The first thing to remember is that seed packets can contain hundreds or just a handful of seeds. For the former, consider the size of your border or container and sow just enough, perhaps with an extra 10% in case of losses along the way. In other words, there is no point in sowing 100 seeds of a plant that will grow up to 30cm wide unless you have a very large border or lots of pots to fill.
Also, remember that perennials come back year after year, so there’s no waste like annuals or biennials that end up in the compost pile.
So if you want color, fragrance and interest in summer and fall this year and beyond, sow perennial seeds from February to July.
Many gardeners shy away from growing perennials from seed, fearing they will take too long to grow, but sowing perennials early in the year will yield flowers they will be proud of.
My top ten first year flowering perennials from seed are:
- Achillea millefolium or Achillea ptarmica
- Agastache aurantiaca or Agastache rupestris
- Pink alcaeus
- Calamintha nepeta
- Cephalaria gigantea
- Delphinium x belladonna
- purple echinacea
- Gaura lindheimeri
- Perovskia atriplicifolia
- Verbascum chaixii Album
For the majority of perennial seeds, however, you will need to leave the seeds uncovered (check the seed packets). Press them to the surface to ensure good seed-to-soil contact.
Cover the seed tray with cling film to retain moisture or place it in a mini-propagator.
Ideally, you want to give the seed tray some bottom heat, either from a heat mat in a greenhouse or on an indoor windowsill above a heater. Read the instructions on the seed packet, as some perennials may require a process called “stratification” which involves placing the seed in potting soil in a plastic bag and refrigerating it for six weeks before sowing.
Place the seed tray under bright direct light. As soon as the seedlings start to emerge, remove the cling film.
Like all seed sowing, check your containers regularly.
Make sure there are no signs of slugs or “damping off” occurring on any of the seedlings.
This is a disease caused by different fungus-like organisms, causing seedlings to collapse and die.
In three to five weeks, the seeds will have germinated, but don’t be surprised if some seedlings grow more slowly than others. It’s normal.
When the seedlings are large enough, about 12 cm in height, harden them off for 10 days to acclimatize them to outdoor temperatures, sun and wind exposure before planting them outdoors from late May.
Make sure they get enough water each day and, if necessary, pinch off the tops of young plants to encourage strong, bushy growth.
Thus, by growing your own perennials from seed, you will have the advantage of being economical.
You will bring color and fragrance (if any) to your borders, pots and containers during the first summer.
Plus, you can be happy knowing they’ll come back year after year and grow better, stronger, and more floriferous.