Dayboro Veggie ROI Calculator: is it cheaper to grow or buy?
Real supermarket prices vs actual growing costs. Find out which vegetables save me the most money.
I pull current retail prices from my price tracking system (updated regularly from major Australian supermarkets) and compare them against what it actually costs to grow each crop in Southeast Queensland. My growing cost estimates account for seeds, water at SEQ rates ($3.50/kL), and fertiliser. Not your labour, because honestly, if you are counting that, you should probably just go to Woolies.
Is it actually cheaper to grow your own vegetables in Dayboro?
The short answer: for most crops, yes. Sometimes dramatically so. But not for everything, and the devil is in the details. Potatoes at $4/kg from Woolies are genuinely hard to beat once you factor in the space they need and the water they drink. I still grow them because I enjoy it, not because it saves money. Herbs like basil on the other hand are an absolute rort at the supermarket. A tiny punnet for what I could grow by the bucket load for almost nothing.
The key factors that swing the equation are yield per square metre, days to harvest, and the current retail price. Crops that produce heavily in a small space (think zucchini, cucumbers, tomatoes) tend to deliver the best return on my gardening investment. Crops that take up heaps of room and produce modest yields (corn, pumpkin) can actually cost you more than buying them, unless you have space to burn. I do, which is why I still grow them.
What costs to consider when growing your own
My calculator accounts for three direct costs:
Seeds and seedlings
Seed packets from Bunnings or your local nursery typically cost $3 to $8. Premium varieties (heirloom tomatoes, fancy herbs) can cost more. I save seeds from my own crops season to season, which drops this cost to near zero after the first year.
Water
SEQ water rates are approximately $3.50/kL (1,000 litres). My calculator
uses crop specific watering needs. A thirsty crop like cucumber at 12L/week costs
roughly 22 cents per week to water. Over a full growing season water costs are
typically $1 to $5 per crop. Mulching heavily reduces this by 30 to 50%. I mulch
everything.
Fertiliser
A basic seasonal fertiliser cost of $1 to $5 per crop depending on how hungry it is. Heavy feeders like tomatoes and capsicum need more. Legumes (beans, peas) fix their own nitrogen and need very little. If you compost, your fertiliser cost approaches zero. I've been running mine close to zero for years.
What I don't include
Labour: the calculator does not price your time. If your hourly rate matters, gardening is rarely competitive with Woolworths. But most backyard gardeners don't garden for the wage. I garden because I enjoy it.
Setup costs: raised beds, soil, tools. These are one off costs that amortise over many seasons. My break even analysis (members only) factors in a typical $150 raised bed setup.
The most profitable vegetables to grow in Southeast Queensland
Based on current supermarket prices and realistic SEQ growing conditions, herbs consistently top my profitability charts. Basil retails for over $30/kg at the supermarket but costs almost nothing to grow. The same goes for most leafy herbs. Among "proper" vegetables, lettuce, spinach, and kale deliver strong returns because they produce multiple harvests from a single planting (cut and come again), their retail prices are high per kilogram, and they grow fast in Dayboro's climate.
Crops that take up less space tend to win on ROI. Lettuce at 0.15m² per plant with 52 days to harvest is hard to beat. Compare that to pumpkin at 2m² per plant and 102 days. Pumpkin needs 13 times the space and twice the time for a modest retail price of around $3/kg.