Seed packets are packed with information, some of it useful, most of it marketing. New gardeners either ignore the packet entirely or get overwhelmed by the details and make poor decisions.
Here’s what you actually need to pay attention to: six specific numbers that determine whether those seeds will succeed in your garden or waste your time and money. Everything else on the packet is secondary.
Let’s decode seed packets so you can make informed buying decisions and actually grow what you’re planting.
Number 1: Days to Maturity (The Most Important Number)
This tells you how many days from planting (or transplanting) until the plant produces a harvest. It’s usually written as “Days to Maturity: 75” or “Matures in 60-70 days.”
Why it matters more than anything else
If your growing season is 100 days and you choose a tomato variety that needs 85 days to maturity, you’ll barely get a harvest before frost. Choose one that matures in 60 days, and you’ll be picking tomatoes for weeks before cold weather arrives.
How to use this information
Calculate your growing season length first. Take your last spring frost date and count forward to your first fall frost date. That’s your available growing season.
For example: Last frost May 15, first frost October 1 = approximately 140 days
Now look at days to maturity on seed packets:
- 50-60 days: Short season, produces quickly
- 70-80 days: Medium season, standard timing
- 90+ days: Long season, needs warm weather for extended period
The critical detail most people miss
For transplants (tomatoes, peppers, etc.), days to maturity counts from when you transplant them outdoors, NOT from when you start seeds indoors. For direct-sown seeds (beans, squash, lettuce), it counts from the day you plant them in the ground.
Real-world example
A tomato packet says “75 days to maturity.” You start seeds indoors 6 weeks before your last frost. You transplant them outside after the last frost. Count 75 days from that transplant date, that’s when you’ll get ripe tomatoes.
If you only have 90 days of frost-free weather and you plant a 75-day tomato variety, you get 15 days of harvest window. Plant an 85-day variety instead, and you’ll be racing frost with unripe tomatoes in fall.
What to do with this number
Match it to your growing season. If you have a short season (less than 120 days), prioritize varieties under 70 days to maturity. If you have a long season (150+ days), you can grow anything. Medium seasons (120-150 days) can handle most varieties but should avoid the longest-season crops.
Number 2: Planting Depth (Get This Wrong and Seeds Won’t Germinate)
Usually shown as “Plant 1/4 inch deep” or “Sow 1-2 inches deep.”
Why it matters
Seeds need specific conditions to germinate. Too deep and they run out of energy before reaching light. Too shallow and they dry out before roots establish. Each seed size has evolved to germinate at a certain depth.
The rule of thumb
Plant seeds 2-3 times as deep as the seed is wide. A tiny lettuce seed barely gets covered with soil. A large bean seed goes down an inch.
How to actually do this
- For tiny seeds (lettuce, carrots, herbs): Press them onto the soil surface and barely dust them with soil or vermiculite. They need light to germinate. “1/8 inch” on the packet basically means “barely covered.”
- For small seeds (radishes, beets): 1/4 to 1/2 inch deep. Use your finger to make a shallow depression, drop the seed, cover lightly.
- For medium seeds (beans, peas, cucumbers): 1 to 1.5 inches deep. Your finger to the first knuckle is about right.
- For large seeds (squash, pumpkins): 1 to 2 inches deep. Push them down with your finger past the first knuckle.
Common mistake
Planting everything 1 inch deep because it seems like a standard depth. Small seeds planted too deep never emerge. You’ll assume they were bad seeds when really you buried them.
Number 3: Spacing Requirements (Ignore This and Plants Fail)
Listed as “Space 12 inches apart” or “Thin to 6 inches.” Sometimes shows both in-row spacing and between-row spacing.
Why it matters
Plants need room for roots, air circulation, and light. Too close together and they compete for resources, don’t produce well, and get disease problems from poor air flow.
How to use this information
Take it seriously. If it says 18 inches between plants, that’s not a suggestion. You might be tempted to squeeze in “just one more” plant, but overcrowding causes more problems than empty space.
- For transplants: Measure the recommended distance between plants when you set them in the ground. Use a measuring tape or stick to ensure proper spacing.
- For direct-sown seeds: Plant seeds closer than final spacing (they won’t all germinate), then thin to the recommended distance once seedlings emerge. This is where people fail, they don’t thin, thinking they’re wasting plants. You’re not. You’re giving survivors the space they need to thrive.
