A seed packet is a compressed instruction manual, and four of its numbers do nearly all the work. Here is what each one actually means, plus the frost-date arithmetic that tells you when to sow.
Nora Finch
These two get confused constantly. Days to germination (often 5-14) is how long until a sprout breaks the surface - it tells you when to stop worrying that nothing's happening. Days to maturity (often 50-120) is the span from planting to first harvest, and it's the number that decides whether a crop fits your season at all.
One catch: for crops usually transplanted (tomatoes, peppers), 'days to maturity' typically counts from transplanting outdoors, not from sowing - add the indoor seedling weeks on top. For direct-sown crops like beans, carrots, and lettuce, it counts from sowing. The packet rarely says which convention it uses; transplant crops use the transplant convention by default.
Almost every timing instruction hangs off two local dates: your average last spring frost and first autumn frost (a quick search for your town or postcode finds both). 'Sow indoors 6-8 weeks before last frost' and 'direct sow after all danger of frost' now become real calendar dates - count backward or forward from yours.
The autumn date matters just as much and gets ignored: a 100-day winter squash sown in midsummer will meet the frost before it meets maturity. Quick check for any packet: days to maturity plus today's date must land comfortably before first frost, with a couple of weeks' margin for cool-season slowdown.
Sowing depth follows a simple rule the packet encodes: plant a seed about twice as deep as it is wide. Big bean seeds go down 3-4 centimeters; dust-fine seeds like lettuce barely get covered - and some (check the packet) need light to germinate and just get pressed onto the surface. The most common germination failure is tiny seeds buried like bulbs.
Spacing numbers look wasteful at sowing time and turn out exact at harvest. 'Thin to 25cm' exists because crowded seedlings compete for light, water, and air, and all of them stay stunted - crowded carrots are the classic, growing tangled threads instead of roots. Sow a bit thick to insure against failures, then genuinely thin to the stated distance, however brutal it feels. (Row spacing is the second number; in raised beds, the plant-to-plant figure in all directions is the one to honor.)
'Full sun' means six-plus hours of direct light; 'part shade' means three to six. These are minimums for fruiting, not suggestions - a tomato in four hours of sun grows a handsome plant and almost no tomatoes. Match packet to plot honestly; shade-tolerant crops (lettuce, spinach, herbs like mint and parsley) exist for the dimmer corners.
Some packets list a soil-temperature range for germination, and it explains most 'dud seed' complaints: pea and spinach seeds rot in warm summer soil; basil, squash, and pepper seeds sulk or rot in cold spring soil. Sowing by soil warmth rather than air temperature - or just respecting the packet's indoor/outdoor timing - is the difference between 90 percent germination and 10.
The 'packed for' year matters: seeds are living things with shelf lives. Most vegetable seeds keep two to five years stored cool and dry (onions, parsnips, and lettuce fade fastest), losing germination rate as they age - old packets aren't useless, just sow them thicker. F1 hybrid on the label means great uniform performance but seeds not worth saving (offspring vary wildly); open-pollinated or heirloom seeds breed true and can be saved year over year.
Everything else - 'pinch tips for bushier plants', 'support required', disease-resistance codes like VFN on tomatoes - is bonus advice worth a skim. When the packet and a gardening influencer disagree about your crop in your climate, the packet wins: the breeder wrote it for that exact variety.
Indoor-raised seedlings need a week of gradual outdoor exposure before transplanting - an hour of sheltered shade the first day, building daily toward full sun and overnight stays. Skipping it scorches and shocks soft seedlings; the packet assumes you'll do it.
You can, and you'll harvest less from more plants - crowded seedlings stay small and stressed. If pulling sprouts feels wasteful, snip the extras at soil level (no root disturbance) and eat them as microgreens.
The big four: soil too cold (most warm-season crops want 15-25°C), seeds buried too deep, soil dried out mid-germination, or old seed stored somewhere hot. Re-sow at the right depth into warm, consistently moist soil and most 'failures' succeed on the second try.
Variety matters more than price - a packet's genetics decide flavor, disease resistance, and fit for containers far more than its cost. Pay for the right variety for your space and season; among reputable suppliers, the cheap packet of the right thing beats the premium packet of the wrong one.
