It seems I’m not the only Shetland gardener disgruntled by rogue mail order nurseries. One of my readers reported receiving tiny plug plants, stuck loosely into larger pots, while another let off steam about the patronising attitude she was met with regarding an unsolicited substitute. Thankfully, such experiences are still exceptions to the rule, and I, for one, am fully gruntled as opposed to disgruntled once more, after receiving a perfect consignment yesterday, with every plant in peak condition.
My mentor, the late Johnny Copland, was a great plantsman and had a sharp eye for a business opportunity, and preferred suppliers that sent out generous chunks, large enough to be divided into several smaller portions.
Division is still the best known and most widely practised method of increasing herbaceous perennials, but it isn’t always the best for the plants in question, nor is it the most satisfactory for the gardener. Lifting and chopping up a large clump is not only hard physical work but creates a lot of wastage. There’s always debris, bits of roots without shoots and vice-versa. While some plants are indeed rejuvenated by this intervention, others, especially those resentful of root disturbance, are weakened and take time to make good their losses.
Then there are those “Medusa” creatures that are a headache when lifted. Euphorbia griffithii and its cultivars fit this bill. When lifted they present with a knot of long, snaking, tangled roots, difficult to replant, and virtually impossible to fit neatly into a pot. Their white sap is a skin irritant, so always wear gloves when you handle them.
Taking basal cuttings of border plants is a much better option, and one that puts no strain on the gardener’s back. Early spring is the time when plants start to put out new starchy, vigorous shoots. Follow them back to where they are attached to the crown or rootstock of your subject, and cut them off with a sharp knife. More often than not, especially in the case of erigerons (flea bane), leucanthemumns (Shasta daisies) and heleniums, they already come with a few small roots attached. Other suitable plants for this form of vegetative propagation are geraniums, Dicentra spectabilis (large bleeding heart), linarias (toad flax), ajugas (bugle), border as opposed to alpine sedums, asters, and the above-mentioned euphorbias.
No special equipment is needed, but basal cuttings root most rapidly if provided with bottom heat; that’s where a propagator or a heat mat comes in handy. But don’t worry, you don’t even need a greenhouse to be successful. A cold frame comes in handy, but failing that, a well-lit shed or a windowsill will do. I root mine in a frame, and have had excellent results from just setting them into a piece of sheltered, well-drained ground outdoors, where they are ready to transplant or pot up within a couple of months.
Pots work better than seed trays, as they hold a greater depth of soil and don’t dry out as rapidly as trays during warm, sunny weather. You also need a suitable rooting medium, and that’s where I’m a little stumped.
We all probably know one of those really talented bakers who churn out the most delicious cakes and tray bakes at the flick of a finger. When you ask them for the recipe a vague, glazed look comes over their face, they never weigh or measure anything and are hard-pressed to give detailed instructions. I used to think that was just a way of getting out of passing on a closely guarded recipe, but there are indeed individuals who just throw a few ingredients together and always end up with a masterpiece.
Making my cutting compost is rather like mixing the dry ingredients of a cake: I start with a heap of milled peat, add some vermiculite, a bucket of grit or very, very coarse sand – the kind found on some Shetland beaches – and, hey presto, it’s ready to use. I’d say, roughly speaking, you want two parts of peat or sterilised loam to one part of vermiculite, and one of grit. If you use too much of the latter ingredients, your compost will not stick together, if two much of the former, it won’t contain enough air pockets, which are crucial to rooting.
I’ve completely given up on rooting hormones, and still have the same rates of success as before. They have a very short shelf life, and since learning that they’ve probably lost their power while still sitting in the garden centre I consider them nothing more than placebos; they make the gardener feel better, but do nothing for the plants.
Use a dibber, or similar, narrow, pointed tool, to stick your cuttings into the pot, firm them in very gently, cram as many in as you can and water them well. Thorough watering will wash small particles into the lower areas to settle around your cuttings and give them a firm hold.
Now we need just two more bits of equipment. If you have a cache of those white or opaque supermarket polythene bags, they now have a useful purpose – apart from recycling them as bin liners or wrapping tees of mutton in them for the freezer. You’ll also need a few short, thin sticks, preferably of equal length. The sticks, about three placed between the cuttings, so they protrude a little above the tallest of them, are the tent frame so to speak. You then place your opaque plastic carrier over them, pull the whole thing tight and crumple the open end underneath your pot. This will preserve moisture and is vital to success.
Check your cuttings from time to time, water when necessary and watch out for the first signs of growth. New leaves will start to emerge as soon as the first roots are formed, and the time has come to remove the plastic tents. Unless you’re in a hurry, rooted cuttings can survive for a considerable time in their original quarters. When the nursery took a back seat to allow for the expansion of the garden all propagation was suspended, and we’ve just begun potting up basal cuttings, struck in the spring of 2007.
Just as shoots have the ability to root, roots have the ability to produce shoots, and root cuttings are an ideal way to increase poppies, pulsatillas, eryngiums (sea hollies), some Asiatic primulas, or basically any plant that produces a fat, juicy storage root. Such plants are difficult to divide, and if you want to increase a particular cultivar, seed is no option, as more often than not the offspring won’t be true to type.
If you’ve ever tried to lift and transplant an Oriental poppy, you’ve probably found that a year or two later the poppy, as if by magic, has reappeared in its original place. Every scrap of root left behind, even well below ground, has managed to produce new growth.
There’s no need to lift the whole plant, unless you have another reason for doing so; simply scrape and fork away the soil on one side, then sever a few roots just below the crown, follow them down into the soil with a small hand fork or trowel until you can pull them up in their entirety.
Now comes the important bit. Have a seed tray handy to hold your roots, and place them all facing the same direction, so you’re never in doubt what was top and what was bottom. Cut them into short lengths – about three or four centimetres is ideal – then dibble them into a pot or tray filled with the mixture described above, the cut end flush with, or just slightly below the surface of the compost. Make sure you don’t stick them in upside down. Encase in a plastic bag – white or opaque and wait.
Finally, some plants produce handy rhizomes, neither roots nor shoots, but equally suitable for vegetative propagation. They can be found above ground, just below, or snaking along the soil surface. I use this method for epimediums, bergenias and some geraniums. Select young, healthy rhizomes and proceed as for root cuttings.
Vegetative propagation is the only way to keep cultivars, also known as garden varieties, going, as you end up with an exact replica of the plant you want. It doesn’t take long to collect your material, trim it, and nature will do the rest. Half a day’s effort should reward you with enough plants to stock a good-sized border.
If you want to find out more about all aspects of propagating your plants, I recommend Peter Thompson’s Creative Propagation. It covers all aspects of this subject, and has excellent full-page instructive drawings. I still use the first edition, published two decades ago, despite finding its index nothing short of infuriating. The page numbers given never relate to the plants listed, but there’s a handy alphabetical table that makes up for that. I’m sure this fault would have been corrected in the later editions.