Rainbow Fertilizer Grow a Garden – Fertilizer Guide, Effects & Cost
Quick Overview
How It Works
The rarest fertilizer. 50x growth speed boost with increased rainbow mutation chance for 2 hours.
Fertilizers do not stack. Applying a new fertilizer will replace this one. Only one fertilizer can be active on a crop at a time.
How to Get Rainbow Fertilizer
- Beanstalk Event
Event only: Rainbow Fertilizer is exclusively available through in-game events. Keep an eye on event announcements and contribute actively to maximise your chances of obtaining it.
Strategy Tips
Apply to multi-harvest crops like Tomatoes or Blueberries to maximise the number of harvests per session.
Combine with growth-boosting pets for compounding speed bonuses.
Use during longer play sessions so you can benefit from multiple harvests within the duration window.
Apply just before harvesting to ensure the full multiplier is captured on the sell.
Target your highest-value crops (Legendary/Mythical rarity) for the biggest absolute gain.
Reserve this fertilizer for your absolute best crops. The multiplier is massive – save it for Prismatic or Mythical crops.
Coordinate with event timing: apply at the start of a long session so the full 2-hour window is used.
Stack with weather events (rain, night) that already raise mutation rates for maximum effect.
Apply at the start of a growth cycle so the entire growth period benefits from increased mutation chance.
Use on crops with inherently higher mutation chances (rare seeds, event crops) for the best returns.
Remember: fertilizers cannot stack with each other. Only one fertilizer can be active at a time per crop.
Related Fertilizers
Community Notes
This fertilizer guide is based on the latest Grow a Garden update. Effects, costs, and availability may change during special events or game updates. Fertilizer behaviour (especially Silver Fertilizer's permanent-application chance) is community-verified and may vary slightly between sessions.
March 2026