Seed Starting Basics: Packet Knowledge

Updated: Feb 19

One thing that surprised me when getting into growing flowers and vegetables from seed was how vastly different their needs all were. I wasn’t even sure at first as to what pieces of information were important. Here is a list of all of the information I now track, what they all mean, and why they are important.

General knowledge

  • Date of first and last frost – this is something you will need to look up, and it will help you calculate when to plant transplants outdoors. In the Treasure Valley, the last frost date in the spring is May 9th and the first frost date in the fall is around October 11th. The last frost date is when it is safe to plant all flowers and vegetables unless otherwise noted, and first frost date is when most plants are wiped out.

  • Plant zone and plant temperament – plant “hardiness” helps determine a few things.

  • Zone: The zone is indicated on the seed packet, but you will need to look up your own zone to know what works in your area. Eagle, ID is zone 7a. Many plants are hardy in lower zones. Anything at your zone or lower will grow well in your area.

  • Temperament: Once you know what plants grow in your zone, they can be further split into spring planted plants or summer planted plants. Tender annuals only survive in warm weather (typically planted in May after the last frost), while hardy annuals (also called cool season or cold tolerant flowers) generally prefer cooler growing conditions, meaning that transplants can tolerate a light frost, so therefore can be planted earlier (typically March). Annual, hardy annual or tender annual are usually the words used on the plant packets. If nothing is indicated, it’s typically an annual to be planted out after the last frost.


  • Days to germinate: While less important than other measures, it helps to know if you should start seeing sprouts in a few days or much longer. If covering seeds with a dome on a heat mat, the days to germinate will be sped up, and you will want to check your seedlings sooner so they don’t “dampen off” and die from too much moisture.

  • Plant depth: Tied to light or dark requirements, this tells how deep the seeds should be planted. Most seeds need to be covered with 1/8th or 1/4th an inch of soil, which is a light sprinkle of soil.

  • Light or dark requirements: While most seeds some need a light sprinkle of soil to germinate, some need no soil, which on the seed packet is indicated by “they need light to germinate”.


  • Days to maturity: I found that this measure was one of the most important to note. The days to maturity tells how long you can expect to get fruit or flowers after you seed something. So, if you start seeds on April 1st for a hardy-annual plant that says 90 days to maturity, it will bloom or fruit in early July provided that the spring isn’t colder than normal. In the Treasure Valley, I have found that most of my plants bloom or fruit far later than the expected days to maturity, and we have had multiple years of colder than normal spring seasons.

  • When to start seeds: This measure is tied to the last frost date. For annuals, knowing your last frost is May 10th, and the seed packet says start 4-6 weeks before, you would start seeds March 29th at earliest, and April 12th at latest, and transplant them May 10th. But, for hardy annuals, you can plant them out 4-6 weeks before last frost (March), so you would back-calculate from that date as to when to start seeds. So, if you are planting hardy annuals out 4-6 weeks before last frost (March 29th), and a seed packet says to start it 10 weeks before planting out, you would start the seed indoors on January 18th.


  • Plant spacing: This is helpful to know when planting transplants outside. Many plants are planted 6” or 9” apart, but some plants, like zucchini grow very large, so they indicate 2 feet apart. I always take the most conservative estimate, but to do that, you also need to know how tall they will grow. If something is planted 9” apart but grows 3 feet tall, you can’t plant it next to another 9” apart plant that only grows 12” tall because the taller plant will shade out the shorter plant and it won’t thrive as well as it should.

Other interesting information

  • Brand: I keep track of the brand of seed I bought so I can remember from year to year where to re-purchase it, or if I didn’t love that brand, I would know to go elsewhere.

  • Long name: Some plants have a common name and an official name and trying to search by the common name doesn’t always give accurate results. For example, a Black Eyed Susan is the common name of Rudbeckia.

  • Variety: If you have ever tried to purchase tomato seeds online, you will see that there are so many varieties it is almost overwhelming. I now track which variety I purchased so I can remember from year to year.

Amazingly, not all of this information is available on the seed packets, so that meant a lot of googling from plant to plant to know when to start them, how deep to plant, and more. And since I didn’t want to do it every time I needed the information, I wrote it all down. The first year of growing, I spent countless hours putting a spreadsheet together of all of the needs of each plant. With each plant as a row on my spreadsheet, I organized them from top to bottom for the ideal time of when to start the seeds. This was calculated from knowing my last frost date and when to start the seeds.

Let me know if you found this information helpful!


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