Crocus are amongst the most colourful of late winter/early spring flowering bulbs, and are adaptable enough to be planted in almost any area of the garden. They are actually corms, not bulbs.
There is a huge colour range within the Crocus Genus, ranging from pure white through yellows, blues, and the deepest of ruby reds. Many are bi-coloured, with several striped Crocus of note. Pink however, seems evasive, though many of the colours verge on certain shade of pink - depending upon the ambient light.
Crocus are grown from corms - though often mistakenly sold as bulbs. No matter, the cultivation is basically the same. Crocus are easy to grow, though there is often disappointment with initial plantings. Mice, squirrels and other garden rodent being the main culprits.
The versatile Crocus corms can be planted virtually anywhere in the garden, and this includes in all types of borders, naturalised in the lawn, rock gardens, raised beds, containers and more or less anywhere where there is enough depth of soil to plant the corms. The main criteria is being planted in full sun, though some do quite well in dappled or light shade.
There is nothing that quite lights up[ the garden after the dull months of winter, than the first of the crocus peeping through - normally in March, though late February in a mild winter can also be the starting point.
Some Crocus flower in the Autumn - not to be confused with Colchicums, which are commonly known as Autumn Crocus. Colchicums are generally larger flowered, and belong to the Lily family, whilst Crocus belong to the Iris family - Iridaceae! The vast majority and most well-loved Crocus are those that flower in the Spring.
Planting Crocus - The spring flowering Crocus, are normally sold in garden centres during late summer through to autumn and this is the time when to plant crocus bulbs. Crocus bulbs should be planted as soon as possible. However, I have been forced to keep crocus right through to February before planting with seemingly little adverse affects - either at flowering time of the following year. However, it is far better to plant your Crocus with plenty of time to get settled in for the winter.
Crocus should be planted at around three inches deep, and care should be taken not to break the new shoot that may ne emerging even as you plant them. If more than a centimetre long, then trickle in some sandy soil - or even sand - around the corm to prevent damage to that shoot. It already holds the flower bud for the spring flowering period.
Planting Crocus in Containers - For the best display results, Crocus should be planted in groups of three or four bulbs around 2in 5cm apart. These will then emerge as small clumps of flowers in the spring, giving the impression that they are 'mature' clumps of bulbs. Far better that planting as single bulbs. The same number can be planted - given the size of the container - but with a far better show of flowers in the spring if planted in groups. Planting depth is the same as for garden planting.
Planting Crocus in The Lawn for Naturalising - Crocus are ideal bulbs or corms for naturalising - either in lawns or around the base of trees and large shrubs. In lawns, it is often suggested that you cut out a slice of turf and simply position the bulbs then firm the turf back down. In my own experience, it is far better - with less damage and a better show the following spring - if a little bit more care is taken and the bulbs planted individually in their flowering situation. In the case of long term naturalising, the bulbs can be planted singly. They will bulk up after a year or so with seedlings popping up everywhere. If a more immediate effect is desired, then plant in close groups of four or so bulbs/corms. these can be lifted and divided after a few years.
After-Care of Crocus Once They have Flowered. - The biggest mistake - as with any bulb - is to cut the foliage down before it has died down naturally. Allowing the foliage to keep growing after the bulbs have flowered, is essential to ensure flowers for the next year. It is during this time of foliage growth, that the bulb builds up food reserves to ensure a flower bud is formed for the next year.
If bulbs are naturalised in lawns, then plant them in individual drifts that can be left un-mown for the first three or four mowing cuts in the spring. So, the grass will look a little untidy. It is either that, or waste your time and be disappointed the following year when there are fewer flowers to be seen.
Crocus Not Flowering - In 90% of cases, this is due to the fact that the foliage has not been allowed to die down naturally. There are other reasons why Crocus do not flower listed below in 'Problems'.
the easiest and quickest way to add to your Crocus stock, is by lifting any mature clumps in their dormancy period - mid summer is best - and removing the small cormlets from the main Crocus Corm, and replant elsewhere. These may take two years to flower, but with larger offsets, they will flower the following spring.
Growing Crocus from Seed - is relatively simply, but it will take up to three years for you to see any flower. Simply gather the ripe seed before the pods open and scatter their contents. Sow the seed in seed trays - thinly - and leave place in coldframe, or with propagator plastic top over seed tray. Keep cool and away from direct sunshine. Leave the emerged seedlings in place for a couple of years, then lift the small corms that will have formed, and plant in flowering position during the dormant period - early to late summer. Do not expect to see flower for another year. The seedling corms will not necessarily be the same colours as the parent from which you gathered the seed.
During the planting time - and just after, mice and squirrels take a fancy to the ready meal you have just provided. This is not such a problem with established clumps. Very often we are asked why newly planted crocus do not flower the next year. The general reason is that the corms have disappeared!
Another cause of there being no flowers - especially with the yellow types, is the fact that birds are on the look-out for food in the late winter, and are quite partial to a helping of Crocus flower buds. Sparrows seem to be the main culprits, though wood pigeons are also a nuisance in this respect.
Vine weevil Beetle - or their larvae - can be a problem with Crocus in containers - especially if planted in old compost!
There are a few storage problems that can be troublesome, but as crocus are rarely 'stored' then this is not a significant problem for the amateur gardener. Moulds resembling Botrytis are the main culprits.