Gardeners love and hate what the weather throws at us and the extremes of climate change are piling on the agony. Dramatic fluctuation in weather patterns will intensify, perhaps more quickly than we imagine and many of our plants won’t be able to adapt to this.
Plants need oxygen and water and have developed strategies to access them in widely differing environments ranging from bogs to deserts. Few can cope with both extremes. Our plants absorb oxygen through their roots but, like us, they drown when submerged in water.
If some of our favourites turn into frizzled stumps by the end of summer or drown in a winter sog, replace them with different species. But finding suitable alternatives is challenging.
Before making any changes, check out the problem area to try to improve growing conditions there. It could be an entire bed or a small patch. Start by trying to improve soil quality. Mulch with good home compost, farmyard manure or some other organic material. This increases humus, creating a fine, crumbly texture.
Humus-rich soil retains and slowly releases moisture thereby protecting plants from the worst water fluctuations. Any mulch acts like a porous umbrella, reducing the speed and ferocity of rain, while retaining moisture during a dry spell.
Check whether there’s any runoff into a bed. I started noticing to my horror that my south-facing, fairly dry herb bed was beginning to sog up. During winter storms, too much water had been rushing down a greenhouse downpipe, so some ran along a path into the bed. Blocked or inadequate drains can be sorted.
The corner of another bed was much wetter than its surroundings. When laying a new path, the builder had laid impenetrable foundations, preventing any drainage from the bed. A planter slightly raised above the soil now sits on the soggy ground.
Try to identify plants that are coping with the new conditions. It’s not completely clear why some succeed while others don’t but start by identifying winners. In 2014, the RHS surveyed gardening professionals to collate a list of plants that can tolerate these fluctuations. Some suggestions are listed on ‘Wet and dry soils’ on rhs.org.
As well as checking our own gardens, talk to friends and neighbours. What is the experience of local nurseries?
Are there any common factors making some groups of plants more likely to succeed than others? Do spreading ground cover plants have a similar effect to mulches and influence how quickly the soil absorbs and releases moisture? Can some deep-rooted shrubs and trees cope more easily?
Do types and shapes of roots and leaves make a difference? Which plants seem to be more susceptible to winter rot than others? This is highly complex and there are no clear answers.
Persicaria affinis ‘Darjeeling Red’ tolerates moisture fluctuation reasonably well. It forms a semi-evergreen carpet, with short spikes of pale pink flowers deepening to crimson poking through the leaves from midsummer to autumn.
The deciduous hardy geranium species, Geranium macrorrhizum, forms a dense surface mat and seems to be highly effective. Like another attractive winner, Alchemilla mollis – lady’s mantle – hardy geraniums are tough resilient plants. And with its blaze of little scarlet flowers, Geum chiloense ‘Mrs Bradshaw’ does well.
As a clump gradually spreads, it may be able to have some control over surrounding moisture.
Another of my favourites, Hemerocallis, spreads widely, forming a near-surface mat, with the crowns just above soil level. Hemerocallis throws out a succession of delightfully fragile blooms over many weeks, whatever the state of the soil.
All these plants are tough and resilient, but why they have some tolerance of water fluctuations and other similar species don’t needs much more investigation.
Plant of the week
Lord Rosebery apple trees bear pretty bright red fruits in early autumn. These have creamy flesh and a hint of strawberry but do not keep for long.
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