Meyer Lemon
A Meyer lemon is the most rewarding hard plant on this list: get the light right and you get fragrant blossom and real, sweet-tart lemons in your living room. Get it wrong and you get yellow leaves and frustration. It is unapologetically demanding about sun — 6+ hours direct, supplemented with a grow light through dark winters.
Feed it a dedicated citrus fertiliser through the growing season, keep watering even (citrus drop leaves and fruit if they swing between drought and flood), and hand-pollinate the indoor flowers with a small brush to set fruit. Watch hawkishly for scale and spider mites, which love indoor citrus. High effort, high reward.
Needs 6+ hours of direct sun. A grow light is often necessary through winter to keep it fruiting.
Water deeply and drain; citrus hate both drought and wet feet
Low — keep to a consistent rhythm and don't let it dry out hard.
Citrus oils and psoralens are mildly toxic to cats and dogs; the fruit is fine for people.
Keep evenly moist; water when the top inch dries
Feed with a dedicated citrus fertiliser
Hand-pollinate flowers with a soft brush to set fruit
Inspect closely for scale and spider mites
Yellowing leaves often mean inconsistent water or low light