Hot water treating seeds: what is it and when to do it

Marissa Schuh, horticulture Integrated Pest Management Extension educator, and Natalie Hoidal, vegetable Extension educator

As farmer's market and CSAs wrap up, attentions turn to relaxation.  This is also a time of year when some farms choose to save and hot water treat seeds. 

Is hot water treatment right for your farm?

A sous vide helps keep water at a steady temperature. It is the most advanced piece of technology needed to use hot water to treat seeds. Photo: Marissa Schuh, UMN Extension.

If you’ve been disappointed by seedborne diseases when saving your own seeds, hot water seed treatment is one way you can reduce the chance that these diseases show up. Diseases that are thought to be seedborne include bacterial spot, bacterial canker, and black rot, among others.

This process needs to be performed very carefully, as you can kill seeds if directions aren’t followed to the letter. The Ohio State University has good videos and fact sheets about how to hot water treat your seeds.

Treating Seeds: Now or Later?

We often get questions about when growers can hot water treat their seeds. Some people treat them right after harvesting them. Others prefer to do this in the winter when they have some downtime, while others prefer to do it right before planting in the spring.

This past winter, U of M Extension educators treated seeds at three different times to see if the time of treatment would impact germination. We also tested the treated seeds against an untreated control. While this was a small demonstration project, we did not see any consistent differences across treatments or controls. The takeaway: as long as you follow the instructions carefully, hot water treatment at any time should not impact germination.