Woad Plant Care: Tips On Using Woad Plant Dyes
Indigo blue was a pretty hot color 5,000 years ago. The production and trade of this dye became hotly contested when Eastern Indian merchants began to introduce indigo to Europe where woad was the preferred dye. Confused, yet? What is a woad plant and what other interesting woad plant information can we dig up? Is there a difference between indigo and woad plant dyes? Read on to find out.
What is a Woad Plant?
Woad (Isatis tinctoria) is an erect biennial that grows to between 1-3 feet (30-90 cm.), sometimes up to 4 feet (1.2 m.) in height. Its leaves are bluish green overlaid with a powdery white fluff. The leaves are narrow and lightly serrated to wavy. The plant blossoms with small yellow flowers in the spring of its second year of growth and develops into blue/black fruit. The plant was cultivated for centuries as a medicinal and source of blue dye.
In some areas of the world, the once valuable woad plant is considered a weed and, indeed, grows as such.
Woad Plant Information
Woad was indigenous to southeastern Europe and rapidly spread throughout during prehistoric times. In most of Europe, woad plant dyes became the predominate blue dye of choice and, in fact, is sometimes referred to as “dyers woad.” The blue dye from woad plants was used by ancient peoples of the British Isles to paint their bodies in the hopes of frightening their foes.
On the other hand, Indigo (Indigofera tinctoria), a native of southern Asia was the popular choice for blue dye there. Production and trade was controlled by India. The import of indigo dyes began to increase amongst woad producers. They united to fight the importation of indigo and save their livelihoods. Slowly but surely, despite legislation, indigo took the upper hand and became the preferred dye in Western Europe.
Of course, by the late 1800’s, the introduction of synthetic indigotine (synthetic indigo dye) made the dispute between woad and indigo purveyors a moot point. Still, while the blue dye from woad plants does bleed and fade with age, it is just this fading that makes it a unique and worthy dying medium. If you are interested in using woad as a dye, the best thing to do is grow your own. Keep reading to find out how to grow woad plants.
How to Grow Woad Plant
Woad is very competitive and can displace valuable crops, native vegetation and rangeland. It also has an extremely long tap root (3-5 feet or 0.9-1.5 m. long) that makes it almost indestructible. Hence, many places deem woad too invasive and label it a noxious weed.
That said, woad seed can be obtained online or if you happen upon a patch of it, you can harvest your own seeds. Sow seeds thinly space in March in seed trays. Cover lightly with soil and keep moist.
When the seedlings are large enough to handle, transplant them outside, leaving a foot of space between each. Woad likes an alkaline soil, so an application of lime, one week prior to planting, will give them the proper soil pH. Keep the woad seedlings moist.
Do not replant woad in the same area as other Brassicae. Like other members of the cabbage family, woad is susceptible to clubroot, which can be passed from member to member, so practice crop rotation.
Woad Plant Care
Once established, other than water and a little fertilizer, there is little additional woad plant care until harvest. Woad needs lots of nitrogen, so fertilize with a high nitrogen food of dried blood meal or hoof and horn meal.
Woad will be ready to harvest in July all the way through September. In some areas, woad can be harvested until November, but the onset of fall frosts will likely lessen the color.
To harvest your plants, use sharp pruning shears or garden scissors to cut the newer leaves back. Avoid the old leaves which are easily recognizable by their blue hue. The old leaves don’t have the chemical in them anymore that will become dye. Cut the old back too, though, just don’t use them in the dye-making process. It is better to cut all of the leaves of a plant back at once and then let it regrow.
Now you are ready to use the leaves for dye extraction. Put the fresh leaves into a jar and cover with almost boiling water. Seal the jar. Soon the water will become colored and begin to bubble a bit. At this juncture, alkali is added to the colored water, shaken and the solution turns green.
Fabric is then dyed using the green/yellow colored dye. Where’s the blue? Once the fabric is exposed to air, oxidation takes over and voila! You have a lovely blue. The process is finished by setting the dye in acid and then it’s washed and rinsed.
Comprehensive instructions can be found online, but it sounds like some trial and error might be required. Apparently, the dye is tricky to work with.
Controlling Woad Plant Weeds
For those of you who wouldn’t think of cultivating woad and just want to get rid of the darn things, there are both chemical and non-chemical controls.
Non-chemical methods of eradication include hand pulling, which since the tap root is so deep, is quite difficult. Also, revisit the woad site every couple of weeks, as the plant readily self-sows and can do so for many years. You can mow it for a very temporary control, or try some goats on it.
