Five indoor growing mistakes we see most often

We hear the same story across the counter most weeks. The plants looked fine for a month, then the lower leaves went, the new growth stalled, and the fruit never filled. Nine times out of ten the cause is not an exotic deficiency. It is one of the five below, and every one of them is cheaper to fix before you plant than after.

1. Undersized extraction

Air is the part people spend last and regret first. An indoor space with a light in it makes heat, and the plants themselves add humidity every hour they are awake. If the fan cannot replace the volume of the room roughly once a minute, the temperature climbs, the humidity sits high overnight, and you get soft growth, weak stems and a standing invitation to powdery mildew.

Work it out before you buy. Multiply length by width by height in metres to get the room volume in cubic metres, then look for a fan rated well above that number in cubic metres per hour - the ducting, bends and a carbon filter all rob you of airflow, so you want headroom rather than an exact match.

If you would rather not size the two parts separately, our fans and filters page lists matched combos as well as standalone 250mm and 315mm fans. Whatever you pick, run the shortest, straightest ducting you can - every extra bend costs you airflow you paid for.

2. Feeding at full strength from day one

Bottle labels are written for a plant in full stride, not a seedling with three true leaves. A young root system cannot use that much salt, so the excess stays in the medium, the concentration climbs, and the plant starts pulling water back out of its own tissue. The first sign is usually burnt leaf tips that people read as hunger, so they feed more.

Start at roughly half the label rate and move up over a fortnight while you watch the newest growth. A base like Canna A + B is designed to be run this way, and a root stimulant such as Rhizotonic is worth more in those first weeks than any bloom additive. Save the heavy hitters in our nutrients and additives range for when there is a plant big enough to use them.

3. Letting the root zone cook

Warm water holds less dissolved oxygen than cool water, and roots sitting in warm, low-oxygen conditions are where root disease starts. In an Auckland summer a black pot on a concrete floor under a light will sit far warmer than the air in the room.

• Keep pots off bare concrete and out of direct light where you can.
• Pale pots run cooler than dark ones in the same spot.
• Air movement across the floor helps more than most people expect.
• Water early in the light period so the medium is not saturated through the warmest hours.

4. Watering on a timer instead of by weight

A fixed schedule ignores the two things that change daily: how big the plant is and what the weather is doing. The same pot that needed water every second day in October may need it twice a day in February.

Pick up the pot. Learn what it weighs soaked and what it weighs when the plant is ready for the next feed, and let that - not the clock - tell you when to water. In coco you are aiming to water little and often with a small amount of run-off each time; in a peat or soil mix you want a proper wet-and-dry swing. Our growing media and pots and trays pages cover what suits which method.

5. Starting cuttings bare

A cutting has no roots and no way to replace the water it loses through its leaves. Anything that shortens the gap between "cut" and "rooted" improves your strike rate. A rooting gel seals the cut surface and delivers hormone right where it is needed, which is why it is the single cheapest improvement most propagators make.

Clonex comes in 15ml for a handful of cuttings, 250ml for a season, and 1L for commercial trays. Pair it with Jiffy pellets and keep the humidity up for the first week. There is a full walk-through in our guide to taking cuttings with Clonex and Jiffy, and everything for the job sits under propagation and cloning.

A ten-minute check before you plant

Frequently asked questions