Update 2020: WE have now created a video showing how to tell your male and female flowers apart
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We LOVE nettles. They are an absolutely fantastic super-food, super-medicine, abundant, native (in UK at least) and they're free! What more could you ask for? The young leaves are protein rich and great additions to soups/stews, and the seeds are used by herbalists for a nutritious energy boost in people with burn-out. If you want to skip straight to recipes, here is a link to nettle soup, and one for nettle oatcakes.
In this blog there are a few notes about:
the best time to harvest the seeds and leaves,
seed gathering: the identification of the male and female plants of common nettle so you can gather the seeds effectively - because they are only produced by the female plants and not the males
the identification of the 3 main species of nettle found in the UK, and what isn’t a nettle.
Leaf harvest
nettle leaves: a young fresh spring leaf on the left, on the right is tough, stingy leaf that can be found after flowering. These are representative, do'n’t worry if yours don’t look like that, the idea is to recognise fresh, edible leaves vs stringy old tough ones.
Yummy nettle leaves are best gathered for eating or for making tea at two times in the year, when they are still fresh, green and tasty looking and BEFORE they have flowered:
in spring
in late summer/early autumn (IF they have been cut back, there will be a 'second flush' of fresh leaves).
Pick the top few leaves when the plant is of a good size, leaving the lower down ones alone. Once the nettles have started to flower, the leaves are traditionally no longer used - they are said to contain insoluble calcium carbonate crystals that are hard to flush out of the body, can build up in the kidneys and give you kidney/back pain, particularly if you are prone already to kidney infections or have kidney troubles... theoretically, if you had loads, you could create kidney stones. In addition, when they flower, all the 'goodness' and energy of the plant is now directed to creating the best flowers and seeds they can, and the leaves are now neglected, dry, tough and stingy - so why would you want them anyway?
Seed harvest
However, no need to ignore nettles completely once the leaves are over - the seeds are edible and medicinal. Common nettle is the best to harvest seeds from (easier to collect and more abundant in the hedgerow) but the scientific name reveals a problem: (Urtica dioica) dioica = dioecious 'two houses' which means they have separate female and male plants.
So, the males produce pollen to fertilise the female plants which in turn then produce the seeds. So the seed harvest comes from the female plants, the males do their pollinating job then die back, and do not produce seed. The harvesting problem arises because they can be tricky to tell apart - both male and female plants have similar looking 'strings' of flower clusters hanging from their 'armpits' or leaf axils. I have noticed a few blogs making the very easy mistake of putting up pictures of the 'seeds' but have misidentified the male flowers.
It is important to be able to ID the seeds properly or you won't be getting the medicinal benefits from them.
The male/female flowers are edible too, but just not full of all the nutritional goodies such as protein and good fats that the nettle seeds contain. It would be like eating an almond blossom instead of the actual almond. which one will give you more nutrition?
Male id: female id
The male and female plants tend to grow together in large clumps, sometimes in clearly defined female and male sides to the patch, so look at a large patch and start observing. Males have comparatively stringier flower clusters that overall tend to point across or up at the ends, whereas the female clusters overall hang pointing down (this is exacerbated more when heavy with seed - they will be really laden down and be much more chunky than the male flowers).
To get your 'eye in' , I recommend you sit with a very large nettle patch for a couple of hours in high summer on a hot, sunny day - this is because the male flowers open with an (inaudible) pop and fling out their stamen and pollen into the wind. This is best seen in sunlight to see the powdery pollen drifting by. Then once you can identify these little clusters of male flowers with four stamen pointing out the corners, you can look across to the female plants and view their fluffy stigmas which gives them a frosty, brushy look designed to catch the pollen out of the wind. See pictures below.
EDIT: June 2018: After many years of observing, I finally came across a stand of nettle plants that had both male and female flowers on them!After research, I discovered that some rarer subspecies (U. dioicia subsp. gracilis or U. dioicia subsp. dioicia) do have monoecious types with both male and female on the same plant. Here is a paper on the occurrence
Just remember the seeds look like little bishops hats so if you have those, you have seeds. On this species you'll find the males at the top of the stem, with fat clusters of female seeds below.
