Poisonous Plants: A Garden Designers Guide

A Garden Designer’s Guide To Poisonous Plants

Poisonous Plants

On average, two gardeners a year die in the UK as a result of poisonous plants. There are poisonous plants lurking in almost every garden, dangerous to humans and animals alike. Many poisonous plants 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 especially 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 eat.

Even the humble potato is poisonous when raw and cooking will not eliminate the poisonous green parts. The milky sap of the beautiful euphorbias (spurge) will burn and blister skin and will send you to a 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.

Poisonous Plants for Pets

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. As is the exquisite blue Aconitum (monkshood), sometimes found growing wild in shady chalk soils.  Dainty, dancing aquilegias, and the stunning range of irises are also highly poisonous. So too are winter-flowering Lenten roses (hellebores). 

The delicate blue pulsatillas (pasqueflowers) 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.  Its brown seed pods contain shiny black seeds containing strychnine!

The delightful coloured 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 to, 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 all 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.

Common Poisonous Plants

Latin Name

Common Name

Poisonous Parts

Aconitum Spp.

Aconite

All

Agapanthus Orientalis

Agapanthus

Sap

Alder Buckthorn

Alder Buckthorn

 

Anthurium Spp.

Anthurium

 

Malus Sylvestris

Apple Tree

Seeds

Zantedeschia Aethiopica

Arum Lily

All parts, especially berries.

Asparagus Officinalis

Asparagus

Small red berries.

 

Autumn Crocus

All plant and bulb

Rhododendron Spp.

Azalea

All

Gypsophila Paniculata

Baby’s Breath

 

Helleborus Foetidus

Bearsfoot Hellebore

 

Fagus Spp.

Beech

 

Prunus Dulcis

Bitter Almond

Kernels

Robinia Pseudoacacia

Black Locust

All except flowers. The bark is very toxic.

Dicentra Spectabilis

Bleeding Heart

Foliage and Roots

Sanguinaria Canadensis

Bloodroot

All

 

Blue Bell

 

Echium Spp.

Blue Devil

 

Scilla Spp.

Blue Squill

 

Buxus Sempervirens

Boxwood

All

Cytisus Scoparius.

Broom

Seeds, especially if chewed before swallowing.

Aesculus Parviflora

Buckeye Bottlebrush

 

Euonymus Spp.

Burning Bush

 

Zantedeschia Aethiopica

Calla Lilly

Leaves

Menispermum Canadense

Canada Moonseed

 

Euphorbia Lactea

Candelabra Cactus

 

Euphorbia Lathyris

Caper Spruge

 

Lobelia Spp.

Cardinal Flower

 

Lobelia Spp.

Cardinal Flower Blue

 

Dianthus Spp.

Carnation

 

Gelsemium Sempervirens

Carolina Jessamine

 

Ricinus Communis

Castor Bean

All

Nepeta Cataria

Catnip

Stems and leaves

Apium Graveolens

Celery

 

Ranunculus Sceleratus

Celery-leaved Buttercup

All especially leaves.

 

Cherry

Kernels

Prunus Laurocerasus

Cherry Laurel

Kernels

Abutilon Hybridum

Chinese Bellflower

 

Abutilon Hybridum

Chinese Lantern

All

Toxicodendron Vernicifluum

Chinese Lacquer Tree

All

Sophora Japonica

Chinese Scholar Tree

 

Dioscorea Batatas

Chinese Yam

 

Solanum Pseudocapsicum

Christmas Cherry

All

Euphorbia Pulcherrima

Christmas Flower

 

Helleborus Niger

Christmas Rose

All

 

Chrysanthemum

Leaves and Stem

Clematis Spp.

Clematis

All

Symphytum Officinale

Comfrey

 

Helleborus Lividus

Corsican Hellebore

All

 

Cotoneaster

Red Berries

 

Cyclamen

Flowers

Narcissus spp.

Daffodil

Bulbs

 

Daphne

All but especially berries.

 

Day Lily

 

Delphinium spp.

Delphinium

All

Lilium Longiflorum

Easter Lily

Leaves, stems and flowers

 

Echium

 

Sambucus Nigra

Elderberry

All, especially roots and berries.

Alocasia Brisbanensis

Elephant Ears

All

Hedera Helix L.

English Ivy

Leaves and berries.

