Italian arums – fantastic late foliage

Invasive man’s excellent Invasive Plants in Arlington blog (that’s Virginia, near Washington DC, for you Brits) recently highlighted a plant that may well prove a problem in his area. Italian arum, Arum italicum, is a delightful foliage and fruiting plant which he notes has appeared in the park at the Long Branch Nature Center and he’s worried about it becoming invasive. He may be right to be concerned, it could well prove to be a problem there, but his observation also highlights the fact that citing a plant as invasive is, well, not cut-and-dried.

Both in my garden in Northamptonshire, England, and up here in north east Pennsylvania I’ve been growing a number of cultivars of Arum italicum – indeed this is quite a hot plant with new introductions appearing in mail order nursery lists every year. Seneca Hill Perennials, from where a number of mine came, has an especially good range. They’re invaluable tuberous-rooted perennials, with beautifully patterned foliage in fall and winter followed by fat spikes of sparkling red berries. ‘White Winter’ is a firm favorite in Britain and growing in popularity in North America too.

Arum italicum is a rare British native and, in gardens, the brightly white-veined, arrowhead-shaped foliage is a feature all winter. It’s also escaped from gardens outside its native range on the British south coast but is never a problem. Here in Pennsylvania in zone 5, many forms seem to be hardy in the garden which is perhaps a surprise for a plant centered on a Mediterranean distribution; Britain, in zone 8, is at the northern edge of its range.

But a recent dramatic overnight temperature drop to 0F/-18C has separated the men amongst the cultivars from the boys here in PA. Most looked pretty sad on that chilly morning with their foliage flat on the ground but have perked up well. ‘McLement’s Form’, photographed yesterday, is especially well marked with black spots as well as bold white veins and has recovered well. ‘Gold Rush’ features additional yellow markings on large leaves and still stands out. ‘Jet Black Wonder’, from Plant Delights, however, has never recovered and most of its foliage remains collapsed even after yesterday’s 50F/10C . Not exactly a star here at this time of year.

So these varieties which carry appealing foliage color into winter are invaluable. But will they prove invasive here in PA, where they overwinter but are not vigorous? I doubt it. And in colder areas? Highly unlikely. So when we cite a plant as invasive, we need to qualify our remark by saying where. And when we come across an introduced plant in the wild, let’s not instantly assume it’s going to blot out the native vegetation everywhere – “it’s not native so it must be invasive,” as I’ve heard said, is simply preposterous.

A non-native may prove troublesome, in which case we must take steps to deal with the problem. But if it simply settles down, becomes naturalized and behaves itself – so what? Invasive Man says he’s out with his weed whacker to wipe out the arums and as the plant is said to be “all over the place in one wetland in Rock Creek National Park” (which is nearby) maybe he’s right. But if a seedling turns up along the roadside outside my garden then I’m not going to whack it. I’ll just keep an eye on it.

I’m simply going to admire the unexpected cold-hardiness of many forms of these Italian arums and value their presence in the garden at a time of year when some interesting foliage color is so valuable.

Comments

[william]

Arum italicum is a real pain in North Wales, both in the
garden - http://www.mygarden.me.uk/october2005.html
and locally in the area. It is terribly difficult to get rid of and is spreading locally especially along roadsides - it's invasive!
Like the blog - excellent!

[Graham Rice]

I wonder how much of its tendency to spread in North Wales is as a result of the change in climate which has created an expanded range in which it could happily grow? In these times it can be difficult to determine if a plant is simply expanding naturally outside its previous range (in this case on the south coast of England, not so very far away) or spreading where it does not belong.

[William]

Interesting! I was under the impression that Arum italicum we grow in gardens with its characteristic marbling was not native to the UK? i.e ssp. italicum and the 'native' is ssp. neglectum. (Stace, 1997, p.778).

[Graham Rice]

The identity of the forms of Arum italicum which we grow in gardens, and which are native to Europe and southern England, has recently been clarified.

Arum wizard Peter Boyce published an article in The Plantsman (March 2006) in which he discusses why, following extensive field research, separating A. italicum into three subspecies cannot now be justified. He therefore unites two subspecies, subsp. neglectum and subsp. italicum into one subspecies - subsp. italicum.

It appears that leaf shape varies greatly, as does the extent of white leaf markings, and many populations show noticeable variability in both features and in the combination of the two. So, he points out, retaining two subspecies is unjustified.

So... the question, perhaps, is this: If a plant escapes from a garden or is introduced by people into an area which, perhaps as a result of climate change, it could have spread to by "natural" means - does it matter?

Perhaps we should be open to the fact that, as the climate changes, native floras around the world are simply going to change as well and that holding back this change by management (ie weedkiller) needs very careful consideration.

[Invasives Man]

Just came upon your remarks on Italian Arum and I must say they are thoughtful and well-put. I agree that some caution is warranted in labeling a plant "invasive" and most definitely climate can be a major factor. In this case, the deciding factor for me was the confirmation that the plant has proven to be a major issue in a nearby park. One other point is that as the climate warms, we may see plants that have not been a problem before within a climate zone becoming a problem. For example, Kudzu seems to be increasing its range northward here in the States. Cheers, Invasives Man