Posted: 06/03/2015 at 15:50
We converted a summerhouse to a greenhouse simply by replacing the roof; it's of wood (red cedar) construction. I've left it unheated since we've been here (3 years). Last year I decided to sow seeds from my hollyhock, penstemon, lupin and aquilegia (I did it as soon as I collected them, I didn't dry them out or anything as they appeared to be dry enough). Once sown in the pots, I scattered the tops with fine grit then kept them watered, cutting down on the watering as winter came in. All these were left in the greenhouse throughout the winter - in fact, they are still there. And all of these, without exception, are now growing well (around 6-7 cm high) and I will have loads to put out in April when it's warmer. If they grow outside and they are perennial, then it stands to reason that the seeds will quite happily grow in an unheated greenhouse...it's really shelter from hard frosts and winds that they require until they grow up a bit. After all, Mother Nature provides a self-seeding mechanism for these plants and She doesn't baby them at all!