Some common Garden plants with TOXIC flowers

Every country has differing native plants  that were known to the medicine folk.  When introduced to other countries their restriction on usage were forgotten.   As a result people have major illness, allergies and have effectively been poisoned.  Using these or any other plants with these in tension is not recommend or encouraged with this list.
Scientific name	Common names	Scientific name	Common names
Achillea millefolium	Yarrow, milfoil	Lantana camara	Lantana, red sage, shrub verbena
Anconitum spp.	Monkshood	Lathyrus spp.	Sweet pea (seeds)
Clematis spp.	Clematis, virgin's bower	Lobelia spp.	Cardinal flower
Colchicum spp.	Crocus	Narcissus spp.	Daffodil, jonquil
Convallaria majalis	Lily of the Valley	Nerium oleander	Oleander
Daphne mezereum	Daphne	Nicotiana spp.	Flowering tobacco
Datura spp.	Jimson weed	Papaver somniferum	Opium poppy, common poppy
Delphinium spp.	Larkspur	Phoradendron spp.	Mistletoe
Dicentra Formosa	Bleeding heart	Physalis spp.	Chinese or Japanese lantern
Digitalis purpurea	Foxglove, digitalis	Rhododendron spp.	Azaleas, rhododendrons, rose bay
Euphorbia spp.1	Euphorbia	Ricinus communis	Castor bean, African coffee tree
Hippeastum spp.	Amaryllis	Zantedeschia aethiopica	Calla lily
Hyaninthus spp.	Hyacinth	Zigadenus spp.	Death camas, alkaligrass, wild onion
Jasminum spp.	Jasmine

¹Poinsettias are not considered poisonous, but they are not edible. If eaten, all plant parts may cause varying degrees of mouth irritation and vomiting, but not death. The cultivated rubber tree Heavea brasiliensis, Manioc or cassava (Manihot), and Castor bean (Rincinus) are close relatives, which are poisonous. With its close genetic ties to the rubber tree, which is where natural latex is derived, those who are sensitive may also be sensitive to the latex from poinsettias.

Altered from http://www.ext.colostate.edu/pubs/garden/07237.html