20-20-20 Fertilizer: Instructions for use and precise dosage

20-20-20 fertilizer is a balanced fertilizer containing 20% nitrogen, 20% phosphorus, and 20% potassium — the three elements every plant needs, in equal amounts. It is completely water-soluble, meaning you mix it into a watering can or bucket and use it to water your plants. The basic dosage for potted plants is one gram per liter of water, and this guide details the rest: exactly how much for each type of plant, how often, and the mistakes that kill plants.

What the three numbers mean

Every bag of fertilizer carries three numbers in the same order — N-P-K. In 20-20-20, all three are equal, which is why it is called a balanced fertilizer:

• 20% Nitrogen (N) — responsible for foliage and green growth. A deficiency looks like pale or yellow leaves, especially the older ones.
• 20% Phosphorus (P) — responsible for roots and blooming. Especially important for a young plant that has just been planted.
• 20% Potassium (K) — responsible for the plant's resilience: resistance to heat, drought, and disease.

Because of this balance, it is suitable for almost everything — houseplants, flowers, shrubs, ornamental trees, and fruit trees — and that is why it is the first fertilizer you should have at home. More specialized fertilizers (for flowering plants, citrus, orchids) come later, when there is a specific need.

Instructions for use: dosage table

The following dosages are according to the manufacturer's instructions on the packaging. Mix the powder in water until fully dissolved and water with it instead of regular watering.

For delicate houseplants — ferns, calatheas, orchids — it is best to start with half the dosage (half a gram per liter) and see how the plant reacts before increasing it. Plants in small pots, in confined spaces, and without good drainage suffer from fertilizer excess much faster than a plant in the garden.

How to fertilize correctly — four steps

1. Water with plain water first. This is the step most people skip and the most important one. Dry roots meeting fertilizer solution get burned. Moist soil protects them.
2. Dissolve completely. Mix the powder in water and ensure there are no granules settled at the bottom. A granule that touches the root directly will burn it.
3. Water the soil, not the leaves. Pour around the plant until water begins to come out of the drainage holes.
4. Empty the saucer. After half an hour, pour out what has collected. Fertilizer water left in the saucer concentrates salts and damages the roots.

When not to fertilize

• In winter. Most plants are in partial dormancy, not growing, and not consuming. Fertilizer left in the soil accumulates. Reduce significantly or stop completely.
• In the first few weeks after planting or repotting. Fresh potting mix already contains nutrients, and the roots are still recovering. Wait 4-6 weeks.
• When the plant is sick or wilting. Fertilizer is food, not medicine. A stressed plant cannot absorb it, and it will only cause harm. First, diagnose the problem.
• On a heatwave day, on dry soil. Wait for the morning or evening hours.

What fertilizer excess looks like

Excess fertilizer is easy to confuse with a deficiency, which is why many people add more — and make it worse. The signs:

• Brown and dry leaf tips, especially on young leaves
• A whitish crust on the soil surface or on the side of the pot — these are accumulated salts
• The plant stops growing despite receiving light and water
• Leaves wilt despite the soil being moist

What to do: Stop fertilizing and flush the pot — water slowly with clean water until it exits the drainage holes, wait a few minutes, and repeat two or three times. This flushes out the accumulated salts. Return to fertilizing only after the plant recovers, and at half the dosage.

Suitable products

All of these are available from us with home delivery:

• 20-20-20 Fertilizer, 1 kg bag — the powder this guide covers. One bag is enough for very many waterings.
• Liquid Universal Fertilizer — if you prefer not to measure powder. Measured by capful and mixes instantly.
• Fertilizer Drops for Houseplants and Herbs — the simple solution for a few pots at home, no bucket and no calculations.
• Slow-Release Osmocote — for those who forget to fertilize. Scatter once, and the granules release nutrients over months.
• Liquid Humus — an organic, gentler alternative, especially good for vegetable gardens and herbs.

For all options: Fertilizers · Soil and Growing Media