Should You Soak Seeds Before Planting?

If you’re new to seed sowing, it can seem like a tricky process to get right. There are many factors to consider, from supplies to how many seeds to sow. But before you pop any seeds into the soil, you need to determine whether you should soak the seeds first.

Soaking seeds supplies your plants with a jump start right at the beginning of their lives. The water both softens the seed shell and supplies water to the seed interior. Once soaked, seeds use that moisture to push out new growth. 

By soaking seeds before planting, especially in a well-lit place, you’re mimicking the rainy weather and light conditions seeds in nature would be exposed to. The difference is that you’re doing it in a bowl on your counter instead of outside.

However, not all seeds do well if soaked. Some are too tiny to soak, and will just disintegrate. Others have been biologically programmed to sprout after going through a fire. Every seed is different. With a little knowledge, you can discover what the optimal conditions for your seeds are. 

Is Soaking Seeds Necessary?

The plants we see around us wouldn’t be here if nature didn’t have a knack for finding a way to survive. That being said, gardeners often try to trick plants from the other side of the world into growing in a place that isn’t their natural climate or growing conditions. Because that is so often the case, soaking is a great way to start your seed’s life. 

The natural way to germinate seeds is to let nature be. However, if you’re excited to grow a specific plant, you don’t want to leave it to chance. Plants produce thousands of seeds in the hope that just two or three will survive and reproduce. When you’ve gone to the trouble of purchasing seeds, those aren’t the odds you want. 

As a general rule of thumb, your seeds will sprout even if you don’t soak them. But with soaking, the germination time decreases and the germination rate increases. Seeds that have a continual flow of moisture have much higher chances of success.

If you’re on a schedule, or the climate only gives you a short window to grow, soaking your seeds can make all the difference.

The Effects of Soaking Seeds

Seeds are surrounded by a seed coat. While the insides of a monocot and dicot seed are different, the seed coat in both cases exists to protect the baby plant until it’s the right time to sprout. They contain the parts that will sprout and become the plant’s first leaves and stem as well as food for the initial growth.

The seed coat is a part of the seed’s natural defenses against the harsh forces found in nature. It prevents the seed from sprouting when conditions are not at their finest. By seed soaking, you’re telling the seed it’s the right time to germinate. 

Let’s take sweet peas as an example. Sweet peas are early-season crops. A single pod has many seeds in it, sometimes 10 or more, and the plant produces around a thousand seeds in total. Those seeds need to keep from germinating until the seed senses that it’s cool enough and wet enough that the plant will be able to live a full life and reproduce the following season. 

For gardeners who collect their precious sweet pea seeds and bring them safely inside for storage, those seeds won’t come up against the normal forces they would in nature that wear down the seed coat over time. It might pass through a digestive system, or be walked over by animals, or stuck between rocks.

Come late fall or early winter when it’s time to start the growing process, you need to replicate these effects indoors. In the case of sweet peas, that means nicking the seed coat and soaking for 24 hours. This process mimics what the seed would go through in nature.

Which Seeds Need Soaking Before Planting?

Not all seeds are easy to soak. Small seeds in particular can clump together in water and be a nightmare to work with afterward. Larger seeds with thick seed exteriors are ideal for soaking to kickstart the germination process. Wrinkled seeds like peas do especially well after soaking.

Here is a short list of seeds that like to soak:

• Peas
• Beans
• Pumpkins
• Winter squash
• Chard
• Beets
• Sunflower
• Lupine
• Fava beans
• Cucumbers

Most other medium-to-large vegetable and flower seeds with thick coats benefit from soaking. 

After soaking your seeds for 12 to 24 hours, many larger seeds can be directly sown into your garden. While this isn’t an option for everyone, especially those growing with limited space or in regions with frost, direct sowing generally reduces risk of shock and root problems later on.

Seeds You Shouldn’t Soak Before Planting

There are plenty of small seeds that won’t benefit from soaking. Not so much because they don’t have a seed coat that needs moisture to trigger germination, but because they are so small that it is just not practical. 

Smaller seeds such as basil, chia, tomatoes, lettuce, black-eyed susans, foxglove, and lisianthus are all examples. Sowing them in trays or direct-sowing in areas you can keep the soil evenly moist should be sufficient.

They still work in much the same way. Their seed coats need to be moist in order to germinate. But by watering first thing in the morning and keeping the area shaded, you’ll speed their germination time anyway.

Tomatoes, basil, and chia all have a seed coat that absorbs and holds moisture around the seed to improve germination. Keeping the soil moisture consistent is all they need for survival. If you soak them beforehand, they can become soggy and clumped together, making them harder to sow.

There are also seeds such as zinnias and bachelor’s buttons that have a paper-like seed coat. These seeds come from very dry regions where seeds will sprout at the first sign of rain. These seeds can be direct sown into moist soil without presoaking.

Other Germination Methods

Seeds can germinate by other methods too. For smaller seeds like tomato or pepper seeds, try placing them on a damp paper towel, wet sphagnum moss, or fine-textured moistened vermiculite.  Keep the medium evenly moist and the continual moisture will help the seeds germinate.

Allow the seeds to soak up the water and watch for signs of germination. Be sure to spritz every 12 hours so it doesn’t dry out. As soon as the seeds have germinated, transfer them to seed trays or directly into your garden.

Remember that seeds generally need to be planted at a depth of twice the seed width unless otherwise indicated by your seed supplier. And if the seed has stuck to the paper towel, tear out the segment of paper towel it’s stuck to and plant it!

There are some other unusual ways to start seeds. Some plants have evolved only to germinate at certain times during a year or after major events like a fire. Some seeds, especially tree seeds like tulip trees, golden rain trees, oaks, and sweetgums need to experience chilling for an extended period of time before they get to the right conditions for germination. These can benefit from a short period of time in the refrigerator crisper drawer before soaking and planting.

How To Soak Seeds

To soak your seeds, use any regular bowl or jar and fill it with filtered warm water. If the water is too hot for you to leave a finger in, it’s too hot for your seeds. Aim for water that is just barely warm to the touch, but not hot.

Place the seeds in water and let the pre-soaking process continue for 8-24 hours, depending on the seed size.

Immediately after the seed soaking period is over, the seeds need to be planted out. They cannot dry out again as that will keep them from germinating at all. Be sure to know where the seeds are going and have your garden or seed trays ready to go.

After soaking the seeds and transplanting them, keep the soil moist for the first few weeks of growth. While your seeds are in this tender and young state, they can’t dry out without the risk of dying.

While young, their roots only extend a few inches deep into the soil and they need moisture near the soil level. After they become established, you can begin to water less frequently and prepare to enjoy the fruits of your garden!

What Happens When You Soak Seeds Too Long?

Many new gardeners assume that if soaking the seed for 12-24 hours is recommended, then soaking them for longer is even better. This isn’t the case!

If you over-soak your seeds, you’re cutting off the oxygen to the baby plant inside the seed, and it essentially suffocates. If the seed has died, it won’t germinate, so it’s important to ensure that doesn’t happen.

As a general rule, aim for an overnight soak whenever possible. If you can’t plant right away in the morning, drain off the excess water from your seeds, cover the container with something breathable like a kitchen towel or paper towel, keep it in a cool place, and then come back to it later in the day when you’re able to plant.

Make sure to plant those seeds as soon after draining off the water as you can, as they’re already waking up in there and may start to sprout!