a few plants on my rooftop surprise me. A tomato that handled the heat better than its siblings. A basil that refused to bolt. A chilli pepper that kept producing even when the wind tried its best to snap it in half.
Saving seeds was a quiet ritual I repeated every year on my garden, so this year I decided to do it here at the Rooftop. Seed saving isn’t complicated — it’s just a small ritual of noticing, choosing, and preserving. And because my rooftop is my laboratory, my refuge, and my micro-ecosystem, these seeds carry experience. They remember the reflected heat from the tiles, the surprise gusts of wind, the shallow soil and the occasional chaotic watering schedule. They are not just seeds — they are adapted to this place and to me.
My unexpected star this year was an heirloom tomato I picked up casually at a garden centre.
Why Save Seeds at All?
As I mentioned in a previous post on a rooftop, every plant works harder. So my focus are on those that proved something (1) plants that grew well in pots, (2) the flavours I loved most, (3) branches that survived the gusty afternoons, (4) flowers that attracted bees and, (5) leaves that didn’t sulk in heat.
If a plant thrived here, chances are its offspring will understand the assignment too. Importantly saving these seeds helps reduce costs, preserve heirloom genetics and share little treasures with friends and members of your community.
When are seeds ready?
The moment you actually harvest seeds is slower than most people expect. Nearly every plant, regardless of family, asks for the same thing: time. Time to ripen fully, to dry naturally, to complete the cycle instead of being rushed. Tomatoes and peppers show their readiness by softening and deepening in colour far past the eating stage. Beans rattle in their pods like tiny instruments. Basil and coriander become weightless and papery, releasing seeds with the gentlest touch. Squash and cucumbers go gloriously overripe — which is perfect, because what’s inside becomes beautifully mature. For flowers seed heads dry and crumble easily.
Cleaning Seeds Correctly
There are two universal methods – the dry and the wet method – depending on the crop.
The Dry Method
This method is best for beans, peas, basil, coriander, chillies and flowers. It consist on letting pods/flower heads dry, after which we shake or rub the dried parts to release seeds. Be sure to remove debris before you collect the seeds for the final drying session.
The Wet/Fermentation Method
This method works best for tomatoes, cucumbers and some squashes. As the seeds sit protected inside a jelly that needs time to dissolve. I scoop them into a small jar and let them ferment gently for a day or two. It’s not glamorous, but the transformation is honest. Once rinsed and freed, the seeds feel like they’ve shed the last attachment to the previous season and are ready to dry.
We moister – seed don’t.
Drying is the moment where everything can go right or everything can quietly fall apart. Seeds forgive many things — uneven watering, less-than-perfect soil, the occasional clumsy hand — but they do not forgive moisture. Even the smallest hint of damp is enough to ruin an entire batch. This is the part of seed saving where patience is not optional. Seeds must become completely dry, dry to the point where they sound like tiny stones when moved, dry to the point where they break cleanly rather than bend, dry to the point where the paper beneath them stays crisp and unchanged.
I’ve learned to give them time, even when they look ready. Seeds often pretend. They hide moisture deep inside their coats, and if you rush this stage, they will quietly mould in storage long before spring arrives. So I spread them out, let them breathe, and wait until the air itself tells me they’re safe. It’s the slowest part of the process, but also the one that decides whether you’ll have seeds next year — or just a little envelope of disappointment.
A Place to Rest Until Spring
Once the seeds are fully dry, they need a quiet, stable place to rest. Seeds are living things, even when they look like dust. They’re asleep—but they’re listening. Light, heat, and especially moisture are their wake-up calls, so the goal is simply to avoid all three.
Some people use envelopes; I use Eppendorf tubes — a small residue of my scientific life blending seamlessly into my gardening one. Each tube gets a label in pencil, taped on with transparent film because I’ve learned the hard way that ink fades and stickers don’t like humidity.
Seeds deteriorate faster when temperatures swing up and down, so avoid sunny shelves, kitchens that heat up when you cook, and any spot near heaters or vents. And moisture is their natural enemy; even a hint of damp can lead to mould. If you live somewhere humid, slipping a few grains of uncooked rice or a tiny silica packet inside the container will help keep the air dry.
I’ve learned to check on my seeds every month or so—not to fuss over them, but to make sure nothing has decided they’re lunch. Mice, moths, and the occasional weevil all consider seeds a treasure. Metal tins and glass jars stop them, paper does not.
Good seeds stay firm, dry, and unchanged. Seeds that have absorbed moisture become soft, swollen, or discoloured. If you open your container and catch even a faint whiff of mustiness, they’re already compromised.
A Note on Seed Longevity
Some seeds are marathoners; others are sprinters. Tomato and pepper seeds keep well for years, while things like parsley or parsnip seem to have opinions about ageing and decline quickly. Rooftop seeds, with their harsh childhoods, often germinate strongly in the first year or two, and then slowly lose energy.
If in doubt, I do a tiny germination test on a piece of damp kitchen paper. If most seeds wake up, they’re ready for the season. If only a few stir, I sow more densely—or simply thank the old seeds for their service and start fresh.
Data from this site.
Final Thought
People often think seed saving is about frugality or tradition, but for me it’s about continuity. These plants are chosen for resilience — the kind you only build when you grow in conditions that are slightly unreasonable. When I sow these seeds next year, I’m planting survivors, shaped by the same rooftop that shapes me. And that, for me, is the real joy of it.
I have shared my method for saving seeds at home, choosing plants, and keeping them for next season. What about you? Have you ever saved seeds? Which ones are your favourites?
Share your story — I’d love to know.
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