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When to cut back Wild Grasses,
pruning pointers, and winter seed heads
By Anno Torr
As autumn ticks away and gardeners prep for the winter months, knowing just what and when to prune can be confusing, especially to the new gardener. Many of us default to what they’ve been told – or seen done – over the years. But is our timing right? For example, I see many grass clumps shorn of their warm leaf cover as early as May, exposing uncovered soils to the elements, reducing wildlife cover needed as temperatures drop, and decreasing food supplies. But, when is the best time to cut back the wild grasses? And which shrubs should avoid the winter snip? Let’s investigate, Watson!
Wild grasses: when to cut
Knowing a little about how a grass plant functions will help you plan your cuts.
In wild grassland and savannas where browsers and a natural fire regime are active grasses are continually pruned throughout the growing season, munched by strong teeth or snipped at by locusts, termites, rodents and other small animals. And once every few years they’re burnt off by hot fires. And they’re well adapted to, even dependent on, these disturbances that remove old plant material, stimulate new growth and help to disperse the grass seeds.
Adaptations to fire and grazing and cutting:
Growth points are at or close to the ground in the culm, the lower section of the stem from which the leaves and inflorescence grow and where the movement of water and nutrients is managed. This puts them out of reach of the browsers and pruning shears.
Grass plants store reserve nutrients in the culms and roots which they activate when disturbed.
They respond automatically to being burnt, eaten or cut back by pushing out new leaves as quickly as possible. And this is where the stored reserves come into play; these extra nutrients are used by the plant for regrowth until there is enough greenery for photosynthesis to kick into action once again. And growth during the rainfall season is rapid.
Cutting back wild grasses within a garden setting:
Cutting at any time stimulates growth but if done in autumn or early winter as the rains dry up, temperatures drop, and plants approach dormancy, new leaf formation slows down. And, with the spring rains far off – September – the grasses face a long, dry stretch through which they will draw on their stored reserves to produce enough new leaf to enable photosynthesis. An early cut then could deplete these reserves before the growing season begins, weakening it and reducing its lifespan.
So, the best time to cut? As close to the first spring rains as possible.
As Landscape Architect, Emmarie Otto, wrote in a 2016 article for The Indigenous Gardener, “The wild grasses are cut at the end of winter, and in our area, we have found that the best to do it is just before spring arrives, i.e. at the end of August when the new growth starts”. Plus, the dense grass cover helps to insulate the soil through winter, protecting it from the elements.
And, for those with a mix of wildflowers amongst the grasses, Emmarie writes; “We either leave the [flowering] plants to seed and then cut the flowers and harvest the seeds for replanting, or we let the plants reseed themselves in the garden”.
But, be careful about burning/ cutting too late; if done just as plants mobilise the reserves to begin its spring regrowth it could lead to protein damage.
Grasses and wildlife:
While most of us have no need to provide for the large herbivores a patch of wild grass is very important to rodents, birds, and insects.
Hares and Rodents:
Grass as food: Springhares and many rodent species like scrub hares, Southern African Ground Squirrel, Cane-rats, White-tailed mouse and Gerbils, eat grass seeds and the nutritious base of the plant where the nutrients are stored. And they find warm refuge beneath the dense matting that forms towards the end of the growing season.
Grass for nests:
Many rat and mice species live in the grass; the dormouse and Grass Mouse build nests in the grass; Climbing Mice live in tall grass, Gerbils rats in short grass habitats. These animals help to keep ecosystems in balance, so, please, do not put out any poisons specifically for rats and mice; they make up the bulk of food for owls. In the Upper Highway area, many owls are dying a slow, painful death after eating poisoned rodents.
Birds like weavers and finches use the grasses to weave nests, or find refuge; others, including Mannikins, finches, doves and other small species, eat the seeds still available on many grass species through autumn and early winter.
A diversity of insects feed on grasses and shelter beneath the mat of leaves. Locusts and termites are well-known in this regard, but grass plants are an important habitat for many other insects too. Harvester termites cut up sections of the plants into short pieces – culm and leaves, for example – which they take into their nests and plant in their fungi gardens. Fungi are an important food source of the harvester termite.
Autumn and winter interest:
In our need to tidy up we can overlook the beauty of dying grasses and the crisp, brown seed heads of flowers past their prime. Imagine this landscape without the tall stems and dried balls of old Cyanotis flowers; a little bland, perhaps, despite the fluffy spires of yellow Bulbine and the sharp Aloe forms. What I find most attractive about this arrangement as autumn ends are the waves of biscuit-coloured grasses with the odd green stem, and the chocolate balls and stems that would, in most gardens, be cut down by now.
What to cut off at any time, and when NOT to prune!
Cut off any damaged or diseased branches as soon as you discover them. Make sure to clean your pruners with disinfectant like alcohol or household cleaners; never bleach because it can corrode your tools and damage the plants.
Do not prune spring-flowering species in autumn or winter because you will cut off the spring flowers. Most of these species set their flower buds as far back as summer, slip into sleep mode through winter, to wake up as the weather warms in spring. Prune these species immediately after their spring flower show.
Deciduous shrubs: Do you give in to the temptation to snip off a few stems as the leaves fall and bare the plant’s structure to your critical eye? When leaves change colour before falling an important process is taking place unseen to the gardener’s eye. At this time, the plant moves sugars and other resources from the leaves to the branches, stems, even the roots, where they store them safely through the winter and disperse them again when energy is needed for new leaf and bud formation. Cutting off these stems and branches during this process can cut off important nutrient resources before they have been tucked away.
A simple 4-step reference to pruning:
Basic pruning: as you cut back each stem, keep in mind the size and shape of the plant. You’re looking to keep the centre of the plant open to allow in some sun and air movement.
First to remove: dead, damaged, diseased wood
Then, weak, spindly stems, crossing branches that rub against others.
Once done, keep in mind the size and shape to which the plant should be cut and cut back to this height and shape. If needed, old woody stems can be pruned right back to the base.
Evergreens: trim back any stems that are too tall, outside of the general shape of the plant.