Crocuses
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Late winter brings with it a hint of spring that some plants are quick to act on. Crocuses, for one, need no second bidding and are always well in bloom before the month is out. Indeed, in mild places some of them will have been in flower for some time, bursting through the ground with an exuberance that seems almost excessive when most other plants are so soundly asleep.
Beautiful as they are, it’s probably just as well that crocuses flower early, or with their diminutive stature they could easily be lost among the larger spring flowers. And of course their blooming season is very brief, so prize them while you may.
The 80-odd species of Crocus are found naturally from Europe to Afghanistan and as far south as North Africa. Their principal homeland is that promised land for bulb hunters — Turkey — and the Balkan to Greek region as a whole. Indeed, the name Crocus is derived from Krokus, a Theophrastian Greek word for saffron, which is made from the stigmas of Crocus sativus.
Crocuses aren’t really bulbs, but corms. A close look at the perforated papery covering of the corms reveals a similarity with others in the iris family, such as Gladiolus.
While they didn’t reach the exalted status of the tulip, early European gardeners certainly prized the crocuses of Turkey too, with the result that many of the species are now very rare in the wild. The recent Yugoslav conflicts posed a threat to not only the human inhabitants of the region, but also some 20 plant species, including Crocus rujanensis. The trade in these rarest species is now strictly controlled, and in some cases prohibited, so this is an example of where gardeners can do their bit for conservation by keeping alive those rarities already in cultivation. Really, it’s the least we can do after having brought them to the point of extinction.
So what’s available to crocus growers and how can you get the best out of them?
Well, bulb specialists certainly offer a good range of species and cultivars, but as is often the case, garden centres tend to stick to a selection of the tried and true. For anything really unusual, you’ll probably need to scour the mail order catalogues.
Of course not all crocuses are winter- to spring-blooming; some flower in the autumn, though you shouldn’t confuse autumn-flowering true crocuses with the similar looking plants of the genus Colchicum, which aren’t even close relatives. A well-selected group of crocuses will provide flowers from mid-autumn to mid-spring, possibly with a brief lull during the coldest days of winter.
Although C. serotinus always gets the rave reviews, for its scent as much as its purple flowers, my favourite among the autumn-flowerers is the pale purple C. nudiflorus. That’s because it always seems to take me by surprise, usually bursting through from under the cover of some other plant. Its disguise is helped immensely by the fact that its leaves don’t appear until after the flowers have faded. Crocus speciosus also flowers early, often slightly before C. nudiflorus. It’s very attractive, though I find its rather more open flowers less appealing.
Many would regard the Saffron Crocus (C. sativus) as the star of the autumn crocuses. There’s no doubt that its historical significance and aura of culinary superiority give it importance, but to me it’s not the prettiest of crocuses, although it is nicely scented. Because the Saffron Crocus is sterile it can’t really be a true species, so botanists now regard it as a form of C. cartwrightianus.
From just after the shortest day crocuses really start to spring into action. The one that blooms most reliably in winter is C. chrysanthus. The species is yellow with maroon marking on the exterior of the petals, but cultivars can be found in any shade of cream, yellow, mauve and purple, including bi- and multicolours.
As C. chrysanthus comes to an end so the similar C. vernus takes over. Coming from further north, in Italy and Austria, it waits until certain that spring has really arrived and in cool areas it can still be flowering in early summer. Its usual colour is mauve, though again there are cultivars in many shades and patterns. C. chrysanthus and C. vernus are the crocuses that take best to being grown in lawns and they’ll often naturalise and multiply well if happy.
Crocus versicolor is also quite widely grown, which is not surprising as it’s a very striking plant. Native to southern France, western Italy and Morocco, it’s notable for the striping of its flowers. Those of the basic species are white but they’re often purple-striped with darker interiors to petals and sometimes with bronze markings. The cultivar ‘Picturata’ is the form most often seen and it’s everything a crocus can be.
