seed starting: the question of timing
It’s the time of year when I start to notice friends and comrades starting to ask questions about when they should start the seeds they want to grow this year.
In this post, I am going to outline some of the basics in terms of how to figure that out based on where you live and the info that is usually included on seed packets.
As with all things, there are areas for nuance, and just about every gardener develops their own specific approach. And, of course, the Fuck Around and Find Out method is a perennial favorite for many (if not at the beginning of the seed-starting season, then frequently by the end of it).
With that said, though, there are always gifts to be found from looking at some of the basics, and then honing your approach from there to fit your life.
The main bits of information you’ll need to calculate when to begin seeds for a particular type of plant are your average last-frost date, stratification time and methods (when applicable), the cold and heat tolerance for the plant friend in question, and whether the plant friend is well suited to succession planting.
Last frost date
According to the Old Farmer’s Almanac:
A frost date is the average date of the last light freeze in spring or the first light freeze in fall.
The classification of freeze temperatures is based on their effect on plants:
Light freeze: 29° to 32°F (-1.7° to 0°C)—tender plants are killed.
Moderate freeze: 25° to 28°F (-3.9° to -2.2°C)—widely destructive to most vegetation.
Severe freeze: 24°F (-4.4°C) and colder—heavy damage to most garden plants.
When it comes to seed starting, the date we’re most focused on is the last spring frost date. This date is derived from averages of past climate data for an area, and is obviously only an estimate: nevertheless, it is an estimate that provides a useful guide for timing our seed starting.
You can search for the average last frost date on sites such as https://garden.org/apps/frost-dates/.
Once you find your last frost date, I recommend marking it on your calendar, and then adding a notation on each preceding week with how many weeks it is until your last frost date. Here at the Wild Within Acres, we are 13 weeks until our last frost date.
Most seed packets will mention how many weeks until your last frost date you want to start that type of seed.
These dates are based on decades of gardeners’ experiences on what timing best equips the plants to have adequate root and stem development to be able to survive when they are transplanted into the garden (or their final, largest container for the year): seedlings that haven’t reached certain milestones in their growth are less likely to be able to survive and thrive through the transplanting process.
Conversely, you also don’t want to start them too soon. Some plants can get to a point at which their root system is unable to meet the plants’ needs in their container. As a result, the plants are already stressed, depleted, and hungry when it comes time to transplant them; consequently, they are less able to devote the energy and resources toward successfully establishing themselves in their garden home.
For many seeds—particularly the annuals that make up a significant amount of what many home gardeners grow—the last frost date may be the only main piece of information one needs in order to calculate when to start different seeds. If the seed packet says to start them 6-8 weeks before your average last frost date, look to your labeled calendar, add that seed to your to-do list for the week, and you can be reasonably confident that you’re getting it going at the right time!
Some types of seeds, however—and particularly perennials and biennials—may list another date range that needs to be factored in when figuring out when to start tending to the seeds: a stratification period.
stratification timing and methods
Stratification refers to a period of exposure to a particular combination of temperature and moisture—frequently cold and moist—that assists a seed with recognizing that it’s time to start growing. Basically, stratification is a way for us to expose a seed to the messages it would get from the web of nature regarding when it’s time to get started with the hard work of growing up.
If you have ever had a particularly frustrating time getting some plants to grow from seeds, it may be that stratification is the missing key!
Stratification times are usually listed based upon how many days the seeds need to be exposed to cold and/or warm moisture in able to convince them it’s their time to shine.
For example, the seeds for mad-dog skullcap (Scutellaria lateriflora) benefit from 60 days of cold stratification before getting them started in seed-starting mix, while many lavender species (Lavandulas spp.) benefit from 20-40 days of cold stratification.
And then you have tricky little buddies like ramps (Allium tricoccum). These notoriously slow germinators benefit from a 60-day period of cold stratification, followed by a 60-day period of warm stratification (i.e., dark, moist, and at room temperature), followed by another 60-day period of cold stratification (back into the fridge!): this convinces the seed it has survived two winters, at which point it can be more easily coaxed to sprout.
