How to Read a Seed Package
Updated: Oct 25
Whenever I teach a gardening class, no matter how beginner or advanced, I almost always take the time to go over how to read a seed package. It is that important! If you can understand everything the seed company is trying to convey on that package, you should have no problem getting that seed to grow successfully. Quality seed companies want you to succeed and provide you with all the information you need to do so.
There are a number of essential details on a seed package. Let’s take a look at them one by one.
What’s In A Name?
Will that little seed grow up to be a giant elm tree or a tiny radish? Obviously we need to know what each seed is. However, we need to know more than just what it generally is, we need some specifics.
Most seed packages will have more than one name on it. It will almost certainly have a common name, for example: basil. It may also have a variety name that describes the type of basil it is, such as “Genovese”. There may also be a Latin or scientific name on the package. Did I just hear you groan there? I know they can be intimidating, but scientific names are very important in the plant world. Bluebells are a classic example. A bluebell here in Alberta usually refers to the Virginia Bluebell or Mertensia virginica, but ask for a bluebell in the southern United States, England, South Africa or anywhere else, and you will be shown a completely different plant. Common names can be very regional. That is why we have scientific names. A plant’s scientific name is the same no matter where you are or who you talk to, and no other plant has the same name. That works for any other living thing in the world too, by the way. If you want to know even more, here is a really good article.
Binomial Latin names
In general, scientific names are made up of two words. These words are often derived from Latin (why we call them Latin names), from a specific characteristic or from whomever first discovered it. The first word is the genus that the plant belongs to and the second word is the species. Together, they form the specific epithet. The genus is more general, and the species is more specific. The genus is always capitalized and the species begins with a lower case letter. The two words together are always italicized. There may also be a variety name at the end in either quotation marks or after the word var. For example:
Helianthus tuberosus ‘Smooth Garnet’
Genus: Helianthus (sun loving)
Species: tuberosus (forming tubers)
Variety: Smooth Garnet (smooth, red skinned variety)
Common name: Smooth Garnet Jerusalem Artichoke
When to Plant
Every single seed package should indicate the correct time to plant those seeds. This may be stated as a particular time of a specific month (such as early May), it may relate to outside temperatures (such as once all chance of frost is gone) or it may be in relation to your average Last Frost Date (LFD) (such as 1 week before your LFD). If you do not know your LFD, you can find it here or google your specific location. You should also know your average First Frost Date (FFD). The number of days between these two dates is your average number of growing days. We will need this number in just a minute. Keep in mind that these dates are averages and every year is different! If there is still a foot of snow on the ground, don’t try planting those bean seeds no matter what the date is. Seed companies will give timings based on where their company is located so keep that in mind. If the seeds are from a company in Florida and you live in Alberta, the directions to seed outdoors in February will not work for you. Using dates relative to LFD are best as they work no matter where you are located.
When to plant outside (using Last Frost Dates or key phrases)
2-4 weeks before LFD (as soon as soil can be worked- not frozen or sloppy wet) Direct seed: carrot, Asian greens, peas, radish, spinach
0-2 weeks before LFD (cool season crops) Direct seed: turnip, kohlrabi, kale, cabbage, lettuce, Swiss chard, beets, parsley, potatoes, Calendula, bachelor’s button, larkspur, California poppy, sunflower, sweet pea, Lavatera, forget-me-not, black eyed Susan Transplants: broccoli, cabbage, cauliflower, parsnip, leek, kale, parsley
0-1 weeks after LFD (after any chance of night time frost) Direct seed: bean, corn, cucumber, cauliflower, onion, cilantro, nasturtium Transplants: snapdragon, ornamental kale, dusty miller, Dracaena, pinks (dianthus), stocks, Osteospernum, phlox, pansy (Viola)
2-4 weeks after LFD (Warmer night time temperatures) Direct seed: Zucchini, storage turnips/rutabaga Transplants: tomatoes, peppers, summer and winter squash, melons, eggplant, herbs, remaining annuals and perennials
The package will also let you know if the seeds need to be started indoors and then transplanted outside once the weather is warmer. Many Mediterranean plants such as tomatoes, peppers and herbs will require this as they need warm temperatures for germination and have a long number of growing days. If the seeds need to be stratified (put through a cold cycle) or scarified (scratching of the hard outer coat of the seed) before planting, the seed package will let you know and should give you instructions on how best to do it.
Days to Maturity
This is how long your seed will take to either produce ripe fruit or growing to a suitable size for harvesting leaves, stems, or roots. If the package states that the seeds need to be started indoors and transplanted outdoors, the number of days is from the day it is transplanted outside, not the day you put the seed in the soil indoors.
This is where our number of growing days comes in handy. Here in Calgary, our LFD is around May 23rd and our FFD is around September 15th (remember that these are averages!). That gives us 114 growing days. We compare this number to the days to maturity to ensure we have enough days of warm weather for a plant to grow to until we can eat it.
My seed catalog says tomatoes need to be started indoors 6-8 weeks before my LFD. They can then be transplanted outside when we have warm nighttime temperatures. That is around 2-4 weeks after the LFD (see above). In Calgary, that is around June 13th (May 23rd plus 3 weeks). From June 13th until my FFD (September 15th) is 93 growing days. Some vegetables can grow even with some frost, but not tomatoes. So then I look through my catalog at all the different tomato varieties. There are a lot! I need to find a variety with days to maturity of 93 or less. If I want to be sure of getting ripe tomatoes on the vine, I would probably look for around 80 days or less. Remember, every year is different and we want to be able to account for variations in weather.
