Shady Soils with Medium Moisture
Blue wood aster Symphyotrichum cordifolium
Large-leaved wood aster Eurybia macrophylla
White snakeroot Ageratina altissimo
Woodland goldenrod Solidago caesia, S. flexicaulis
Crane’sbill Geranium maculatum
Golden grounsel Packera aurea
Sunny and Dry Soils
Black eyed coneflower Rudbeckia hirta
Beardtongue Penstemon digitalis and P. hirsutus
Wild Rose Rosa virginiana
Meadowsweet Spirea alba
Little Bluestem Schizachyrium scoparium
Butterfly milkweed Asclepias tuberosa
Smooth blue aster Symphyotricum laevis
Downy goldenrod Solidago puberula
Wild Strawberry Fragaria virginiana
To make the seed bombs, the ingredients are simple: clay, organic matter, water and a pinch of seeds. Mix equal parts compost or potting soil with clay (potters clay or cat litter clay with no added chemicals) with a little bit of water until you have a dough that sticks together but is not soggy. Experiment with rolling it into pea size balls. Next press your finger into the ball to create a bowl shape. This is where you will place a pinch of seed. For large seeds like milkweed, use 3 seeds; for small seeds a pinch will do. Gently roll the seed into the inside of the ball and set aside. If you are using large seeds such as acorns, you will need a golf ball size bomb. Seeds from maple, ash or wild cherry will need a ball the size of a grape. The seed bombs can be left out for a couple of hours to firm up, but you do not want them to dry out inside. They should then be stored in a plastic bag in the refrigerator until you are ready to engage in your guerilla seed bombing action. Please remember that this is not an action for state or national parks or your local conservation land (unless they have given you specific approval). Try this in your yard, neighborhood, school, or other private land with permission from the landowner.
Fall to early spring is the best time to make and throw seed bombs. The seeds of many northern species need to experience a winter cold period before the seeds will germinate. Sowing the seeds during the cold and wet time of year will give these seeds the best chance to work their way into a soil niche and provide the cold stratification they need for germination. By mid-May, the landscape begins to warm and the soil dries out. This makes late spring a more risky environment for seed germination if you cannot provide supplemental water.
How and When to Seed Bomb
Sunny and Moist Soils
New England aster Symphyotrichum novae-angliae
Tall white aster Doellingeria umbellata
Swamp milkweed Asclepias incarnata
Common milkweed Asclepias syriaca
Blue Vervain Verbena hastata
Rosy meadowsweet Spirea tomentosa
Boneset Eupatorium perfoliatum
Joe-pye weed Eutrichium spp.
Wild clematis Clematis virginiana
Switch grass Panicum virgatum
The ancient art of encasing seeds in earthen balls and spreading them in areas devoid of vegetation was revived in the 1970’s by Masanobu Fukuoka, the pioneer of Japanese natural farming, in his book One Straw Revolution. Since that time there has been a grassroots movement to create these so-called “seed bombs” to improve the low success rate of wild seed dispersal. Clay and organic matter are mixed with seeds and thrown into abandoned lots, roadsides, railway lines, deforested lands, and anywhere one hopes to add more plant species. While there is no science demonstrating the effectiveness of this method of seed dispersal, it is an interesting and fun way to engage people in restoring vegetation, particularly if seeds of native species are used.
Seeds are for sale on our online store, both as individual species packets and as four seed bomb mixes for various growing conditions.
by Heather McCargo
It is also important to know that many native trees, shrubs and wildflowers have seeds that cannot dry out. For example, acorns must be collected and stored in a zip-lock bag in the refrigerator. If you let them sit around on the dashboard of your car or in your house, they will die. Therefore, before collecting seeds, make sure you have researched the seed storage and germination requirements of the species you are planning to use in seed bombs.
Oaks Quercus spp.
Maple Acer spp.
Wild cherry and plum Prunus spp.
I germinated from seed last summer and they grew several feet but never flowered. I live in Maryland in Zone 7. I didn’t plant any this summer but have a nice patch of them growing again this summer in the same place they grew last year. They must be growing from last summer’s roots?
Hi Marck, native is important for creating & maintaining a healthy ecosystem, but non-natives can also be beneficial for monarchs and other garden visitors. There’s no reason you can’t have both, in my opinion…good luck with all your milkweed!
Hi Joan, I’ve always used tap water.
Hi Steve, you can try mulching and see if it comes back, but it’s a risk. You could always try and get some seeds as back up. It’s a fast growing milkweed and we grow it annually in zone 5. good luck!
I’m in Zone 9B- nursery plant grew well over 6 feet- allowed pods to disperse seeds and also harvested seeds for 2018 season.
Attracted so many Monarch butterfly’ caterpillars- hatched 25 even during Hurricane Irma and let them fly. Not as many aphids as other varieties of milkweed, did notice an increase in Lady Bugs as a result.
Very interesting plant- now a monarch hatchery, use cuttings to allow them munch, pulpate, transition into monarchs.
Very easy… try it out
I live in Michigan and purchased several stems of this plant at a local market. I would like to harvest the seeds to start indoors early spring. Should I dry the stems and “balls” or leave them in water and give them an occasional fresh cutting until they open?
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Has anyone had an itching/burning sensation on arms after working with Asclepias physocarpa? I was recently smashing and rinsing aphids from my plant and when finished, about 15 minutes later, had a very unpleasant burning/itching sensation on my arms?
Hi Fran, you’re on the borderline for hardiness. If you leaf mulch the plants before winter they might come back. Otherwise, you could overwinter indoors or start seeds indoors next spring.