There’s a fungus for all weather, wet or dry. We value many, like mycorrhizal fungi, but it’s hardly surprising that this ancient kingdom of organisms, much older than plants, has produced pathogens that foil us in the garden. So try to get one step ahead of disease by keeping plants strong and healthy. Pests and diseases always put the boot in when a plant is stressed and struggling.
So keep a close eye on plants. I always walk round every morning to catch any problems at an early stage.
Make sure the ground is moderately fertile, but not too rich and don’t overfeed with nitrogen-based fertiliser that produces lush sappy growth. Ensure good drainage: fork in compost or top dressing with leafmould and then mulch with organic material.
Airborne fungal spores stick to wet leaves and multiply rapidly in warm weather. When watering, keep leaves drier by aiming the hose or watering can at the ground and avoiding leaves.
Although you can’t stop Phytophthora infestans, late blight, felling your potatoes, you can shelter tomatoes beneath an awning to keep the leaves dry, even while watering.
But unfortunately during a wet summer border flowers like nicotiana, roses and bedding plants won’t escape downy mildew. This is when the tell-tale signs of discoloured blotches on the up-per surface of leaves with grey fungus beneath appear.
Lift and destroy any damaged leaves or stems when you first see them, removing one source of infection and improving the plant’s appearance.
Bin infected material, as spores will persist after composting. But nothing is as simple as that. There will be millions of these spores in the surrounding atmosphere so you’re reducing, not eliminating the problem.
As well as growing in healthy, free-draining ground, avoid planting too closely. No one wants bare patches in a bed, but leave enough space for some air circulation. You can cut back or remove plants that have gone over, even if they were healthy, to make more space.
Petals falling on nearby leaves or buds set up the same airless rots. I was nearly reduced to tears when my glorious peony display caused havoc when beautiful blooms were blown to pieces during the recent rains. And deadheading is paramount with multi-headed roses, even if you have to ca’ canny to avoid knocking the petals off neighbouring the flowers you’re trying to protect.
Although foot and root rots are caused by the interplay of many factors, wet, airless soil often plays a part. These rots can damage and kill vegetables and ornamentals. As roots decay and the stem starts to rot at ground level, a plant is starved of water and nutrients.
Leaves become stunted and yellow. With edibles, there can be little or no crop and if you lift the plant, you’ll find virtually no root.
Spores will probably persist in the soil for several years, so you need a 4-5 year rotation for veg. And you may have to avoid growing a susceptible ornamental species. But, first and foremost, you need to improve drainage as I described above and destroy affected plants. Try to lift and remove as much soil round the roots as possible.
Predictably there are also fungi for dry conditions, with powdery mildew a major offender.
The fungus coats leaves in white, usually towards the end of summer. Keeping the soil moist does help, but courgettes seem to attract the fungus, whatever you do.
In my experience, this seems to happen naturally as a plant reaches the end of life, so simply ignore the problem. Sadly, here’s never a magic wand to solve every problem in gardening.
Plant of the week
Shrub Rose ‘Kathleen’ has palest blush pink flowers that open from bright pink buds and is repeat flowering. The single flowers are fragrant and popular with bees. ‘Kathleen’ grows to a little over 2 metres and makes a small climber or can be grown in a hedge.
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