Some Poisonous, Injurious and Invasive Plants of Wilden Marsh
Wilden Marsh is in the middle of its injurious and invasive plant growing season right now, and I’m yet again attempting to control their spread. I like to encourage as wide a range of vegetation as possible on the marsh that is advantageous to fauna and the Reserve, as long as the injurious and invasive plants can can be controlled and the animals eating them are not being poisoned. It’s not the case that I’m trying to prevent injurious and invasive plants from escaping Wilden Marsh, its more a matter of controlling them once they get on to the marsh from surrounding areas. I’m not aware of any animals living on Wilden Marsh stupid enough to eat plants that are likely to kill them, but the risk is always present I suppose.
There are other plants on the marsh requiring care in handling, but those listed below are the main ones; at least they are the main ones that I can recall at the moment.
People ask why I always wear gloves when out on the marsh. Well, apart from protecting my hands from biting insects and many kinds of stabbing thorns and spiral viruses, they protect me from some of the following:
Japanese knotweed (Fallopia japonica): is one of the world’s most invasive species. Its invasive root system and strong growth can damage concrete foundations, buildings, flood defences, roads, paving, retaining walls and architectural sites. It can also reduce the capacity of channels in flood defences to carry water. Believe me, you don’t want this plant growing in your back garden, although many people do without knowing it. We don’t have Japanese knotweed on Wilden Marsh now, but we have had and it is growing close by.
Japanese knotweed has a large underground network of roots (rhizomes). To eradicate the plant the roots need to be killed. All above-ground portions of the plant need to be treated repeatedly for several years in order to weaken and kill the entire patch. Picking the right herbicide is essential, as it must travel through the plant and into the root system deep below ground level.
Himalayan balsam (Impatiens glandulifera): is extremely invasive. This balsam has been brought under control on Wilden Marsh through grazing, but it would quickly return with a vengeance if grazing was ever to cease here. Hoo Wood ridge is heavily carpeted with Himalayan balsam.
Spear thistle (Cirsium vulgare): the UK Weeds Act 1959 classifies the spear thistle as an injurious weed. Nitrogen-rich soils promote its spread. The flowers are a rich nectar source for honey bees, wool-carder bees, and many butterflies. The seeds are eaten by goldfinches, linnets and greenfinches. The seeds are dispersed by wind, mud, water, and possibly by ants; they do not show significant long-term dormancy, most germinating soon after dispersal and only a few lasting up to four years in the soil seed bank. Seed is also often spread by human activity such as hay bales. Spear thistles spread very quickly on Wilden Marsh; I cut them manually in July in an attempt to control their proliferation.
Creeping thistle (Cirsium arvense): is a perennial species of flowering plant in the family Asteraceae, native throughout Europe and northern Asia, and widely introduced elsewhere.
Like other Cirsium species, the roots are edible, though rarely used, they induce flatulence in some people. The taproot is considered the most nutritious part. The leaves are also edible, though the spines make their preparation for food too tedious to be worthwhile. The stalks are edible and more easily despined. Bruichladdich distillery on Isle of Islay lists creeping thistle as one of the 22 botanical forages used in their gin, The Botanist.
The feathery pappus is also used by the Cherokee to fletch blowgun darts.
As with spear thistles, I like to control their spread of all thistles with manual cutting and grazing. I follow the maxim: “Cut the thistle in May and it will grow back in a day; cutting in June is a month too soon; cut it in July and it will die.”
Blackthorn (Prunus spinosa): the shrub, with its savage thorns, is traditionally used in Britain and other parts of Northern Europe to make cattle-proof hedges. If you are unfortunate enough to be pricked on the hand by a blackthorn, it can swell up alarmingly quickly and the puncture is likely to fester without treatment. The surface of the thorn is coated with bacteria specifically designed to cause pain and inflammation; it’s one of the blackthorn’s protection mechanisms to ward off grazing animals.
The fruit is similar to a small damson or plum, suitable for preserves, but rather tart and astringent for eating, unless it is picked after the first few days of autumn frost. This effect can be reproduced by freezing harvested sloes.
The juice is used in the manufacture of fake port wine, and used as an adulterant to impart roughness to genuine port. In rural Britain a liqueur, “sloe gin”, is made by infusing gin.
