A seed packet holds more information than most beginners realize. Once you know what each section means, you can plan your entire season from a $3 envelope. Here's everything printed on a typical seed packet — decoded.
Days to Maturity (DTM)
This is the most important number on the packet. "Days to maturity" tells you how long from planting (or transplanting) until the crop is ready to harvest. A tomato with "75 days" planted as a transplant on June 1 should be producing by mid-August. For direct-sown crops like carrots, DTM counts from the day you put seed in the ground. Use DTM alongside your first fall frost date to know whether a crop has time to mature in your season.
Sowing Depth and Spacing
Depth matters more than you'd think. Seeds planted too shallow dry out before germinating. Too deep and they exhaust their stored energy before reaching light. Follow the packet precisely — "½ inch deep" means ½ inch, not "roughly buried." Spacing tells you both row spacing and in-row spacing. "Space 12 inches apart in rows 24 inches apart" means each plant gets a 12x24 inch block of territory. For succession planting, spacing affects how many seeds per row you're planting and how quickly you'll exhaust your packet.
Light Requirements
Seed packets use standard light categories: Full Sun (6+ hours direct), Part Sun or Part Shade (3–6 hours), and Full Shade (under 3 hours). Most vegetables want full sun. Lettuce, spinach, and some herbs tolerate part shade, especially in hot climates where afternoon shade prevents bolting. If your garden gets less than 6 hours, focus on leafy greens and herbs rather than tomatoes, peppers, and squash.
Direct Sow vs. Start Indoors
Some crops resent transplanting and must be direct sown: carrots, beets, radishes, parsnips, and most root vegetables. Others benefit from a head start indoors: tomatoes, peppers, and eggplant (which need 6–10 weeks before transplanting). The packet will tell you which applies. "Direct sow after last frost" means put seeds in the ground. "Start indoors 6–8 weeks before last frost" means you'll be growing seedlings inside before moving them out.
The Packet Date and Germination Rate
Every packet is printed with a "packed for" year. Seeds remain viable beyond that date — tomatoes often last 4–5 years, onions are best used within a year — but germination rates drop. A packet rated "85% germination" from two years ago might be down to 60%. If you're using old seed, sow more densely than the packet recommends and thin the extras. A quick germination test: fold 10 seeds in a damp paper towel, seal in a plastic bag, and check after the DTM listed for germination. Count how many sprouted to estimate viability.
Hybrid (F1) vs. Open-Pollinated (OP)
Hybrid seeds (labeled F1) are bred crosses between two parent varieties, selected for vigor, disease resistance, or uniformity. They produce reliable crops but seeds saved from hybrids won't come true to type. Open-pollinated and heirloom varieties breed true — save seeds this year, plant them next year, get the same plant. For beginners, hybrids often offer more predictable results. If you want to save seeds and build a self-sufficient garden, start learning beginner gardening with open-pollinated varieties.
Frequently Asked Questions
- Can I use seeds past the packet date?
- Yes, with a germination test. Most seeds stay viable 2–5 years if stored cool and dry. Run a simple paper towel test before planting a full row to avoid wasting bed space on dead seed.
- What does "thin to 6 inches" mean?
- Thinning means removing extra seedlings after germination so remaining plants have the listed spacing. It's painful but necessary — crowded seedlings produce less than properly spaced ones. Snip extras at soil level with scissors rather than pulling, to avoid disturbing neighbors' roots.
- What's the difference between "days to germination" and "days to maturity"?
- Days to germination tells you how long until seeds sprout (often 5–14 days). Days to maturity tells you how long from planting or transplanting until harvest-ready. Both appear on most packets.
- Does it matter which brand of seeds I buy?
- Quality varies. Look for seed companies that list germination rates and test their seeds annually. Small regional seed companies often carry varieties better suited to your specific climate than national chains.
- Why do some packets say "not for sale in California"?
- California has specific regulations on certain GMO and treated seeds. If a packet lists state restrictions, it's a labeling and compliance issue, not a quality concern for the varieties themselves.