East Anglia is not an easy climate for plants. Newcomers to East Anglia are taken aback by its bleak winter climate and dry summers. They are surprised to learn that this is the norm, rather than a recent phenomenon. East Anglia has a climate that is as dry as parts of California. Add to this the cold east wind of spring and its scorching summers, and you have a severe test for garden plants. By way of example, It comes as no surprise to East Anglians to hear that sandstorms in 1668 overwhelmed Santon Downham and covered 1000 acres. We have a testing climate.
Erodiums, which are near cousins of the Pelargonia and Geraniums, thrive in the garden here at Pentlow Mill. The silt, gravely soil suits them well. The tougher members of the race seed themselves and behave like natives. (Suffolk has some native Erodiums found near the coast on sand). There are many that are completely hardy and ask only for a sunny, well-drained soil. Once their tap-roots are down, then they never need watering. There are species for many places, from the vigorous Pyreneean E. Manescavi to the tiny E. Chamacyoides. If they are happy, then they will flower for six months of the year, and last for twenty years or more without fuss. Although they are well-known to alpine gardeners, and described as 'among the most fascinating of plants' by Reginald Farrer, they are surprisingly neglected now, considering the value they have in dry sunny gardens.
Because Erodiums thrive on benign neglect, they do well at Pentlow Mill. Like many gardeners, we have a dreadful hankering to collect species and 'botanise'. We try to resist the urge to turn our garden into a botanical 'Stamp Album' by collecting species, but with Erodiums, we find the urge irresistible.
As far as I know, nobody has revised, and tidied, the nomenclature of Erodiums in the same masterly way that Dr Yeo sorted out the Geraniums, so the Erodiums in cultivation tend to be confusing in their naming . We have a reasonable collection of Erodiums, but in few cases can one be sure that they came from the wild. Many of the Erodiums in cultivation that are given specific names are actually hybrids. Generally speaking, these hybrids very seldom set seed, and many of them are mules. Misnaming is rife in the trade.
The Erodiums in cultivation seem to fall into distinct groups. There are the fine-carroty-leaved mountain ones with woody stems, exemplified by petraeum, or macradenum, the coarser-leaved ones from Spain such as Carvifolium, Daucoides or Manescavi, and the round-leaved ones such as Corsicum, Chamadryoides or Pelargoniiflorum. The Erodium Petraeums, which hail from the Pyrenees to asia minor, have a number of subspecies and regional variations, with flowers that vary from the clear pink to the purple veined and blotched, with leaves from olive green to the intensely silvery and fragrant. Fortunately, they hybridise easily with offspring that are occasionally fertile. Erodium Daucoides will cross with Manescavi to produce endless fertile variants. The Rounded leaved group will also hybridise but I've never got fertile seeds from the first generation. I have found only the tiny Chamadryoides, from Majorca, to be hardy, so there is probably little to be gained from crossing them.
The 'Petraeum' group forms woody sub-shrubs, and will propagate easily from cuttings. The best time for this is, I think, in early April, when growth is starting but before they have limbered up into flowering. You'll get success at almost any time in the summer. I strike them in wet sand in full sun in a greenhouse.
Growing the finer Erodiums from seed is tricky, particularly as some varieties, such as the Greek E. Chrysanthum, are dioecious and it is the devil's own job to get both sexes. Of the hundreds of seeds I collect each year, I am pleased when I get thirty seedlings. The success rate is increase if the parent plant in such a hot dry place that it fears of its life. Erodiums will cross. To do this, they need to be stressed with dry hot conditions. My best successes came when I used old clay drainage pipes, filled with pea-shingle and sharp sand. These pipes are placed vertically on a sand or shingle raised bed. Each Erodium is planted in the top, in a cold greenhouse in full sun. They need to be nurtured generously for a year, and then left to suffer. You can water the raised bed occasionally, but not the plants or the drainage pipes. If it is a sunny year, and you are careful with the regime, you will be rewarded with seedlings that set themselves in the gravel. Erodium seeds sets best when it is fresh. You will get better, and faster germination if you sow within a month of collecting seed. Once seed has germinated, it must be pricked out into individual pots as soon as it has produced its first true leaf. If you leave seedlings in the seedpan, you will get casualties when you eventually prick them out. Erodiums hate their roots to be disturbed when they are in leaf.
An early mistake I made was to try to make crossings from the Sardinian Erodium Corsicum, which is slightly tender here, and E Pelargoniifolium, which is really best considered a biennial. The result was magnificent, and even featured on the front page of a gardening magazine, but it was neither hardy nor long-lived. I wish I still had it.
