Persicaria amplexicaulis – Firetail or Red Bistort – Firetail is also called Polygonum amplexicaule – Fire Tail and is part of the Polygonaceae family of plants. Persicaria amplexicaulis – Firetail is a clump forming herbaceous perennial. It grows to about 1 meter tall and produces tiny red flowers on spikes in summer and fall. You can plant it in any soil in the sun or partial shade. Propagate by division in spring and cut it back after flowering.