What We Learned: Reusing Plastic Jugs for Seed Starting

This write-up is starting with a shout-out to the two Master Gardeners who conducted the mini session titled Seed Starting at the MasterSeed Starting with in Plastic Jugs Gardener Association of the Central Rappahannock Area (MGACRA) Seed Swap held on February 1, 2025. Attending the mini session inspired the following experiment being conducted by the Hanover County Master Gardeners. It’s important for Master Gardeners to know that their efforts have a positive effect, so thank you Nancy and Lynette.

The University of Maryland Extension has a webpage that gives detailed instructions on how to reuse plastic jugs to sow seeds during the winter, All the Dirt on Winter Sowing.

This informal experiment was designed to try to determine if there is a difference in sowing success across the following variables:

  • Type of growing media: seed starter vs potting soil 
  • The opacity of the container: clear vs translucent 
  • Size of container: half gallon jug versus 1 gallon jug

Hanover Master Gardeners conducted a seed-sowing activity on Sunday, March 2, 2025. Interested Hanover Master Gardeners were invited to participate. 

  • We prepped the jugs and marked the handles with different colored duct tape to designate the sowing medium to be used in the jug, red for seed starter and gray for potting soil. 
  • We planted seeds for vegetables, herbs, and flowers. 
  • Each plant type was sown in four jugs. Seed starter was in two jugs and potting soil was in the other two jugs. 
  • We had more gallon-sized translucent jugs than any other type of jug. We distributed the half-gallon jugs and the clear gallon jugs among the different species. This experiment would be better if we had equal numbers of the different types of jugs.
  • Each jug was sealed with the colored duct tape that had been placed on its handle. Using different colored duct tape makes it easy to know what the growing medium is inside the jug. 
  • When all sowing and labeling were finished, the 38 jugs were placed in the Hanover Master Gardeners’ Horticultural Learning Center (HLC) demonstration garden. 
  • The jugs will be checked weekly, and growth progress will be recorded in a spreadsheet. 

It will be interesting to see what the results are!

The seed sowing experiment concluded on Friday, March 28, 2025. The variables of this informal experiment were:

  • Type of growing media: seed starter vs potting soil 
  • The opacity of the container: clear vs translucent 
  • Size of container: half gallon jug versus 1 gallon jug

There was mixed success in getting the different varieties to germinate. The species that sprouted quickly and grew the best were the bush green beans. However, the bean plants took a hit during the last week of the experiment. The leaves appeared to be damaged by too much heat and sunlight. It would have been better to pot the beans a week earlier. Lesson learned: Don’t leave plants in the containers for too long.

Many of the species sprouted and grew but the data showed no discernible difference across the variables. Several species had a poor showing but they did poorly across each of the different variables. Conclusion: size of container, soil medium, and opacity of the container neither deterred nor provided better germination and growth.The one downside to the ½ gallon containers was that they dried out faster than the gallon containers, thus requiring a little more attention. The ½ gallon containers were misted twice during a 2 week dry spell. The gallon containers required no additional water during the four week long experiment.  

The seedlings are to be potted and sold at the Hanover Master Gardeners’ Annual Plant Sale on Saturday, May 10, 2025.

After successfully sprouting seeds this year, it’s time to think about next time. The plan for next winter is to sow seeds much earlier, end of January to middle of February. It would also be interesting to see if this method of germination could be successful with seeds that require stratification in order to sprout.

➤