Keyhole gardening, push/pull control of pests and growing amaranthus

Some take away ideas for gardeners from the Oxford Real Farming Conference and some questions about roses

Jan 22, 2025

🌱 I'm Sally Morgan, an organic gardener and botanist who loves to experiment. Here you can read about matters relating to climate change, sustainability, organic gardening and growing veg, helping you to become a climate savvy gardener 🌱☀️🌧️❄️🌡️

This week I finish my round up of topics that grabbed my attention at the Oxford Real Farming Conference.

Tomorrow’s Climate

Last week I focussed on Perrine Bulgheroni’s talk in this session. This week, I cover the remaining two speakers: Rafael Pflücker and Meshark Sikuku.

Rafael Pflücker is a professor of ecological agriculture at the Universidad Científica del Sur in Peru. He spoke about his work with Agronegocios La Grama overseeing the implementation of a regenerative agroforestry model on a ginger farm and how that has enabled the farm, now organic, to become climate-resilient. Originally the ginger was grown as a monocrop. The plant grows for two years before the roots are large enough to be harvested, but this necessitates digging up the plant and disturbing the soil. The change to agroforestry and growing the ginger between rows of trees, protects the soil during the vulnerable harvest stage.

The farm has diversified over the last 20 years without losing its focus, getting a balance between different crops that grow well together. With their regenerative agroforestry method, the ginger productivity is the same, but the quality is far better as there are fewer pests, especially nematodes that damage the roots and there is extra revenue from the secondary crops – turmeric, lemon, avocado, moringa, and banana for example. They also grow cover crops and have free ranging animals to add nutrients, including chickens, guinea pigs and a few goats.

I looked up the farm’s website and it’s a really impressive operation. The three founders worked as organic inspectors and travelled around Latin America for two years certifying organic farms, an experience which showed them how important it was to support small farms and local communities. La Grama became the first Peruvian exporter of organic ginger and later turmeric, passion fruit, star fruit, and avocado. Today, it has 280 employees and 31 agronomists and supports 290 small farmers who cultivate their products over 800 hectares.

I don’t know about you, but I always read labels on fruit and veg to see where they come from. When buying bananas, I always look out for organic bananas from the Dominican Republic, mostly because we published an article on the organic production of banana in Organic Farming magazine. The organic farmers were using agroforestry systems to protect the soil and boost biodiversity, with profits being invested in local schools. If anybody would like a pdf of the article let me know.

So when I was digging around for information on La Grama, I noticed that they had set up their own import company in US and Europe, called Ipoki- so that’s a name to look out for on the label.

Reading about this forwarding thinking farm reminded me of my visit to Villa Rosa Blanca’s organic coffee plantation in Costa Rica, which had established an agroforestry system for shade and pest control. I wrote about my visit here: Coffee, climate change and the importance of shade

Meshark Sikuku is the Farm Systems and Sustainability Co-ordinator for Ripple Effect, an organisation that works across six East African countries. In this part of the world, smallholders tend to be located in remote areas, with few roads, no power and rely on rain-fed farming. These small plots of land, when managed correctly, are incredibly productive and feed many families, but they are vulnerable to climate change, especially extreme weather, such as drought and flooding.

Meshark presented 3 practical solutions which would work for smallholders and gardeners around the world.

Keyhole gardening

Meshark described keyhole gardens as simple, sustainable, and manageable structures that boost food production in small spaces, particularly in arid environments.

Section across a keyhole garden (Credit Shutterstock.)

They are so simple to make. Mark out a circular space, place a ‘basket’ in the middle which will act as a compost bin (could be made from chicken mesh), build a wall around the outside with a keyhole path to the basket, fill with soil and plant up. The presence of the compost basket in the middle means nutrients seep into the soil at root level. Don’t water the plants, water the compost instead. This will keep conditions perfect for decomposition while, at the same time, watering the plants, getting water deep down to the roots.

I first discovered keyhole gardens during a visit to a smallholding in Kenya many years ago, and I’ve adapted this idea for use in my own garden ever since. To save myself the hassle of hauling wheelbarrow loads of compostable material, I often use a mesh composter, half-buried in the centre of a large vegetable bed, which functions just like a keyhole garden. I’ve also noticed that you can buy in-ground composters, which work on a similar principle. This concept is somewhat like trench composting, though the idea of digging a trench might not appeal to no-dig enthusiasts. To avoid attracting vermin, I prefer using garden waste rather than kitchen scraps when composting directly in the ground.

Push pull biocontrol

The push pull method of integrated pest management is getting a lot of traction worldwide. Weeds like Striga and pests, such as the corn borer moth, are a major problem in maize crops so this simple, yet effective technique developed in Kenya is a great alternative to chemicals.

Meshark showed us this slide of the push pull method used by smallholders in many African countries to reduce the number of pests in their maize crop

It’s a technique that manages pests by using plants to repel (push) and attract (pull) them. The legume, Desmodium, is intercropped with the main crop. It releases volatiles that repel pests and also lures beneficial insects, while its roots release chemicals that control the parasitic weed Striga and reduces its seed bank in the soil. It also acts as a living mulch, protecting the soil and trapping moisture.

