Climate change and plants

Temperature hits zero (F)

Half an hour ago at 7.21am this morning, according to our friendly local online weather station here in Pennsylvania, the temperature hit -0.2F. That’s about -18C for you Brits. (Yes, just about everywhere in the world has switched over to Celsius except the US which sticks to Fahrenheit - and feet and inches, gallons, pounds and ounces etc).

Thermometerminus5400 Nothing wrong with a cold night like this here in USDA zone 5, of course, (Britain, by the way, is mostly in zone 8) where the record low for this time on this day is -16F (-26C)  – except that we have no snow.

A foot or two or more of snow provides that insulating blanket to keeps plants a littler cosier than the icy air around them and reduce temperature fluctuations but a combination of El Ninho and global climate change seems to have eliminated all but about 3in of snow so far this winter. The recent United Nations report on climate change reveals how bad things are and The Independent newspaper in the UK laid out clearly what we’re in for as temperatures rise. With rainforest turning to desert we might end up being thankful for the resilience of Japanese knotweed.

One interesting sideline – thermometers vary. I’m sure our local online weather station is accurate, the thermometer outside our kitchen window reads -1F, and  the electronic thermometer with its sensor outside agrees. But the thermometer outside our bedroom window reads -11F and the big thermometer on a tree in the woods, which I can see from where I’m sitting writing this, reads -5F.

Either way, the plants will not be happy.


Christmas flowers in London

Over the Christmas holiday we’re staying with my daughter Lizzie in Kingston-upon-Thames, on the southern edge of London not far from Henry the Eighth’s Hampton Court Palace. It’s the place where the Saxon kings of England were crowned, we just walked past the stone on which they were crowned on the way back from dinner this evening. And today I took a short walk.

I walked round the block where Lizzie lives and noted everything in flower in her neighbours' front gardens. It’s an area of semi-detached, brick houses built in the 1890s (duplex town houses to American readers, I think) with tiny front gardens. The number of plants in flower was amazing. Here is the list: Aster novi-belgii cultivar, Brachyglottis (Senecio) ‘Sunshine’, Calendula cv, Campanula poscharskyana, C. portenschlagiana, Centranthus ruber, Choisya ternata, C. ternata ‘Sunrise’, Convolulus sabatius, Cornus alba ’Sibirica’, Corydalis lutea, Cyclamen persicum cv, Dahlia ‘Bishop of Llandaff’, Escallonia cv, Fuchsia (various bedding types), Hebe (six different), Hypericum ‘Hidcote’, Impatiens cv, Jasminum nudiflorum, Kerria japonica ‘Flore Pleno’, Kniphofia cv, Lamium maculatum, Lobelia (trailing bedding type), Lobularia maritima (Alyssum) cv, Lonicera periclymenum, Mahonia ‘Charity’, Nicotiana alata, Pelargonium ( “geraniums” - more than a dozen different ivy-leaved and zonal types), Primula (five hybrid primroses and polyanthus), Prunus subhirtella ‘Autumnalis’, Rosa (seven garden roses of various kinds, including ‘Iceberg’ with leaves, flowers and hips), Solanum laxum (S. jasminoides ‘Album’), Viburnum x bodnantense, Vinca difformis, Viola (many different pansies).

If you count all the different cultivars, it comes to well over sixty – in just three or four hundred yards.

Many were hangovers from summer, a few were spring flowers feeling precocious. The most interesting, in many ways, was the dogwood, Cornussibirica500 Cornus alba ‘Sibirica’. Normally, it’s showing off its naked, bright red stems at this time of year. But it was more or less in full leaf, and in flower, and it also carried a couple of bunches of white berries! Its stems were less bright than usual because they were shaded by all the leaves!

Normally, only about three or four of these would be in flower at the end of December. It’s certainly been a strange season.


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.

Mcclements400Arum 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.

Goldrush400 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. Jetblackwonder400 ‘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.


The Final Flowers of the Fall

Here in the chilly north east corner of Pennsylvania (zone 5), far from balmy Bucks County down in the south of the state near Philadelphia (zone 6 and 7) where most of PA's gardeners seem to be, we've already had a sharp frost. But today I've just ducked in out of the rain after checking which few plants are still in flower here on 1 December. The forecast, by the way, is bizarre: 65F/18C, thunder and snow! Back in England, the papers have been carrying comment on the weird autumn weather for the last month, like this in The Guardian.

Here, after more than a shock a few weeks ago when we had two nights of about 20F/-6C, it's two single-flowered chrysanthemums in the old-fashioned style which stand out and are still carrying flowers. Not the hummocks we see each fall in pots on the front steps of suburban homes, looking like painted footballs waiting to be kicked over the fence. These are all very well if all you need from a perennial is a few weeks of color and a lob into the garbage. In fact, plant them in the garden and some, though not all it seems, will come back next year and make more relaxed and more elegant plants. No, the two I've noted here, both from Niche Gardens, are 'Jettie' and 'Niche's October Glow'.

Jettie500 'Jettie', from Plant Delights, is white, but not quite white. The heads of flowers are rather crowded - the opposite of the superb rose pink 'Country Girl', also from Plant Delights, and also Niche Gardens,whose open airy habit is most distinctive - as is the fact that the frost turned the foliage of just this one variety, out of about 20 I've been growing this year, to bright yellow. Anyway, the flowers of 'Jettie' are only about an inch and a half across, and gathered together perhaps a little too tightly. But the back of each ray floret (petal) is pale pink and the color shows through just enough to take the purity out of the white.

Willswonderful500_1

There are one or two flowers remaining on the lovely 'Will's Wonderful', from Seneca Hill Perennials (we'll get into the difference between that and 'Color Echo' from Plant Delights another time - one day when we're feeling in a finicky sort of mood).

Nichesoctglow500_2

But the other November star is 'Niche's October Glow' , again from Niche Gardens. Two and a half inch single flowers are held in more open, rather tall heads - each ray is peachy pink fading faintly to yellow at the tips and with a neat yellow ring around the eye. Very pretty. Just one problem - not a flower on the plant is symmetrical, each has a petal or two which is a little longer than all the rest, or a few unusually wide spaces between the rays, so puncturing the elegance of each flower. Lovely color, valuably late – but flawed. Shame.

But hey... two perennials still in flower here on 1 December - excellent. And the Judy Barker, holder of the National Collection of these chrysanths in England, now has stock of these varieties so they should be available there before too long. And perhaps, there, and in zone 7 or 8 here in the US - they may be coaxed into flower for the holidays.