Keen growers, however, are never satisfied to grow just the common varieties and for those prepared to seek them out, there are many treasures waiting in the catalogues. Because crocuses all tend to be fairly similar, the trick is to be able to identify the plants. That gives them an appeal for collectors who delight in the minute difference between the many species, subspecies and varieties. But if you find it difficult to differentiate between all the forms of something like C. sieberi, and who doesn’t, look to a few of the more distinctive species.
For very early spring flowers try C. biflorus, which is usually white shaded with mauve. The subspecies nubigena has distinctive brown-striped petals and brownish anthers.
For intensity of colour it’s hard to better C. gargaricus, the flowers of which are an intense golden yellow. It most commonly blooms in August.
Crocus tommasinianus from Hungary, Bulgaria and the Yugoslavian region is often described as being among the best-known species but that doesn’t mean you’ll find it in every garden centre. It has very narrow leaves and mauve flowers on long white tubes. The petals are darker inside and are tipped with purple.
Cultivation
Like most bulbs and corms, crocuses require good drainage. They tend to fall into two distinct camps though: those like C. chrysanthus and C. vernus that prefer some organic matter in the soil and will grow happily in lawns, and those that prefer open gritty soil and that are more at home in a rockery. So take the time to do a little research on the origins of your crocuses because you need to know which type you’re dealing with.
Crocuses need around half a day’s sunlight to do well. They can be grown under deciduous trees that don’t leaf up too early, but don’t appreciate being heavily shaded at any time. If the tree canopy is very dense, thinning out some of the branches may help. If you must grow crocuses in full shade, try C. banaticus, a mauve flower that seems far more tolerant of shade than most.
On the other hand, you don’t want the conditions to be too hot and dry either. Most crocuses develop their roots during summer and still need to be reasonably cool and moist even if they don’t appear to be active. That’s something to remember if you’re intending to lift the bulbs — lift spring-flowerers in late summer or early autumn and autumn flowerers in late spring.
Provided the growing conditions are good, crocuses are only very rarely troubled by pests or diseases.
Planting
Don’t just throw the corms in the ground; work the soil over well and add a general garden fertiliser before planting. Most crocus corms should be planted at around 5cm deep, which corresponds to the old rule of thumb that the depth of soil above the bulb should be roughly equal to twice its height.
Also, while it may seem obvious, do make sure that you plant the corms the right way up. That’s the pointed end facing upwards.
Crocuses in containers
Some of the fussier alpine species, such as the beautiful C. korolkowii, are easily damaged by poor drainage during winter rains and usually do better if grown in an alpine house or in containers. And there’s no reason to restrict container crocuses to just those that need the treatment; they’ll mix in quite happily with other bulbs for some potted spring colour.
Use containers at least 20 cm deep and build the soil up in layers. Use coarse gravel chips for the bottom layer to ensure good drainage. Next, add a layer of free-draining potting mix to about ½ the depth of the box. Add a little general fertiliser so that the bulbs get a good start. Plant the corms in this layer with their bases nestled in the compost. Fill the remainder of the box with a gritty soil mix so that the corms are about 5–6cm under the soil. A topping of fine gravel or bark chips will keep the crowns dry and rot-free.
Crocuses in grass
The sight of massed crocuses flowering on what was, a few weeks previously, plain lawn is one of the wonders of spring. However, it’s not always easy to work that miracle. The main problem is knowing when it’s safe to mow the grass. Don’t attempt to mow while the crocus foliage is still green. It should be left to die off naturally because, like any other plants, crocuses depend on their foliage for photosynthesis. Crocus foliage usually disappears quite quickly, so the lawn need not get to overgrown.
And of course you need to keep foot traffic to a minimum when there are bulbs in the lawn. Too much traffic and the soil will become very compacted or the flowers will be trampled.
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While they’re just one genus among the myriad of spring bulbs, crocuses certainly reward a closer look. And their small size and ease of cultivation allows them to be grown in any garden, even if you have only a windowbox.
Copyright Geoff Bryant
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