It’s rather fortunate that Christmas falls at a time of year, in the northern hemisphere at least, when any necessary gardening tasks can probably wait, for a month, if you are too busy preparing festivities. Also, the weather tends to be against us during the winter as it can do more harm than good to trample beds and borders while they are waterlogged or frozen. I’ve mentioned before that I think that compacted soil, soil which has had all the air pockets squeezed out of it, is often the major factor in preventing plants from thriving.
Plants need to be able to access air in their root zone, in order for them to respire, as well as above ground where their leaves and shoots are visible. If you walk on waterlogged soil then the air pockets, that exist between all the particles that constitute the soil, are compressed which forces the air out and, due to the presence of excess water, these spaces are then filled with water rather than air. In order for air to move efficiently from above ground to below ground there needs to be an uninterrupted route from the free atmosphere to the air held in all the soil pockets underground. If the soil becomes waterlogged, with its open structure destroyed by trampling, then this free exchange of gases is halted and any plant roots are at risk of dying.
One of the things, that I reckon can lead to a person being considered ‘green-fingered’, is how gentle they are with compost while they are performing operations like potting on plants or preparing pots of compost when striking cuttings during propagation. I know that, in the past, I had a horrible habit of really firming compost down, by pressing all around the edge of the pot with my thumbs, when potting up plants. This had the same effect that trampling does on garden soil; it squeezed all the air out of the potting compost and this, in turn, had a detrimental effect on the ongoing vigour of the plants that I’d potted up.
It was many years ago now that I had the privilege of watching a true plant propagator / nurserywoman, Marina Christopher, pricking out, and potting on, seedlings. Seedlings were knocked out their seed trays, with a deft ‘up and out’ movement, in which, somehow, all the contents of the tray were deposited, right way up, on the potting bench where each seedling could then be gently separated and inserted, with minimum handling, into a pot of non-compacted, gritty, compost. Grit is added to compost in order to ‘open it up’. This term describes how the generally large particle size of horticultural grit imparts larger air pockets, in the otherwise fairly finely structured potting compost. Larger air pockets facilitate better gaseous exchange, leading to healthier root development, and therefore a greater degree of success in the resulting new plants.
Similarly, forking in coarse grit, to compacted garden soil, can help to ‘open up’ it’s structure, improve drainage and guard against future compaction and waterlogging. Soils with the finest particle size, generally those containing a lot of clay, are most prone to compaction, waterlogging and therefore poor root growth and plant establishment. Adding organic matter can have a similar, structure improving, effect, in the short term, because the organic matter helps to ‘open up’ the soil structure. Unlike inert materials, like gravel, the organic matter will break down over time and its ameliorating effect will be lost.
This brings me neatly to the application of sterile organic matter as a mulch on top of beds and borders; this is an operation that can be performed in the winter months whenever the conditions are not too wet. I use the term ‘sterile’ because mulches are one of the ways to minimise the prevalence of weeds in cultivated areas, but they will only do this if the applied organic matter is free of weed seeds itself; i.e. ‘sterile’. Bagged mulches, like ‘spent mushroom compost’ or ‘well-rotted horse manure’, have generally been through a composting process where the temperature reaches a level at which any weed seeds present will be rendered non-viable. This may not be true of mulches made up of garden compost or manures that have come directly from farms or stables. Other ‘sterile’ mulches may be comprised of organic matter which would never have had weed seeds in it to begin with; i.e. something like ‘RocketGro Magic Mulch’. I used a lot of this product, this year, and it has proved to be a very effective weed suppressant.
Whatever organic matter you choose to add to the surface of your soil, it has a beneficial effect on soil structure because its naturally fibrous structure will boost the humus content of the soil. This ‘living’ constituent of the soil not only helps in preventing compaction but also greatly aids water absorption, especially in sandy soils which might otherwise be prone to drought, which in turn reduces plant stress in the kind of hot and dry summer which we’ve just had. The beauty of adding a thick, two or three inches deep, blanket of organic matter in the winter months is that it’s gradually drawn down into the soil by worm action. Encouraging worms is another way of ‘opening up’ the soil as they naturally produce air ‘corridors’ as they burrow and squirm their way throughout the root zone, dragging organic matter down as they go.
I’m sorry that this has turned into an essay about soil structure rather than anything more Christmassy! I think I probably write this every year, the very nature of gardening tasks is that they tend to be on a twelve month cycle, but now, during the leafless months, is the time when you most appreciate evergreens and, especially, those most festive of plants : ‘The Holly and the Ivy’.
Thanks to the balmy spring and hot summer, I’ve had berries on hollies that I don’t think I’ve ever had berries on before. Normally the reason why you don’t have berries on any particular holly is because they are ‘dioecious’; they have separate male and female plants and only the female ones will produce berries.
As far as I know, they are not able to choose whether they identify as male or female so it is up to you to ensure, if you are purchasing a holly in order to have winter berries, that you choose a female variety from the start. Just to add to the confusion, something that has always made me chuckle, is that Ilex x altaclerensis ‘Golden King’ is most definitely a female variety and Ilex aquifolium ‘Silver Queen’ is defiantly male, grown for its striking variegation and NOT for its berries!
On that shattering ‘bombshell’, I shall just wish you a very merry Christmas and happy gardening in the New Year.