A native rust fungus is being investigated as a biological control but isn’t available as yet.
The other option is chemical control. Consult your local extension office for recommendations regarding herbicides for use in your area.
An article by Ashley Walker
© copyright 2016
Woad (Isatis tinctoria) is a naturalised hardy biennial member of the Brassicaceae or cabbage family and was probably introduced into the UK from Europe. There are no close relatives in the UK but there is a similar plant from China called Chinese Woad (Isatis indigotica) which is primarily is grown as a medicinal plant but is also used as a source of indigo. Various web sources including Wikipedia assert that indigotica and tinctoria are botanically indistinguishable. I have recently obtained some Chinese Woad seeds from a German company (Rühlemann’s) so intend to find out the truth of the matter next year. Woad will grow up to four feet high and here in Hertfordshire it flowers in May. The flowers, like so many dye plants, are yellow and make a terrific show in spring.
Unfortunately Woad is classified as a noxious weed in many western states of the US so if you live in one of these states please find out what the restrictions are before you even consider growing it. Here in the UK although it has naturalized and self seeds readily it is not invasive and only tends to grow in disturbed ground. Seeing it in the wild is a rarity. I have been reading about its invasiveness in the US and I now understand that it can invade wild areas of the West with ease probably because these areas are similar in habitat to its native eastern European and Asian plains. It is now classified as a noxious weed in the following states Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. I have not found any reports of problems in the East of the US so would appreciate it if anyone who has any knowledge of this could let me know. Many thanks.
More information can be obtained from this short online document here. For really comprehensive information see here.
The flat winged seeds of woad contain more than one seed
Woad generally produces masses of large seed “pods or cases” that are only viable for one year. These take a few months to mature and start falling or being blown to the ground by August. The seeds will then start to germinate as soon as the weather becomes wet (inhibitory chemicals in the seed case are washed away by rain). By late October/November new plants will have grown to a substantial size (big enough to harvest). Many seeds will not germinate until the following spring and a few of these will grow and flower in the same year. Those that do, will probably return to a rosette stage towards the end of summer which leads to the unusual sight of rosettes growing at the top of a long stem. Some second year plants will also survive flowering and also return to producing rosettes at the end of summer. These second year rosettes also produce indigo in the leaves.
Left a smooth edged leaf rosette and right a toothed leaf plant
A second year plant that survived its first summer and has returned to the rosette stage (sometimes called a “crown rosette”)
There appears to be a great deal of phenotypic variation between Woad plants. There are big differences in leaf colour ranging from blue/green to pale yellow/green and leaf shape from toothed to smooth-edged. Because of this variability, Woad seedlings can be easily mistaken for weeds at first, especially if they have popped up in unexpected places. However, all Woad plants have a highly distinctive aroma, once smelt never forgotten! It seems likely that plants also differ in the amount of indigo they contain, so there is probably scope for plant breeders to improve the stock.
Isatis tinctoria or Dyer’s Woad is an easy-to-grow biennial that originated in the Caucus area near Turkey. It was valued for its rich blue pigment, and archeological evidence traces its use as a natural dye back to the Neolithic period in France, the Bronze age in Austria and Germany, the Iron Age in Northern Europe and the British Isles, and the Pharonic period in Egypt.
In Traditional Chinese Medicine, Isatis indigotica, or Chinese woad, was used for centuries for its distinctive blue dye as well as its antiviral and antibiotic benefits (learn how to dye with woad). Much of the scientific literature, including over 100 journal articles just in the last 15 years, we owe to the diligent research of Chinese scholars. For over 2,000 years, Isatis root, Ban Lan Gen and Isatis leaf, Da Qing Ye, were recognized for their ability to cool a fever and stop a cytokine cascade in the body during both viral and bacterial infections, including the flu. In China many households have Ban Lan Gen tea granules in the medicine cabinet as a preventative decoction during cold and flu season.
Woad root has a mild taste. Woad leaf, on the other hand, has a mustardy, cabbage flavour, similar to many other plants in the brassica family. The leaf and second year closed flowers were used as a food source in famine. The flavour is more pungent in the second year.
The Woad to a Sustainable Blue Part 12: Woad our Plant Ally
Woad is one of the most amazing plants. Not only because of its dye content, but its herbal abilities, and its ability to thrive even in face of sub-prime growing conditions like marginal soils and summer frost.
At the same time, many people do not want woad to grow or thrive in their areas. Termed an invasive species, or a noxious plant and toxic to animals, woad has gained a negative rap through-out many areas.
