Liquid Gypsum and Wetting Agent Kit for waterlogged clay lawns and beds
A two-product kit for lawns and beds on clay where water sits after rain, or stays soggy for days. On clay, a lot of that water is sitting on top because the surface has sealed over and it cannot get in. The kit puts both answers in one watering can. The gypsum adds calcium to the clay to help keep the surface open. The wetting agent helps the water, and the gypsum carried in it, soak in evenly across the whole area you treat, so the low spots that are already wettest get no more than their share.
You get Liquid Gypsum and Wetting Agent for Lawns & Soil in matching sizes, for about 10% less than buying them one by one. Full rates and directions for each are on those two pages.
Which kind of waterlogging have you got?
- Water sits on top. The soil a spade's depth down is drier. The surface has sealed. This is the job for the pair.
- A screwdriver stops hard within 5 to 10 cm. That is compaction. Aerate or fork first, then use the pair straight afterwards so it gets down the holes.
- A 30 cm hole filled with water is still full the next day. A high water table, a subsoil pan or no gradient. No bottle will fix that; it needs physical drainage.
All three tests are in the How to Use tab, and the Do I need liquid gypsum? test walks you through them. Run them before you buy.
| Months | What to do |
|---|---|
| September to November | First window. Gypsum and wetting agent together in one can. Get it on before the winter rain. |
| December to February | Leave it. Nothing goes on frozen, snow-covered or waterlogged ground. |
| March to May | Second window. Gypsum and wetting agent together again, in the same way. |
| June to September | Use the spare wetting agent on its own for dry patch once a week while a dry spell lasts. |
On clay that comes apart in water, the gypsum goes on once a month in both windows: six applications at the clay rate on the Liquid Gypsum page, then about every three years. For a lawn that only puddles now and then, one application in autumn and one in spring at the lawn rate.
Aerating in autumn? Apply the pair straight after, so it runs down the holes.
One application of both together in one can at the standard lawn rate for each product, at 1 litre of mix per m². The same amount of wetting agent again is left for summer.
| Size | Covers | Price |
|---|---|---|
| 500 ml each | 50 m² | £24.29 |
| 1 litre each | 100 m² | £37.79 |
| 5 litres each | 500 m² | £137.69 |
On clay that comes apart in water, the gypsum goes on at a higher rate and covers less. That rate is on the Liquid Gypsum page, and the liquid gypsum calculator works out how much you need.
We formulate and blend the wetting agent here in Stockport. It is plant-based. The liquid gypsum we buy in ready-made from a specialist supplier: gypsum suspended in water, with fulvic acid added by the supplier. We pack it here in Stockport.
Why water sits on clay, and what the pair does about it
Clay that seals over
Where clay comes apart in water, rain knocks the finest particles loose and they settle into a skin that water struggles to pass. As gypsum mixes into the water lying on the surface, its calcium helps hold the particles together, so the surface stays open. It works hardest on clay that comes apart, and still helps, though less, on clay that holds together if the surface seals. The crumb test tells you which clay you have.
A surface that sheds water
A crusted or dried surface makes water bead and run off. The saponins in the wetting agent lower the water's surface tension so it soaks in. That effect on water-repellent ground is well studied in turf.
Together: the gypsum goes where you put it
Gypsum applied in water can only work where that water goes. On a surface that sheds water, the dose drifts to the low spots, where the water is already standing, and the rest gets little. With the wetting agent in the can, the water and the gypsum in it soak in across the area you treat.
Why autumn and spring
Gypsum works by holding calcium in the water lying on the soil while rain is falling, so it needs to be down in the wetter months. That means September to November, before the winter rain, and March to May.
No trial has tested liquid gypsum and a wetting agent applied together, and none has compared autumn application with spring. Both are reasoned from how each product works. The studies behind each product are on the Liquid Gypsum and Wetting Agent for Lawns & Soil pages, and the evidence on gypsum is weighed up in does liquid gypsum work on clay soil?
How to use the kit
First, three tests
- Crumb test. Drop a dry, pea-sized crumb of soil from about 10 cm down into a glass of rainwater, not tap water: tap water carries enough calcium to skew the result. Look at it at ten minutes and again at two hours. A milky cloud spreading from the crumb means the clay comes apart in water, which is where gypsum works hardest. Clear water does not mean gypsum is no use: it still helps, though less, where the surface seals. Step by step: Do I need liquid gypsum?
