A living vegetable garden: welcoming beneficial insects, birds and hedgehogs
A flower strip cut the damage from one pest by 61 % in a Swiss trial. The figures from the studies and ten moves ranked by effort.
To have fewer aphids and slugs without spraying anything, invite the ones that eat them. A sown flower strip cut the damage from a wheat pest by 61 % in a Swiss trial. A hedge, on the other hand, showed no measurable effect on the pests of neighbouring fields.
The figures from the studies
Three pieces of work give figures. None concerns a private vegetable garden. Two are about fields, the third about gardens with no distinction for vegetable plots. Keep that in mind as you read them.
The flower strip in the Swiss trial held only seven annual plants. There were dill, corn chamomile, chervil, cornflower, coriander, buckwheat and poppy. Three of them are edible. In the trial, the pest's predators were more numerous in the strips. They were also, in part, in the neighbouring wheat.
Albrecht's synthesis says something else that is useful. The effect on pollination drops quickly as you move away from the flowers. It is stronger with perennial, older and more varied strips. In your vegetable garden, therefore, put the flowers among the vegetables, not at the back of the garden.
The limits of these figures
We do not know whether the effect holds on 30 m² of vegetables. The trials cover hectares, with a landscape around them. In a small town garden, the visitors also depend on the neighbouring gardens. Nobody has measured how many fewer aphids you get on your broad beans after sowing cornflower. The mechanisms are proven at large scale. The moves, for their part, cost little.
Who comes to eat what
In a living vegetable garden, pests have predators. Some can be seen, others come out at night.
| Who | Why you want them | What they need |
|---|---|---|
| The hedgehog | It eats beetles, earwigs, caterpillars, slugs and snails (Natagora) | A passage between gardens, a shelter in the shade, no chemicals |
| Ladybirds, hoverflies, ground beetles and earwigs | They go after aphids (RHS) | Open flowers near the vegetables, from spring to autumn |
| Birds | They bring the hedge to life and eat berries in winter (Woodland Trust, for ivy) | A thick hedge, thorny if possible, not trimmed from April to mid-August |
| Amphibians and dragonflies | They colonise a new pond without being put there (Natagora) | A pond without fish, and a dense planted area close by |
The hedgehog is a protected species in Belgium. You do not catch it and you do not move it. Natagora points out that it needs several hectares to live. Your garden alone is not enough. It needs a passage to the neighbouring gardens.
To recognise the small helpers, the guide Garden helpers shows the larvae, often more useful than the adults and far less known.
Ten moves, ranked by effort
The table runs from the five-minute move to the weekend job. Start at the top.
| No. | The move | Time | For whom |
|---|---|---|---|
| 1 | Stop chemical insecticides and slug killers | 0 minutes | Butterflies, hedgehogs, ground beetles |
| 2 | Program the robotic mower to run between 10 am and 5 pm | 5 minutes | Hedgehogs |
| 3 | Open a 13 cm by 13 cm passage at the foot of the fence | 15 minutes | Hedgehogs |
| 4 | Put a rough sloping board at the edge of the pond or the pool | 15 minutes | Hedgehogs, toads |
| 5 | Leave a pile of dead leaves and branches in a corner | 30 minutes | Hedgehogs, ground beetles, toads |
| 6 | Keep a corner of nettles, ivy and brambles | 0 minutes, then leave it alone | Butterflies, birds |
| 7 | Sow flowers among the vegetables: coriander, dill, cornflower, calendula, borage | 1 hour | Hoverflies, bees, ladybirds |
| 8 | Set up a hedgehog shelter: a wooden box filled with dry grass, placed upside down under a bush | 1 hour | Hedgehogs |
| 9 | Plant a hedge of at least five native species | A weekend, between mid-November and the end of February | Birds, insects, hedgehogs |
| 10 | Dig a pond of 3 to 25 m² | A weekend | Frogs, newts, dragonflies |
According to Natagora, robotic mowers have become the biggest source of worry in recent years. The hedgehog comes out at nightfall. A robot that runs from 10 am to 5 pm does not meet it.
Flowers among the vegetables
The effect drops with distance. So sow your flowers along the edge of a bed or in clumps between the rows. The plants in the Swiss trial suit this well. Coriander, dill and chervil are sown in the vegetable garden like vegetables. Add later flowers. Calendula and borage reseed themselves from one year to the next. The guide Calendula and borage says how to let them do it.