Taxus Baccata

English Yew

Foliage, Berries, bark, seeds.

 

European Spindle

 

Robinia Pseudoacacia

False Acacia

All except flowers. The bark is very toxic.

Festuca Arundinaceae

Fescue

 

Digitalis Purpurea

Foxglove

All including water from cut flowers

 

Geranium

 

Heracleum Mantegazzianum

Giant Hogweed

 
 

Gladiolas

 

Gloriosa Superba

Glory Lily

All, especially tuberous roots.

 

Hellebore

 

Ilex Aquifolium

Holly

Berries, Rest of Tree

 

Honeysuckle

All, specially Berries

Equisetaceace

Horse Tail

All

Aesculus Hippocastanum

Horse Chestnut

Buds, nuts, leaves, bark, seedlings, honey. Conkers

Hyacinth Orientalis

Hyacinth

Bulb

 

Hydrangea

 

Papaver Nudicaule

Iceland Poppy

All, especially sap.

 

Iris

Tubers

Hedera Heliz

Ivy

All including blackberries.

Euonymus Japonicus

Japanese Spindle Tree

Berries and Seeds

 

Jasmine

Sap and Berries

 

Juniper

 

Laburnun Anagyroides

Laburnum

Black Seeds if they are chewed or crushed.

 

Laurel

All

 

Lenton Rose

 
 

Leyland Cypress

 

Convallaria mejalis

Lily of the Valley

All

Lupinus Perennis

Lupìne

All especially pods with seeds.

Phoradendron Villosum

Mistletoe

Berries, leaves and stems

Aconitum Napellus

Monkshood

All, especially roots.

Ipornoea

Morning Glory

Seeds

Quercus Spp.

Oak Tree

Foliage and Acorns

Nerium Oleander

Oleander

All, if used as cut flowers water too.

 

Orange Day Lily

 

Solanum Spp

Ornamental Pepper

All

Pastinaca Sativa

Parsnips

 
 

Peace Lily

All

Philodendron Scandens

Philodendron

All, including roots.

 

Poppy

 

Solanum Tuberosum

Potatoes

All including tubers, sprouts and unripe berries.

Ligustrum Ovalifolium

Privet

Berries

Trifolium Pratense

Red Clover

All

 

Red Maple

Leaves, especially dried.

Quercus Rubra

Red Oak

Buds, young shoots, sprouts, acorns.

Rhododendron Simsii

Rhododendron

All

Rheum Rhabarbarum

Rhubarb

Leaves

Ruta Graveolus

Rue

 
 

Schefflera

 
 

Skunk Cabbage

 

Cotinus

Smoke Bushes

Sap in stems, shoots and leaves.

Symphoricarpos Albus

Snowberry Bush

Berries

Saponaria Officinalis

Soapwort

All especially seeds and roots.

Spartium Junceum

Spanish Broom

Seeds, especially if chewed before swallowing.

Euonymus Europaeus

Spindle Tree

Pink Fruits, All tree

Euphorbia Lathyris

Spurge Laurel

White Sap

Hordeum Jubatum

Squirreltail Barley

Seedheads

Senecio Jacobaea

Staggerweed

All

 

Star of Bethlehem

Bulbs

Iris Foetidissima

Stinking Iris

Orange seeds inside the fruit.

Toxicodendron Succedanea

Sumacs

 

Festuca Arundinacea

Tall Fescue

Seed head, stem and leaf.

Senecio Jacobaea

Tansy

All

Tulipa Spp.

Tulip

 

Catharanthus Roseus

Vinca Rosea

 

Parthenocissus Quinquefolia

Virginia Creeper

Berries, leaves.

 

Wild Cherrry

Leaves, Bark, Cherries

Prunus Serotina

Wild Black Cherry Tree

Twigs and leaves.

Helleborus Niger

Winter Rose

All

Wisteria Sinensis

Wisteria

All, especially seeds and pods.

Taxus Baccata

Yew

Foliage, Berries, bark, seeds.

For more information on poisonous plants or if you are looking to train as a professional garden design see our online courses here

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Duncan Heather

Duncan Heather is one of Europe’s foremost garden designers, to-date having won five gold, one silver & one bronze medal and three best of show awards for his design work. Duncan sat on the SGD council from 2004-7 during which time he was responsible for producing the first industry standard fee scale as well as instigating the publishing of the first standard contract.

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