Apartment and balcony gardening in New Zealand comes with a specific set of constraints ground-level gardens don't have: limited floor space, real weight limits, and often far more wind than you'd expect. None of it rules out growing your own food, but it does change what's worth planting and how.
Weight is worth checking before you fill a balcony with pots, not after. Saturated potting mix is heavy, and a row of full-sized containers along a balcony edge adds up faster than people expect. If you're in a body corporate or unit title building, or renting, check what load limits apply before committing to large containers, and place the heaviest ones near load-bearing walls and corners rather than the centre of an exposed slab. Lightweight fabric grow bags or plastic pots instead of glazed ceramic or concrete cut a meaningful amount of weight for the same growing volume.
Pot size should match what you're growing rather than being one-size-fits-all. Herbs are the easiest fit: parsley and chives are both spaced at 15-20cm apart in the ground and do fine in a similarly modest pot, while basil (25cm spacing) and rosemary (a much larger 60cm spacing, since it grows into a genuine woody shrub) need more room to spread. Mint should always go in its own pot regardless of size, since it spreads aggressively by runner and will swamp anything sharing a container with it. For vegetables, lettuce (30cm spacing) and dwarf beans (10cm spacing, and they need no staking) are two of the more forgiving container crops, and strawberries (30cm spacing) do well in a hanging basket or trough where their fruit can spill over the edge away from slugs. Tomatoes and capsicums, both spaced at 45-50cm in the ground, need a genuinely large pot, at least the size of a half wine barrel, to crop well in a container.
Mint should always go in its own pot regardless of size, since it spreads aggressively by runner and will swamp anything sharing a container with it.
Drainage matters more in a container than in the ground, because there's nowhere for excess water to go except through the pot itself. Every container needs proper drainage holes, and it's worth lifting pots slightly off the balcony floor, using pot feet or even a couple of offcuts of timber, so water can actually drain rather than pooling underneath.
Wind is a genuinely bigger problem at height than most new balcony gardeners expect. Upper-floor balconies catch stronger, more constant wind than a ground-level garden, which dries out pots faster and can snap or topple taller plants. Low, bushy crops like herbs, lettuce and strawberries cope with this far better than anything tall and top-heavy; if you do grow something taller, stake it early and group pots together for mutual shelter rather than spacing them out along an exposed rail.
If you travel or simply forget to water, a self-watering pot with a built-in reservoir, or a simple wicking system, buys several extra days before plants dry out completely, which matters a lot in a small container that has far less soil buffer than a garden bed.
Finally, be honest about your light before you plant anything. Most apartment balconies face one fixed direction and get a predictable, unchanging number of hours of sun through the day, unlike a ground-level garden where you might have several different spots to choose from. Watch your own balcony for a full day before committing: a north-facing balcony in most of the country gets genuinely strong sun and suits fruiting crops like tomatoes, while an east or west-facing one gets a shorter window that suits leafy greens and herbs better. A south-facing balcony that gets only a few hours of direct sun, or none, is genuinely limiting. Don't fight it by planting tomatoes that will sulk all season; lean into shade-tolerant options like parsley and mint, or partial-sun crops like lettuce, instead.