Meanwhile, trap plants, like Brachiaria grass, are planted around the field to lure pests away. The drought tolerant Brachiaria grass is also a palatable fodder crop while its roots binds the soil together and reduce soil erosion This dual strategy reduces pest damage without relying on chemical pesticides.

Can we use similar techniques in our growing spaces? Yes and we probably do it already. For example, you can plant chives between rows of carrots to repel any aphids, and grow pot marigolds and nasturtiums to attract the aphids.

This is a topic that has long interested me and I write at length about biocontrol and companion planting in my book, The Resilient Garden and Allotment Handbook.

Amaranthus (Amaranthus cruentus)

The third approach suggested by Meshark was to grow amaranthus. Long considered a weed, it’s found all over East Africa and its dispersal is helped by cattle that eat the plant and spread the seeds in their dung. Described as a super plant due to its high nutrient content, people have been encouraged to grow it as a crop, to eat the leaves and use the seed as a grain. It thrives in arid regions and is really helping to overcome food insecurity.

You can see the potential height of amaranthus here, so it needs support. I love the hazel trellis around the amaranthus growing in Priure d’Orsan in France

I have grown amaranthus of a number of years so I thought I would add some more information about this resilient crop.

In fact, I wrote about it in Amateur Gardening Magazine last year:

“Amaranthus is another spinach alternative. This statuesque plant with deep red foliage was cultivated by ancient civilizations in Central and South America and is now widely grown for its tasty leaves and seeds, which are used as a gluten-free grain, going under various names, such as callaloo, Chinese spinach and tangerio. In the UK, it is better known by the name love-lies-bleeding after its long tassels of red-pink flowers. There are many species including some perennials, but amaranth is not hardy in the UK – yet. Unless you live in particularly mild area, it’s grown as an annual. The plants need a sunny, open bed and once established, they are low maintenance and resilient. If you want flowers and seeds, keep chopping back the shoots to encourage new ones.“

Growing amaranthus: I sow mine under cover in April and May, pot them on and plant out in late May / June when they are sturdy plants about 15 cm in size. They can reach a metre or more so will need support, unless you cut the shoots regularly to get fresh leaves. I like to plant some in my ornamental beds too.

I have never collected the seed for grain but Real Seeds sells a mixed grain amaranth population mix. Real Seeds writes:

“These make up to 200,000 seed per plant, are very easy to thresh. The seeds don't need grinding - you just add them to whatever you are cooking. This is our own special mixed population bred from our trials - we have been working on this for about 20 years now. It produces early and gives a good yield of seed that is easily threshed. Very filling and nutritious, we add it to rice when cooking, it adds both flavour and protein. Simple harvesting instructions supplied. Start from late April in pots as though tomatoes, & plant out when bigger - they are very robust once six inches tall and romp away even in cool weather.”

Has anybody grown amaranthus and have any recommendations re the variety? Is it better to grow the green form rather than the one with purple leaves? I’d love to know.

A bit of biochemistry: Amaranthus is C4 plant like maize and sugar cane, which means that is has a different photosynthetic pathway compared with wheat, which is a C3 plant. C4 refers to the first photosynthetic product being a 4C sugar, whereas wheat has a 3C carbon sugar. C4 plants mop up more CO₂ than C3 plants because of their specialized photosynthesis process and leaf anatomy. Plants rely on the key enzyme RuBisCO to fix CO₂. However, RuBisCO can also bind to oxygen, leading to photorespiration, which wastes energy and releases previously fixed CO₂. C4 plants suppress photorespiration by maintaining high CO₂ levels around the enzyme. C4 plants are particularly efficient in hot, dry conditions as they can continue to fix CO₂ even when their stomata are partially closed to conserve water. So, C4 plants like amaranthus, can thrive in challenging climates and absorb more CO₂ than most C3 crops like wheat.

Roses - help needed

I spent a lot of time researching different plants to find out how they are responding to climate change, particularly the extremes and flipping of conditions from hot and dry to mild and wet.

In my focus at the moment is the rose. It’s grown around the world and in a wide range of climates, but the shift in climatic conditions is affecting some rose cultivars more than others, particularly in their tolerance of pests and disease.

So I need your help. If you grow climbing roses, whether in the UK, Europe, North America or further afield, I’d be really grateful if you could spend a few minutes giving me some feedback.

Looking back over the last 5 years:

How have your climbing roses coped with drought? Did any cultivar cope better than the others?
How have your climbing roses coped with extended periods of wet weather or flooding?
Have you seen more or less in the way of pests or disease, such as black spot or mildew?
For those climbing roses with a single flush of flowers, has the flowering time changed?
Have any of your climbing roses been affected by an unseasonally last frost? How did they cope?
Plus any other observations that could be linked to climate change

When replying could you indicate where you live / zone and the cultivar if known. Responses can be sent by email, DM or posted in comments. And if you know of somebody who grows roses and would be happy to answer these questions, please share this post with them. The more the merrier. Thank you !!! ❤️

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Happy Gardening

Sally

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