Aim for flowers from spring to autumn. At the end of the season, ivy takes over. It flowers from September to November, when almost nothing is left for insects. Its fat berries then feed thrushes and blackbirds (Woodland Trust). If an old wall is covered with it, leave it.
The hedge and the pond, the two big jobs
A hedge did not reduce pests in neighbouring fields in Albrecht's synthesis. It serves another purpose. Birds shelter and feed there. The hedgehog sleeps in it and insects spend the winter there. Natagora advises at least five native species, ideally 75 % of which bear fruit, pollen or nectar. Thorny species like hawthorn and blackthorn protect nests. Plant between mid-November and the end of February, out of frost. Trim between November and February. Never from April to mid-August, when birds nest. The full plan, the species and their flowering months are in the guide Planting a bee-friendly country hedge.
The pond is the longest job. The Natagora sheet gives 3 to 25 m², an irregular shape and three depths. Allow one zone of about 30 cm, another of about 50 cm and a part of 80 cm to 1.20 m. That last one does not freeze in winter and does not dry up in summer. Put no goldfish or koi carp in it. They eat the eggs, tadpoles and larvae. Dragonflies find a new water point on their own. The step-by-step is in Digging a small garden pond.
And pests, in the meantime?
Beneficial insects reduce pests without removing them. The RHS, the British horticultural society, explains. In spring, aphids multiply before their predators are numerous enough. It advises tolerating them when possible. If a plant suffers, squash the colonies between two fingers. The guide Aphids, let them be or step in says where to draw the line. For the rest, the guide Pests and diseases of the vegetable garden gives the symptom, the cause and the move for the most frequent problems.
When you sow coriander or chervil among your vegetables, the app gives you their sowing period in your region. Find them here.
FAQ
Does the hedgehog really eat slugs?
Yes. Natagora lists slugs and snails among its prey, with beetles, caterpillars and earthworms. A chemical slug pellet can therefore poison it second-hand.
Is a hedge enough to bring aphids down?
The studies do not show it. In Albrecht's synthesis of 18 studies (2020), hedges did not increase pest control in neighbouring crops, unlike flower strips. The hedge serves as shelter and larder for birds and hedgehogs.
When to trim a hedge without disturbing birds?
Between November and February, while the vegetation is dormant. Natagora advises absolutely avoiding trimming from April to mid-August, the nesting period.
Should you put fish in the pond?
No. Goldfish and koi carp stir up the mud and eat the eggs, tadpoles and dragonfly larvae (Natagora). A pond without fish attracts more life.
Which flower to sow first?
A plant you can also eat, like coriander, dill or chervil. All three were part of the flower strip in the Swiss trial. They flower if you let a few plants bolt.
Photo: Nikola Tomašić, Unsplash
Sources
- Albrecht M. et al., The effectiveness of flower strips and hedgerows on pest control, pollination services and crop yield: a quantitative synthesis, Ecology Letters 23 (10), 2020, p. 1488 à 1498 (18 études sur les ravageurs, 17 sur la pollinisation)
- Tschumi M., Albrecht M., Entling M. H. et Jacot K., High effectiveness of tailored flower strips in reducing pests and crop plant damage, Proceedings of the Royal Society B 282, 2015 (blé d'hiver, plateau suisse)
- Muratet A. et Fontaine B., Contrasting impacts of pesticides on butterflies and bumblebees in private gardens in France, Biological Conservation 182, 2015 (3 722 jardins, 2009 à 2011), résumé de Conservation Evidence
- Natagora, Réseau Nature, Fiches jardin naturel : Accueillir le hérisson (mise à jour 11/2021)
- Natagora, Réseau Nature, Fiches jardin naturel : La mare naturelle (mise à jour 11/2021)
- Natagora, Réseau Nature, Fiches jardin naturel : La haie sauvage et la plantation (mise à jour 11/2021)
- Hedgehog Street (People's Trust for Endangered Species et British Hedgehog Preservation Society), Link your garden (trou de 13 cm sur 13 cm)
- RHS, Aphids (ennemis naturels, pucerons qui se multiplient au printemps avant leurs prédateurs, tolérer et écraser plutôt que traiter)
- Woodland Trust, Ivy (floraison de septembre à novembre, ressource pour les insectes en automne, baies pour les oiseaux)
He gardens in Belgium and tries out in his own vegetable patch what the app recommends. His articles always start from a source you can check and a step you can take this weekend.
