Saint Catherine’s Lace, Giant Hogweed and virtual Hemlock

I was shaken from complacency recently after giving an innocent – I believe – plant to a friend who commented a few days later that I’d given him the virtual equivalent of Hemlock. And I could have, so I need to be more careful.

I bought seeds of Giant Hogweed (Heracleum mantegazzianum), or so I thought, a decade or more ago. Fortunately they were not! My seedlings grew into wonderful plants, 2m high, with many green branched stems holding aloft panicles of pure white Saint Catherine’s Lace flowers. But I never questioned the name. So I gave him one of these, labelled, wrongly, Giant Hogweed (with my usual enthusiasm). Wrongly, for it does not get to 4m, does not have red stems, has different leaves, does not have one central stem...

It’s important, too, because I read Heracleum mantegazzianum contains phytotoxic chemicals so even contact with the leaves, let alone the sap, can be a problem for some people. Obviously I have not had this potential skin blistering.

Should I start wearing gloves when I handle this Heracleum, and move the plants that are too near the path further away, to be cautious? Probably. Not just for visitors, or for J. The stems are hairy, and remind me of zucchini plant hairs (my sister is allergic) and of Primula hairs (I became allergic to Primula hairs the year I worked in a nursery, getting worse over time). Phytotoxic chemicals may be different to general allergens but are very serious. So...the plant by the path gets dug out immediately after it finishes flowering.

Now Heracleum sp., my Saint Catherine’s Lace – too large to be called a Queen Anne’s Lace – is still a wonderful plant for the garden with its size, exuberance and purity. It’s almost as wide as it is high and showing off its large umbels of delicate white flowers just now, in huge clumps.

It’s perfect in the large country garden.

Jill Weatherhead is horticulturist, writer, garden designer and principal at Jill Weatherhead Garden Design who lives in the Dandenong Ranges east of Melbourne, and works throughout Victoria (www.jillweatherheadgardendesign.com.au)