How do I feed plants properly?

Plants in the open ground rarely need much feeding if the soil is decent. Plants in pots always do, because watering flushes nutrients straight out. Confusing these two situations is behind most feeding mistakes in both directions.

What you'll need

• General purpose fertiliser (optional)
• Watering can (optional)
• Tomato feed (optional)

Step by step

1. Work out whether the plant actually needs feeding.Plants in good garden soil usually do not. Plants in pots, hungry crops and anything flowering or fruiting heavily do.
2. Read the three numbers on the packet.N-P-K: nitrogen for leaf growth, phosphorus for roots and establishment, potassium for flowers and fruit. High-nitrogen feed on a tomato gives you a large green plant and few tomatoes.
3. Feed only during active growth.Spring through late summer for most plants. Feeding a dormant plant in winter does nothing useful and can damage roots.
4. Water the plant before feeding, never onto dry soil.Fertiliser on dry roots burns them. Water first, then feed, or feed immediately after rain.
5. Use the stated dilution or weaker.Half strength twice as often is safer and generally better than full strength. Overfeeding is more damaging than underfeeding.
6. Switch to a high-potassium feed once flowering starts.Tomato feed works for almost anything that flowers or fruits, not only tomatoes. It is the most useful single bottle in a garden.
7. Use slow-release granules for pots and containers.Mixed into the compost in spring, they feed for months and remove the need to remember.
8. Improve the soil rather than feeding, in the open ground.Compost and mulch build fertility that lasts. Liquid feed is a short-term correction; organic matter is the long-term answer.

Tips

• Signs of overfeeding: white crust on the soil surface, brown crispy leaf edges, and lush weak growth that attracts aphids.
• Homemade comfrey or nettle feed is effectively free and works well — nettle is high in nitrogen, comfrey high in potassium.
• Ericaceous plants such as blueberries, camellias and rhododendrons need specific acidic feed. General feed slowly makes them worse.

Common mistakes

• Feeding a struggling plant — Poor growth is more often water, light or root problems. Fertiliser on a stressed plant adds damage rather than fixing the cause.
• Using high-nitrogen feed on fruiting plants — You get lush foliage and very little fruit. Switch to high potassium once flowers appear.
• Feeding at more than the stated strength — Excess fertiliser burns roots and can kill a plant faster than neglect.

Questions people ask