Nasturtium, Sweet Pea, Milkweed, Lupine, and Morning Glory seeds ready to be scarified and soaked.
Although most wildflower seeds can simply be scattered on bare dirt, there are several varieties that will have a better germination (sprouting) rate with just a little extra work before planting. Seeds such as Morning Glories, Lupine, Sweet Pea, and more have very hard seed coatings, which you can see just by looking at them. For the most successful (and quickest) germination of these seeds, you can scarify and soak the seeds before planting.
Seed Scarification: nicking, breaking, softening, or otherwise weakening of the seed coating meant to speed up germination.
You can see the hard, almost walnut-like seed coating on these Nasturtium seeds. For best germination, you can nick the outer coating and soak the seeds overnight before planting.
How To Scarify Seeds: Why Do Some Seeds Need This?
Tough seed coats are nature’s way of protecting seeds from accidentally sprouting early. If water were to penetrate the seed coat as soon as the seeds were planted by the gardener (or dropped by the current generation's flowers) the endosperm inside each seed could be triggered to germinate at the wrong time. Imagine having your seeds sprout just before the arrival of winter, or during a devastating drought - either would make a terrible schedule for tender seedlings!
To combat this unwanted outcome, some plants have developed thicker, tougher seed cases for their offspring. This allows the natural freezing and thawing cycles of winter (or exposure to a rainy season in warmer climates, or even passage through an animal's digestive tract) to slowly soften the seeds up, only permitting water to pass through and reach the endosperm when the correct time arrives. This built-in timing is why planting in fall is so successful for so many varieties - and is exactly what you're trying to outwit by scarifying seeds before sowing.
These tender milkweed sprouts arrive on a carefully-timed schedule. If they were to accidentally germinate in fall instead of spring, they would not survive the onset of winter.
What happens if I don't scarify seeds with hard outer coatings? You may still get sprouts followed by strong, healthy plants. However, you should expect a lower percentage of your overall planting to germinate, at a slower rate.
Common Seed Varieties That Need Scarification
Many native plants and wildflowers require scarification, as they are very likely to have mechanisms in place that control the timing of their germination - a trait that has allowed them to evolve wonderfully in our local climates. When in doubt, assume that your natives need to be soaked before planting at the least!
Note: Most vegetable seeds are soft and do not require any scarification.
Although this isn’t a comprehensive list, here are some of the common garden seed varieties that germinate and grow more quickly with scarification and soaking:
Morning Glories, Nasturtium, and Sweet Peas
Lupine, Milkweed, and Joe Pye Weed
Poppy Mallow, Columbine, and Moonflower
Spinach, Winter Squash, and Beans
Morning Glories are one of the seeds that benefit from scarification and soaking to speed up germination.
How To Scarify Seeds: Get Your Ingredients Together
We scarified and soaked five different seed varieties in less than one hour.
A simple look around your kitchen and workshed should suffice for gathering all the tools needed for this process. You have several options for tools to nick the seed coats. We used sandpaper, a file, and a nail, in our experiment. The file works best on bigger seeds, while the sandpaper is a great choice for smaller seeds.
All the ingredients you'll need to scarify and soak your seeds.
Scarification Tools: file/rasp, sandpaper, nail, several bowls, room temperature water, and peat moss/plastic baggies if you’d like to store the seeds overnight.
How To Scarify Seeds: An Easy Step-By-Step Process
As soon as you have the ingredients together and your seeds, the process is quite simple:
1. Using the tool of your choice, nick the seed coat so that the inside (which is usually lighter in color) shows through. You want to be careful to do as little harm as possible, so as not to damage the seed. Repeat this process for all of your seeds.
A file makes nicking these Morning Glory seeds fairly easy.
You can see that these seeds were nicked just enough to reveal the lighter-colored innards of the seed, and no more.
Sandpaper is also an easy way to nick seeds. One easy method is to rub seeds together in between two sheets.
The Lupine seed on the left has been scarified with sandpaper. The one on the right has not.
2. Place the seeds in a bowl of tepid water and let soak overnight. As soon as the seeds start to noticeably swell, remove them from the water immediately and get them in the ground as soon as possible. You can also layer your seeds among damp peat moss, and store in a plastic baggie in the refrigerator overnight (or longer) to mimic a cold, wet spring. This process is called stratification and is a common approach with milkweed seeds.
Soak the seeds overnight until they are plump. Plant as soon as possible.
Add water to the peat moss.
Place your scarified seeds in a plastic baggie and mix. Leave overnight (or longer, depending upon the information that accompanies your seeds).
Other Seed Scarification Techniques:
There are several other techniques out there, depending on your preference and materials available:
- Place the seeds in the freezer overnight and then soak at room temperature for a few days, until seeds start to swell.
- Place seeds in the freezer overnight and then put them in boiling water, letting them soak in the hot water for several hours.
Seed Stratification: a process of mimicking a cool, moist winter to break dormancy and encourage sprouting that involves layering seeds among moistened growing media such as sand, peat and soil and subjecting to cold temperatures.
- To stratify seeds, place them in a bag with coarse sand (or a 50/50 mix of sand and peat moss) and shake for 60 seconds. Add enough water to make damp and let soak overnight.
- After nicking seeds, place them in between soaked paper towels in a plastic baggie and let sit overnight in the refrigerator.
- In fall, layer seeds in a pot with growing medium and plant the pot in the garden.
What Results To Expect From Seed Scarification
Many gardeners are used to planting their seeds without scarifying or soaking them beforehand. If you decide to try this process, what can you expect in terms of results?
Our collective experience has shown us a higher success rate with the native seeds we planted, meaning that we've seen a higher percentage of seeds sprout into seedlings than when we just sow them without any form of pre-treatment.
Additionally, you can expect your seeds to sprout more quickly, which is a hands-down great reason to spend the extra few moments that seed scarification takes. This is especially true for gardeners living in extreme cold or high-altitude areas, who have a very short growing season to contend with.
Do you have experience scarifying your seeds before planting? Please share your tips in the comments below!