1Know Your Berries Before You Blend
Blueberries are the workhorse. Mild, slightly sweet, a little earthy — they blend into almost anything without fighting the other flavours, and they turn every smoothie a deep, gorgeous purple-blue. Fresh work fine in summer, but frozen blueberries are genuinely superior here: they're picked and frozen at peak ripeness, they chill the blend without diluting it, and the colour is more intense than anything out of a punnet in February. Keep a bag in the freezer at all times and you're always five minutes from a decent smoothie.
Strawberries are the crowd-pleaser. Bright, jammy, unmistakably sweet with just enough tartness to stay interesting — they're the berry most people reach for first, and with good reason. They freeze beautifully: hull them, lay them flat on a tray, freeze until solid, then bag them up so they don't clump into one giant strawberry brick (a trick worth knowing for any fruit you plan to store). One thing to watch: fresh strawberries are mostly water, so using them straight from the fridge adds liquid you might not want. Frozen, they're concentrated and thick.
Blackberries bring something completely different — a deeper, slightly winey flavour with real tartness and a faint floral note that lifts a blend unexpectedly. They're the most assertive of the four, which means a small handful goes a long way. They freeze well, though their seeds can make a finer-textured smoothie feel a little gritty if your blender isn't powerful. A high-speed machine handles them easily; a standard blender might struggle with a large quantity.
Then there's açaí — technically a drupe, botanically speaking, though it behaves like a berry in the bowl. Harvested from palm trees native to the Amazon basin in South America, it has an unusual flavour profile: earthy, chocolatey, faintly fruity, a little bitter on its own. It's almost always sold frozen as a purée or in flat packs, which is exactly the form you want. It blends thick and rich, makes the base of a bowl rather than a sip-through smoothie, and pairs naturally with banana, mango, and coconut. Don't expect the bright berry sweetness of the others — açaí is its own thing entirely, and better for it.
The short answer on freezing: blueberries and strawberries, always. Blackberries, yes when you find them. Açaí comes pre-frozen — just keep it in the freezer and you're set.