1. When to Sow. You'll find terminology for when you can begin growing the seed different on different packets; each seed supplier wants to be unique. Look for key phrases like: "Start Indoors"; "Sowing Indoors"; "Sowing Outdoors"; "Direct Sow". This is where you find out the best time to begin growing the seeds. Some seeds can be started indoors while others should only be sown outside. Finding this out as soon as you buy the packet is important for determining a planting schedule.
Some seed packets will be very specific by saying something like, "start seeds 3-4 weeks prior to your last frost date," or "start from seed indoors 4-8 weeks prior to the last frost of spring," or "sow after all danger of last spring frost and soil has warmed thoroughly." This makes it easy if you know your average Last Frost Date (link to my article: "Know Your Last Frost Date").
If the packet says something like, "direct sow after danger of frost", that means plant outside only. If there is no mention of starting seeds inside, that also means you should sow outside only.
Others will include information for both starting indoors and for sowing outdoors. For those seeds you can do it either way.
2. Where to Sow. This is a very important piece of information too. If the packet says "sow in fertile soil in full sun," that's what you need to do for best results; don't sow in unamended soil in the shade and expect anything good to grow. "Direct sow in well drained soil" means that full sun isn't as important as the soil. Take the time to prepare the site for your seeds.
For starting indoors, the assumption is usually that you're growing in a nice soil medium or potting soil so packets will rarely tell you to do that. The packet may say something like, "place in a warm location and keep moist" or "do not let the soil dry out." That's an important clue to keep an eye on the seeds and new sprouts so they don't dry out and die.
3. Seed Depth. Different seeds require different conditions to germinate; you can't plant everything the same. Placing the seed at the proper depth will improve germination results. The "Seed Depth" or "Planting Depth" will usually be described in inches. If it's a specific number like 1/2", try to get close to that depth when you sow. If it's a range like 1/2" - 1", you have a little more leeway, but you still need to get within that range.
"Surface-sown" or "lightly cover seeds" means you don't need to place seeds in a measured hole; you can sprinkle them on the soil surface and sprinkle a little soil over them to keep them from blowing away.
4. Seed Spacing. Packets will also be very specific about how far apart the seeds should be sown. This helps ensure that the plants will have enough room to grow. Often it's expressed as a range of inches that the seeds are apart from each other, along with how far apart rows should be. While many traditional gardens may have plants 6"-10" apart in rows that are 2'-3' apart, you can usually plant a block of plants in a bed with everything 6"-10" apart from each other; it comes down to how you garden, with rows or blocks.
The packet may also tell you to "thin plants" to a certain spacing. This provides a number for how far apart the final plants should be. For example, onions can be sown close together and after germination should be thinned to 5"-7" apart for bulbing varieties or 2" apart for bunching varieties.
5. Days to Germination. Knowing how long it takes for the seeds to send a sprout to the surface helps you determine if conditions and seed viability are good. It also tells you if you should relax and not worry while the plants are growing. Some seeds only need a couple days to germinate while others may need a couple weeks. Don't assume something's wrong if you don't see plants right away.
Packets will give a specific range of days for "days to germination" or when "seedlings emerge." Within this range of days you should begin to see little green seedlings begin to break through the soil surface. If at the end of the range you still don't see plants, that's when you should become concerned. The soil heat or moisture may be wrong or the seeds could be bad. Give it a few extra days before you completely sow over again.
A few years ago my squash seeds were late in germinating and I became concerned. Just about the time I began to sow again, the first seedlings emerged. My guess is that we had a few cold nights that lowered the soil temperature enough to delay germination.
6. Soil Temperature for Germination. This information is only available on very thorough seed packets like those from Territorial Seed Company. The soil temperature needs to reach certain levels for all seeds to germinate. As mentioned above, if you sow when the soil is too cold it will affect how well the seeds germinate.
Most seed packets cover this subject with the general information described in "When to Sow" as described above.
