Dealing with Plant Disorders: Non-nutritional Disorders Part 2
By Steve Malsher MCIHort
Welcome to part 2 of our non-nutritional plant disorders blog. This is the final part of our mini-series with pest and diseases expert, Steve Malsher, who has discussed many of the garden pests, plant diseases and disorders that could be harming your garden at this time of year. Last week, Steve looked at frost, drought, fasciation and water-logging, which leaves the likes of high temperatures, shade and rose balling still to discuss.
Firstly, let’s revisit what a plant disorder is: Disorders are plant problems that are caused by a complication within the environment in which the plant is being grown. They are often called Plant Physiological Disorders and they tend to be of two types: those caused by nutritional disorders and those caused by non-nutritional disorders.
Sun and High Temperature
In contrast to water-logging, which we discussed last week, excessive sunshine and heat can also cause problems. For example, scorched areas of leaves, typically found on the sunny side of plants, effecting leaves that are higher up.
Woodland plants such as Acer palmatum are especially vulnerable to sun damage, but many plants can suffer high-temperature damage after a heatwave. Others to take extra care with are Camellia and Lonicera. Typically, brown patches appear on leaves and, in the case of apples, fruit on the most exposed side of the tree develops a reddish-brown burnt patch which often has a flattish appearance.
Few plants will thrive where shade is very dense, particularly when coupled with dry, impoverished soil (one only has to look under a conifer or laurel hedge). It is unfortunate that shade-tolerant plants, in many cases, are not very colourful in flower. However, there is some consolation in their attractive or interesting foliage. Plants for shade gather what light there is through large leaves that are rich in chlorophyll and, therefore, are often very green. Variegated plants are less successful in shade than in sun as they lack the quantities of chlorophyll needed.
The solution depends on what is causing the shade. If it is a building, consider painting walls a lighter colour, or adding a mirror in a courtyard to reflect the available light. One can also use light coloured materials for garden features.
If it is trees that are creating the shade, consider lifting the crown of the tree by removing the lower branches or thinning the crown to allow more light through. It is likely that the soil will be poor and dry, therefore improving with lots of well-rotted organic material.
Planting under trees in the autumn allows the plants to become established due to the minimum leaf cover.
There are many plants that cope with shade and these should be used rather than trying to force sun-loving plants. Those that flower during winter/spring are particularly useful as they tend to need less light earlier or later in the year, often becoming dominant through the driest, shadiest part of the year.
Perennial plants to try;
- Alchemilla mollis AGM. – Yellow flowers from early Summer to Early Autumn
- Bergenia ssp. – Pink or white flowers in spring
- Hosta ssp. – Grown mainly for foliage, with some stunning examples of shape and colour in the leaves, but also have blue or white flowers. Beware: slugs love them so keep them under control.
- Dryopteris felix-mas AGM – Fern grown for foliage and height. H1.2m S 1.2m
- Digitalis ssp. – Foxgloves, a variety of coloured flowers borne on a tall spike, very easy to propagate.
- Epimedium ssp. – Pink, white or yellow flowers in the spring, foliage can be removed when flowering.
This is a disorder in which the flower buds develop normally but do not open. It occurs in Rosa, Camellia and Paeonia ssp. Cool, wet weather saturates the outer petals and then the sundries and fuses them into a tight, papery shell, preventing the bud from opening.
Good air circulation is crucial to dry the buds quickly. When planting roses, choose an open (but not exposed) site. With existing plantings, increase ventilation by pruning correctly and cutting back overhanging trees and shrubs.
Water plants in the evening, avoiding hot, sunny conditions, and always direct water at the base of the plant, rather than the foliage and flowers. Remove balled buds promptly before botrytis sets in as it can infect other blooms or nearby plants, causing dieback of the stems.
It is often far easier to garden with the conditions than try to change them. If the garden is too shady for your herbaceous border, then grow ferns and shade-tolerant plants. If the garden is dry and hot, grow Mediterranean plants which can cope with the conditions.
Some of the best gardens in the country, such as Beth Chatto’s garden in Essex, work with the conditions and the plants thrive. All healthy growing plants will cope with pests, diseases and disorders far better than plants that are struggling to grow where they are not happy.
Nicholsons are happy to advise on any issues in your garden, or with testing of soils. Get in touch by emailing email@example.com or calling 01869 340342 to see how we can help you…