READING THE LEAVES; The foliage of a plant can tell you a lot about its health and help correct nutrient problems.
We all have them, plants or plots, in need of some cures or tender loving care. We need solutions to our outdoor ailments, many of which are a mystery to the gardener.
There are some problems that we seem to grow up knowing about - greenfly on roses, carrot root fly, or infestations of daisies in a lawn - and we've got an idea of the solution. In these cases, it's off down to the garden centre to buy a potion. Listening to the panelists on Gardeners' Question Time on the radio as they examine preserved parts of plants may lead you to believe that you need to be a plant pathologist to keep a garden in rude health.
But did you know you can tell a lot about your plant's health just by looking at the leaves? So, in the midst of our growing season, I'm going to present a short guide on diagnosing leaf problems and some solutions that will give you answers before you bend the ear of the likes of Alan Titchmarsh.
Let's start with yellowing leaves, which can point to a number of issues - sometimes to over- or under-watering, but often to a nutrient deficiency.
If the older leaves are yellowing and dropping off and the plant is generally stunted, it's probably a nitrogen deficiency - this is particularly obvious when lawns go yellow. Sometimes heavy use of bark chippings as a mulch can suck up all available nitrogen. To fix, apply nitrogen-rich fertiliser to lawns and wellrotted manure to flowerbeds. Yellow or brownish-red discoloured areas between the leaf veins can indicate a magnesium deficiency. This can happen when the soil is too acidic or after heavy periods of rain which can wash nutrients out of the soil.
Magnesium deficiency is common in tomatoes, apples, grapevines, raspberries, roses and rhododendrons. The cure here is a dose of Epsom salts - apply as a foliar spray by diluting at a rate of 200g salt to 10 litres of water and add some mild liquid detergent. Do this fortnightly until you see results.
Yellowing leaves is also a common problem with camellias and rhododendrons planted in soil that is not acidic enough for them. Yellowing between the veins of their leaves indicates that they are not able to access sufficient iron and manganese.
The solution is to plant in the correct soil pH, but if this is not possible, add sequestered iron and feed plants with fertiliser formulated for ericaceous plants.
Poor flowering and lack of fruit, though, can be caused by lack of potassium and this too can be detected by looking at the foliage.
The leaf tip may appear scorched around the edges and the underside of the leaf may show brownish-purple spotting. Apply a high potassium feed such as sulphate of potash to rectify. Black splotches often indicate a fungal disease. Most gardeners are familiar with rose black spot on the leaves which then turn yellow and drop.
Control of infected material is important here - gather fallen leaves and don't dump them on the compost heap as the fungus will overwinter and start again in spring. Fungicidal sprays can help but will need to be repeated. For an easier life, try and choose roses bred with good resistance to black spot.
Doctors will always tell you that self diagnosis is a bad idea, but as a gardener I'm delighted to advise you to have a go at solving the issues. It can be very satisfying when you read the leaves correctly!
For an easier life, try and choose roses bred with good resistance to black spot
COMMON AILMENT Fungicidal sprays can help in the battle to control black spotting on roses
DEFICIENT Yellowing leaves are often a sign that the plant is lacking in nitrogen
DANGER Bark chippings as mulch can suck all availale nitrogen out of your soil and turn leaves yellow
MARKED Tomato plants with leaf spot
HEALTHY Vibrant green colour means no problems here