Cleaning Seeds for Propagation
It’s essential to remove the flesh when collecting and save seeds. In addition to being a source of moisture and decay, the tissue often contains chemicals that discourage seed germination. While it’s easy to extract large seeds by hand, small fruits like raspberries, goji, and mulberries have tiny seeds that are difficult and time-consuming to remove.
In the wild, the consumption of fruit by birds and other animals removes the flesh via the animals’ digestive processes. Freed from the fruit, and surrounded by newly digested nutrients, the seeds are free to grow. While sifting through feces may be an effective way to gather seeds; I’m optimistic that we can avoid that.
The Decanting Method
Decanting is the process of physically breaking down the fruit in water and allowing the dense, viable seeds to sink to the bottom and flesh to float to the top.
Step 1 – Gather
To begin, gather fruit when it is ripe, as gating too early may result in collecting unviable, immature seeds. Fortunately, most fruit offers visual cues as to when it’s ready. Animals disperse fruit seeds, so plants have evolved ways to attract animals when their seeds are available for dispersal. As an example, tomatoes, strawberries, and raspberries turn red. Another clue that the fruit (and seeds) are ready is that they quickly come free from the plant—falling fruit is usually a good sign that it’s ready to pick.
Step 2 – Macerate
To access the seeds, we’ll need to break the fruit up into a pulp, which is easily achieved by putting the fruit in a bowl or bucket and manually squeezing the fruit with your hands. Adding some water to the bucket may help loosen the seeds from the pulp. For larger batches, consider using a clean paint mixer at the end of a drill. Remember, we’re trying to break the fruit up without damaging the seeds. You’ll be tempted to use a food processor, but that’s likely too aggressive.
Step 3 – Add Water
To separate the seeds from the pulp, we’re going to take advantage of the fact that viable seeds are denser than water. Once your fruit is well mashed, start adding water. Continue to stir and break up any larger pieces of fruit. Free of seeds, the fruit will float to the surface. Before moving on, I like to let the mixture settle for a moment.
Step 4 – Pour Off the Water and Pulp
At this stage, most of the pulp will have floated to the top. Remove it by gently tilting your bucket and pouring off the top third of the liquid and pulp. You may pour off some seeds in this process, but the bulk of the seeds should be at the bottom.
Step 5 – Rinse and Repeat
Add more water and continue to break up and larger pieces of flesh manually. Let the mixture settle and pour off the top third to half of the water. With each rinse, the water will become cleaner until you can see the seeds at the bottom of the bucket. At this point, pour off the rest of the water until only the seeds remain.
Step 6 – Dry Cleaned Seeds
Now that you’ve removed the water, pour your cleaned seeds out onto a flat surface. I like to use a baking sheet with a few pieces of paper towel to absorb excess moisture. Let your seeds dry for a day or two and pick out any remaining bits of flesh that may have escaped the decanting process.
Step 7 – Store Seed
Most seeds stay viable when stored in a cool, dry location like a well-ventilated basement or refrigerator. It’s worth noting that the viability of seeds will degrade with time. Congrats! You’re on your way to being an expert at cleaning seeds!
If you enjoyed this and would like to learn more, check out the Forest City Plants Online Propagation Course.
Here’s a video of Akiva Silver of Twisted Tree Farm cleaning mulberry seeds