(Do you see how, with the seeds wanting two whole winters just to start growing, over-harvesting of these plant friends in wild spaces is such a huge concern?)
The absolute easiest way to handle the matter of stratification for any plants who grow in climates that are similar to where you live is to simply sow them in the fall where you would like them to grow, and then hope for the best that birds and critters don’t relocate them. Seeing as how I am writing this in January, it is likely that anyone reading this soon after I post it has already missed that window.
Another option that frees you from needing to keep track of too many dates is to get the seeds all set up in your seedling pots, flats, or soil blocks, and place them outside somewhere where they can be protected from the birds and critters, but still easily accessed to keep an eye on and water/tend to as needed.
And yet another option is to do your cold stratification in your refrigerator. To do this, simply scatter the seeds on a piece of damp paper towel or (in the case of very small seeds) in some damp sand or seed-starting mix. Seal the seeds up in a baggie (or other appropriate container), and then label them with the species and the start and end dates of the stratification period and place them in your fridge.
No matter what your brain tells you, you will not remember what they are or when you started them.
I also find it helpful to mark the end dates of the stratification periods for the seeds on my seed-starting calendar, rather than relying on my memory for when I should be moving some seeds from the fridge to their seed-starting blocks.
You can find more detailed info and images about seed stratification in the refrigerator at https://blogs.cornell.edu/biocontrolbytes/2025/01/22/stratifying-perennial-wildflower-seeds/.
The stratification time is in addition to whatever duration of time before your last frost date a seed packet recommends starting the seeds.
For example: as I mentioned, lavender seeds benefit from an approximately 30-day/4-week period of cold stratification.
Because lavender seedlings are pretty slow growers, it is frequently recommended that they get started 8-12 weeks before the last frost date.
To add that all together: 4 weeks cold stratification plus 8-12 weeks seed starting time means that they should be put into cold stratification 12-16 weeks before last frost date. This means it’s time for me to get those seeds stratifying already!
Cold and heat tolerance
These last two points (cold and heat tolerance, succession planting potential) are simply some bonus points that I am adding a mention of because of their potential for taking some of the mental pressure off of seed starting perfectionism.
It can be helpful to have a basic understanding of how tolerant a particular type of plant is to different temperature extremes.
Plant friends who have a wider bandwidth of temperatures and conditions that they can survive and thrive in are ones that you can grant yourself a bit of extra grace and wiggle room in regards to when you start their seeds.
Conversely, plant friends that tend to be finickier about the conditions they need to flourish (e.g., hot peppers are notoriously cold sensitive, while spinach will quickly bolt if it gets too hot for its taste) may be ones to really prioritize starting at the recommended time.
So if you notice when you are filling out your seed-starting calendar with the timing for when to start which seeds and you notice that one week is particularly high-demand for seed starting…
it’s totally okay to shift some of the plants that are more resilient to different temperature ranges to a preceding or following week so that you can prioritize the seeds for more tender species!
succession planting potential
In a similar vein, plants that are frequently succession-sown through a season are ones that offer some added flexibility to your seed-starting plans.
Because these plants are well suited to starting in multiple “waves” throughout a growing season to allow for a more spaced out harvesting period, you know that there is wiggle-room available in relation to when to start them.
A good list of vegetables that are well-suited to succession planting in many climates can be found at https://www.johnnyseeds.com/growers-library/methods-tools-supplies/market-gardening/succession-planting-interval-chart-vegetables.html.
Conversely, plants that have too long of a lifespan between germination and harvest to allow for succession planting are ones that it makes sense to be extra vigilant about starting at their recommended time.
Having a good sense of which of the plants you’re growing this year allow for succession sowing can, again, come in handy if and when you notice that there are some overloaded weeks in relation to seeds to start that are followed by less demanding weeks.
Move some of the more forgiving and flexible plants to the other weeks: let the process keep being fun, rather than running yourself ragged right at the very onset of the season!
There is always more to learn regarding starting seeds and tending seedlings, and I am sure that I will have more to share on the topic as the season goes on.
But for now, this should be enough to get you starting on putting together your seed-starting calendar for the year. Happy growing!
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