WE’VE had quite a bit of rain of late, and some snow to boot; enough to thoroughly moisten the ground without turning the garden into a soggy mess, as is usually the case in October. The summer of 2008 has brought the longest drought I can remember, and towards September this state of affairs was beginning to stretch my patience.
September is the traditional month for dismantling and replanting borders, but all such activity had be postponed because plants don’t settle, let alone make new growth, in dust-dry soil. Having to water everything in pots on a daily basis became a dreaded chore, and prompted us to review our potting medium at Lea Gardens.
Peat-based compost dries out rapidly and can be extremely difficult to re-hydrate. That’s the summer scenario. During autumn and winter peat becomes saturated like a sponge due to its phenomenal water absorbing capacity. Neither is conducive to plant growth.
I believe Great Dixter is the only plant nursery in the country that still grows all its plants in sterilised loam. Loam doesn’t dry out nearly as quickly as peat, nor does it turn soggy during the wet season, making it a much better growing medium all round. We have decided to follow the Dixter example by shifting to loam-based compost. Using loam is especially useful for plants lifted from the open ground for potting. With young and/or fragile plants the transition from loam to peat can be a tricky one in my experience, often resulting in considerable losses.
Because it comes free of charge, we’ve always used loam for what we term “rough potting”, usually applied to open ground trees and hedging plants. This potting soil is based on skimmed and composted turf, a process that takes between 18 and 24 months. The turf is stacked green to green, brown to brown, with a generous sprinkling of lime between the layers, and left covered in black polythene until all growth is killed off.
This takes care of the living weeds, but leaves any seed present in it, in a viable state. German nurseries I have visited over the years are much more relaxed than the British ones, and don’t worry about “weedy” pots. Plants are grown as nature intended them. Alas, in this country nobody would buy such plants. That is why most nurseries use sterile peat or pre-germination weed killers for their pot-grown plants.
There are ways around this. In the past we have used a two- or three-inch topdressing of peat-based compost to prevent germination of weed seeds present in the loam underneath. Sadly this only works in large, deep pots. At Dixter they use an old-fashioned but highly efficient open flame steriliser. The loam is shovelled onto an open-ended metal trough above the flame, then tipped out, and rapidly refilled.
Over the years I’ve searched in vain for such a contraption, but have come across a reasonably priced electric steriliser with a two bushel (70 litre) capacity. A full load takes about an hour to reach a temperature of 70°C and only uses four units of electricity. This process kills all pathogens, roots and weed seeds, while – I’m not sure how it could possibly do this – allegedly leaving beneficial soil bacteria intact.
Top loading and emptying the machine, via two pull-out doors at its base, is child’s play, but the important thing is to prevent over-heating. That’s where a kitchen pinger comes in handy. The end product, once cooled down, can be enriched with the famous John Innes base fertiliser, and plants love it. What I like about this traditional approach is its sustainability. Growing turf doesn’t take long, provided soil fertility is kept up to scratch. We’re in the lucky position of having half an acre of “lawn” at the ready, to be stripped before it is turned into new plantings.
We’ll still use some peat-based compost for rhododendrons and other ericaceous plants. We’ve been scraping “mooldy bletts on da hill” during summer and autumn. From next spring onwards we’re going to resurrect our dormant peat banks. The plan is to take off a thinner fell than usual to be laid down in the greff, and to turn the ensuing fat layer of mossy peat into compost with the help of an industrial shredder.
We have over the past decade used commercially produced processed peat, but have found the air porosity in it far too low for our requirements. This product only became usable as compost with the addition of vast quantities of a component called perlite that can soak up and contain excess moisture. Finding the perfect growing medium is a complex and complicated affair. Having run Lea Gardens on a shoestring for half a decade has left certain areas in a state of neglect. The most neglected were the herbaceous lining out beds, a place where seedlings or small divisions are grown on for a year until they’re ready to be potted up. No harm came to the strong and vigorous through a lack of regular weeding and feeding; if anything, they seemed to thrive under such a regime, and we have lifted large clumps for autumn potting these past weeks.
These beds also hold my collection of old primroses, horned violets and auriculas. There were rows of strong, vigorous and floriferous plants in the spring of 2007. A year later they were less so, and I meant to lift, divide and replant all of them this spring, but never got around to it. Lawn daisies had self-seeded prolifically in the area, and by the time I knuckled down to the lifting process this autumn, they had taken full possession of the beds.
Inexplicably the violas and auriculas had survived unharmed, while the primroses had dwindled alarmingly. I have no explanation for this. Vine weevils were obvious suspects, but failing to find a single larva among the roots of the survivors prompted me to look for other causes. On closer inspection I found a lot more primroses, tiny, barely visible plants among the close carpet of fat green daisy rosettes.
Three weeks later, the survivors, lifted and planted into large trays of manure-enriched compost, were transformed creatures; the stunted, sickly yellow leaves had turned a fresh green and there was new growth in the centre of the crowns. I can only surmise that the dry summer, combined with the daisy competition, had brought my precious old primroses to the brink of extinction. Some have probably succumbed, and I’ll have to search for replacements.
Autumn is a great time for taking stock, for replacing losses and for making lists of plants to try the following spring. The mail order catalogues have started to arrive in the post, and browsing through them is one of the great gardening joys at this time of year.
Finally, allow me to recommend two essential plants that are bound to bring a cheer to your garden on the greyest, dullest, wettest and windiest October day. Gentiana sino-ornata is the legendary sky-blue Chinese gentian. It is in flower from the middle of the month and well into November, and forms a low, rich green mat, studded with large trumpet flowers, marked with vertical silver lines. It likes an acid soil, and revels in a block of mossy peat.
Nerine bowdenii is a South-African bulb and is perfectly hardy in Shetland provided it is planted in light, well-drained soil and given a sunny aspect. It throws up two-foot stems of bright sugar pink flower heads that last for weeks on end. If the autumn tempests attempt to spoil it, cut it, and display it in a vase.