I then decided to try to cross the members of the 'petraeum' group. Progress was steady, and twelve years later I had my first successes. The trick was to get fertile offspring from the F1 hybrids, which was a rather reckless ambition considering that even the parents were shy seeders in East Anglia. The F1 hybrids tended to be stubborn mules. My first ambition was to increase the pink and magenta colours and make the upper-petal blotching more intense. To get the beautiful silver-foliage too, particularly when scented, is a bonus, but I've never got all these characteristics on one plant. I wish that I could be sure of what parents were used in the process, but one has little control over the mating process. For a reason I forget, the beds that I use for Hybridisation are called the London School of Economics. Proximity is the primitive method I use, since I have never had success with the sable brush.
Something I've noticed about hybridizing erodiums is that the first-generation hybrids tend to be almost sterile, but the more generations down the line one goes, the more fertile seed there is. I've now reached the stage where I've been able to select a number of hybrids to act as 'mothers', as they seem very eager to produce seed in the ordinary garden, and they throw a great variety of offspring. This has made the whole business of seed-collection much easier, and I no longer submit my erodiums to the 'torture' of planting them in land-drains.
The good hybrids tend to flower for an extended period of time, from the beginning of May to the middle of November. At any one time, they are never startlingly colourful, as an Aubrieta or Armeria might be, but then they flower over a long spell. They often have reddish leaf-stems and have a tendency to flower in panicles, rather like their cousins, the Pelargonia. Where on also gets silvery foliage, this is a pleasant bonus, but it is rare to get anything but white, clear pink, or yellow flowers. Some hybrids have scented leaves; not so intense as with some of the Pelargonia or Geraniums, but a pleasant bonus nonetheless.
Erodiums sulk if they are left in pots, and so will never be the perfect nurseryman's plant. They will do anything to get their tap-roots down to the water-table, and will twinter if kept in the conditions that one sees in the Garden Centres. If you strike them from cuttings in the early spring, pot them on into a gritty soil in a long pot, and get them planted into their permanent positions just as they are beginning to flower, but before they have wrapped their roots round and round the pot in their frustration to get their roots down, then you will have a happy plant. Once its root has got down, then it can be left to grow, and will last for ages. I have several plants that are over twenty years old, and show no signs of age.
Although I still have ambitions for further hybridisation, we have got some Erodium Hybrids that make excellent garden plants in our dry sunny climate. I like flowers where the colour of the spotting on the upper petals has run into the petals themselves, making the upper petals a deeper pink than the lower ones. I like striking veining, and large intense black blotches. However, we have good clear pinks, where the flowers are almost symmetrical and plants that creep along the ground on shrubby stems, producing an abundance of small veined flowers that peep out from the leaves. We have some plants with intense silver foliage and pink veined flowers and others with heavily blotched white flowers.
I hanker after yellow-flowered erodiums, but Erodium Chrysanthum is a shy parent, and I have just one cross, with E Absinthioides. I'd like to use Erodium Chamadryoides as a parent in order to produce something with its delicacy, but cannot find a suitable mate. It will, of course, mate happily with Erodium Corsicum to produce plants that are sold as 'reichardii Album' and 'Reichardii Roseum', but the results seem to be sterile.
I am slightly wary about naming and releasing plants, because it takes a few years to be sure that a particular hybrid is going to be a good garden plant, but one or two are already getting into circulation. I'll be providing plants for AGS plant-stalls if there is any demand.
As a hint to any nurseryman who would like to produce good commercial plants, I'd recommend that you give the parent plant a good haircut in the early spring as soon as the first signs of growth are noticed. Root the resulting cuttings in pure sand in a warm sunny greenhouse. Pot them on into a sandy potting compost as soon as they have rooted, and leave them in the warmth until May, at which point they should be gradually hardened off and plunged in sand. Although they are still young plants and their roots are fresh and vigorous, they will be flowering well by the middle of June and ready for sale. Do not leave them too long in pots in the hope of producing a larger plant, for they will take a long time to recover once they have tasted confinement. One hopes that the purchaser of the plant will appreciate that he has bought it at the perfect time for planting, though it may look a bit under-rooted.
In our garden, although they will happily thrive in the front of a border in sandy loam, they do best in raised beds, roughly knee-height, and filled with nothing but 'pea-shingle' gravel. The soil can be well-composted when the bed is created, but Erodiums like to send their roots some way for nourishment. Above all, Erodiums must have sun, and the more the better.
There are a few Erodiums that are indispensible. They are