With the clocks having ‘fallen’ back, at the end of last month, it really feels that winter is almost upon us and gardening can become more of a chore, than a pleasure, during the colder, darker, days. The upside is that there tends to be less urgency in the tasks that have to be performed as plants are generally becoming dormant, less active, so many late autumn / winter gardening tasks can wait until you are in the mood, or the weather is to your liking.
The exception are those tasks which rely on there still being some residual summer heat in the soil and the need for plants to be active enough to make some new root growth. Chief amongst these is the lifting and dividing of herbaceous perennials, which is a pretty essential gardening task if you are to keep your borders healthy and vigorous. In the days when gardening was generally governed by a series of strict laws, not something we go in for so much now, we were supposed to lift and divide everything in the herbaceous border every three years.
Obviously there will be some border plants that are so vigorous that they could be lifted and divided practically every year, Rudbeckia fulgida var. deamii (‘Black-eyed Susan’) being one such plant. Others are best left alone to make impressive clumps without being divided; I find that any Echinacea (‘Coneflower’) that proves perennial in my garden is best left alone and not divided. Hardy geraniums, such as the ever popular Geranium ‘Rozanne’, can be divided frequently, if you want lots of new plants to provide ground cover, or left alone to make impressive clumps as a foil to other border plants with different leaf forms, such as spiky grasses or large leaved hostas.
While you are assessing your borders, to see what you might be able to lift and divide, you might as well cut down any herbaceous plant that has finished flowering and is contributing nothing that might benefit the winter garden. Interesting seed heads, or a strong skeletal structure, even after flowering, are enough to allow a summer perennial a stay of execution into winter and not be excised until the spring tidy-up. I really like the seed heads of Iris sibirica, remaining stiffly upright throughout the winter and especially good when crowned with a hoar frost, but their strap-like leaves do turn to a soggy mush which may require thinning in order to reduce the number of slugs and snails which would otherwise revel in their slimy embrace.
Once you have found a suitable perennial, for lifting and dividing, then the process is pretty straightforward. It’s particularly satisfying if your chosen plant is a really congested old clump of something like Alchemilla mollis (‘Lady’s Mantle’) which gets particularly woody after a few years. Once you have dug up your chosen clump, knocking off any excess soil, you may find it easier to take it to a bare area of ground, or onto a protective sheet on the lawn, for the next operation.
If the plant is the sort which is a mass of shoots and fibrous roots, hardy geraniums are a prime example, then the classic method of teasing them into smaller sections is to insert two border forks into the clump, back-to-back (the curve of the tines pointing away from each other). With the backs of the forks touching, the tines inserted into the congested clump, then the divisions can be made by forcing the fork handles together, being careful not to trap your fingers. This eases the corresponding tines apart and separates the clumps into separate pieces. This process can be continued until you have fist sized divisions for replanting. Use some to replace the parent plant and some for planting elsewhere, or for potting up in fresh compost, providing you with new plants for free, to do with as you please.
If the clump that you have dug up is really congested and woody then the ‘back-to-back’ method may simply break your forks, or your fingers, and in this case it is perfectly acceptable to chop up your perennial with a sharp spade or, in really tough specimens, slicing it up using an old, redundant, hand saw. I find that really ancient clumps of Miscanthus sinensis, more usually divided in the spring, can only be divided into suitably small sections by using and old ‘D’ saw that I keep specially for this purpose.
If you are dividing perennials in order to maintain their vigour, replanting some divisions back into the border, then it’s a good idea to fork some organic matter, plus a small amount of feed, I still rely on ‘fish, blood and bone’, into the border soil where the replanting is taking place. You don’t want to add loads of nitrogenous fertiliser at this time of year, where it promotes leafy growth just when plants are being cut down by frost, but a small amount of fertiliser will help the new divisions make some root growth before the soil becomes really cold. Similarly, it’s a good time for a really thorough weed of the borders, followed by the addition of an organic mulch layer, to keep the soil looking good and weed free until next spring.
Last month I suggested that dahlias are traditionally left in situ until the first frost has blackened their leaves but I think that now is plenty late enough, whether they’ve been frosted or not. Lift them from their outdoor positions, knock excess soil from their tubers, cut their stalks down to an inch or two and, if you are following every rule, leave them upside down on greenhouse staging, or whatever drying space you have, to allow moisture to drip out of the severed stems. I’m not entirely sure this upside down stage is really necessary but it can’t do any harm. Once suitably dry the tubers can be stored, labelled correctly if known, in empty flower pots (wooden wine boxes if you’re posh) somewhere frost-free and out of the way. Under the greenhouse staging is suitable only if the greenhouse is equipped with a heating system which keeps it above freezing however severe the winter is. N.B.—now is a good time to check any such heating apparatus!
I’d always believed that the reason for planting tulips later than other bulbs was to try and reduce the risk of ‘Tulip Fire’ although I don’t know how scientifically proven this is. If your tulips have succumbed to this fungal disease in the past (spotty leaves, twisted growth, early death) then the spores will remain in the soil for at least three years and subsequent bulb plantings are likely to get infected whatever time you plant. Growing them in pots and containers, where they tend to do better anyway, means that you’ll be using fresh compost so they should remain healthy for at least the first couple of years.
Anyway, now’s the time to plant them, wherever you choose to do so, and it’s definitely time to get a wiggle on if you still have other spring flowering bulbs to get into the ground. With luck there should be some nice days of autumnal weather to get outdoors and finish bulb planting amidst the autumn colour – gale force winds and driving rain permitting!
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