While humans tend to interfere with a plant’s growth processes, the truth is that seeds intrinsically have everything they need to germinate, thrive, flower, and reseed themselves—under the right conditions, anyway. But mitigating factors, from increasingly abrupt weather changes to the rise of invasive species, mean that they need a little more help from us than they should.
How to Cold Stratify Seeds and Why It's Necessary for THESE Crops
For example, you might buy seeds and go to the trouble of germinating them indoors, planting the resulting seedlings when and where they’re most likely to be successful. That’s great, but you might be skipping a crucial step for many seeds: cold stratification. Many seeds need the intense, wet cold of winter to germinate in the spring. If you put your seeds in the ground before winter sets in, they’ll (hopefully) experience those conditions, but you can also fake the process indoors.
Most of your tall, pointed flowers will need stratification: agastache, larkspur, foxglove, liatris, delphiniums, and hollyhock, to name a few. But it’s not just the tall ones: rudbeckia, aster, coneflower, lupine, monarda, lavender, and the notoriously difficult to germinate sowthistle and poppy all need this cold snap to ensure good germination. As a rule of thumb, before you buy flower seeds, check the planting instructions to see if they will benefit from it.
Vegetables generally don’t need stratification, but you should always check. Asparagus and artichokes (both perennials) benefit from the cold, as do a number of herbs, from chamomile to chives (although I’ve grown both successfully without it).
