Mighty Hogweed is Avenged.....

Turn and Run

There has been a lot of talk about the dangers of the Giant Hogweed plant taking over riverbanks and waste ground. The band Genesis warned of the impending invasion back on their Nursery Crime LP in the 1970’s, but I for one was too pre occupied with cleaning my chopper bike and fraying my flared jeans to listen. Now they are here with vengeance and as Gabriel stated “They are invincible. They seem immune to all our herbicidal battering”. Which isn’t entirely true, so what‘s all the fuss about?

What is it?

Giant hogweed is usually biennial, forming a rosette of jagged, lobed leaves in the first year before sending up a flower spike up to 4m high in the second year and then setting seed. True biennials only live for two years, dying after flowering, but giant hogweed does not always behave as a true biennial and in fact some are perennial, coming up year after year. The plant tends to grow in really inaccessible places.

Background

The giant hogweeds were introduced into Britain and Europe from the Caucasus Mountains in the nineteenth century. The earliest documented reference to their introduction was from the Royal Botanic Gardens Kew Seed List of 1817 where giant hogweed, under the name of Heracleum giganteum was listed among seeds supplied to Kew by the Russian Gorenki Botanic Gardens.

They were soon introduced into the horticultural trade, so were widely planted in ornamental gardens.  Unfortunately they quickly escaped from cultivation and came to Ireland in the 1880’s, and are now widely naturalised as invasive species throughout much of Britain and Europe.

Impressive

Although an impressive sight when fully grown, giant hogweed is invasive and potentially harmful. Chemicals in the sap can cause photodermatitis or photosensitivity, where the skin becomes very sensitive to sunlight and may suffer blistering, pigmentation and long-lasting scars.

The large leaves of the plant create sufficient shade to suppress indigenous herbaceous understorey plants along banksides.

OPW

Between 1998 and 2001 the Office of Public Works commissioned the Central Fisheries Board (now IFI) to conduct a four-year control/eradication programme in the Mulkear River County Limerick catchment area where Giant Hogweed was widespread and restricting angler access.  Colonies often presented continuous linear stands that extended up to 2km along the river bank.  The herbicide Glyphosate was applied to plants in a catchment-wide approach in March, May, July and September of each year. The application was similar to the Japanese Knotweed treatment where the stems were injected.

The control programme almost completely eradicated Giant Hogweed from the treated sites by the end of the four year study.  Native plants such as Butterbur (Petasiteshybridus) were able to re-establish in the area.

The facts: what does it look like?

• Giant hogweed (Heracleum mantegazzianum) is a close relative to cow parsley.
• It has thick, bristly, reddish-purple stems and can reach over 3m (10ft) in height.
• The flowers are white in a flat-topped clusters that can be as large as 60cm (2ft) across.
• It commonly grows on riverbanks and wasteland.
• Its leaves, stems, roots, flowers and seeds contain toxic components which can be transferred by contact and make exposed skin extremely sensitive to sunlight.

What to do if you come into contact

After coming into contact with the plant, the burns can last for several months and the skin can remain sensitive to light for many years.

If the sap of the giant hogweed comes into contact with your skin, it can cause severe, painful burns and make your skin sensitive to strong sunlight.

If you touch a giant hogweed, cover the affected area, and wash it with soap and water.

The blisters heal very slowly and can develop into phytophotodermatitis, a type of skin rash which flares up in sunlight. If you feel unwell after contact with giant hogweed, speak to your doctor.

Herbicidal Battering

Although there is no statutory obligation for landowners to eliminate giant hogweed, local authorities will often take action to remove infestations in public areas and it’s best to leave it to the professionals if there are a lot of plants.

First, consider whether this can be done using non-chemical means such as digging out or suppressing with mulch. Where these methods are not feasible, chemical controls may need to be used. Seek advice from the Environment Agency before undertaking spraying near rivers, streams and ponds.

When controlling giant hogweed always wear gloves, cover your arms and legs, and ideally wear a face mask when working on or near it. Cut plant debris, contaminated clothing and tools are potentially hazardous too. Wash any skin that comes in contact with the plant immediately. Ensure that contractors working on your land are aware of the risks and competent to deal with this weed. 

Strike by Night - Naturally

Consider if non-chemical controls are an option;

On a garden scale, appropriate measures include pulling up young plants by hand when the soil is moist. Do this in May when the giant hogweed has reached a reasonable height, but before it has produced its flowering spike. For larger plants it might be necessary to loosen the roots with a fork first.