Weed control and noxious plant rangers seem quite concerned with the possibility of woad growing in certain areas. A year or so ago, I was harassed by the local weed control person over having grown woad in the past. The person claimed that woad had been declared an invasive species in BC, and that she “had” to come onto my property to see that there was no woad growing – at all. Now, I checked the regulations, and woad is on a “potential invasive species” list that is based on the Washington State regulations. It’s a potential because it’s listed in Washington even though it is not present in Washington. In BC, it can only be added if it is proved that the plant is present, however I’m fairly sure that the only place it’s been in BC is in dyer’s gardens.
Ironically, that “potential invasive species” list contains a disproportionate number of normal, medicinal herbs. A good quarter of the potential invasive plants are HERBS that the average person would grow in their garden, like normal garden sage. Last time I tried to grow sage, it died, not exactly invasive plant behaviour.
Sure, animals don’t eagerly devour herbs because they wait until they actually need the herb’s properties before eating it. So, if the list is based on what animals are willing to eat and not willing to eat in a normal day, well yeah herbs would not be in their diet unless needed. What I find strange is that plants with known herbal properties are being blacklisted as invasive plants that must be dealt with using toxic chemical soups (aka. herbicides).
So, why are so many herbs on a government invasive species list?
Working with Woad Regulations:
If you are in an area that actually has wild-growing woad, don’t be afraid to wild craft it as a dye from anywhere. Also, you can use wild woad as an herb if you know that the plants have never been treated with toxic chemicals. Alternatively instead of woad, Isatis tinctoria, if you were warm enough you could try a different Isatis spp. the Chinese Woad, Isatis indigotica.
If you can grow woad, of either strain, I would encourage you to think of adding it to your natural dye garden. It is an amazing plant, and well worth the little time and effort that it takes to grow and process it.
Note: In areas where Woad has noxious weed status, most people recognize the second year woad plant and not the first year plant. If you can recognize the first year plant, you will get a much better natural dye harvest than if you tried it with second year plants.
Woad In The Garden:
Woad is a puller, and will take a fair amount out of the soil. With a good dose of compost and mulch at the start of the growing season, it can help improve clay soils and other hard packed soil due to its deep taproot. As a brassica, woad should have at least 3 years break before being planted in a place where other brassicas were grown, and same with other brassicas to woad. This will keep your garden soil healthy, and prevent soil born challenges.
Woad For Natural Indigo Dye:
Most claim that woad does not produce half as much indigo per kg of leaves when compared to Indian indigo. But, with the right extraction process the difference can be decreased quite substantially. Woad has a faster hand than Indian grown indigo, and has an amazing range of other color potential. I sincerely suspect that Woad is the only single dye plant that can actually give a full spectrum of color, which is quite impressive.
Woad as an Herb:
Woad is a wide-spectrum antibiotic, as well as being anti-fungal, and a broad spectrum anti-viral. Being a natural option for these applications, woad can contribute to health and combat even normally antibiotic resistant bacteria. Remember, no matter how easily bacteria adapt to commercial antibiotics, they never seem to adapt to herbal options. Garlic is still effective and it’s been around for how many thousands of years?
Keeping A Supply of Woad:
Woad seed will remain viable for 4-5 years. If you are saving some of your own seed, which I recommend when done with care, you should grow plants out for seed every 3 years. This will insure you have plants fully adapted to your particular growing conditions, and also insure a constant supply of healthy and viable seed.
I learned the seed lesson the hard way. I had grown woad and saved seed consistently, then stopped for several years due to my other studies. When I again tried to grow woad, my seed was 5 or 6 years old – and out of over 100 seeds I only had 2 germinate and only one survived the summer. That one plant, thankfully, continued to survive and will provide me with seed to continue growing woad. Next time, I won’t wait so long to grow out my seed! Or maybe, I won’t do quite so thorough a job of eradicating the little volunteers next time.
As the first year plants are used for dye, and the fall roots for medicine, you should have no spreading problems. Just leave 3 or 4 plants for seed in the third year, and keep one seed stalk per plant when they flower. Those 3 or 4 stalks should provide you with enough seed for the next 3-4 years planting and harvesting until you save seed again.
In rare conditions, woad can be grown as a perennial instead of a biannual. However, the indigo content gradually decreases when woad is treated as a perennial and not permitted to go to seed (by trimming off the stalks as they try and grow). Keeping Woad as a biannual is probably the best plan for a consistently high indigo yield, and for keeping consistent seed.
Our Plant Ally:
I hope you enjoyed the information, and will think about keeping woad alive as a relevant part of natural dyeing, and possibly natural medicine. I hope you enjoyed learning about woad as much as I did when first researching this amazing and awesome plant.
