Plant care calculator

Plant fertiliser Calculator: Find the Right Dose for Every Plant

Calculate the exact fertiliser dose and feeding schedule for your plant based on species, pot size, growth stage, and season.

Quick Answer

By factoring in your specific plant type and environmental conditions, you can precisely tailor your care routine to ensure optimal health and prevent common issues like root rot.

Updated Reviewed Reading time: 8 min

Enter your details

Enter your details below to generate a custom recommendation.

Plant

Fertilizer

Environment

Optional. Enter in °C for Metric or °C for Metric. If blank, the season selection is used.

Container

Units

Static Reference

How this calculator works: Plant fertiliser Calculator: Find the Right Dose for Every Plant

Visible baseline values

These baseline ratios and decision rules are included directly in the page so visitors can review core guidance before using the interactive calculator.

Scenario Baseline Rule Safety Note
Foliage plant baseline Reference label dose x pot-volume factor x plant demand x stage x health x temperature x selected strength. Apply to moist soil and avoid feeding stressed or recovering plants.
Succulent baseline Use a very dilute balanced feed; demand multiplier is low compared with foliage and flowering plants. Overfeeding succulents is a common cause of weak growth and root stress.
Dormant or recovering plant Recommended output is pause feeding / do not fertilise. Correct light, drainage, pests, or root stress before adding fertiliser salts.

Methodology: Dose = reference label dose x pot-volume factor x plant nutrient demand x growth-stage modifier x health safety modifier x temperature modifier x selected strength.

The Problem

Many plant owners guess at their care routines, leading to root rot, burned leaves, or stunted growth. Generic advice doesn't factor in specific plant species and local climate.

When to Use This Tool

Use this calculator when you bring home a new plant, when seasons change, or if your plant is showing signs of distress.

Who is this for?

  • Beginner houseplant owners looking to avoid common mistakes
  • Advanced collectors wanting to optimise growth rates

About this calculator

Determine feeding schedules and dosage for healthy growth Using this calculator removes the guesswork from your plant care routine.

How to Use

  1. Enter the required growing conditions including Unit System, Plant Type, Growth Stage, Plant Health, Pot Size, fertiliser Type, fertiliser Strength, Season, Location, and Temperature.
  2. Get your personalized recommendation.

The Importance of Precision

Every plant species has adapted to specific conditions in the wild. By mimicking those conditions in your home, you can dramatically increase the lifespan and vitality of your collection.

Visual Diagnosis: fertiliser Burn vs Fungus Gnats

If your plant is showing signs of distress, it's critical to visually confirm the root cause before altering your feeding schedule. Below is a high-resolution comparison to help you definitively distinguish between fertiliser salt burn and pest damage.

Close up of fertiliser burn on a houseplant leaf showing crispy brown edges

fertiliser Burn: Notice the distinct crispy, brown edges and yellowing tips. This occurs when excess fertiliser salts build up in the soil and physically draw moisture out of the leaf tissue via reverse osmosis.

Close up of fungus gnat damage showing pale leaves and gnats on soil

Fungus Gnat Damage: Characterized by the overall paling and yellowing of lower leaves, accompanied by tiny black adult flies resting on the soil surface. The larvae attack the root hairs, mimicking nutrient deficiency.

fertiliser Calculator Variations & Requirements

VariationLight RequirementWatering FrequencyDifficulty
StandardBright IndirectWeeklyMedium
VariegatedHigh LightWeeklyHard
DwarfMedium LightBi-WeeklyEasy

Troubleshooting & Diagnostics Guide

1 Plant is dropping leaves despite following the recommendation

Diagnosis: Drafts, sudden temperature changes, or pest issues not related to the calculator's focus area.

Treatment: Isolate the plant, check for pests, and ensure it is away from heating/cooling vents.

Glossary of Terms

Transpiration
The process of water movement through a plant and its evaporation from aerial parts.
Photoperiod
The period of time each day during which an organism receives illumination.

Frequently Asked Questions

Is it safe to use this calculator for succulents?
Yes — the calculator automatically reduces the dosage and feeding frequency when you select 'Aloe Vera / Succulent' to prevent root burn. Succulents require far less fertiliser than tropical foliage plants.
Will using fertiliser bring my dying plant back to life?
No. If your plant is actively dying from root rot or severe pest infestation, fertilizing it will only cause further stress and chemical burn. You must resolve the primary issue before introducing nutrients.
Should I use liquid or slow-release fertiliser?
It depends on your lifestyle. Liquid fertiliser gives you precise control over dosage and is immediately available to the roots. Slow-release granular fertiliser is lower maintenance but harder to flush if you overfeed.
Why does the calculator suggest quarter-strength?
Most commercial fertilizers are highly concentrated, and manufacturers often recommend doses that are too strong for indoor plants. Diluting to quarter-strength prevents salt buildup in your soil and protects delicate root tips.
Do I need to water the plant before fertilizing?
Yes. Never apply liquid fertiliser to completely dry soil, as this can severely burn the roots. Always water the plant lightly first, wait 30 minutes, and then apply the fertiliser solution.
Why are the tips of my plant's leaves turning brown and crispy?
Brown, crispy tips are a classic sign of fertiliser burn caused by excess salt buildup in the soil. You must flush the pot thoroughly with plain water to remove the excess salts.
My plant is growing long, weak stems after fertilizing — why?
This happens when you apply high-nitrogen fertiliser but the plant doesn't receive enough light to support dense growth. You should reduce the fertiliser dose and move the plant to a brighter location.
How do I know when my plant goes dormant?
Most houseplants enter dormancy in late autumn when daylight hours shorten. The plant will completely stop producing new leaves. During this time, stop fertilizing entirely and re-evaluate using our Sunlight Calculator in the spring.

Scientific References

  1. Source: fao.org

  2. Source: content.ces.ncsu.edu

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