If you want an easy and convenient way to grow flowers to attract pollinators to your garden or to simply start a pretty wildflower patch in your yard, you need to make seed bombs.
Here are the 11 most commonly asked questions about how to plant them.
Also known as “seed balls” or “earth balls”, seed bombs are made of plant seeds wrapped in a ball of soil (usually clay) with compost and are then dried. The soil offers a growing medium and the compost offers nutrients for seeds to germinate.
Seed bombs are a seed dispersal method initially used by guerilla gardeners to place seeds in areas not easy to access.
It is an ancient method developed by Japanese farmer and philosopher Masanobu Fukuoka in the early twentieth century. Traditionally, farmers used seed balls as a no-till method to plant fruits, vegetables, rice, and barley.
Nowadays, seed bombs are used to add a green cover in areas with minimal vegetation cover, especially in urban areas, such as freeway banks and borders along roadsides.
For most home gardeners, seed bombs are a convenient way for growing wildflowers in their yard with compact, hydrophobic soil.
The best time to plant seed bombs depends on the type of seeds used.
For annuals such as corn, kale, and radishes, the best time to plant their seed bombs is during spring, once the harsh frost conditions have passed.
For perennials such as apple trees, bananas, and alfalfa, the best time to plant the seed bombs is in the fall. During this time, the seeds experience a cold, moist phase, or “stratification”, which helps increase the chances of germination in spring.
Also, don’t plant the seed bombs in the afternoon heat; instead, plant them in the evening.
Always plant during the rainy season when the seed bombs will receive 3 to 5 inches (76 to 130 mm) of rain. Or else you will have to carry out supplemental watering for the seeds to germinate.
Avoid planting during the windy season because the seed balls may land in the wrong microclimate.
To work well, seed bombs need to be planted in places that receive 10 to 12 inches of annual rainfall. Water is important as it breaks seed dormancy and stimulates germination.
The area should also get at least six hours a day of sunshine. Sunlight is critical as it triggers the germination process for many plant species, for example, marigolds, cosmos, and California poppies, among others.
However, some flower seeds will do well in shaded areas like foxgloves or honesty.
You can also grow seed bombs indoors in a greenhouse, in a polytunnel during the cooler months when there is frost to offer them a good start.
Place 1 seed bomb in every square foot of space (or 10 seed bombs every square meter).
This is to allow enough spacing amongst the plants to prevent them from competing for resources because the seeds will eventually grow and become mature plants.
You can go further, but be careful not to go overboard. When the plants grow far apart, they may not have as much aesthetic appeal.
Once you have planted the seed bombs, you should not break them up. The bulk of the seed bomb offers a growing medium for the roots of the seedlings to take hold.
If you break up the seed bombs, the seeds may be eaten by small animals and pests. You will also be interfering with the compost, which provides the seeds with much-needed nutrients.
It is not necessary to bury seed bombs because the clay acts as the growing medium for the seeds.
All you have to do is throw the seed balls into a target area and wait. After some time, part of the clay ball will disintegrate, and the seed will grow.
For better results, you can plant the seed bombs about one inch deep in the soil. Before you do so, remove all the unwanted plants and weeds from the planting area to provide adequate space for the seeds to grow and thrive.
When you remove all the roots present in the soil, the seeds will germinate faster, and your plants will be healthier.
Seed bombs, once planted, don’t need much care.
You only need to be sure that the planted area receives water from time to time. You can do so by spraying the area regularly, like a few times a week.
In addition, check if the area receives sufficient sunlight for seeds to germinate well.
Seed bombs are designed for planting bare land outdoor with little care. But if you so desire, seed bombs can also be grown in pots.
Here are some general tips to care for your seed bombs in pots:
- Place one seed bomb in each pot to avoid plant overcrowding
- Regularly water the seed bombs
- Check the pot’s drainage; the pot should have sufficient holes to let out the excess water. Though various plants have varying water needs, their seeds should not be in stagnant water.
- Place the pot where it gets adequate sunlight.
How long seeds germinate depends on the seeds, as some take longer to germinate. It also depends on the growing conditions such as the availability of water, and temperature.
Under optimal conditions, seed bombs can sprout as early as 3 days. But it can also take 1 month. And some seeds may only germinate in the following year because some seeds may still be dormant.
Here is a time-lapse video of seed bombs:
When stored properly, seed bombs can last for 2 to 3 years, which is the average longevity of most seeds.
It would be best to keep the seed bombs in a cool, dry, and rodent-proof area.
Birds, especially ravens, crows, robins, and jays, may snatch your seed bombs because they resemble nuts, eggs, or acorns, which are what birds enjoy. Even rodents can feast on seed bombs.
Nevertheless, you can take the following measures to reduce such problems:
– Don’t overstuff each seed ball with too many seeds. Birds will then learn that it is not worth the effort to peck open a seed ball for just a few seeds.
– Throw some empty “seed bombs.” When you place plenty of seeds in the seed bombs, the birds will learn that they are ideal food sources. On the other hand, by putting some empty seed bombs, the birds will pick them up, find them empty, and begin to ignore them.
– Deposit seed bombs sparingly. Many seed bombs on the ground will attract the bird’s attention, but one or two may go unnoticed.
– Thoroughly dry the seed balls. By properly drying the seed bombs, birds will find it hard to extract the seeds and leave them.
– Provide food with easy access. Birds like easy pickings. When you offer them an easier food source nearby, they will see that the seed balls are not worth the effort. You can offer them sunflower seeds or nuts by placing bird feeders at different places in the garden.
– Avoid planting while they are watching. Before you throw the seed bombs, look around to see that no birds are watching.
Check out our DIY guide to make seed bombs.
Fukuoka, M. (1985). The natural way of farming. Tokyo: Japan Publications.