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What's It For? - Sulphate of Potash

Potash strengthens plants and makes them more weather and disease resistant. It also encourages flower formation and colour, leading to better blooms and higher fruit yields. It is particularly beneficial to tomatoes.

Apply it from early spring to November as a base dressing before sowing or planting. Sprinkle it evenly over the whole area (2oz per square yard) and work it into the top 4 inches of soil with a hoe or rake. As a top dressing to established plants, apply early in spring (1oz per square yard generally and up to 4 oz per square yard for fruit trees and bushes). Sprinkle evenly between rows of vegetables, amongst flowers and over the whole area covered by the branch spread of trees, shrubs and fruit bushes. Hoe or rake in and, if dry, water well for maximum benefit. Do not apply as a heap at the base of the stem and shake off any that lodges on the foliage. It may also be dissolved in water (1oz in 2 gallons) and used as a liquid feed.

The following information has been taken from the packaging of the fertilizers that are sold in the Trading Hut. For more information about fertilizers, their uses and explanation of the labelling see the RHS web site.


Sulphate of Potash is an inorganic fertilizer with NPK Values 0-0-48.

It is a plant food that promotes flowering and fruiting. It also encourages the ripening of fruit. Use it round fruit bushes and trees to encourage better and larger fruits.

Directions for Use

Scatter 35g/sq.m. (1oz/sq.yd.) evenly around the plants. Some more greedy fruits, such as raspberries, gooseberries and currants can be given up to 70g/sq.m. (2oz/sq.yd.). Lightly fork or hoe in. Repeat once or twice through the growing season. Sandy and light soils will need top dressing more frequently i.e. 3 or 4 times during the growing season.

Application Advice

Use the recommended amount. Apply evenly between the plants, without touching the plant itself. Avoid using on windy days. Water well in after applying. Wash hands after use. To be used only where there is a recognised need. Do not exceed recommended application rate.


Store in a cool, dry place away from children, pets and foodstuffs.

Other Information

Using too much Sulphate of Potash can lead to Magnesium deficiency.


SulphateOfPotash (last edited 2014-02-14 12:41:08 by PaulHowarth)