Soil science in the rose garden
The rose garden is proving to be problematic. The roses themselves are showing signs of replant disease. This refers to the problem of re-establishing plants in soil where the same species was grown previously. Roses are a case in point, but this can apply to other species. The soil was changed the last time the rose garden was replanted, but the evidence suggests it did not work. Examining the soil more closely suggests that it is hungry. It has received some manure in the past but not as generously as I would like. We could try a few other things to amend the soil and thus help the roses.
It is possible in the future we will replant the rose garden. But this will prove to be a large project, so for now we will try to work on the soil. Amazingly we know more about the surface of the moon than the soil under our feet. Far from being simply dirt, soil is full of life that we know little about. Soil is an ecosystem full of different life forms. These include archaea, bacteria, actinomycetes, fungi, algae, protozoa, nematodes, earthworms, ants, insects...Some of the soil fauna break down waste material, such as leaves into new useable materials and food for other living things. Others are able to fix nitrogen and make it available to the plant. Some bacteria and fungi form symbiotic relationships with plants, greatly increasing a plants access to more nutrients and water. Earthworms play a part in improving soil structure and aeration. Healthy soil plays an important role in locking carbon. In fact, scientists state that more carbon resides in soil than in the atmosphere and all plant life combined.
In short, if you want to look after your plants, you need to look after your soil. There is a growing movement in agriculture called regenerative farming. Many farmers across the world are waking up to the fact that conventional practices of soil management and the use of chemicals are not sustainable. The soil is becoming increasingly degraded and unable to support much life. Regenerative farming looks at restoring soil health, sustainability, and negates the use of chemical fertilisers and pesticides. Much of this can be applied to gardens and is backed by scientific research.
Simply adding organic matter be it compost or manure, will start to solve many soil issues. If it is sandy soil, organic matter will help improve water retention. Added to clay soil it will help with drainage. In every case it will add nutrients back to the soil and feed the soil ecosystem, which then makes nutrients available to the plants. This organic matter is simply applied as a 3-5in mulch. No digging involved. Over recent years digging has become frowned upon. Digging upsets, the soil fauna, much like you would be upset if someone turned your house upside down. It destroys the networks made by fungi, and provokes nature into action. Nature abhors bare soil, and will aspire to cover it up again with vegetation. Nature will bring the organic matter into the soil for you, there is no need to dig it in. If you want to learn more about 'No Dig', have a look at Charles Dowding's work.
In a garden context most of the time it is not necessary to introduce biostimulants and mycorrhizal fungi. They are normally already present. However, if you think your soil is in poor shape, applying mycorrhizal fungi to the roots of a new plant maybe beneficial. I am tempted to experiment with biostimulants in the rose garden, to give the roses every chance of recovery. Adding lime may be beneficial, it helps to open up the soil, improving drainage, and calcium is needed by both soil fauna and the plants. We may use Caliente Mustard as a green manure. The mustard once fully grown, is cut up and forked into the soil. This releases gages that act as a biofumigant which will kill of harmful pests and increase the activity of beneficial soil microbes.
Good soil health is a major part of a healthy garden. In the coming years, as the soil is improved you will see a marked improvement in the garden’s performance, and all being well a good display of roses.
William Stanger
William Stanger of Four Winds Horticulture is a local Garden Consultant and international writer. He is advising Whatton House on the garden’s regeneration. He has worked at various gardens in the U.K and New Zealand including The Savill Garden and Dunedin Botanic Garden. He has a M.A. in Historic Designed Landscapes and a BSc Hons in Green Space Management.