Garden Chemical Shelf Life

Can you use last years garden chemicals for this season? Do your herbicides, composts, fungicides and pesticides have a shelf life and if so for how long? Let’s look at ready made garden chemicals, mix them yourself chemicals and dry goods.

Ready Mixed Garden Chemicals

These chemicals should not loose their potency from one year to the next.
Do not store them in conditions of extreme heat or cold.
The factory based mixing should have been done so there is no chemical reaction between the constituent parts of the mixture.

Mix them Yourself Garden Chemicals

Concentrates that that you have mixed yourself can go off within a day or so, certainly the shelf life is less than a week.
The concentrate will last but the act of mixing with water can cause problems.
Impurities in the water and even air bubbles can start a chemical reaction that renders the solution unviable or not fit for purpose.

Dry Garden Chemicals

As long as powders and granules are kept dry, in suitable packaging and at a reasonable temperature they will have a good shelf life unless indicated strongly on the packaging.
Growmore and granular fertilisers should have a good shelf life.
Mix it your self fertilisers like Chempak have a good shelf life but make sure they are properly dissolved when mixing them.
Composts and soil mixtures have a shelf life of around six months. Fresher the better.
Where a product can get damp or starts damp it will deteriorate.

Other Issues on Garden Chemical Shelf Life

Always read the instructions and dilute to the correct strength.
RHS advice on garden chemicals
Pesticide safety education programme
Beware old chemicals should not be kept after they have been declared unsafe by EEC regulation.
Treat homemade organic chemical mixes with the same care as bought chemicals.
Keep equipment clean and wash out when you are finished.
Pesticides and other chemicals don’t spoil suddenly. They deteriorate over several years and even at 70 to 80 percent they may still be effective.