Viable, healthy tomato seeds should sink because they are dense, while underdeveloped or bad seeds, along with pulp, often float; however, some good seeds can float initially and sink later as they absorb water, so it's best to ferment, rinse, and then only plant the ones that sink after the process is complete to ensure quality.
In theory the good, fertile seeds are heavy and will sink and the infertile, light seeds will float. You can scoop off the floating seeds but do this after shaking the jar (above) because as the gel around the seed ferments it will produce gas, lifting the seeds to the surface.
✅ Sinking Seeds are usually healthy and viable. They are dense, full of stored food, and more likely to germinate. ⚠️ Floating Seeds might be empty, damaged, or immature. They often have air pockets or poor internal development, which makes them lighter and less likely to grow.
Some people claim that placing seeds in water allows you to determine if they will germinate. These people say those that sink will germinate while those that float will not. However, this isn't completely true!
Seeds are viable when you can see a blush at the blossom end. Ripened half way up is better, and ripened all the way up is even better.
Tomato seeds typically germinate in 5 to 10 days if given optimal conditions. You'll know seeds have germinated as soon as you see green plant emerging from the growing medium.
Count the number of germinated seeds and divide them by the number of seeds tested. This will give you the germination percentage. Less than 80% germination means your seeds still have some viability but that you will need to sow them more thickly in order to get a good crop.
It is not a true test of seed viability like it says it is. Some of the seeds that float go on to germinate. The test is nonsense. The real test of seed viability is to plant the seeds correctly, about 1/4th of an inch deep and see if they grow.
Above-ground symptoms include leaf yellowing and browning, stem cankers, and stunted and wilted plants. Rhizoctonia girdles or constricts lower stems (known as "wirestem") and pythium causes stunting, browning, and malformation of the root system. Damping-off is more likely to infect large seeds (corn, bean, pea).
Place the roll into a plastic bag and keep it in a warm place (70° to 80° F). Remember to label each roll with seed type. Check the seeds in two or three days and every day after that for a week or so. When a root or cotyledon protrudes through the seed coat, the seed has germinated.
As it turns out, germination is incredibly complex & varies from plant to plant & seed to seed 🌱 The claim that floaters are no longer viable stems from the idea that those seeds contain fewer carbohydrates & therefore won't have the energy needed to properly sprout. As shown here, that isn't always the case!
Damaged seeds have a higher chance of floating on water because the damage can result in the development of air pockets, which makes the seeds less dense than water. Therefore, when placed in water, the damaged seeds float.
Healthy seeds are denser and have a solid structure, which causes them to sink. - The seeds that float are likely to be damaged or hollow seeds. These seeds are less dense and have a poor internal structure, which makes them buoyant.
In September, use your abundant tomatoes for fresh salads, salsas, and BLTs, or preserve them by making sauces, roasted tomato soup, chutneys, jams, or freezing/dehydrating them for later. For plants, top the plants to focus energy on ripening, prune leaves, and ensure consistent watering to maximize the harvest before frost, using green tomatoes for fried green tomatoes or relish.
Baking soda can help tomato plants by deterring some pests (like aphids), controlling powdery mildew by creating an alkaline environment, and potentially making fruit sweeter by reducing acidity, but it must be used sparingly as overuse raises soil pH, leading to nutrient issues, poor drainage, and potential sodium toxicity, so a diluted spray or light sprinkle around the base (not directly on roots) is key.
Top 4 Common Seed Starting Mistakes To Avoid!
Tomato seeds should sprout within two weeks, so something is wrong if you don't see your seedlings emerge within this timeframe. Poor seed quality, an unsuitable environment, and incorrect planting practices could all be to blame.
If your seeds are green or white, throw them away. Unviable seeds will always be useless, even if you provide an ideal environment for them, they will never germinate. Also, the germination time of seeds differs, you can google the germination time of the seeds you are prepared to grow.
Conveniently, the fungus and unviable seeds will float to the top, while the good seeds will settle to the bottom of the jar.
Germinate seeds faster
The paper towel method creates prime conditions for seeds to germinate in less time. Depending on the type of seed, the controlled moisture and heat conditions within the bag can enable seeds to germinate in a few days. You'll have a home or garden filled with bright new leaves in no time!
The truth is seeds don't expire. They lose viability if stored improperly. While most seed companies will tell you to replace seeds every 2-3 years, those seeds will keep for decades and will germinate when planted if kept in a cool, dark, and dry place.
A “ragdoll” consists of a rolled tube of moistened paper containing the seeds to be tested for germination, placed in plastic bag and stored in a warm place for several days. Seedlings are counted as they ger- minate and are removed, giving the per- centage of actual germination.