Never let hogweed set seed, but allow the flower spike to form and then remove it before the flowers fade. At this stage, the plant is less likely to survive trimming than earlier in the year. Remember that perennial forms have been identified and preventing them from setting seed will not reduce giant hogweed populations quickly.

Giant hogweed prefers moist fertile areas often near waterways. It is essential that weedkiller never under any circumstances enters waterways. 

The seeds are viable for up to seven years so the natural method of eliminating the plant on a small scale would be to chop the plant down as they flower

Disposing of giant hogweed

Giant hogweed is a controlled waste (similar to Japanese knotweed) so, if it is taken off site, can only be disposed of in licensed landfill sites with the required documentation. To avoid this, dispose of any plant material (dug up or cut down) by composting or burning.

The smaller, native hogweed, Heracleum sphondylium, is not classed as controlled waste but should still be disposed of with care to avoid human contact.

“Mighty Hogweed is avenged. Human bodies soon will know our anger.” Why didn’t everyone listen to Genesis in the 1970’s? All of this could have been avoided.

Alternative Lawns

 Photo: Avondale garden one year after planting.

It’s the height of grass cutting season. I’m out there in the garden twice a week with my hover mower taking the top growth of the grass off before it gets too long to cut. Cutting grass isn’t the most enjoyable thing I do in the garden but I must confess there is a sense of satisfaction when it’s looking manicured and neat, in much the same way as tidying the house. It’s more a case of doing the job because I know it’ll take longer if I don’t keep on top of things and not because I love cleaning or cutting grass. 

Confession

I’ve even considered getting artificial grass in some areas and went as far as pricing some of this very environmentally unfriendly plastic  up the other week. It’s much the same as buying a carpet, and for the type of material that actually looks like grass and not something from the greengrocers table, it’s about the same price as a woolen Axminster too.  

Once the area to put the plastic grass is cleared of weeds, the sand (or underlay you could say) has been put in and the edging has been put in the artificial lawn could cost as much as €60 per square metre to lay. It wouldn’t be so bad if that’s all that was needed, but there is an annual maintenance of cleaning, weeding and brushing, so we might as well just stick to real grass unless you are in a penthouse apartment with a small patio area on the roof and can’t get the lawnmower in the lift.

Scrutiny

The idea of lawns is under scrutiny at the moment because it’s classed as monoculture and isn’t really of benefit to the environment once feeds and chemicals are applied, some people even resorte to sraying their dead grass with a green dye in summer. That and the fact they need watering and cutting uses up vital resources. The natural lifecycle of grass is to die off a lot in certain times of the year but we seem determined to keep it looking green all year. Things get more worrying when we realise the smell of freshly cut grass, so often comforting and nostalgic, is a chemical alarm call: a bouquet of fragrant volatile organic compounds that plants release when under attack. 

Real Alternatives

Alternatives such as Avondale park in London developed by Lionel Smith from reading University are totally grass free areas. You wouldn’t be able to play football on them though as they are made from soft-stemmed perennial plants that spread without using seed and live for longer than two years. Most of them have been grown in a greenhouse to give them a good start and have varieties such as red-flowered daisies (bellis), white-flowered buttercups (ranunculus) and bronze-leaved bugle (ajuga). None of the plants have needed to be watered since planting and no fertilizers are needed. The Grass-free lawns are planned not exceed 3.5in (9cm) in height, or they will turn into a meadow.

Research indicates that grass-free lawns can produce up to 90% more flowers, contain over 25% more invertebrate life, and support up to ten times as many visits from twice as many pollinator species as wildflower turf. Mowing is reduced by up to two thirds, rainfall can be absorbed up to twice as fast as a turf lawn and grass-free lawns need no chemical additives.- Ever.

The key to a good lawn made this way is that they can multiply with runners or roots, and that they're allowed time to knit and blend before the first cut.  This type of planting would only really be practical on small scale areas as it would be quite difficult to grow and maintain the amount of plants for a rural garden with an acre lawn. 

