---
title: How to use fertilisers with your seedlings
description: Learn the best practices for fertilizing seedlings, including timing, dilution, and signs of nutrient deficiencies to ensure healthy growth.
---

[Skip to content](https://www.theonlinegardencenter.com/how-to-garden/how-to-use-fertilisers-with-your-seedlings#main-content)

## ![5 step guide to fertilising seedlingsStep 1 Wait until true leaves appearDo not feed immediately after germinationWait until seedlings have 23 true le-1](https://www.theonlinegardencenter.com/hs-fs/hubfs/AI-Generated%20Media/Images/5%20step%20guide%20to%20fertilising%20seedlingsStep%201%20Wait%20until%20true%20leaves%20appearDo%20not%20feed%20immediately%20after%20germinationWait%20until%20seedlings%20have%2023%20true%20le-1.png?width=1024&height=1536&name=5%20step%20guide%20to%20fertilising%20seedlingsStep%201%20Wait%20until%20true%20leaves%20appearDo%20not%20feed%20immediately%20after%20germinationWait%20until%20seedlings%20have%2023%20true%20le-1.png)

## How to use fertilisers with your seedlings

Seedlings don’t need much feeding early on — but once they start growing, the right fertiliser makes a big difference. Too little and they stall. Too much and you burn them.

This is about timing and balance, not quantity.

## Quick answer: how to fertilise seedlings

Start feeding seedlings once they develop true leaves, using a **diluted, balanced fertiliser** every 1–2 weeks. Always water lightly first and avoid overfeeding.

## 5 step guide to fertilising seedlings

Step 1: Wait until true leaves appear

- Do not feed immediately after germination
- Wait until seedlings have **2–3 true leaves**
- Before this, they don’t need it

Step 2: Use the right fertiliser

- Choose a **balanced liquid fertiliser**
- Avoid strong or high-nitrogen-only feeds
- Gentle is better than aggressive

Step 3: Dilute properly

- Use **half strength (or less)**
- Seedlings are sensitive
- Overfeeding causes more harm than underfeeding

Step 4: Water before feeding

- Lightly water first
- Prevents root burn
- Helps nutrients absorb evenly

Step 5: Feed little and often

- Every **1–2 weeks during active growth**
- Watch plant response
- Adjust if needed

## Best fertilisers & why

- Balanced liquid fertiliser 
    - Easy to control
    - Best for general use
- Seaweed-based feed 
    - Gentle and low risk
    - Supports root development
- Diluted organic feeds 
    - Improve overall plant health
    - Slower release

Avoid heavy or slow-release fertilisers at this stage — too strong.

## Common issues, pests & diseases

Overfeeding (burnt seedlings)

- Leaves curl or scorch
- Growth stalls
- Fix: flush soil with water and stop feeding

Weak, pale seedlings

- Cause: nutrient deficiency
- Fix: introduce light feeding

Seedlings collapsing

- Often unrelated to feeding
- Usually watering or airflow
- If this is happening, fix it here: [https://www.theonlinegardencenter.com/how-to-garden/how-to-prevent-damping-off-in-seedlings](https://www.theonlinegardencenter.com/how-to-garden/how-to-prevent-damping-off-in-seedlings?hsLang=en)

## Nutrient deficiencies to watch for

This is where most people guess. Don’t — the signs are clear:

**Nitrogen deficiency**

- Pale, yellowing older leaves
- Slow growth  
  → Fix: use a balanced feed with nitrogen

**Iron deficiency**

- Yellow leaves with **green veins** (new growth first)  
  → Fix: iron-rich feed or improve soil pH

**Phosphate deficiency**

- Dark, purplish leaves
- Poor root development  
  → Fix: balanced fertiliser

**Potassium deficiency**

- Yellowing or browning at leaf edges
- Weak overall growth  
  → Fix: use a feed with higher potassium

**Magnesium deficiency**

- Yellowing between veins on older leaves  
  → Fix: magnesium supplement (e.g. Epsom salts in small doses)

If you can read the leaves, you can fix the problem quickly.

## Best fertiliser, soil, lighting & growing conditions

- Light 
    - Bright light is essential — feeding won’t fix poor light
- Soil 
    - Good seed compost first
    - Nutrients added later through feeding
- Water 
    - Even moisture
    - Avoid waterlogging
- Feeding 
    - Light, consistent, diluted

Feeding supports growth — it doesn’t replace good conditions.

## Time of year

- Start feeding in **spring once growth begins**
- Continue through active growth
- Reduce feeding in slower periods

Seedlings don’t need pushing — just steady support.

