Lime
Amendment
Lime is a soil amendment used to raise the pH of acid soil. In UK gardens it is commonly supplied as ground limestone or chalk. It can help crops that prefer less acid conditions, including brassicas, but should only be used after a soil test confirms it is needed.
What it is
Lime neutralises soil acidity, moving pH towards neutral or alkaline conditions. Ground limestone acts gradually, while chalk is another traditional liming material. The effect depends on soil type, starting pH, rainfall and the material used, so the result cannot be judged by appearance alone. Lime does not fertilise soil in the same way as compost or manure, although correcting excessive acidity can improve nutrient availability. Chalky and naturally alkaline soils do not need it. Too much lime can lock up nutrients and cause yellowing, particularly in plants that prefer acid conditions.
What to do
Test the soil first and apply lime only where the result and planned crops justify it. Follow the product label or guidance from the RHS for timing and quantity, taking account of your soil type. Spread it evenly over a cleared bed and incorporate it lightly if appropriate, then allow time for it to react before planting. Liming is often useful before brassicas where club root is a concern, but it is not a cure-all. Do not apply lime at the same time as well-rotted manure. Use garden compost and mulch alongside liming to maintain soil structure and moisture.
Tips
Check pH every few years rather than adding lime routinely. Most vegetables favour about pH 6.5, while potatoes usually prefer slightly more acid soil. Never lime an already alkaline or chalky bed. Keep lime dry, use it carefully according to its label, and plan separate application times for manure.
Lime: frequently asked questions
What is lime?
Lime neutralises soil acidity, moving pH towards neutral or alkaline conditions.
How do I improve lime?
Test the soil first and apply lime only where the result and planned crops justify it.
What are some tips for lime?
Check pH every few years rather than adding lime routinely.
General guidance for UK gardens and allotments. Page updated 18 Sep 2026.