Male flowers. They look like little pumpkins when closed. The close-up picture on the right shows an open flower with curled in stamens (white, upper flower) and below that, a translucent flower with the stamens un-flung and pollen dispersed. These will not produce the edible seeds, only the pollen.
Fluffy, frosty anenome-like female flowers catch pollen out of the air. Picture Wikimedia Commons
Nettle seeds
So - Seed ID: the seeds grow on the female plant. They are encased in what looks like green bishops hats (mitres) gathered in funny geometric clusters and are best gathered when green. Once brown and dry, the seeds are of no use. Also, when you pick them green, they don't keep their properties well if you try to dry them as their oils go rancid quite quickly, so they are best used fresh. However, you can dry them for up to a year or keep them for a short time in an airtight container in the freezer (up to 3 months).
To gather your seeds, just snip off the strings into a bag or cut down the nettle tops, tie upside down inside a linen bag and give them a good shake to get them out! Others suggest pressing them through a seive too. They can be a bit tricky to get at but very worth it.
Nettle seeds in cases from the female plant - looking like bishops mitres.
Seed uses
The seeds of nettle contain essential fatty acids Omega 3 oils and are used by herbalists to support kidney and adrenal function and as a boost when over worked adrenals impacts on energy levels. How this works is not clear, but two papers have looked at the liver and kidney protecting effects based on the traditional use and can be viewed here: 1 & 2. Horse salesmen used to give nettle seeds to horses for a few weeks before sale as it would give them glossy hair and a youthful, energetic manner, so there must be something to learn from them.
Christina Stapely, a historical herbalist finds making an ointment with the seeds gives a mild warming sensation that is more 'convenient' for those who may want to try urtication therapy (stinging affected joints with nettle leaves)for reducing the symptoms of osteoarthritis. Let us know if you try it!
Bonus Info for botany geeks - here's a quick identification of the three types of nettles
This section is about identifying between the differnt UK nettles(Nettle family Urticaceae). Most people know what nettles look like and if you aren't sure - touch it, you'll soon find out!
Roman Nettle (Urtica pilulifera) ball-like flower clusters.
Dwarf nettle (U. urens) is a smaller compact plant with smaller compact leaves! The urens part means 'burning' so they are said to have a stronger sting. This plant is on the point of growing flowers.
The three main types you will come across if you look really hard are the Common (Urtica dioica), Dwarf (U. urens)and Roman (U. pilulifera).
The common nettle, as described before, is the one most likely found around the hedgerows followed by the dwarf nettle. The dwarf nettle has much smaller, darker leaves arranged in a distinct compact stepping way (see picture). Find it in disturbed ground e.g. around allotments.
The Roman nettle (U. pilulifera) is very rare - it hasn't been spotted recently by the BSBI and I have personally seen only once on a rubbish dump in Kew Gardens, but it was said to have been introduced to the UK by the Romans to keep warm in the winter using urtication (beating themselves with the stings to increase circulation). It has very specific looking balls of flowers/seeds (see picture), so I thought it worth mentioning. If you ever spot it, let me know!
Both the Roman and dwarf nettles do not have separate female and male plants unlike the dioecious U. dioica, instead both sexes of flowers grow on same plant and are called 'monoecious'.
On another side note, the common nettle also has a sub species called 'fen' or 'stingless nettle' (Urtica dioica subsp. galeopsifolia) so if you ever find a plant you are convinced is nettle but doesn't sting - it could be that one.
White deadnettle (Lamium album): No stings and white flowers. Other deadnettles have pink or yellow versions.
Don't confuse nettles with dead nettles: They may have a similar leaf, but don't be fooled, they are in a totally different family - the mints (Lamiaceae). They have red, white and pink 'hoodie' shaped flowers which are arranged in a whorl around the stem. The leaves don't generally look as sting-y or as crimpled/3D as true nettle leaves either and are unpleasantly aromatic when crushed. Though they are edible, they won’t give you the benefits of true nettle. Foraging is about getting your eye in for the different species you may come across, so keep checking and comparing as you go out and about.
Happy botanising! Kim x
Remember that nettles provide an important source of food and a home to lots of wildlife, so please check your plants for caterpillars and eggs before gathering, and leave plenty of plants for them too.