Should I use a rotavator on my garden?

A rotavator does a specific job very well: it reduces a large area of rough, weed-free ground to a workable tilth in an hour rather than a weekend. Almost every problem people have with them comes from using them for a different job — clearing weedy ground, loosening compacted soil, or as an annual routine — where the machine actively makes things worse.

Safety

What you'll need

• A rotavator sized to the plot
• Boots, eye protection and ear defenders
• A cable and pipe detector (optional)
• A fork for removing weed roots first

Step by step

1. Clear perennial weeds completely before it goes anywhere near the ground.Couch grass, bindweed, ground elder, docks and mare's tail all regenerate from root fragments. A rotavator turns one bindweed root into fifty cuttings and distributes them evenly across the plot. This is the single most consequential rule about the machine.
2. Check for services and obstructions.Cables, water pipes, old paths, buried slabs and tree roots. A tine catching a slab throws the machine hard, and a tine finding a cable is a serious incident. Probe the ground with a rod first if you do not know its history.
3. Wait until the soil is right.Wet soil smears into a glazed pan under the tines and comes out as heavy sticky lumps. Bone-dry soil turns to dust and blows away. Moist and crumbling is the window, and on clay that window is narrow.
4. Set the depth shallow and make more than one pass.Full depth on the first pass is how machines buck and how pans form. Take a shallow first pass, then a second at greater depth if you need it, working across the direction of the first.
5. Let the machine set the pace.Walk behind at the speed the tines pull, with the drag bar set so the machine works rather than skitters. Fighting it is exhausting and is how people get hurt.
6. Understand the pan you are creating.Rotating tines smear the soil at the base of their cut. Every pass at the same depth builds a compacted, polished layer immediately below — typically at 150 to 200mm — which is precisely the depth at which garden compaction is most commonly diagnosed.
7. Follow it with a fork through the base if you have used it on a new plot.Once the tilth is made, go through with a fork at 300mm to break the smeared layer the machine just created. This step turns a rotavated plot into a good one.
8. Then stop.Rotavate once to break in ground, then move to permanent beds, surface compost and no further machine cultivation. Annual rotavating oxidises organic matter, destroys aggregate structure and builds the pan deeper each year.

Tips

• Hiring is almost always right. A domestic rotavator sits in a shed for 360 days a year, and the hire machines are heavier and do the job better.
• A small tiller and a full rotavator are different tools. Small tillers cultivate 100 to 150mm and are useful for seedbeds; full-size machines dig deeper and are the ones that create pans.
• If the plot is small enough to fork in a weekend, fork it. The machine's advantage only appears at scale.
• Rotavating turf in is possible but slow and needs several passes, and the grass often regrows through. Cutting the turf off, or covering it, gives a cleaner result.

Common mistakes

• Rotavating a weedy plot to 'clear' it — It does the opposite. Perennial weed roots are chopped into propagating fragments and spread evenly. A plot that had bindweed in one corner ends up with it everywhere.
• Using a rotavator to fix compacted soil — It loosens above the tines and compacts below them. The reported result is usually a bed that looks lovely in March and puddles by June.
• Rotavating in every year as a routine — Structure, worm populations and organic matter all decline measurably with repeated tillage. The bed needs more feeding each year to produce the same crop.

Questions people ask