Sow Thistle (Prickly) (Prickly Sowthistle, Field Sowthistle, Perennial Sow Thistle, Spiny Sow Thistle)

There are 130 species of Sow Thistle (Sowthistle), some with spiny leaves and some with smooth leaves.  All can readily readily soak up nitrates from the soil, and in large quantities nitrates may reduce the oxygen carrying capacity of the blood.  If the Sow Thistles are growing on nitrogen-rich soil (e.g. soil that has had chemical fertilisers added, or rich potting compost) then feed in small quantities only, but if grown on poor soil then they are safe to feed.  See also Sow Thistle (Smooth).