This is an important question at our house, with lots of weeds and two teens looking to make some extra money.

I decided to take a mathematical approach to this question.

Crop loss and control costs for weeds in New Zealand are estimated to be about $1.2 billion per year. Add another $1.3 billion for biodiversity losses, and the total bill for weeds comes to $2.5 billion per year.

So what should I be spending on weeds? Let’s do a few calculations.

New Zealand has a land area of 268,021 km². That’s 26,802,100 hectares.

Our property is 0.6 hectares.

So our property is 0.00000002 of the land area of New Zealand.

Multiplying New Zealand’s total weed bill of $2.5 billion by 0.00000002, I should be paying about $50 a year to control weeds on my property.

My husband set the price of a 20 litre bucket of weeds at $2 (and I agreed to pay triple price for each bucket of pure thistles—hazard pay and all). That $50 is only going to pay for 25 buckets of weeds (or only 8 buckets of thistles).

Darn. I’m seriously being over-charged for weed control…