I know that can sound complicated but days to maturity also work in another way. They can let us calculate how many crops we can plant in succession of a certain vegetable in one growing season.
Succession planting example:
Bok choy is a super-fast growing vegetable. Toy Choi specifically has about 40 days to maturity. It is an Asian green and I can direct seed it outside as soon as the soil can be worked. In Calgary that is 3 weeks before our LFD of May 23 (see above), which is May 2nd. Add 40 days growing time and we come to June 11th, when I pick it all and immediately replant. 40 more days brings us to July 21st. Once again I pick and replant. See where I am going here? Depending on the year, I may be able to harvest right until mid-October before it gets too cold or snowy. That means I can grow 4 or even 5 successive crops of Toy Choi in one season!
This does require Mother Nature to be fairly accommodating and definitely requires good organization skills on your part, but you do see the potential here, right? Interested in more in-depth scheduling for your vegetable garden? Take a look at the series of articles (starting with Crop Planning: An Introduction) for an in depth look at crop planning.
Days to Germination
This is the number of days between planting a seed and the seed sprouting (stem poking through the top of the soil). Although this is not mandatory to know, it is handy if you have been waiting for what seems like forever and there is no sign of life yet. Comparing how long you have waited to the given days to germination help with the decision to keep being patient, or to give up and reseed. Note that roots may begin to form before the stem starts to poke through the top of the soil.
Number of Seeds
Keep in mind that the number of seeds in a package can vary between 5 and 500, or even more for bulk packages. That’s a big difference! Know how many seeds you will need before you purchase and check the package before you buy. Smaller sized seeds tend to come in larger amounts per package.
Buying bulk seeds will be cheaper per seed than buying smaller packages. It makes sense to go in with a buddy (or two) to buy a larger size package if you are all buying the same thing. Heirloom and heritage seeds also tend to be slightly more expensive as do brand new hybrids. Remember, no matter how expensive the seed, it is usually much, much cheaper than buying a starter plant or full size perennial.
This is important! It should be on every single package of seeds you buy. If it isn’t, mark it on there yourself as soon as you bring the package home. In the following years, knowing how old those seeds are will help you know what proportion will germinate. Seeds lose viability over time. The longer they are stored, the less will germinate when planted. A good way to check viability is to take a few seeds and place on a slightly damp paper towel. Place the paper towel in a clear plastic bag and store in a warm place (top of your fridge is ideal). Keep checking to see if and how many seeds sprout. Counting the proportion that has sprouted versus those that haven’t sprouted will give you your germination rate to apply to your remaining seeds.
Seed life when stored properly (ie. cool and dry)
5 + years: Brassicas (broccoli, Brussels sprouts, cauliflower, cabbage, collards, kohlrabi…) the chicory group (endive, escarole, radicchio), cucumber, kale, lettuce, melons, summer squash, winter squash, mustards, radish, rutabaga, turnips, basil, sunflower
4-5 years: beets, Swiss chard, peppers, tomatoes, eggplant, celery, salsify
3-4 years: beans, carrot, peas
2-3 years: asparagus, okra, parsley, chive, dahlia, marigold
1-2 years: corn, leek, onion, parsnip, spinach, salvia
Not all packages will have this, but it can be very helpful. I use this to determine if I should plant more than one seed in each pot. A germination rate of 75% or less and I usually double up on the seeds in each hole to ensure I have at least one plant growing. Remember to thin out later if you get more than one sprout per container. If you have poor germination, knowing the germination rate may help explain what is going on. If only half of my Black Krim tomatoes come up and the package tells me that the germination rate is 97% (and it is a package from the current year) then I know something else is going on (bad soil is the usual culprit).
Depth and Spacing
The package will tell you how deep to plant the seed. This is important! Too deep and the seed many not sprout, too shallow and the sprout may not be sturdy enough to survive. A good rule of thumb is 2-4 times as deep as the seed is thick. There will also be directions for how far apart to space each seed when you plant. Usually there is a distance given for the space between each plant in a row and a distance given between each row. If you are not planting in rows, but more intensively, then use the distance between plants within a row for the space required all the way around a plant. There may also be additional instructions for thinning the plants once they are growing well.
Will the plant take some shade? Is it drought tolerant? Will it be okay with higher pH soils? The package should not only give you general guidelines for sunlight, temperature, soil and moisture, but also identify any special conditions needed. Fertilizer information may also be included. Ensure that the final location your plant will rest in has these conditions. It may also point out any particular pests or diseases that a plant is prone to. Pay attention to these and take the appropriate actions to ensure your plants are the healthiest they can be. If it is a seed for a perennial plant, there should also be an indication of the hardiness zones that the plant will tolerate and the full size the plant will reach at maturity.
When to Harvest
If this is an edible plant, the package may give you suggestions for determining when it is ready to pick and eat, besides the date to maturity. It may be a change in colour or a specific size. When in doubt, look at the picture on the package or in the catalog to tell if yours are ready.
You now have everything you need to successfully grow those seeds. Carefully read your packages and translate that information into the correct conditions and care to give those seeds their best life.
Yummy gardening everyone!
West Coast Seeds (www.westcoastseeds.com) for everything seed starting, seed sales and timing charts, etc.
Bartholomew, Mel “All New Square Foot Gardening” for charts on germination times and temperatures, percentage germination, days to maturity, planting schedules, seed storage, and most vegetables, herbs and annual flowers.
Eldorado Weather (https://eldoradoweather.com/canada/climate2/Calgary.html) for in depth Calgary climate information.
Don’t forget your local garden centre or greenhouse!