- Screwdriver test. If a long screwdriver stops hard within 5 to 10 cm of moist soil, that is a compaction pan. Fork or hollow-tine aerate first; neither product relieves compaction.
- Hole test. Dig a hole 30 cm deep and 30 cm wide in the problem area, fill it with water and time it. Water still sitting there after 24 hours means a high water table, a subsoil pan or no gradient. No liquid product will fix that; you need physical drainage.
Then, each application
- Fill the can with water and add the wetting agent first, at its own rate, and stir.
- Measure the gypsum dose into a heatproof mug, stir in a little boiling water for 60 seconds, then add it to the can at its own rate and stir.
- Water on at 1 litre of mix per m², through a rose or a knapsack sprayer, on ground you can walk on. Never into standing water: wait until the puddles have gone.
Keep each product at its own dilution and do not average the two. Mix fresh each time and never store the mix. Keep both out of the same can as Liquid Phosphorus or any phosphate feed.
Rates and timing
Each product has its own rates for lawns, beds and clay that comes apart in water. Use the rate on each product page:
- Liquid Gypsum: rates for lawns, clay that comes apart in water, after aerating, and beds and borders.
- Wetting Agent for Lawns & Soil: rates for lawns, beds and dry patch.
Apply at 1 litre of mix per m². On clay that comes apart in water, the gypsum runs as six monthly applications: September, October and November, then March, April and May. After that, about every three years. For a lawn that only puddles now and then, one application in autumn and one in spring.
For summer dry patch, apply the wetting agent on its own once a week while a dry spell lasts, at the lawn rate on its product page. Keep the gypsum to the programme above.
The liquid gypsum calculator works out quantities for the clay programme on a lawn or on beds and borders, and for the spring and autumn lawn rate. More on each job: liquid gypsum for clay lawns and liquid gypsum for clay soil.
Treat both as any garden concentrate: store out of reach, and keep pets and children off the area while you apply. Keep the wetting agent concentrate and any run-off out of ponds and watercourses, because soap nut saponins are toxic to fish.
Liquid Gypsum and Wetting Agent Kit: questions
It depends on why the water is sitting there. If it is on top because a clay surface has sealed, the pair helps the water get in. If the ground is compacted, aerate first. If the water has nowhere to go, from a high water table or no drains, no bottle will fix it. The three tests in the How to Use tab tell you which you have.
September to November, before the winter rain, and again March to May, with both in the same can each time. On clay that comes apart in water that is six monthly applications, then about every three years. A lawn that only puddles now and then needs one in autumn and one in spring. Leave it over winter and never apply it into standing water. Use the spare wetting agent on its own for dry patch from June to September, once a week while a dry spell lasts.
Not overnight. Gypsum works over a season. It works hardest on clay that comes apart in water, and still helps, though less, on clay that holds together if the surface seals. Organic matter and keeping off wet clay do the lasting work.
On soil that takes water readily, the gypsum alone is enough. The kit is for ground where water sits on top or runs off. There, gypsum applied on its own tends to collect in the puddles. The wetting agent spreads it across the lawn.
Yes. Wetting agent into the water first. Then the gypsum: measure the dose into a heatproof mug, stir in a little boiling water for 60 seconds, and add it to the can. Each goes in at its own rate. The one thing to keep out of the gypsum can is Liquid Phosphorus or any phosphate feed.
At lawn rates the wetting agent goes in at half the gypsum's rate, so the same bottle size supplies twice as many applications over the same area. Use what is left on dry patch from June to September, once a week while a dry spell lasts.
Yes, about 10% at today's prices (November 2026): £24.29 against £26.99 for 500 ml of each, £37.79 against £41.99 for 1 litre of each, and £137.69 against £152.99 for 5 litres of each.
We formulate and blend the wetting agent ourselves, plant-based. The liquid gypsum we buy in ready-made from a specialist supplier: naturally mined gypsum suspended in water, with fulvic acid added by the supplier.
Yes: Liquid Gypsum and Wetting Agent for Lawns & Soil are each sold on their own.