Do low temperatures harm seeds?

For the first time in many years, we are experiencing a real winter in Warmia – with frost, snow, and temperatures clearly below zero. It is therefore not surprising that one of the most frequently asked questions in recent days is: “Do low temperatures harm seeds?”

In the case of tomatoes, the answer is: no – low temperatures not only do not harm seeds, but can actually improve their longevity. The tomato (Solanum lycopersicum) does not require stratification, that is, a period of cold necessary to initiate germination (as is the case, for example, with wheat or rye).

Tomato seeds belong to the so-called orthodox seeds. This means that they can be dried to very low moisture levels and tolerate subzero temperatures very well, including deep freezing. This phenomenon is widely utilized in gene banks around the world.

Research in seed physiology shows that lowering the storage temperature significantly slows down aging processes, degradation of cell membranes, and oxidation of storage lipids. In practice, this means a longer lifespan and better biological quality of seeds.

For this reason, tomato seeds can be safely stored at temperatures far below zero, provided they are properly dried. We ourselves use storage temperatures reaching below –50°C, which is consistent with gene bank standards.

Why do not all vegetables respond in the same way?

It is worth remembering that tolerance to low temperatures mainly applies to orthodox seeds, such as tomatoes. Other vegetable species may respond to frost much more poorly, especially if their seeds are small, oil-rich, or sensitive to damage of cell membranes.

Peppers should not be stored at temperatures below zero – studies indicate a decline in germination energy and seed viability. Arugula and some cucurbit species also tolerate freezing poorly, especially when combined with fluctuations in moisture.

Therefore, during the winter period it is always worth paying attention to the plant species and the method of seed storage. In the case of tomatoes, however, you can rest easy – frost does not harm them.

Scientific sources

Ellis R.H., Roberts E.H. (1980). Improved equations for the prediction of seed longevity. Seed Science and Technology.

Bewley J.D., Black M. (2013). Seeds: Physiology of Development, Germination and Dormancy. Springer.

FAO / IPGRI (2014). Genebank Standards for Plant Genetic Resources for Food and Agriculture.

Royal Botanic Gardens, Kew – Millennium Seed Bank. Seed Storage Behaviour and Longevity.