As the days begin to lengthen, and seed catalogs start arriving in your email and postal box, it’s time to think about placing your orders for this year’s garden show. I’ve always been a big fan of seeds as a source of material for the garden, which grew on me when I was a propagator at the Berry Botanic Garden. Mrs. R.S. Berry was famous for her ability to grow an amazing array of difficult and rare plants from seeds. She obtained many of these seeds in the Himalayan Mountains and Valleys of China during expeditions funded by collectors including Frank Kingdon-Ward and Joseph Rock.
Saving seeds is a very important part of curating a plant collection, as historic plants can succumb to pests and disease and cloning may not always be an option. Saving seeds preserves a plant’s genetic material, minus whatever disease may have caused its demise. Let’s look at some seed sowing techniques and tips to ensure your success in the upcoming gardening season.
It-s best to start with a high quality soil mix. I like Promix HP, with biofungicide and mycorrhizae. It has a peat-based substrate so it retains moisture very well. Also, its HP (high porosity) helps roots development and prevents damping off, a fungal disease that can run unchecked through seedling flats if drainage and air flow are inadequate. The biofungicide and mycorrhizae help prevent disease and encourage strong root growth.
Getting an early start with perennials and woody/tree species from temperate climates is important, as they may require a period of cool weather before they will germinate with rising spring temperatures, a process known as vernalization. I like to sow these species outside as soon as they arrive in the winter, ideally with seed flats out and exposed to the weather by January, at the latest. This way, if it’s an early spring, they should have been sufficiently chilled to induce germination. With seeds having longer germination times, I like to top dress with some grit. This helps prevent the growth of mosses that can overtake peat-based soils before seeds have a chance to germinate. You can buy grit (crushed quartzite) at feed stores. Packaged as turkey or chicken grit, it’s relatively cheap and as you are only using a thin top dressing, a little goes a long way.
Once seeds have germinated provide consistent temperatures and good air flow to prevent damping off. High Tech to low tech, there is lots of information available on seed germination practices. Bottom heat can be very beneficial. This is the hydronic bottom heat system I built for the Historic Greenhouse at McMennamins Edgefield.
The internet is a great source of seed growing tips and tricks. A favorite and very comprehensive book on sowing seeds is Norman Deno’s Seed Germination, Theory and Practice. Another recommended book on propagation (and much more) is Peter Thompson’s Creative Propagation, A Growers Guide.
For annual seeds, bottom heat and supplemental lighting can encourge an early start to the growing season. These systems can seem technical and daunting; however, basic electric heating pads and LED grow lights will do the trick. ures are well within the realm of affordability.
Sometimes, seedlings can establish as quickly as cuttings. Camellia sasanqua on the left, is almost as large as the Camellia japonica cutting made at the same time the seeds were sown. The tree peonies at Gaiety Hollow have presented unique challenges. They are difficult to propagate by cloning as they have to be grafted onto herbaceous rootstock. Fortunately out of 20 seeds that were sown, one was viable and heading toward a healthy start. Fungicides should be used as a last resort. Focus on cultural conditions first.
When working with seedlings, the best advice is sow thinly. This will help prevent the dreaded damping off disease where a healthy flat of seedlings start to topple over suddenly, caused by a number of different fungal pathogens, the stem of the plant is severed, and the seedling dies. Sowing thinly also makes it easier to move the plant on when it comes time to repot. I usually sow a 1/4 – 1/2 of the packet and save the rest. That way if I find a particularly popular or successful plant, I can regrow it next year, in case the seed company is out of stock.
Sulfur is one of the least toxic fungicides to have on hand. It can be dusted or mixed with water to make a spray. Be aware that sulfur is acidic in nature, so can change the pH of the soil.
Here are a few of my favorite seed sources.
Outside Pride: Based in Independence, Oregon, this online-only retail offers a remarkable array of flowers, grasses, and cover crops, including large seed packet sizes.
NARGS: The North American Rock Garden Society offers a seed exchange to its members. Even if rock gardens aren’t your thing, the exchange provides access to thousands of different seeds collected from member gardens. Many selections are drought tolerant and will thrive under tough conditions.
Plant World Seeds: For those that like the uncommon, this is a great source for everything from unusual bulb seeds to rare trees.
Nichols Garden Nursery: An old standby from nearby Albany, this is a great source for herbs and vegetables, including unusual and heirloom varieties.
The Thyme Garden: Situated in the coast range between Corvallis and Waldport, its a great source for unusual herbs and flowers.
I hope these tips and resources provide a good start to the growing season! The warmth of spring will be here soon so start now by getting your seeds ordered and sown.