Crocus are easy to grow provided you follow a few basic rules, and the rules are shorter than for almost anything else in the catalogue. Plant them shallow. Plant them where the summer sun reaches. Then leave them alone. Nearly every crocus that disappoints has fallen foul of one of those three.
When Do Crocus Flower
There are three separate seasons and most people only know one of them. The autumn crocus open in September and October, well before anything else is thinking about it, the winter flowering kinds follow from January, and the large flowering sorts everyone pictures come in March. Buying from all three turns a fortnight of crocus into about five months.
The winter ones are what to add if you only add one. Chrysanthus varieties open in the first half of February across most of the country, when there is very little else out, and they are small enough to go in places that would be wasted on anything larger. February is where crocus earn their keep.
Soft pink, and out in October before anything else has started.
January and February, soft yellow, one of the earliest of all.
March, striped, and the one most people picture.
How Deep Should You Plant Crocus
No more than 5cm, and that is deliberately shallower than it feels right to plant them. Planting too deep is often the cause of crocus failing to flower and not readily increasing, and unless the soil is especially light it also prevents them naturalising. If in doubt with crocus, err shallow. It is the opposite of the daffodil rule.
The ground underneath matters more than the depth above it. Crocus like a well drained sandy loam and an open sunny aspect, so plant on a layer of sand if your soil is heavy and does not drain, and add potash when planting and they will thrive. Cold does not trouble them at all. Standing water does.
Why Do Crocus Fail To Flower
Almost always because it went in too deep, or because the spot bakes in February but never in July, or because the clump has sat there so long that it has strangled itself. The first two are fixed by lifting and moving them. The third is fixed by dividing, which is a job for June.
The summer one surprises people. They need summer warmth to remain free flowering, which means a crocus under a dense shrub or on a north facing bank can come up perfectly well for two or three years and then simply stop, because the corm never gets the baking it needs in July to set a flower for the following spring. Sun in February is not the point. Sun in July is.
Why Will My Crocus Not Open
Because it is not warm enough yet, and that is the flower working properly rather than failing. The flowers will remain closed during bad weather and at night, protecting their nectar for visiting bees and butterflies on sunny days, and they open and shut on temperature rather than on the clock.
It is worth watching on a bright cold morning. A crocus that has been shut for three days will open within minutes of the sun reaching it, close again the moment a cloud crosses, and be shut before tea. Nothing is wrong with it. Plant them where the low winter sun actually lands and you will see them open far more often.
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Can You Grow Saffron Crocus In Britain
Yes, and rather well, which surprises people who assume it needs a Mediterranean summer. The crocus responsible is sativus, it flowers in October rather than spring, and it was being grown commercially in Essex six hundred years ago in the village that is now Saffron Walden, where the chalk suited it and the wool trade wanted the dye.
The yield is the reason it costs what it does. Each flower carries three deep orange stigmas, picked by hand on the morning the flower opens, and it takes roughly a hundred and fifty flowers to make a single gram of dried saffron. A garden row will season a few risottos rather than pay for a holiday.
What Is The Difference Between Autumn Crocus And Colchicum
They are not related at all and they are constantly confused. Colchicum is often sold as autumn crocus and is nothing of the kind, being a much larger goblet on a bare stem in September with no leaves whatever, and the leaves that follow in spring are big, coarse and untidy for months on end.
Both are worth growing and it helps to know which one you are buying. A true autumn crocus is small, carries its narrow leaves with the flower or shortly after it, and includes the saffron. A colchicum is the one that will flower dry on a windowsill with no soil and no water at all, which is a trick worth doing once.
When Should You Divide Crocus
When they get congested, and not before then. If they become over congested they should be divided after the foliage has died down and immediately replanted, which in practice means June or early July, once the leaves have yellowed and before the corms have dried out. Congestion shows itself as plenty of leaves and hardly any flower.
Replant the same day if you possibly can. Crocus corms are small enough to dry out fast in a shed, and a corm that has shrivelled goes back in a size smaller than it came out, which costs you a year. If they are not planted immediately, the autumn kinds can be brought into flower on a sunny windowsill without any soil or moisture and planted out as soon as the flowers have gone over.
Can You Grow Crocus In Pots
Very well, and the winter flowering ones are the best of them for it. For the patio try growing some of the winter flowering varieties in pots, this adds early seasonal colour and shows the true beauty of the flowers, which matters more than it sounds, because a crocus at eye level on a table is a different plant from one at ankle height in a lawn.
Keep the pot outside until the buds show. A pot brought indoors too early gives long floppy stems and flowers that go over in a day, so leave it out in the cold to root, bring it in only once the first blooms appear, and put it back outside afterwards.
Do Crocus Spread On Their Own
They do both, and the two routes work at very different speeds. Corms multiply underground and give you a fatter clump within two or three years, while seed carries them further, so crocus turn up twenty feet away in about five years, and that is the one that makes a garden look as though it has always had them.
Seed needs you to do nothing at all, which is the difficult part. Leave the spent flowers where they are rather than deadheading, leave the grass unmown for six weeks after they finish, and resist tidying the seedheads away in May. The crocus that seed themselves about are always the ones in the part of the garden nobody bothers with.
The great naturaliser, and the one to buy if you want a carpet.
Cream, early, and generous once it settles.
Pure white with a gold throat, and one of the freest to seed about.
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What To Plant With Crocus
Snowdrops in front of them and something later behind. Crocus flower and vanish inside about six weeks, so the useful companion is anything that covers the same ground from April onwards, which is why they sit so well under deciduous shrubs and at the feet of herbaceous perennials that are still asleep in February.
The ones that overlap them most closely are all here. Snowdrops and winter aconites open alongside the first chrysanthus in January, dwarf iris comes in the same fortnight and at the same height, and chionodoxa and dwarf narcissi arrive in March as the large flowering sorts go over, which takes one patch of ground from midwinter through to April on bulbs alone.
At the other end of the year there is colchicum. It flowers in September and October when the garden is emptying out, it wants the same open sunny ground the spring crocus want, and putting the two together means one square metre earning its keep in both halves of the year.
Put them where you will actually see them from indoors. In the weeks when crocus flower nobody walks to the end of the garden to look at anything, so a handful by the back door, or under the window you stand at with the kettle, is worth more than fifty in a border you will not visit until March.