7. Days to Maturity. This may also be expressed as "Days to Harvest" and may be the most important bit of information on the packet for vegetable garden seeds. This is how long it takes for the plant to reach the point when it begins to produce fruit. What's critical to know about this number is that it is based on when the plant is in the outside soil. Though seedlings may be growing for weeks inside, the days to maturity don't begin until transplanting outside. For seeds sown directly in the garden, it is the point when the plant has true leaves.
The reason this is such an important number is because many gardeners may not have a growing season long enough for specific plants. Many varieties of garden plants like melons, heirloom tomatoes, and winter squash have very long days to maturity. On average, my growing season at high altitude is about 130 days. If I try to grow a plant that takes 120 days to mature, I'm pushing the limits of my growing season and probably won't get any ripe fruit.
As important as this number is, it is just a guideline and not a definite timeline. Typically it is the number of days when you should expect fruit, assuming everything about your growing season is average. If you've had great conditions and you've done a great job caring for your plants, you may get fruit sooner. If you've had cool weather and the soil is marginal, it will probably take longer.
Before sowing seeds, have a good understanding of whether the plant will grow to maturity in your specific garden.
8. Light requirements. This goes along with "where to sow." Look for "sun", "full sun", "shade/sun", or an image of the sun on the seed packet. This guidance isn't for where you plant the seed, but rather where the final plant needs to be. Consider how the sun moves during the growing season in your garden, particularly if you have trees or fences. You may sow a seed in a spot with full sun, but at the end of the season that spot may end up in partial or full shade. The plant can suffer if it doesn't have the light requirements listed on the packet.
9. Growing Tips. Many seed packets will provide additional information about subjects like transplanting, weeding, how to water, pollination, thinning, and mulching. This varies greatly between seed companies. If there is extra information on the packet you should pay special attention to it because it is unique and probably important.
10. Fertilization. Few seed packets include this information, but it's nice to know. If you find it on the seed packet you're looking at, you're probably dealing with a company that cares about more than just selling seeds.
11. How to Harvest. This is another helpful piece of information found on few seed packets. This can be beneficial for plants like peas or beans that have different tastes and textures depending on when they're harvested. Suggestions for the size at which to harvest squash is helpful too. You'll seldom find this kind of information on seed packets for common plants like tomatoes that are colorful at harvest, but it's nice to find on less common plants like parsnips (A Baker Creek Heirloom Seed Company seed packet says to harvest parsnips "in autumn after a few light frosts have mellowed and sweetened the creamy-white roots").
12. Diseases and Pests. Information about diseases and pests may be the rarest information on seed packets, but it shows up occasionally. If a hybrid is particularly resistant to a common scourge it will often be mentioned. It may also be mentioned in the form of acronyms after the plant's name, particularly in tomatoes. "VFN" on a tomato seed packet means the hybrid is resistant to verticilium wilt, fusarium wilt, and nematodes. You can find out what all the codes mean with a simple internet search.
13. Seed specifications. All seed packets should tell for what year the seeds were packaged. This may be the second most important piece of information on the packet and is often overlooked. This is usually printed on one of the flaps that seal the packet, either top or bottom. It may be printed in big letters on the front. Regardless of the location, find it before you buy.
Seeds don't last forever and some only remain viable for a year or two. If you end up buying a packet of seeds that is a couple of years old, you may end up with a very low germination percentage. Try to always buy seeds for the year you plan to plant.
Some packets will list the percentage of germination you can expect and how the long the seed life is. This is helpful if you don't sow all of the seeds and want to save the packet to plant next year. I save many seeds from one year to the next because many packets come with more seeds than I can use; I accept a lower germination rate with older seeds.
14. Botanical name. Many seed packets include the Latin name of the plant so you can increase your scientific knowledge. This can be helpful for conversations with botanists, but in practice I don't know many gardeners who use Latin descriptions on a regular basis. Probably because of that commonality, I'm finding that fewer packets include the botanical description and are opting instead for common names. Even when it is included it is often a generic title; on two different seed packets from Territorial Seed Company, one for shallots and one for Spanish onions, only the common name for bulb onions, "Allium cepa", was listed.