## Climate and regional notes

UK & Ireland

- Lower light levels mean slower growth
- Avoid overfeeding

Europe

- Northern regions similar to UK
- Southern regions may need slightly more frequent feeding

USA

- Faster growth in warmer climates
- Adjust feeding accordingly

## Pro tips for better results

- Always err on the side of underfeeding
- Watch the leaves — they tell you everything
- Don’t fertilise dry soil
- Use liquid feeds for control
- Combine feeding with good light

## 10 frequently asked questions about feeding seedlings

**When should I start fertilising seedlings**  
Once they have developed true leaves.

**How often should I feed seedlings**  
Every 1–2 weeks during active growth.

**What is the best fertiliser for seedlings**  
A diluted, balanced liquid fertiliser.

**Can I overfertilise seedlings**  
Yes — and it’s one of the quickest ways to kill them.

**Why are my seedlings pale**  
Likely nitrogen deficiency or lack of light.

**Do seedlings need feeding early on**  
No, they rely on stored energy at first.

**Can I use full-strength fertiliser**  
No — always dilute.

**What causes yellow leaves on seedlings**  
Often nitrogen or iron deficiency.  
See: [https://www.theonlinegardencenter.com/how-to-garden/why-are-my-plant-leaves-turning-yellow](https://www.theonlinegardencenter.com/how-to-garden/why-are-my-plant-leaves-turning-yellow?hsLang=en)

**Is organic fertiliser better**  
It’s safer, but still needs to be diluted.

**Will fertiliser fix leggy seedlings**  
No — that’s a light issue. Fix it here: [https://www.theonlinegardencenter.com/how-to-garden/why-are-my-seedlings-leggy](https://www.theonlinegardencenter.com/how-to-garden/why-are-my-seedlings-leggy?hsLang=en)

## Related guides

- If your seedlings are weak, this is the first thing to fix: [https://www.theonlinegardencenter.com/how-to-garden/why-are-my-seedlings-leggy](https://www.theonlinegardencenter.com/how-to-garden/why-are-my-seedlings-leggy?hsLang=en)
- Your watering needs to be right before feeding — click here: https://www.theonlinegardencenter.com/how-to-garden/how-often-to-water-seeds-during-germination
- Soil quality matters more than fertiliser early on — read this: https://www.theonlinegardencenter.com/how-to-garden/best-soil-mix-for-seed-germination

## Related Articles

### [How to grow ferns from seed (spores)](https://www.theonlinegardencenter.com/how-to-garden/how-to-grow-ferns-from-seed-spores?hsLang=en)

## How to grow ferns from seed (spores)

Ferns don’t grow from seeds in the usual sense — they grow...

by [Mark Foley](https://www.theonlinegardencenter.com/how-to-garden/author/mark-foley)

### [How to prevent damping off in seedlings](https://www.theonlinegardencenter.com/how-to-garden/how-to-prevent-damping-off-in-seedlings?hsLang=en)

## How to prevent damping off in seedlings

Damping off is one of the most common and frustrating...

by [Mark Foley](https://www.theonlinegardencenter.com/how-to-garden/author/mark-foley)

### [How to fix phosphate deficiency in seedlings](https://www.theonlinegardencenter.com/how-to-garden/how-to-fix-phosphate-deficiency-in-seedlings?hsLang=en)

## How to fix phosphate deficiency in seedlings

Phosphate (phosphorus) deficiency is less common than...

by [Mark Foley](https://www.theonlinegardencenter.com/how-to-garden/author/mark-foley)

```json
{
  "@context" : "https://schema.org",
  "@type" : "BlogPosting",
  "author" : {
    "@type" : "Person",
    "name" : "Mark Foley",
    "url" : "https://www.theonlinegardencenter.com/how-to-garden/author/mark-foley"
  },
  "dateModified" : "2026-03-28T22:50:55.948Z",
  "datePublished" : "2026-03-28T22:50:55.000Z",
  "headline" : "How to use fertilisers with your seedlings",
  "mainEntityOfPage" : {
    "@id" : "https://www.theonlinegardencenter.com/how-to-garden/how-to-use-fertilisers-with-your-seedlings",
    "@type" : "WebPage"
  },
  "publisher" : {
    "@type" : "Organization",
    "logo" : {
      "@type" : "ImageObject",
      "url" : "https://www.theonlinegardencenter.com/hubfs/Logo_colour-03-3.png"
    },
    "name" : "TOGC"
  }
}
```