Species of the Month: April 2025

Alexanders Rust Puccinia smyrnii

This rust fungus forms noticeable yellow galls on the leaves and stems of Alexanders (Smyrnium olusatrum, shown in photo below). The species is very often seen on the host plant, but it is under-recorded with just 54 records in the SEWBReC area.

Alexanders Rust is host specific, so is unlikely to be confused with any other species as long as the host plant is identified correctly. Alexanders is an umbellifer, a plant family characterised by their disc-shaped umbels, which are made up of many tiny flowers held on short flower stalks. There are many umbellifers in the UK, but Alexanders' yellowish green flowers make it fairly easy to identify. The plant is robust with a stout stem and dark shiny leaves. More information on how to identify Alexanders, can be found on Naturespot and WildFoodUK.

Alexanders traditionally has a coastal distribution, however it is becoming more widespread in the UK, likely spreading via salted road verges which simulate coastal conditions. There is also some association with castles and other historic sites, likely due to its previous use as a horticultural food plant. Alexanders can be found in much of the SEWBReC area; view a 1km distribution map for the SEWBReC area here. Alexanders Rust is fairly common on the host plant, but much less recorded; view a SEWBReC area map here.

You can see more images of Alexanders Rust on Naturespot and Plant Parasites of Europe. You can view Wales-wide distribution maps here: Alexanders Rust and Alexanders.

If you spot Alexanders Rust during April (or at any other time of year) please send us the record, ideally via SEWBReCORD or the LERC Wales App. Please also remember to record the host plant separately. Instructions on how to submit records are available here.