# Microalgae-Based Biostimulants Improve Biomass Production and Root-Linked Performance Stability in Pelargonium: A Three-Year Greenhouse Study

## TL;DR

A three-year study shows that microalgae-based biostimulants boost biomass and root stability in geraniums, with consistent results across seasons.

## Contribution

This is the first three-year greenhouse study showing consistent benefits of microalgae-based biostimulants on Pelargonium growth and root traits.

## Key findings

- Microalgae treatments increased dry mass by 19.2% and 33.1% compared to the control.
- Root mass increased by over 22% under both microalgae treatments.
- Root-collar diameter strongly correlated with overall plant size (R2 = 0.89).

## Abstract

Microalgae-based biostimulants may help reduce inputs in protected ornamental production, yet evidence across multiple growing seasons remains limited. We conducted a three-year polytunnel trial with six Pelargonium cultivars and applied two strains from the Mosonmagyaróvár Algal Culture Collection (MACC-612, Nostoc piscinale; MACC-922, Chlorella vulgaris). Using a factorial general linear model, we detected significant treatment effects on total dry mass, root mass, plant height, and root-collar diameter (all p < 0.001). Relative to the control, dry mass increased by 19.2% with MACC-612 and 33.1% with MACC-922, while root mass increased by >22% under both treatments. Root-collar diameter was strongly associated with overall plant size (R2 = 0.89). Treatment × year interactions were not significant (p > 0.05), providing no statistical evidence of season-specific treatment effects within the three-year trial. Cultivars differed mainly in response magnitude rather than direction. Overall, microalgae applications improved biomass accumulation and root-linked structural traits associated with plant vigor under this production system.