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The Wicked Garden 1: Poisonous Plants

A Garden Designer’s Guide To Poisonous Plants


There are dangers lurking in almost every garden, and even in the conservatory - dangers to humans, animals, birds and beneficial insects. They are also evident in the wider countryside, along hedgerows, in innocent-looking streams and in woodlands. One such danger is that of poisonous plants, many of which are far from obvious except to the expert. Those discussed in this blog are by no means exhaustive, but illustrate a range of concerns that should be foremost in the designer's mind. You need always to be sensitive to these dangers, whoever your clients may be and unquestionably if they have young children, or pets. Awareness is also in the interests of your own health and safety when designing and working with plants.

A surprisingly large percentage of plants are toxic or poisonous to handle, or to eat. The humble potato is poisonous raw and cooking will not eliminate the poisonous green parts, which should always be discarded. The milky sap of the beautiful euphorbias (spurge) will burn and blister skin and will despatch you to hospital if you should get it into your eyes. Always make sure that your clients know they should wash their hands and those of their children, after handling plants or playing in the garden.


If ' mushrooms' appear in the lawn they are probably not the edible fungus that is tray packed in the supermarket. Don't eat them. Some of the most bewitching plants are the most deadly and therefore particularly dangerous to small children who want to pick 'the pretty flower' and even put it in their mouths. Digitalis (foxgloves) with their purple, pink, yellow and white flowers are attractive to bees but poisonous to humans. The tender and exquisite blue aconitum (monkshood), sometimes found growing wild in shady chalk soils, dainty, dancing aquilegias, and the stunning range of irises – all are poisonous. So too are winter-flowering Lenten roses (hellebores), the delicate blue pulsatillas (pasque flowers) and moisture-loving, spring flowering, golden Caltha palustris (kingcups), often planted at the margins of ponds and found growing wild in wetland meadows.

There are several trees with poisonous fruits, flowers or berries, the most well-known being laburnum (golden chains). With its gorgeous, abundant, pendulous yellow flowers it has been an extremely popular garden tree, but its brown seed pods contain shiny black seeds – poisonous!

The delightful red yellow and orange berries that the birds love are frequently poisonous to humans , including those of the silver-leaved Hippophae rhamnoides (sea buckthorn). In wilder or untended parts of the garden there will almost certainly be familiar stinging nettles, and hogweed, which will blister and irritate the skin.

If garden boundaries abut pastures where sheep, cattle or horses graze, not only should these boundaries be stock proofed, but beware of planting poisonous hedging or other plants that can be reached by inquisitive livestock – they will lean over, pluck and chew indiscriminately on anything that looks enticing within a metre of the boundary. The leaves and fruits of conifers such as Juniperus (juniper) are poisonous to cattle and humans. So too the wonderful Taxus (yew) which forms such a marvellous, dense hedging and is invaluable in the creation of formal gardens There are many other shrubs and perennial weeds that are toxic to cattle and horses – ragwort, seen too often in neglected fields, common ligustrum (privet) hedging and hedera (ivy) are just a few.

Be a responsible designer and check online for a number of excellent books on poisonous plants.

Article by Sue Hook

Does Form Follow Function?

Function and form

Garden & Landscape Design

A long term and continuing debate has been whether form follows function, or function follows form. Initially, as a trained artist, but as a novice, student designer I felt instinctively - and arrogantly - that the function, or functions of the garden could follow its form; in other words I would be able to design the ground patterns and layout I wanted for various areas and could then translate these into a garden that fulfilled the functions required by the (at that point theoretical) client.

Garden & Landscape Design

This approach is not entirely without merit and remains a luxurious possibility if you are fortunate enough to be presented with a completely blank canvas, a rather large working space and a big budget. However I discovered very quickly that most sites - with the occasional exceptions of brand new estate gardens - are not blank canvases, but almost always possess existing features, furniture and conditions that necessarily must be incorporated into a new design, in addition to the wish list of the client. The smaller the garden the more demanding it is in this regard and even if empty will already present its own peculiarities and limitations that cannot be ignored.

Garden & Landscape Design

So I realised that the job of the designer – as distinct from the artist – is to create something that performs its function as perfectly and beautifully as possible. The artist's interpretation of a subject is usually less limited by practicalities, other than those of the medium and materials used. The artist also usually does not have to please anyone but himor herself and so can be controversial and even outrageous . That is why art can be ahead of its time. As a designer you can push the boundaries, indulge in blue sky thinking and introduce innovative ideas, but the bottom line is that the garden must be functional – as a place of quiet reflection and retreat, a source of food, a space for entertainment, play and recreation, storage and utility, all according to your client's needs. It is they who will be paying for, maintaining and using the garden long after you have left.

Garden & Landscape Design

Without any design training it is perfectly possible to achieve all the functional requirements of a garden without one iota of aesthetic consideration. However the resulting garden will not be attractive and will certainly not have the 'wow' factor. Fulfilling these disparate requirements whilst making a garden that is beautiful to behold is the challenge which only a good designer can meet. And this same challenge epitomises the rule of thumb that I subsequently understood – that form follows function.


Article by Sue Hook


Fence Design

Fences: How to Specify & Design Enclosure


Fences can have multiple functions. In addition to defining boundaries they can act as wind breaks, screen unsightly structures or views, create privacy, support climbing plants, and be features in their own right as decorative backdrops to planting. They can be as low as 50 or 60 centimetres, to enclose raised vegetable or formal beds, or above 1.8m high.


If you are designing fencing you must check if there are any planning restrictions on height, or positioning, or if neighbouring properties are likely to be adversely affected. Check the deeds of the property or any documentation such as an official survey, to establish on which side of the fence responsibility for maintenance or replacement lies.


Fencing that is erected by builders and developers frequently comprises unimaginative close board panels, supported by ugly concrete posts. The majority of fencing timber is also rough-sawn, pressure-treated softwood, lacking any defining or attractive features. The fence panels are too often a garish orange-brown, being heavily impregnated or surface painted with chemical preservative.


Solid fencing is a poor windbreak, causing turbulence on the leeward side, which can damage plants. Unless the fence faces south the adjacent soil will also be colder. Being unable to dissipate the force of the wind badly supported panels can collapse after a gale hits them. Much more pleasing supports are made of timber, set into a concrete base and with post caps to minimise ingress of rainwater.


These posts should carry a guarantee against rot, warping or splitting of up to twenty five years. However, your clients may be completely impervious to the negative impact that closeboard fencing has on a garden space, especially a small garden. Some clients may even be delighted with their clean new fence and its white concrete posts. It is therefore up to you , as designer, to open their eyes to alternative solutions, without necessarily demolishing the entire fence. A mood board is a useful tool in helping clients visualise such possibilities.


It's depressing to see that the shelves in DIY stores and builders' merchants that are devoted to exterior timber finishes are still dominated by large cans of timber preservative in three shades of brown – in effect dark, medium and light, though they may be termed oak, chestnut etc. There are more interesting exterior finishes on the market but you, the designer have to bear in mind that these are still relatively costly for coverage of large areas of fence and in the context of a small budget you must decide whether you can justify the expense.


Painting fencing in quiet colour s will reduce its visual impact but you will still be left with the wind-rock/turbulence problem. Perforated or trellis panels spread the force of the wind and look pleasant, if unexciting, even left unpainted.


Willow or hazel hurdles can form attractive short-term fencing in the right setting. Planted, woven willow whips will quickly sprout foliage and develop into a living fence. However you must also bear in mind the required longevity of the fence and also whether it needs to keep out neighbouring dogs and/or deter intruders.

Article by Sue Hook