Common mistake
Planting tomatoes 12 inches apart because they’re small transplants. The packet says 24-36 inches. By July those plants are a tangled mess, producing poorly and developing fungal diseases from lack of air circulation.
Container adjustments
If growing in containers, you can sometimes reduce spacing slightly (by 10-20%), but not dramatically. A plant that needs 18 inches in the ground needs at least a 5-gallon container with 15 inches from other plants.
Number 4: Sun Requirements (We Covered This, But It’s On the Packet)
Listed as “Full Sun,” “Partial Shade,” or “Shade.”
Why it’s on the seed packet
Because it’s critical and non-negotiable. Ignore this and you’ll get disappointing results regardless of everything else you do right.
Quick reminder:
- Full Sun: 6-8 hours direct sunlight
- Partial Sun/Shade: 3-5 hours direct sunlight
- Shade: Less than 3 hours direct sunlight
How to use this on seed packets
Before buying seeds, confirm you have the appropriate light conditions available. If every spot in your yard is full sun and you’re buying shade-loving plants, you’re setting yourself up for failure.
The exception
Some packets say “Full sun to partial shade.” This means the plant is flexible and can handle a range of light conditions, though it’ll usually perform best toward the full sun end.
Number 5: Germination Temperature (Critical for Starting Seeds)
Often listed as “Germinate at 65-75°F” or shown with a temperature range.
Why it matters
Seeds won’t germinate if soil temperature is wrong. You can do everything else correctly, but if the soil is too cold or too hot, seeds sit dormant or rot.
How to use this information
- For indoor seed starting: This tells you if you need a heat mat. Seeds that germinate at 70-80°F won’t sprout in a 60°F basement without supplemental heat. Seeds that germinate at 55-65°F will be fine without heat mats.
- For direct sowing outdoors: This tells you when you can plant. If the packet says “germinate at 70°F minimum” and your soil is 55°F in early April, those seeds won’t sprout. Wait until soil warms up or start them indoors.
How to check soil temperature
Use a soil thermometer (about $10), or search online for “soil temperature maps” that show current soil temps in your area. For reference:
- 50°F: Cool season crops (lettuce, peas, spinach) germinate
- 60°F: Most vegetables will germinate
- 70°F: Warm season crops (tomatoes, peppers, melons) germinate best
- 80°F+: Some crops germinate faster, others struggle
Common mistake
Planting warm-season seeds (squash, beans, cucumbers) right after the last frost date. The air might be warm, but soil temperature is still 55°F. Seeds rot in cold wet soil. Wait two weeks after last frost when soil has warmed to 60-65°F.
Number 6: Hardiness Zones (For Perennials Only)
Listed as “Hardy in Zones 4-9” or “Zones 5-8.”
Why it matters
If you’re buying perennial seeds (flowers, herbs, or vegetables that come back each year), this tells you if the plant will survive winter in your climate.
How to use this information
Check your USDA hardiness zone (you should have looked this up already). If the seed packet says “Zones 5-9” and you’re in Zone 5, you’re at the cold edge. The plant will survive but might struggle in brutal winters. If you’re in Zone 4, that plant will die in winter, don’t buy it unless you’re treating it as an annual.
Why this doesn’t apply to annuals
Tomatoes, peppers, lettuce, beans, squash, all annuals that die each year anyway. Zone ratings don’t appear on these packets because they’re irrelevant. You’re not trying to overwinter them.
Container gardening exception
If you grow perennials in containers, assume they need to be one zone hardier than your actual zone because container soil freezes more thoroughly than ground soil. A Zone 5 perennial in a pot needs to be treated like a Zone 4 plant.
The Other Information That Actually Matters (But Isn’t a Number)
Packet date/year
Seeds lose viability over time. Fresh seeds germinate better than old ones. Check the packet date and buy current-year seeds when possible. Some seeds (onions, parsnips, parsley) lose viability quickly, always buy fresh. Others (tomatoes, beans, squash) stay viable for 3-5 years if stored properly.
Special instructions
Sometimes packets include critical information like “needs light to germinate” (don’t bury these seeds) or “soak overnight before planting” (improves germination of hard-coated seeds like morning glories or parsley).