15. Blooms. Like for vegetable fruiting, many flowers seeds will include the blooming period. It is often expressed as "summer", "midsummer", "fall", or something similar. This is very helpful so you know how long it will take for new plants to flower and for how long the flowers will be produced.
Typically this is information on annual flower seeds. For perennials expect information about how long it will take for the plant to produce flowers; it could be one to two years after sowing.
16. Preservation. Ferry-Morse seed packets include a "preserve by" method on packets so you have an idea of what to do with abundant crops. This is great for new gardeners or new preservers so they understand that there are alternatives to eating everything right away.
17. A picture. Almost all seed packets have a picture of what the plant, fruit, or flower will look like at maturity. The picture is often intended to grab your attention for an impulse buy in box stores and garden centers. It may be a photo or drawing; I prefer a color photo so I can know what to look for at harvest.
Be sure to read the text throughout the seed packet to fully understand what you're planting because some companies may post the same picture for different varieties. I have several packets of tomato seeds from Baker Creek with the same display of various tomatoes on the front; only a sticker with the name of each packet’s tomato variety differentiates them.
Some companies like Livingston Seed will have clear plastic on the front of the packet along with a photo. This helps you see the actual seeds so you know their quality and quantity.
18. Weight. It's pretty universal that seeds are weighed in grams. Initially this may not mean a lot to you other than give an idea of how many seeds are in the packet; 3 grams of sunflower seeds will produce a few dozen plants while 3 grams of radish seeds will produce hundreds of plants. I find it most useful when comparing the price of seeds from different companies and for determining how big a packet to buy. I know 1/2 gram of onion seeds will do me fine and I don't need to buy more.
19. Contents. Look at what the packet actually contains. Some packets will actually tell you how many seeds are in them. Along with weight this gives a good idea of the space you need for all of the seeds. Read carefully. I bought a relatively expensive packet of monster pumpkin seeds only to discover three actual seeds when I opened it; it forewarned me if I had looked at weight and contents more closely.
When you're buying a blend, the photo is often misleading. I've purchased flower seed blends that look great on the front, but when you read the contents you find a list of plants that may be far different from the image. Also for flower seeds it's beneficial to read the contents so you don't buy a blend that may include an invasive species for your area.
For vegetable blends, particularly salad blends, reading the contents will help you identify the plants as they grow. It's nice to know you like the purple leaves in your garden, but looking at the contents of the seed packet can help you identify it as "Orach" (this happened to me).
Also note if there's any filler in the seed packet. "Inert matter" is anything except seeds. "90% inert matter" means it is only 10 percent seeds.
20. Company Name. Pay attention to the name of the company selling the seeds. You may find a favorite for quality, price, information, or find that certain packets have limitations. I love the seeds from Baker Creek Heirloom Seed Company, but I find their seed packets to be hit or miss. Some of their packets are filled with helpful info with a conversational tone that is easy to read, but others are often stingy with information. It helps that their catalog is about the best in the business.
For beginning gardeners I often recommend the seed packets at garden centers from companies like Burpee or Ferry-Morse. Their packets have nice, visual representations of how to sow seeds, along with the important basics.
Ultimately selecting a seed packet comes down to the gardener buying what he or she wants to grow in their garden, but if you like the seeds and like the information on the packet it helps to remember the company that gave you a good product.
Those are the 20 things you can expect to find on seed packets. I've yet to find a company that includes all of them on a single packet. Decide if certain factors are important to you and look for those factors when you get new seeds. If you don't fully understand a statement, number, or picture, refer to my descriptions above and do a little more research on your own.
I recommend saving seed packets after you've sown all of the seeds. I keep each year's seed selection in a box during that season so I can refer back to the packets if I need to be reminded about a variety or to confirm important things like days to harvest, especially when the fruit is slow to set.
Write yourself notes on the packets so you can refer to them in the future and know which ones you liked, or not. They're like mini encyclopedias of gardening information. These little envelopes usually provide everything you need to get the seed in soil and begin growing.