Some plants secrete a sap or fluid from their stems or leaves. At times these may cause an allergic reaction and therefore any maintenance, the use of gloves is advised.
Euphorbia crucifolia – Spurge – an interesting effect from spring to summer, an evergreen that is quick growing and perfect in well drained soil. It has attractive greenish yellow flowerheads. It has a common variety that can become quite invasive, Euphorbia des garrigues can become overwhelmingly settled and you have to entertain the milky sap too.
Hedera – An evergreen and a climber. The cultivated forms offer attractive variegated leaves, berries for winter and a stable habit for wildlife. Hedera helix – English Ivy and a cultivar Hedera colchica (Suphur Heart) it has been argued that Ivy doesn’t really smother other plants or trees – I disagree. By its habit and invasive nature it is a problem in the wrong place. Poison/Common Ivy contain a compound that irritates the skin and the ground is inert for anything else to grow for a period of time. Only Ivy.
Berberis thurburgeii startling results of reds, oranges and yellow in autumn. A versatile plant, has interesting leaves although will cause an allergic reaction when in contact with skin.
Rudbeckia – Black eyed Susan has coarse hairs along the stems that will temporarily be of discomfort. This dissipates quite quickly when cleaned off.
With Irises, care needs to be taken in dividing and transplanting the plants. The storage organ has toxic compounds that can permeate through the skin.
Aconitum carmichaelli or napellus are known not just to be an irritant but highly toxic. It difficult to confuse the dangers but infection could arise from a cut or broken skin so gloves are always advised.
Thistles and stinging nettles along with other abrasive plants (berries) will cause discomfort for a time. Giant hogweed can poses a risk and has damaging qualities although not usually left by others to become a problem.