Roundup.

[manofsteel]

I'm using Roundup GC to clear a neglected patio area of dandelions,docks etc. The instructions are 30 ml to 5litres in a watering can but 30 ml to 1 litre in a spray. The answer may be obvious but why the difference please ???

[Buenchico]

I would assume that it's because a watering can leaves ruddy great droplets of water on the foliage of the weeds, whereas a spray only leaves tiny droplets. A small high-concentration droplet will contain the same amount of the chemical as one which is 5 times as big but with only one-fifth of the concentration.

Chris

[heathfield]

It has been calculated somehow, somewhere, by someone, that a watering can delivers 5 times more liquid than a sprayer, and this is the reason for the different dilution rates. Forget the amount of added water - these dilutions allows the same quantity of the active ingredient to cover the same area. It's not a good idea to use a stronger mix than the recommended amount. The way Roundup works, a stronger solution interferes with the systemic process acting on the weeds, and will actually give a poorer result.