The foliage is sometimes eaten by the larvae of Lepidoptera, including the small eggar moth, emperor moth, willow beauty, white-pinion spotted, common emerald, November moth, pale November moth, mottled pug, green pug, brimstone moth, feathered thorn, brown-tail, yellow-tail, short-cloaked moth, lesser yellow underwing, lesser broad-bordered yellow underwing, double square-spot, black and brown hairstreaks, hawthorn moth (Scythropia crataegella) and the case-bearer moth Coleophora anatipennella. Dead blackthorn wood provides food for the caterpillars of the concealer moth Esperia oliviella.
I do as little as possible to control blackthorn, and I am very careful when working on or close to it. I’ve learned through painful experience, as have the marsh cattle.
Broad leaf docs (Rumex obtusifolius): broad-leaved dock is designated an “injurious weed” under the UK Weeds Act 1959. Leaves of the plant can be used as salad, to prepare a vegetable broth or to be cooked like spinach. They contain oxalic acid which can be hazardous if consumed in large quantities. Dried seeds are used as a spice. In Romania, the leaves are sometimes used as an alternative to other plants in the making of sarmale: a tea prepared from the root was thought to cure boils. Some research has shown a clear link between increasing dock populations and high levels of soil potassium, but other studies conclude that increasing the potassium status does not favour docks.
A large mature broad-leaved dock can produce up to 60,000 ripe seeds per year, and seed numbers in soil have been estimated at 5 million per acre. The seeds contain a chemical that inhibits microbial decay and are capable of surviving in undisturbed soil for over 50 years.
On Wilden Marsh broad leaf doc is gaining ground, and the more it is cut down the stronger it grows. I manually cut the plant to reduce seed spread. The marsh cattle rarely eat doc. Ideally, the doc plant and its roots should be pulled up.
Ragwort (Jacobaea vulgaris): is an injurious species and host plant of the cinnabar moth caterpillar and seven micromoths. Ragwort provides a home and food source to around 170 insect species in all: . This plant is in the top ten of nectar producing plants and a major source of nectar for at least thirty species of solitary bees and eighteen species of solitary wasps. Thirty species of invertebrate use ragwort exclusively as their food source – seven of these are officially deemed Nationally Scarce.
Ragwort is considered biennial, but acts like a perennial on Wilden Marsh, requiring constant annual pulling to control it. I try to pull them prior to it seeding. The weed is pollinated by a wide range of bees, flies and moths and butterflies. Over a season, one plant may produce 2,000 to 2,500 yellow flowers, and the number of seeds produced may be in the region 75,000 to 120,000.
Ragwort contains many different alkaloids, making it poisonous to certain animals. The danger of ragwort is that the toxin can have a cumulative effect. The alkaloid does not actually accumulate in the liver but a by product released during its breakdown can damage DNA and progressively kills cells. The effect of low doses is lessened by the destruction of the original alkaloids in the gut before they reach the bloodstream. There is no known antidote or cure to ragwort poisoning. The alkaloids can be absorbed in small quantities through the skin but studies have shown that the absorption is very much less than by ingestion.
The marsh cattle leave growing ragwort alone because of its bitter taste I suppose. I make sure never to cut the weed and to remove it by pulling only. Ragwort must be disposed of well away from the cattle, as it remains poisonous if consumed: the bitter taste might reduce during the process of drying out.
In ancient Greece and Rome a supposed aphrodisiac was made from the plant; it was called satyrion.
Common Hogweed (Heracleum sphondylium): commonly known as hogweed, common hogweed or cow parsnip, is a herbaceous perennial or biennial plant, in the umbelliferous family Apiaceae that includes fennel, cow parsley, ground elder and giant hogweed. It is native to Europe and Asia.
H. sphondylium is smaller than the more dangerous Heracleum mantegazzianum (giant hogweed), and the two should not be confused. However, it contains some of the same phytophototoxic compounds (furanocoumarins), albeit at lower concentrations, and there is evidence that the sap from common hogweed can also produce phytophotodermatitis (burns and rashes) when contaminated skin is exposed to sunlight. Care therefore needs to be used when cutting or trimming it, to prevent ‘strimmers rash’.
Giant hogweed (Heracleum mantegazzianum): the sap of the giant hogweed plant is phototoxic; when the contacted skin is exposed to sunlight or to ultraviolet rays, it can cause phytophotodermatitis (severe skin inflammations). Initially, the skin colours red and starts itching. Blisters form as it burns within 48 hours. They form black or purplish scars that can last several years. Hospitalisation may be necessary. It is said that is sap gets in the eye, it can cause permanent blindness. One giant hogweed plant popped up on the south marsh last year and a cow ate it, saving me the trouble of dealing with it. Another giant hogweed plant has appeared in the Falling Sands Nature Area.