Going back

Going back a few hundred years, lawns were not expanses of unbroken green. Some medieval paintings of gardens depict carpets of turfgrass stippled with various flowers, such as lily of the valley, poppies, cowslips, primroses, wild strawberries, violets, daisies, and daffodils. People walked, danced and relaxed on these flowery meads, which were meant to imitate natural meadows. In the 15th and 16th centuries, we used white clover, chamomile, thyme, yarrow, self-heal (Prunella vulgaris) and other low-growing meadow and groundcover plants, sometimes mixed with grasses, to create lawns and pathways on which to walk and mingle.

For most of history, however, mixed plant lawns and non-grass lawns have been the exception, in part because a smooth, well-kept, lush grass lawn became as much a symbol as a functional part of the property. It’s not always practical to turn the garden into a vegetable plot either as this would take a lot of time and need maintaining far more than a lawn. 

So for now there probably won’t be too much change in our garden landscape so the poor old tortured grass will just have to stay.

Uncut Petunias and Willow Water

The uncut petunias are putting on a great show.

For the first time in years I didn’t take cuttings from my petunias and verbenas. Generally it’s the first thing I do when buying a tray of annuals. This year I thought I would just let them grow without any cost cutting intervention from myself. The results have been pretty amazing.   

Normally I would get at least four cuttings from each plant before I put it in a basket or container. Pinching the tips out also promotes bushier growth so I thought I was doing the plant a favour.  It turns out that what I usually ended up with were poor parent plants and even sadder looking rooted cuttings. I’m not sure if that’s a growing technique by the nurseries or just that I doubt give the plants a head start with the soil and rooting techniques. This year’s plants are doing me proud in their containers and both varieties of bedding are producing hundreds of rich coloured flowers. 

Rooting Cuttings

Charlotte Haworth from the permaculture institute had the same issue with her plants so looked up an age old recipe for a homemade rotting hormone to give new cuttings the best possible chance of growing into healthy specimens. Here she tells us how the potion is produced from young willow branches.

“There are many ways to propagate plants, which can be broadly divided into sexual and asexual. Taking cuttings is an asexual method, as your new plants will be clones of the mother. The method is simply to cut a new shoot from an existing plant and encourage it to take root itself. 

Natural rooting hormone

Many plants need a little help to grow roots, although some species can be planted straight into the ground. One of these is willow (salix) and an effective way of capturing the rooting hormone present in willow for use on other plants is to make willow water.”

This willow water recipe is based on one Charlotte learnt during her PDC at Permaship in Bulgaria.

Willow water recipe

Ingredients:

Fresh willow branches – use the very ends of the branches where growth is newest. Charlotte used a ratio of 100g of willow to 500ml of water.

Step 1: find a willow tree, and harvest the shoots

“You are only looking for the very tips on the branches, where the growth is newest. I cut about 10cm from the end of the branches of my weeping willow tree, the ones that were touching the ground.

You do not need many to make an effective rooting hormone. About five-ten 10cm branch-ends is plenty.”

Step 2: remove the leaves

“Cut all the leaves off the branches so that you are left with just the thin, springy shoots. The leaves can be discarded or, if you are that way inclined, dried for use as tea.  Weeping Willow, salix babylonica, is an especially potent species.”

Step 3: chop up the branches

“Now that you just have the branches left, chop them up very small and place them in a large bowl or container. Ideally the smaller the pieces of branch the better.” Charlotte left hers  a couple of cms long.

Step 4: watering the willow

“Now fill the container with water, so that all of your chopped-up bits of willow are completely covered. Place a lid of some kind on top of the container, and leave it to stand for about 2 nights, to allow all of the rooting hormone to soak out of the bits of willow and into the water.

If you are using a plastic container to soak the willow in, it is possible that some of the plastic will leach out and become present in the rooting hormone. However, this does not necessarily mean that the rooting hormone will not be effective.”

Step 5: decant the potion

“Once it has been left for a couple of days, separate the water from the branches using a sieve. Do not be alarmed if the resulting potion smells a little unpleasant; this is for plants to drink, not you, so there’s no need to worry.

Now the willow water is ready for use and you can put it into a bottle using a funnel.

Once you have the willow water in a suitable container, it can be kept for some weeks in a dry dark place, and up to two months if kept in a refrigerator.”

Using the Mixture

Charlotte experiments on Rosemary cuttings and after trimming the cutting, she gently dipped the ends into a capful of the potent mixture and planted them into soil. So far the results have been very promising with loads of healthy plantlets. 

Maybe next year this is what I’ll do with my petunias and verbenas.

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