Welcome to Top of the Crops - today, you will learn how to grow saffron in a polytunnel. For more gardening insights, be sure to check out our blog Polytunnel Gardening too!
Saffron is the colourant and spice made from the stigma of the crocus (Crocus sativus). You will need a huge number of crocuses to make cultivation for the purpose of obtaining saffron worthwhile.
However, if you have enough space, a polytunnel could make crocus growing easier, as the sunny, warm and well-drained conditions inside a polytunnel will be perfect environment and could allow for greater levels of success.
Since saffron is one of the most expensive spices in the world by its weight, this may be one crop that is well worth growing commercially or for your own culinary use in the UK.
Unfortunately, much of the saffron on sale is adulterated with less expensive ingredients like turmeric and safflower. By growing your own you can rest assured that you are getting the real deal and can use it in your own culinary creations without spending a fortune for the privilege.
Saffron crocus bulbs can be found through many online retailers. Bear in mind when making the decision to grow saffron crocuses that each bulb will produce only one flower and each flower will produce only three tiny stigmas – the part that is used to colour and flavour food.
50 to 60 crocus bulbs will produce only one tablespoon of saffron. So this is quite an investment of both time and space. That said, these bulbs will multiply rapidly, so your stock will quickly grow over time.
You should be able to grow these crocuses outdoors in southern regions of the UK, but further north will likely need to grow them undercover to grow them successfully. Though they are H6 hardy it is important to remember that the species originated in much warmer climes.
To grow saffron crocuses, you will need:
Saffron crocus bulbs (technically corms).
A trowel or bulb planter.
A polytunnel or other sheltered and sunny location.
Facility to water your crop.
Tweezers for harvesting.
Saffron crocuses are not actually very difficult to grow. They are expensive mostly due to the tiny size of the harvest from each plant, not from the difficulty of their cultivation. Here is a simple step by step guide to growing this crop successfully:
First things first, you need to select and purchase your corms. Of course, you need to make sure that you get the right thing. Crocus sativus is the species that you are looking for. These flower in the autumn but should not be confused with the poisonous Colchium species also described as 'autumn crocuses'.
As well as choosing the right corms, it is also very important to choose the right location in which to grow your saffron crocus crop.
The location that you choose, whether inside a polytunnel or outside elsewhere on your property, should be sunny and sheltered, and the soil should be rich and high in organic matter, free-draining and not prone to waterlogging or compaction, nor to entirely drying out during the summer months.
Saffron crocuses are usually planted out in the late summer, or in early September.
The corms should be planted into prepared soil to a depth of around 8-12cm and around 10cm apart. Where drainage leaves something to be desired and soil is on the heavier side, it may be a good idea to incorporate a little grit into the growing medium.
Ground up charcoal/biochar added to the base of planting holes may help provide the optimum growing conditions for these flowers.
Laying a mulch of leaf mould around the plants may also help to create good growing conditions.
Once you have planted your corms, you should water them in well, then continue to care for them throughout the growing season. Fortunately, aside from providing sufficient water not much care is required. But you will find a few care tips a little later in this guide.
Finally, growing crocuses for saffron involves the harvesting of the crop. The harvest from these crocuses are the long, bright red stigmas from the heart of each flower. These should be collected while you take care to avoid the pale orange upright stamens with pollen on them, since these are not the part you want.
When the crocuses flower in the autumn, usually in October though perhaps later in their first year, you can carefully detach the stigmas from each one very carefully with a pair of tweezers. Of course, if you are growing a lot then this is by far the most time-consuming part of the process.
Remember, growing saffron might not take much work, but there is also only a tiny return since you will need to harvest from around 150 flowers to get just 1 gram of saffron as your yield. You only get three small strands per flower.
The plants from which you have harvested will grow around 30cm tall over the winter and then die back in the late spring. The original corm will be replaced by several cormlets, which will typically take 2-3 years to flower.
Lay out the stigmas to dry on a piece of paper towel in a warm and dry location where they will not be knocked over or blown away. They should be dry within a few days and once fully dried, can be safely stored for later use.
Once the strands have dried they can then be stored in an airtight container and then rehydrated as needed and used sparingly in a wide range of different dishes over the months to come.
Dried saffron is not used in dried form in recipes. Rather, it is soaked in water to rehydrate the strands – usually overnight - before it is used in recipes. As a rough rule of thumb, you will usually need around 2-3 strands per serving for a standard recipe.
The good news is that once you have planted your crocus bulbs, they will require very little care or attention (until the time comes to collect the fiddly harvest) and so are a really low-maintenance crop.
Water when the weather is particularly warm and dry or, of course, if you are growing these crocuses in a polytunnel or other undercover growing area.
If you wish you can also ensure good soil health with the addition of a good quality organic fertiliser once a year. Mulching with a good quality leaf mould, homemade compost or other organic mulch can be beneficial.
Remember, though there are plenty of other crocuses that you might grow, the only one which gives you a yield of saffron is Crocus sativus. Even if you are not that bothered about growing this for the saffron strands, it can still be an attractive autumn flowering crocus to grow.
There are several main types of saffron sold in shops – such as Persian saffron, Kashmiri saffron and Spanish saffron – usually classified according to their region of origin.
These are further divided according to their quality of aroma, taste and colour strength and graded to show their quality.
But most home growers will purchase corms simply labelled as 'saffron crocuses' without paying particular attention to the specific strain or varietal. Unless you are a gourmet chef this is unlikely to be something you will worry too much about.
Saffron crocuses are not typically a crop that is troubled by diseases. However, it can be plagued by certain pests.
For example, it may be susceptible to problems with rodents and with birds. Mice and voles, for example, can sometimes eat the foliage and the corms during the winter months. Rabbits may also nibble on the plants
If these become an issue then organic deterrents and physical barriers may be used to protect the crop.
Most of the time, however, as long as you plant healthy corms in the right location, and keep your crop watered while allowing excess water to drain away freely, then you should be able to obtain a saffron harvest – however small that may be.
Issues like corm rot and root rot arise where waterlogged conditions prevail and where you have overwatered and excess water could not drain away freely. Choose a location in well-drained soil or growing medium and water only when needed and not excessively to avoid these issues.
If you are growing saffron in a polytunnel then it is unlikely to be much more than an ornamental and novelty crop, allowing you to grow just a tiny quantity of saffron to impress your friends and family.
But you may grow commercially if you have a large enough tunnel, or tunnels, to give you enough space for a worthwhile yield.
Even if you are not bothered about growing saffron as a spice, you may still wish to grow these autumn-flowering crocuses for their pretty flowers, which look good to us and also provide a boon for pollinators later in the year. Remember that you should always have flowers in bloom in your garden for the wildlife over as much of the year as possible.
Meacham, J., (2023) 11 Impressive Health Benefits of Saffron. Healthline. [online] Available at: https://www.healthline.com/nutrition/saffron