Back To You:
If you have any thoughts on woad, I would love to hear them. Leave a comment.
To Grow or Not To Grow?
Woad is the easiest source of blue for dyers in the Northeast to grow, since it is perfectly happy with the length of our typical growing season. Other plants that yield blue, including Japanese indigo or dyer’s knotweed ( Polygonum tinctorium ), require a longer growing season and need protection in the spring and fall. Luckily for those of us in USDA zones 5-6 here in New England, woad is a hardy biennial.
Woad is considered a noxious weed in much of the western U.S., including California, Montana, Wyoming, Utah, Idaho, California, Oregon, and Washington state. The classification “noxious weed” means that it is illegal to grow it because it is considered so detrimental to agricultural productivity. Fortunately it is still legal in Massachusetts and the New England states. Check the laws for your area before you plant it.
I originally bought my seeds from Richter’s Herbs in Canada. I tried both their woad and Chinese woad, and found that the Chinese woad did better in our garden and yielded more color. I have been saving the seeds since 2005. The Chinese woad was labeled Isatis indigotica. So, that is the type I grow. The other common variety of dyer’s woad (probably the better known variety!) is Isatis tinctoria.
Planting and Growing
Woad needs very rich soil to produce prolifically, including generous levels of nitrogen. I usually combine composted manure and compost in the bed. Recently I started using a non-vegetarian natural fertilizer (composed of blood and bone meal among other things) and despite being sad about the animal body parts, I was happy with the results. In addition to the usual nutrients (potassium, nitrogen, and phosphorus) woad also benefits from calcium. You will need to amend the soil in the bed again after you dig up your woad crop, as it pulls a lot of nutrients from the soil.
Woad can be direct-seeded into the garden very early in the spring. Here in the lower elevations of Western MA I can plant woad as early as mid-April. Since the seedlings are frost-tolerant and the plant has a long taproot, direct seeding is easiest. I find that the seeds germinate best if not planted too deeply, about 1/2 inch, though I’ve seen a planting depth of 2-3 inches recommended. Woad likes full sun.
Woad seeds on the soil before burying:
Allow at least 6 inches between plants, and more is better. Rita Buchanan recommends 12-18 inches, and Jill Goodwin recommends 9 square inches per plant. I usually seed freely and thin out seedlings once I see how many germinated. When well-fed, the first-year rosette of leaves will grow to more than a foot wide. Woad will tolerate a certain degree of crowding but the leaves will be smaller on a plant with less space to grow. More plants per square foot will not yield more weight in leaves, and I don’t think small leaves yield as much color. To ensure a steady supply of leaves throughout the summer and fall, plant two beds about two weeks apart.
Woad seedlings with more leaves:
Woad seedlings that need thinning:
Woad likes a lot of water and will wilt when it is hot despite its deep taproot. It can tolerate some weed competition but the first-year basal rosette isn’t very tall, so don’t allow the plants to become overshadowed. Too many weeds, especially grasses, make harvesting the woad leaves slow and difficult.
Woad Pests and Diseases
Woad is a brassica, the family that includes mustard, kale, cabbage, and broccoli. It is vulnerable to the same pests and diseases, and benefits from similar cultivation practices.
Rotate the beds you use for woad from year to year. Some places recommend a 5-7 year rotation for brassicas. Woad can suffer from club root, which is another reason to rotate your beds. You might need to add lime to bring up the pH if your soil is acidic. If your woad is suffering from club root, the plants will be stunted, wilted, and obviously not thriving, despite sufficient nutrients and water:
Here are some affected roots:
Mulching suppresses weeds and conserves water, but it also provides shelter for slugs. Around here, slugs are a significant pest for woad. In my experience it is better to weed than mulch woad. Another major woad pest are cabbage white caterpillars. Hyssop is recommended in some companion planting sources to deter cabbage whites. In my experience, anise hyssop attracted pollinators, including cabbage white butterflies, but it did not prevent them from laying eggs on the woad.
Anise hyssop with happy bee:
For pest control, I look for the little white eggs and caterpillars, and pick them off, but it can be hard to keep on top of this. The caterpillars are hard to see, especially when small. They are the same color as the veins on the woad leaves.
Here’s a small cabbage white caterpillar:
As they grow, they get much fatter and bigger, but they stay the same light green color. Here’s the cabbage white pupa as it is morphing into a butterfly:
Woad plant with holes from cabbage white chomping:
Woad is a biennial, which means its life cycle takes two years. It has a leafy phase of growth in its first year. The leaves are the part of the plant that produces blue. During its first summer and fall, you can harvest from the same plants several times.
