The genus crocus (Crocus) belongs to the iris family (Iridaceae). About 90 species are known, in addition to numerous subspecies and hybrids that have been created by crossing different species. The home of the game species are Central and Southern Europe, North Africa, the Middle East and Western China. Many are native to Turkey and Greece. Natural sites include rocky slopes, evergreen oak bushes and coniferous forests.
Small crocus (Crocus chrysanthus), elf crocus (Crocus tommasinianus), sieve crocus (Crocus siberi) and spring crocus (Crocus vernus) play an important role in garden culture. These species are spring bloomers, while the magnificent autumn crocus (Crocus speciosus) is one of the species that blooms in the autumn weeks. The saffron crocus (Crocus sativus) is also an autumn bloomer – its orange thread-like stamps are harvested, dried and traded as saffron for thousands of years. Saffron threads are among the most expensive spices in the world. In addition to cultivation areas in Iran and Afghanistan, there are also saffron cultures in Spain, France, Italy and Austria.
Appearance and growth
Crocuses are often mistakenly classified as bulbous plants. However, they have a so-called stem tuber, which means that it is a thickened part of the stem that grows underground. This tuber is one year old, but every spring one or more new daughter tubers are formed. The old tuber dies. The tubers produce basal narrow leaves reminiscent of blades of grass. Depending on the species, the plants grow to between 5 and 15 centimeters. Crocuses are divided into the group of spring flowering plants, the group of large-flowered hybrids and the group of autumn flowering plants. Flowering time of the first group is in early spring from February to March, the large-flowered hybrids bloom sporadically until April. Autumn crocuses usually bloom from September to October. The predominant flower colours are violet, yellow and white, and there are also two-colour varieties.
The species blooming in spring are important forage plants for bees and bumble bees, which mainly collect the protein- and vitamin-rich pollen.
Location and soil
Early-flowering botanical crocuses thrive best in sunny locations in the garden, the autumn-flowering crocuses also cope well with semi-shade places. The large-flowered hybrids, i.e. the classic garden crocuses, prefer a sunny to semi-shade location. However, it is important to know that the flower is sparser the longer the location is shaded during the day. What they all have in common is their preference for permeable soils, as waterlogging causes the tubers to rot. While the spring flowering species also thrive well on sandy or stony soils, it may be a good garden soil for the autumn crocuses with a clay content. For the early bloomers, however, you should improve heavy soils with a little sand.
For the spring crocuses is the best planting season from October to November, the autumn flowering species are preferably planted in August. The planting depth of the spring crocuses is six to ten centimeters, as is the distance between the tubers. Autumn flowering crocuses are set a little lower because of the larger tubers. However, since crocuses use their migratory roots to make themselves accessible to nutrients and moisture from deeper soil layers over time, it is not a broken leg if the tubers are set relatively flat. Always place about ten tubers next to each other, as the small flowers are best shown off in groups. If you want to turn your lawn into a crocus meadow, a loose, random distribution is recommended. Gold Crocus (Crocus flavus), Spring Crocus, Small Crocus and Elf Crocus are particularly suitable for wildlife. They form dense nests that should be shared after a few years.
Once planted, crocuses do not require any special care. It is important not to cut off the leaves immediately after flowering. They are only removed when they wither, otherwise the plants are weakened and die more quickly. Therefore, if you have planted crocuses in the lawn, you should wait with the first cut of the lawn until the leaves have yellowed. If necessary, fertilizer is applied in early spring as soon as the leaves sprout. An organic liquid fertilizer, which is applied with the watering water, is suitable.
Spring crocuses can be well combined with early flowering bulb flowers such as Winterling (Eranthis) and Snowdrops (Galanthus) as well as shrubs such as Christrose (Helleborus) and Lungwort (Pulmonaria) in a sunny bed with permeable soil. A colourful crocus carpet under deciduous bushes looks beautiful, but the tubers can also simply be placed in the lawn. Especially the lower species are suitable for the rock garden, as are the crocuses that bloom in autumn. In principle, the plants should always be placed in groups so that they achieve sufficient colour effect. However, the low tuber plants can also be planted in the pot, for example together with the net leaf iris (Iris reticulata) or small-flowered daffodils.
Important species and varieties
The large genus of crocuses can be divided into three groups: the early flowering botanical crocuses, the large flowered hybrids (often simply called garden crocuses) and the autumn flowering crocuses.
The early flowering botanical crocuses are characterized by more dainty flowers, which often appear in late winter. Even a blanket of snow and frosty temperatures do not prevent these crocuses from pushing their buds out of the ground. The group of early flowering crocuses includes the elven crocus, the spring crocus and the small crocus. Numerous varieties are available from them. A special feature is ‘Orange Monarch’, a relatively new variety of the small crocus, because the dark orange yellow of the flowers is very unusual for crocuses. From March onwards, the larger garden crocuses will be added, whose colour palette ranges from white to yellow to violet, and the variety ‘Pickwick’ is even striped. In addition to the crocus hybrids, this group also includes the gold crocus, which shows several bright yellow flowers per tuber in March/April. The large-flowered hybrids are now available in a wide range, for example ‘Haarlem Gem’ with light purple flowers, the white-flowered ‘Jeanne d’Arc’ or ‘Queen often he Blues’, whose violet-blue flowers have a silvery shimmer, and the autumn-flowering crocuses will make their big appearance from around September. Three species are most common here: the violet-blue gorgeous crocus, the saffron crocus and the ring autumn crocus (Crocus kotschyanus). The splendid crocus varieties ‘Albus’ (white) and ‘Conqueror’ (sky blue with dark veins) are popular.
The tubers of crocuses form daughter bulbs, which can be taken out of the ground in summer and transplanted. Many species spread to sites they like through seeds themselves. Crocuses are cold germ buds, i.e. the seeds spread need several days of temperature around freezing to germinate. Several years usually pass from the seedling to the flowering plant. The saffron crocus is infertile due to its triple chromosome set and can only be propagated purely vegetatively, i.e. via the daughter onions.
Diseases and pests
Crocuses are only slightly susceptible to diseases. In very rare cases, the tubers may rot caused by a fungus. You should remove the infected tubers and dispose of them with your household waste. In addition, you should not place crocuses or bulbous plants such as daffodils and tulips in this location for several years, as the disease persists in the soil and can infest new plantations. There is no treatment available. The vole, which eats the tubers, would be the main pest. Special traps or deterrents can be set up to combat the rodent. Those who do not want to fight the animals directly protect the crocus tubers with plant baskets made of wire.
Crocuses in the our store-Shop
I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.