How do I fix a waterlogged garden?

Waterlogging has several causes with very different solutions, so the diagnosis matters. Digging drainage into ground that is compacted rather than genuinely wet is wasted effort, and vice versa.

What you'll need

• Garden fork
• Compost or organic matter
• Spade (optional)
• Sharp sand or grit (optional)

Step by step

1. Do a drainage test.Dig a hole 30cm deep, fill it with water, let it drain, then fill again. If it takes more than four hours to drain the second time, drainage is genuinely poor.
2. Check for compaction first.Push a fork in. If it stops abruptly at a consistent depth, there is a compacted pan — often from building work or machinery. That is fixable and common.
3. Break up compaction by forking deeply.Push a fork in as far as it goes and rock it, every 20cm across the area. It breaks the pan and lets water through.
4. Add organic matter generously, repeatedly.Compost and well-rotted manure improve structure so water can move through. This is the main long-term fix and it works on clay.
5. Check where the water is coming from.Roofs, patios and drives shed a lot of water. Redirecting a downpipe into a butt or a soakaway sometimes solves the whole problem.
6. Build raised beds where you need to grow.It is often far easier to grow above the problem than to fix it, and it gives immediate results.
7. Consider planting for the conditions.Willow, dogwood, astilbe, ligularia and many others thrive in wet ground. A bog garden is a better answer than fighting a high water table.
8. Get professional advice for persistent standing water.Land drains and soakaways are a real solution but need designing properly, including somewhere for the water to go.

Tips

• Never dig or walk on waterlogged soil. It compacts badly and makes the drainage worse, and the damage lasts for years.
• Adding sand to clay in small quantities makes drainage worse, not better. Organic matter is what improves structure.
• Aerating a waterlogged lawn with a hollow-tine aerator and top-dressing with sandy compost makes a substantial difference over two or three seasons.

Common mistakes

• Working the soil while it is wet — It compacts and smears, destroying the structure that lets water drain. It makes the underlying problem worse.
• Adding sand to clay — In practical quantities it produces a concrete-like mix. Bulky organic matter is what opens clay up.
• Installing drainage with nowhere for the water to go — It simply moves the problem, often to a neighbour. Drainage needs an outfall or a properly sized soakaway.

Questions people ask