Freezing temperatures remain one of the biggest threats to citrus production, especially in Florida and other regions where sudden cold snaps can severely damage trees. New research suggests that seaweed-based biostimulants may help citrus trees better withstand freezing conditions.
The study was published in Scientific Reports. It was led by Ahmed Abdullah, Shahid Iqbal, Alaiha Asif, KeAndre Leaks and Muhammad Adnan Shahid of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) North Florida Research and Education Center, Davie Kadyampakeni of the UF/IFAS Citrus Research and Education Center, Rashad M. Balal of the University of Sargodha in Pakistan and Zafar Iqbal of King Faisal University in Saudi Arabia.
Researchers evaluated Valencia orange trees treated with a commercial seaweed extract before exposing them to freezing temperatures. They compared three application methods: foliar sprays, root drenches and a combination of both.
The combined foliar and root application consistently produced the best results.
Trees receiving the seaweed extract experienced less cell and leaf damage during freezing temperatures, retained more water in their leaves and maintained greater biomass than untreated trees. The treatment also helped preserve chlorophyll, allowing plants to continue photosynthesis more effectively after cold stress.
One of the biggest benefits was the reduction of oxidative stress. Freezing temperatures trigger the production of harmful compounds that damage plant cells. Seaweed-treated trees activated their natural antioxidant defenses more effectively, limiting that damage. The treatments also increased protective sugars and other natural compounds that help stabilize cells during freezing.
For growers, these findings suggest seaweed biostimulants could become another tool for improving cold hardiness. While products such as microsprinkler irrigation and other freeze-protection practices remain essential during freeze events, seaweed extracts may help trees better tolerate cold temperatures before damage occurs.
The researchers caution that this work was conducted under controlled greenhouse conditions using young Valencia trees. Additional field research is still needed to determine how well these results translate to commercial groves and to identify the most effective application timing and rates.
Still, the study provides encouraging evidence that seaweed biostimulants may strengthen citrus trees’ natural defense systems and reduce the impacts of freezing stress, potentially improving tree survival and recovery following cold events.
Read the full study here.
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