Gardening with Gardner: Decoding a Seed Packet

Gardening with Gardner: Decoding a Seed Packet

Winter is seed shopping time!! The displays of seed packets that appear in garden centers are full of enticing photos of colorful blooms and delicious food. As you start picking up packets and looking them over you may wonder – what does all of this mean??

Annual, Biennial, Perennial

  • Annuals (like sunflowers and most vegetables) are plants that sprout, produce seed, and complete their life cycle all in one year. You will have to sow these each year unless they are self-seeding.
  • Biennials (like foxgloves) require two growing seasons to complete their life cycle. The first year, they focus their energy on vegetative growth. The second year, they reach maturity and go into seed production. Sometimes these plants are short-lived, only lasting a few years once mature, so you may want to start new plants every few years to keep them in your garden.
  • Perennials return year after year. If started early enough, many will bloom or produce in their first year, but they will be more productive in their second and subsequent years. Check the hardiness zones for perennials, though. I often find things that are hardy to zone 6, for example and not my zone 5a (almost 4b!). Sometimes these are called “tender perennials” – i.e. you can get them to come back if you do some work. You might get away with “zone busting” if you have a protected area, mulch well, or can bring plants into a greenhouse, basement, garage, or shed for the winter.

Days to Germinate

This number represents how long, from when you put that seed into or onto the soil, until you see green sprouts! The first leaves that emerge are called cotyledon leaves. If you remember your high school biology, those were the seed halves! The leaves that follow those first ones are the “true leaves,” and are often a very different shape. If you plan to transplant a seedling, general practice is to wait until you have two sets of true leaves.

Pelleted seeds are coated, and sometimes colorful! Often this is done for tiny seeds and makes them easier to handle. The material may be antifungal, contain a light fertilizer, or just be inert material. If you have a pelleted seed, be sure to keep it moist so that coating can break down. You may find it takes a few more days than you expected for a seed to germinate if it’s pelleted.

Days to Maturity

Days to maturity, or bloom, or harvest can be confusing. You might see a symbol on the front of the packet with a number of days — but a number of days for what? This number tells you when the plant flowers or produces fruit (when you can pick!), but is it from when you sow the seed, or when it germinates, or when you transplant a seedling?

Some packets are very clear about “days to maturity from seed, or days to maturity from transplant.” The “days to maturity” number describes the average number of days from planting until it’s time to harvest. For seeds sown directly in the ground, that means from sowing to maturity. For those started inside, the days start from the time of transplanting outside. Keep in mind you can harvest small squash, or cut baby spinach!

There are many things that can affect the timeframe, so it’s best to use it as an estimate or relative planning guide.

  • If seed is direct sown: is the soil cool or warm?
  • Day length can affect the number of days. Many veggies and fruits, and some flowers, mature most quickly during long days, but are slower when days are shorter. If planting for fall, add a week or two!
  • Temperature: tomatoes need warmth to ripen, but lettuce may bolt in heat.
  • Water levels, pest pressure, and the amount of nutrients in the soil or fertilizer added can also affect growth rate and maturity.

Heirloom or Hybrid

Many times, seed packets will say heirloom, open-pollinated, hybrid, or F1 on them,

Heirloom, or open-pollinated plants will stay true to the parent plant, so your next generation of seedlings will take on the same genetic traits of the plant they came from.

Hybrid (or F1) simply indicates a cross between two parents. It does NOT mean that the seeds were engineered, treated with chemicals, or genetically modified. The hybrid offspring may take on the traits of just one parent, or even combine random traits of both parents. This is how we got modern day broccoli from wild mustard. It’s also how I got an orange spaghetti squash! Thanks, bees.

Labeled zip-top bags containing seeds folded into moist paper towels
Labeled zip-top bags containing seeds folded into moist paper towels


Some seed varieties with tough shells germinate best after a little extra effort. You might see a note on a packet that says the seed benefit from stratification, scarification, or both.

Stratification is a cold, moist treatment that replicates the natural conditions these seeds would experience in their native habitat. There are a few ways to achieve this: inside and outside.  Indoors, wrap seeds in a damp paper towel (squeeze the excess water out) and put in a zip-top bag and place in the fridge. You can also mix seeds with damp sand or moistened vermiculite and place that mix in a bag or container in the fridge (this can make for easy sprinkling, especially if you’ll put them right outside). Most seeds will need 4 or 5 weeks in these conditions. 

    • Check on the seeds weekly after about 3 weeks. If seedlings start to sprout in the bag in the refrigerator, remove them immediately and either plant them in the ground or in pots until it’s time to plant outdoors. You don’t want tiny roots to adhere to the paper towel, as they’ll get damaged if you try to remove them and your seedlings won’t grow.
    • If you have just a few seeds to sow and lots of fridge space, you could sow in a small pot (or seedling 6-pack or similar container), put the whole thing in plastic and put that in the fridge. You can also grow seeds that need this treatment by sowing them in pots and setting the pots outdoors in late fall or winter. The seeds will germinate when temperatures rise in the spring.

Scarification is done to seeds with particularly tough coats or shells to simulate natural weathering processes. It’s simply lightly damaging the seed to start to break down a rough, hard seed coat. You can gently rub it on sand paper (or a nail file) or, if a seed has a very hard coat, nick it lightly with a nail clipper. If nicking the seed coat, aim for the broad, smooth part so you’re less likely to damage the vital growth points inside the shell.

Backside of an echinacea seed packet with sowing and growing information.
The highlighted area shows depth, spacing, and mature size of the plant.

Depth, Light, and Space

Finally, when you’re ready to sow your seeds, the packet will tell you how to plant them and how they will grow. In addition to mature size and how much water the plants will require, the packet will also tell you how deep to sow the seeds, how closely, and where they will do best.

Sowing depth: Some seeds need light in order to germinate, and may say to sow on the surface or barely cover. Similarly, some seeds require total darkness to germinate. Common sowing depths are 1/8″ – 1/4″ deep. Often, this equates to about twice the seed size. If you sow a seed too shallowly, it may not develop a good “anchor” in the soil and can be weak.

Spacing: You’ll see two or three kinds of spacing on a seed packet. There is one distance to sow the seeds (often quite close, or 3-4 seeds together), and you may see a second distance for row spacing. For example, you might sow peas 2″ apart but space the rows 6-8″ apart on either side of a trellis. Then there is another distance listed for thinning. This is the final spacing of the seeds after you “weed out” the tiny sprouts to keep only the smallest ones, or transplant the healthy ones to achieve this distance. 

Sun needs: Finally, you’ll see an indication of how much sun your plants should receive: full sun, part sun, part shade, or full shade. This will be the conditions under which the plants will grow best — becoming their most vigorous and most productive. 

Now you’re ready to take to the seed catalogs and garden centers and plan and plant, armed with new knowledge!

An assortment of seed packets
An assortment of seed packets.