Giant hogweed was more plentiful on Wilden Marsh six years ago, but prompt action in dealing with them quickly solved the problem. However, relax your vigilance and you find that they are popping up far too regularly for comfort.
Hemlock (Conium maculatum): is a poisonous herbaceous biennial flowering plant, a member of the carrot family, that grows to a height of 1.5-2.5 m (5-8 ft), with a smooth, green, hollow stem, usually spotted or streaked with red or purple on the lower half of the stem. All parts of the plant are hairless; the leaves are two-four pinnate, finely divided and lacy, overall triangular in shape, up to 50 cm (20 in) long and 40 cm (16 in) broad. The plant is often found in poorly drained soil, particularly near rivers, streams, ditches and areas of standing water. It also appears on roadsides, edges of cultivated fields and waste areas.
Conium maculatum is the plant that killed Theramenes, Socrates and Phocion. In ancient Greece, hemlock was used to poison condemned prisoners. Socrates, the most famous victim of hemlock poisoning, was accused of impiety and corrupting the young men of Athens in 399 BC, and his trial resulted in a death sentence. Although Socrates could have avoided death, he decided to take a potent infusion of the hemlock plant. Plato described Socrates’ death in the Phaedo.
It has been said that poisoned animals tend to return to feed on the plant. Chronic toxicity affects only pregnant animals; when they are poisoned by C. maculatum during the fetus’ organ-formation period, the offspring is born with malformations, mainly palatoschisis and multiple congenital contractures (arthrogryposis). Chronic toxicity is irreversible; though arthrogryposis may be surgically corrected in some cases, most of the malformed animals die. Such losses may be underestimated, at least in some regions, because of the difficulty in associating malformations with the much earlier maternal poisoning.
Small stands of poison hemlock can be controlled through hand removal. Plants should be dug, taking care to remove the entire long taproot. Plant parts should be disposed of responsibly, as plant parts remain poisonous even after dried. Gloves should be used when handling all parts of the plant, and hands should be washed thoroughly afterwards. Disturbance of the soil during manual control may cause the germination of any hemlock seeds in the soil, so the area should be monitored to control any new seedlings.
There is a lot of hemlock growing on Wilden Marsh.
Foxglove (Digitalis purpurea): Due to the presence of the cardiac glycoside digitoxin, the leaves, flowers and seeds of this plant are all poisonous to humans and some animals, and can be fatal if ingested.
Digitalis toxicity (Digitalis intoxication) results from an overdose of digitalis and causes nausea, vomiting and diarrhoea, as well as sometimes resulting in xanthopsia (jaundiced or yellow vision) and the appearance of blurred outlines (halos), drooling, abnormal heart rate, cardiac arrhythmias, weakness, collapse, dilated pupils, tremors, seizures, and even death. Bradycardia also occurs. Because a frequent side effect of digitalis is reduction of appetite, some individuals have used the drug as a weight-loss aid. I don’t need to do anything to control foxgloves, but it’s best not to absent mindedly nibble on this plant.
English Bluebell (Hyacinthoides non-scripta): Even the beautiful common bluebell has a sting in its tail: it’s poisonous!
Bluebells synthesise a wide range of chemicals with potential medicinal properties. They contain 15 or more biologically active compounds that may provide them with protection against insects and animals. Certain extracts, water-soluble alkaloids, are similar to compounds tested for use in combating HIV and cancer. The bulbs of bluebells are used in folk medicine as a remedy for leucorrhoea, and as a diuretic or styptic, while the sap can be used as an adhesive.
In the UK, H. non-scripta is a protected species under the Wildlife and Countryside Act 1981. Landowners are prohibited from removing common bluebells on their land for sale and it is a criminal offence to remove the bulbs of wild common bluebells. This legislation was strengthened in 1998 under Schedule 8 of the Act making any trade in wild common bluebell bulbs or seeds an offence, punishable by fines of up to £5,000 per bulb.
There are quite a few so called “everyday plants” that are poisonous, but many people are unaware of the danger so don’t worry about it. I suppose ignorance is bliss. Daffodils, for instance, are highly poisonous. The world outside the safety of our homes is a dangerous place.