Seed Bombing Was A Gardening Trend Everyone Embraced, But Does It Work?

For the uninitiated, seed bombs, also called "seed balls," can sound a bit like green warfare. Given that they're a known commodity among those who practice guerilla gardening, this isn't too far from the truth. Basically, this method of re-greening involves wrapping seeds in a mixture of clay and soil or compost and tossing the bombs on the open ground to hopefully germinate once conditions are right. Despite being an eyebrow raiser, this practice has mostly been successful, though that statement must be tempered with the understanding of why this method of seeding is necessary in the first place.

Therefore, it isn't a surprise that people ask: Why not just plant the seeds like you do corn or petunias or other plants? This planting technique is very different from your lawn seeding techniques for very good reason. The contents of the seed bombs are often wild flowers and milkweed and other native plants. The practice of seed bombing, which began in the 1970s, was to bring native plants back to areas that have been ravaged by Mother Nature, mankind, and even invasive plant species. In the latter case, seed bombs are often the best way to give native seeds a fighting chance at being re-established in an area that's overgrown with other kinds of plants. 

While much of the information about success rates for seed bombs is anecdotal, a 2024 study in New Zealand showed promise for the use of seed balls in restoring native plants throughout the country. Of the 11 flower species studied, seven had a viability of 95% when dispersed aerially. The study said the way the seeds are encapsulated played a large part in their success. 

Seed-bombing has been successful, though there are a number of factors that determine how well individual seed bombs will work. Often, it is the case that multiple factors come into play that determine the success of a seed ball, including starting with plants whose seeds just naturally have a high germination rate to begin with. In other words, if a seed is known to sprout 80% to 95% of the time, anyway, its chances of success in a seed ball is just more likely. Additionally, the number of seeds you put into a seed bomb makes a difference. Putting only one or two seeds in the balls often increases the success rates of the practice simply because the seeds in the bomb don't have to compete for nutrient resources once the seeds start to sprout.

Additionally, some people who practice seed bombing also start their seeding efforts by soaking the seeds. For seeds with hard shells, like the milkweed seeds you plant to attract monarchs, soaking the seeds can make a huge difference. The practice of soaking the seeds ahead of time often determines if seeds in the bomb sprout. 

Finally, when you plant them also makes a difference. For example, some seeds need a cold period. If you drop those seed balls in the spring without giving them a chance to experience the cold snap of winter, your planting efforts will be unsuccessful. All of this is to say that the likelihood of a seed bomb meeting with success is as individual as the packets of clay and dirt the seeds are packed in.

Lots of recipes for seed bombs exist, though all of them typically share some similarities as far as ingredients go. They usually contain potting soil or humus and are mixed in with pottery clay. (Yes, it's the kind of clay that potters use to make ceramics.) Water is added to make a paste. One to two seeds are added after that. And because seeds can fall victim to birds and insects, some crafty seed bomb makers also add chile pepper to their seed balls as deterrents against foraging wild animals. The balls should also only be the size of an almond. A seed bomb shell that's bigger makes it difficult for the plant to spring forth once it's time to sprout.

It's also not necessary to bury the seed balls in the ground. Instead, you'll drop them onto the open soil, taking care to ensure that they're not competing with other plants for soil access. Often planting them in the evening after a rain works best. Avoid trying to plant them in the beating sun, however. It's just too difficult for the seeds to get the necessary moisture required to grow. 

After the seed bombs have been dropped on the ground, rains, the passage of time, and the elements do the rest, breaking open the seed balls when the time is right. The remnants of clay and soil in the seed bomb then become food for the seeds until they can root into the ground on their own.