Here’s a bed of woad ready to harvest:
If you wish to save your own seed, let the plants over-winter, bloom, and set seed the second year. You don’t need to mulch them over the winter. The basal rosettes will send up a tall stalk early in the spring with tiny bright yellow flowers. The flowers are powerfully, wonderfully fragrant and incredibly cheery. Woad is one of the earliest plants to flower in the spring around here, around the same time as the wild mustards.
Large bed of woad in bloom in May:
The flower stalks will set lots of large, wing-like seeds. They start out green:
They turn purplish-black when they are mature a few weeks later:
Often in the spring around here, it is too wet for the seeds to dry completely on the plant. This is especially problematic if the stalks flop over and the seeds get matted on the wet ground. You may need to stake the plants in the spring if you want to save seed.
The seeds are easy to dry and save. To dry woad seeds fully, cut the stalks when the seeds are mature, and hang them up to dry:
Then strip the seeds off the stems:
Mature woad seeds on one of my first Chinese woad plants:
If you do not wish to seed-save, you can dig up the plants in the winter before the ground freezes, or wait and dig them up in the spring before they bloom. The roots of healthy plants are huge, kind of like parsnips. I have never tried using second year leaves for getting blue, but I’ve read different things. Some sources say they still have the potential to produce blue, and others say they don’t. I have used second year leaves with the boiling water method on alum-mordanted wool, and have obtained purplish-gray and antique rose.
Woad - growing, harvesting and dyeing
I'm completely obsessed about woad. The plant is a relative of the cabbage and it creates a gorgeous blue dye. There's a long history of it being used in Medieval times and before. The great thing about it, is it grows well where I live with very little effort.
The blue dye in woad is the same as in Indigo. We have a lovely long thread about this dye and the plants that create it. But I thought, why not have a thread just for woad?
Indigo doesn't grow well where I live. It needs cosseting, extra irrigation, soil fertility and all sorts of added effort that I'm not interested in giving it. Even though Indigo is more efficient than woad - it produces so much more dye per weight of plant than woad - it is less efficient for me to grow indigo. I don't think that makes sense. But basically, for a tiny amount of effort, I can grow massive amounts of woad and get nearly unlimited blue dye while helping to break up compacted soil. For a lot of effort, I can grow a tiny amount of the more efficient indigo plants and get an itty bitty amount of blue dye.
I'm going to focus my energy on growing woad. Although I admit, I'm still getting to know this plant and what it can do. That's why I started a thread about it, so we can learn together.
My cute little baby woad plants from last spring. I started them indoors last March and planted them out when the frost started to lessen in early April. The ones I planted out after the last frost did better and gave me an extra harvest, so this year I'll plant them out later.
I grew my woad in an area with poor, excessively well-drained soil, and zero irrigation. They had no water or rain from May 1st through to October and did well. They thrived. I got three harvests from them, and could probably have gotten four more. But I wanted to leave the plants to gather energy and make seeds.
Harvesting the dye was interesting. The first attempted, I tried the extraction method which gives a blue powder that we can store and use later. One kilo of leaves gave me 1 gram of blue powder which (according to what I've read) dyes about 10 grams of fibre.
For the next harvests, I tried making woad balls. The leaves are mashed up and then shaped into a ball. The theory is that the balls ferment inside as they dry and convert the dye into a useable form.
What I liked best with this method is that it was purely mechanical. No heat, no excess water, no chemicals. This is a traditional European method and I'm looking forward to experimenting with woad balls this year.
How to harvest woad second year plants:
Harvest woad’s second year plants, to prevent self-seeding, by eradicating them. When you don’t want them to self-seed, the best method is to use a wheelbarrow and garden fork. You use the garden fork to loosen the roots and pull up the plants. The wheelbarrow contains the plants, and you can remove the leaves for your extraction vat with ease.
This also negates some of the need for speed with your indigo extraction vat. Since the roots are still connected, the leaves do not wilt and will lose the indigo precursors slower than if they were cut from the roots immediately.
After removing the leaves from second year plants, you want the plants to dry out. If you throw the newly uprooted plants into the compost pile they can re-root and cause self-seeding problems later. This is a good technique to use if you live in an area with invasive Isatis tinctoria landraces, as you can remove them and still get the dye.
Remember, don’t forget to record your harvest time and technique so that you can get similar results next time. This is important more in regards to general weather, and conditions, rather than exact dates.