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Sowing protocols and decision-making for growing native plants from seed

Written by: Will Larson

Growing native plants from seed is a constant exercise in replicating habitat. We expose the seed to specific pre-treatment conditions to simulate the contexts and pressures that the seed is biologically programmed to respond to in its natural environment. These pre-treatments include warm and cold stratification, light exposure, scarification, and other conditions which unlock various physical and chemical germination-inhibiting mechanisms within the seed. But in addition to the biological needs of the seed, there also exist the priorities of the grower, who chooses various methods of seed-sowing to facilitate germination based on conditions of time, labor, and material costs. How much space we have for seed flats and pots, how much time we have to transplant seedlings, and how much soil and seed we have to use for a particular species inevitably change how we grow plants from seed. In this way, all seed sowing protocols are a negotiation between the seed’s biological requirements for germination and the grower’s goals and costs. There is no one correct seed sowing protocol that works for everyone: it’s simply a matter of finding out what works best for your preferences and growing environment.  Deciding how and when to sow seed is a matter of weighing  your needs as a propagator and satisfying the seed’s specific conditions for germination.


One critical way this negotiation plays out is the timing of sowing seeds. Some growers choose to collect their seeds over the course of the season, cleaning and storing them until the early fall or winter, when they commence sowing all at once. This strategy has some distinct advantages for growing plants from seed at scale. Doing things all at once creates a more uniform result, as all seeds are essentially started at the same time. Starting seeds at the end of the season often means you have containers and pots available for sowing, as you’ve been planting out throughout the season. You also have space available to put all of your sown seeds, as any live plants have been stored or planted by the end of the growing season. From a records-keeping point of view, it is easier to stay on top of documentation and track germination when seeds are all sown at the same time.


While storing your seed to be sown all at once in late fall offers some distinct advantages for streamlining production, there is a different approach when it comes to timing seed sowing which can produce exciting results. When seeds are collected, cleaned, and sown immediately, some native plants can germinate immediately in moist warm conditions, without any pre-treatment or cold stratification necessary. This is incredibly useful for speeding up the process of growing plants from seed, because you can essentially skip an entire winter cold season and have seedlings to plant out in the fall in the first year. I collected ripe seeds of twoleaf mitrewort (Mitella diphylla) in late May, a species that usually requires a cold stratification period, and sowed them immediately after cleaning the seed. A few weeks later, they germinated in the pot, and I was able to grow them through the summer in a container before planting them out in September. It is possible to replicate these results with many other species across a wide array of families, and you end up growing plants much more quickly than you would storing them for later sowing, where they may become dormant and must undergo cold stratification in order to germinate. Sowing as soon as possible after collection can be more logistically demanding, since it requires you to care for sown seed flats, ensuring that they are not predated by rodents or dry out during the growing season. When you are also dealing with planting out existing plants, it can be challenging to juggle both of these stages, especially since seed flats and containers can dry out faster than larger pots. It can also be exceedingly difficult to stay on top of collection and cleaning seed, tracking all of the relevant details, and keeping good documentation. However, it’s important to remember that the best way to ensure success with growing from seed starts with the quality of the seed itself. Fresh seed responsibly collected at staggered ripeness from multiple sources with the proper permissions can make all the difference. Especially with difficult-to-grow species or seeds with unknown pre-germination requirements, collecting, cleaning, and sowing in quick succession often produces the best results.


There are other great examples of how our priorities as growers affect how we decide between different sowing protocols. A standard method of sowing seeds involves the use of containers, either small plastic pots, larger flats, or plug trays. There are a variety of reasons why sowing in containers can be preferable to direct sowing seeds. Especially for smaller amounts of seed, containers provide a much more controlled environment where the grower can easily modify the conditions for each pot based on the preferences of the seed. It is easier to keep track of pots, they are space efficient for growing a large number of species within a very small place. But direct sowing seeds into a prepared seedbed can be very successful, especially for native annuals, biennials, and short-lived perennials, where providing a space for these plants to self-sow and persist across generations is a far more effective means of proliferating a population than growing in pots. I grow a number of self-sowing annuals like rock harlequin (Capnoides sempervirens) and Venus’ looking-glass (Triodanis perfoliata), as well as biennials like fringed gentian (Gentianopsis crinata) in a prepared seedbed intersown with other plants of their particular community type.  Direct sowing is about tailoring habitat to provide the conditions most favorable to the growth of your seeds. Canopy manipulation plays a very important role in providing the conditions needed for seedlings to become established, ensuring that young plants have enough light and space to provide a competitive advantage over established plants. If you decide to direct sow seed, make sure that you are thinking carefully about site selection based on the natural community type and plant associations of a given species, and how you will manage the care of the seedbed after sowing. Scratching in the seeds by hand to ensure that they make good contact with the soil is crucial, as is diligent watering and weeding out competition during the early establishment phase of the seedling.

Sowing density is among the most difficult factors to control for growing plants from seed, and also among the most important. It can be challenging to determine the sowing rates for a given area without knowing the germination rate of a certain population of seed, which can be especially difficult to determine with native seeds because of their stratification or pre-treatment requirements. In lieu of germination testing, observing the seeds you collect is a crucial aspect of success for determining sowing rate. Making note of any insect predation and staggering your collection timing can produce vastly different germination rates from the same species and population. Older seeds may have more heavy rates of insect damage or predation, or have already gone dormant, and thus may respond very differently to the same treatment as seeds collected immediately when ripe. Adjusting your sowing density to these observations can be a critical factor for deciding what containers you use and how many seeds you sow per container. In general, it is helpful to keep in mind that while most native plant seedlings do better when densely sown together,  how many plants ultimately  germinate within a given space will also affect how quickly they must be transplanted in order to maintain healthy growth. Sowing densely can save on soil and container costs, but the seedlings needed to be potted on sooner. Overcrowding causes growth to be checked and leads to greater die-off and disease. Providing more ample space, either by sowing in deeper pots or providing more surface area per seed, gives you the ability to let seeds sit in the pot and develop to a more manageable transplantable size. Some seedlings prefer to be left alone to sit for at least their first growing season, while others, especially fleshy-taprooted plants such as sundial lupine, Lupinus perennis, seem to do much better when they spend as little time as possible in a pot and are planted out into open soil as quickly as possible. Understanding exactly what your needs are as a grower is key to determining the best course of action for your own seed-sowing protocol: Carefully considering these different factors will determine how and when you choose to sow your seeds.