Disease resistance codes
You’ll see abbreviations like “VFN” on tomato packets. These indicate resistance to specific diseases:
- V = Verticillium wilt
- F = Fusarium wilt
- N = Nematodes
- TMV = Tobacco mosaic virus
If you had disease problems last year, prioritize resistant varieties. If you’re starting fresh, disease resistance is a bonus but not critical.
What You Can Safely Ignore on Seed Packets
The marketing copy
“Amazing flavor!” “Prolific producer!” “Gardener favorite!” This is all advertising. It might be true, but it’s not data you can act on.
Pretty pictures
The photo shows the best possible result under ideal conditions. Your results will vary. Don’t choose based on photos alone.
Heirloom vs hybrid designation
This is personal preference, not a quality indicator. Both can be excellent. Heirlooms grow true from saved seeds; hybrids need to be purchased each year. Choose based on the six numbers above, not this label.
Organic certification
If buying organic seeds matters to you, great. But organic seeds don’t grow differently than conventional seeds given the same conditions. This is about supporting certain farming practices, not about plant performance.
Detailed variety descriptions
Nice to read but not essential for making a buying decision. Focus on the numbers first, read the description to break ties between similar varieties.
How to Actually Use Seed Packets When Planning
Step 1: Check days to maturity against your growing season. Eliminate varieties that won’t mature before frost.
Step 2: Verify sun requirements match your available space. Eliminate varieties that won’t work in your light conditions.
Step 3: Check spacing requirements and calculate how many plants fit your space. Don’t buy more seeds than you can actually accommodate.
Step 4: Note germination temperature and plan when you’ll start seeds based on your soil/indoor temperatures.
Step 5: Check planting depth so you know exactly how to sow them.
Step 6: If perennial, confirm hardiness zone matches your location.
This process takes 2 minutes per variety and prevents most seed-buying mistakes.
The Seed Packet Mistakes That Waste Money
Buying without reading
You see “Beefsteak Tomato,” grab it, and plant it. Later you discover it needs 90 days to maturity and you only have 100 frost-free days. You’ll get maybe three ripe tomatoes.
Ignoring spacing
You buy enough seeds for one packet, plant them all because you don’t want waste, and end up with 40 plants in a 4×8 bed that should hold 8. Everything struggles.
Planting at wrong depth
You put lettuce seeds 1/2 inch deep. They never come up. You assume the seeds were bad and buy more, repeating the mistake.
Starting too early
Warm-season crops planted in cold soil. They rot instead of germinating. You replant, losing time and money.
Zone mismatches
You buy perennial lavender rated for Zone 7, plant it in Zone 5, and it dies in winter. You think you killed it when actually it was never going to survive.
All of these are preventable by reading and understanding those six numbers.
Conclusion
Seed packets aren’t complicated once you know what matters. Ignore the marketing and focus on six critical numbers: days to maturity, planting depth, spacing, sun requirements, germination temperature, and hardiness zones for perennials.
These numbers tell you if a seed will work in your garden before you spend money on it. They tell you when to plant, how to plant, and where to plant. Reading seed packets carefully is the difference between seeds that produce abundantly and seeds that sit in disappointing rows doing nothing.
Take two minutes per seed variety to read and understand the packet. Those two minutes save you months of frustration and wasted effort growing varieties that were never going to succeed in your specific conditions.
Key Takeaways
- Days to maturity is the most important number: match it to your growing season length or your harvest will fail
- Planting depth determines germination success: too deep or too shallow and seeds won’t sprout
- Spacing requirements aren’t suggestions: overcrowding causes poor production and disease problems
- Germination temperature tells you when soil is ready: planting in cold soil causes seeds to rot instead of sprout
- For transplants, days to maturity counts from transplanting outdoors, not from indoor seed starting: add 6-8 weeks for indoor growing time
- Zone ratings only matter for perennials: annuals die each year anyway, zones don’t apply
- Calculate how many plants fit your space before buying seeds: don’t overbuy based on enthusiasm
- Fresh seeds germinate better than old seeds: check the packet date, especially for onions and parsley
- Disease resistance codes (VFN) matter if you had problems last year: prioritize resistant varieties
- Read packets before buying, not after: eliminate varieties that won’t work before spending money
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