many articles and several books on the subject. He has also always been heavily involved in his local North Wales Group.

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