Start with the weight you can comfortably carry

Water is heavier than most people expect: a litre weighs a kilogram, so a ten-litre can tips the scales at around ten kilos before you add the weight of the can itself. That is fine if your tap sits beside the border you are watering, but it becomes a chore if you are carrying it down a flight of steps or along twenty metres of path. Before you buy anything, fill a bucket to the size you are considering and walk the route you would actually take. For most small gardens, a can you can carry in one hand and pour with the other is worth more than a large one that leaves you stopping to rest.

Two cans often beat one. A small can kept by the back door for pots, and a larger one stored near the tap for borders, means you rarely fill more water than the job needs.

Match the capacity to the job in hand

Capacity is the single most useful decision you will make, and the right answer depends entirely on what you are watering.

• Two litres is the sweet spot for containers. It waters a decent-sized pot or a couple of hanging baskets, reaches the back of a crowded windowsill, and is light enough to hold steady above seedlings.
• Five litres is the versatile middle ground. It will get round a balcony, a small courtyard or a dozen pots in one trip without wrecking your shoulder.
• Ten litres earns its place in dry spells, when established borders, new plantings and allotment beds need a proper soak. Fewer refills matter more than light weight when you are watering deeply.

If you grow in raised beds or a small greenhouse, a five-litre can with a removable rose gives you the most flexibility for the space it takes up.

Balance, handles and spout length

A good can feels balanced when it is full, not when it is empty. Pick one up in the shop, fill it mentally, and check where the top handle sits. On a well-designed can, the balance point falls naturally under your grip so the weight tips forward into the spout rather than dragging your wrist backwards. The rear handle is just as important: it gives you the control to tilt slowly for a gentle pour instead of sloshing half the water over your feet.

Spout length is underrated. A long spout reaches across a row of pots and into the middle of a border without you treading on anything, and it lets you pour from further back when you want a slow, controlled flow. Plastic cans are light and inexpensive, but avoid anything so thin that the sides flex when filled; galvanised metal costs more, lasts for decades, and keeps water noticeably cooler on a hot afternoon.

The rose decides how gentle the water is

The rose is the perforated end piece, and it has more influence on your plants than the can itself. A fine brass rose breaks the flow into a soft spray, which is exactly what seed trays, newly pricked-out seedlings, young salad leaves and freshly sown lawns need. Coarse holes deliver a faster stream for established shrubs and for sluicing down a patio. Choose a can with a removable rose: twist it off and you have a direct stream for filling saucers, topping up a water butt or watering into the neck of a large pot.

Two habits are worth adopting. Turn the rose face-up while you walk, so it stops dripping down your leg. And check the holes regularly, because hard water leaves limescale that closes them one by one. Soaking the rose in a dilute vinegar solution shifts most of it.

Looking after the can itself

Empty your can after every use and store it upside down so the last drops drain away. Standing water left over winter is the main killer of watering cans: frost expands it, splitting seams and cracking plastic. Galvanised cans should be dried thoroughly and kept somewhere airy to slow rust at the joints, while plastic ones last far longer if they spend summer out of direct sun rather than baking on a patio.

Keep a small can indoors for houseplants, and never use the same one for weedkiller or plant feed unless you label it clearly and permanently. A trace of weedkiller in a can used for seedlings can undo a whole season's sowing.

A seasonal rhythm for small spaces

In spring, reach for the two-litre can with the fine rose for seed trays and newly planted anything, watering little and often. Through summer, the ten-litre can comes into its own: fill it in the cool of early morning or evening, water deeply rather than daily, and let a mulch of compost or bark hold that moisture in the ground. Container plants still need daily attention in hot weather, because compost dries out far faster than open soil.

In autumn, ease off as growth slows, but keep watering new plantings and evergreens until the ground cools properly, as dry roots suffer more in frost. Through winter, most plants need nothing at all, though anything under cover or against a sheltered wall will still appreciate the occasional small can. Match the can to the season, and watering stops being a chore and becomes the most useful ten minutes of your week.