Home › Growing Food

Choosing and Reading Seeds

What the packet is trying to tell you

What is on the packet

A seed packet is a short instruction manual. Look for: sowing depth, usually 2 to 3 times the seed's width; spacing between plants and rows; days to germination; days to harvest from sowing or from transplanting; and the sow-by or packed-on date. The best packets show a sowing calendar bar with months for indoors, outdoors and harvest. Those months assume a temperate climate, so adjust them for yours. A germination rate, for example 85 percent, tells you how many seeds should sprout. If a packet has no date, do not buy it. Freshness is the biggest single factor in whether seeds come up.

Open-pollinated, heirloom, F1

Open-pollinated seeds come from plants that pollinated naturally. Save their seed and the next generation looks like the parent. Heirloom is an open-pollinated variety that has been passed down for at least 50 years, often with better flavour and local adaptation. F1 hybrid seed comes from crossing two chosen parents. F1 plants are vigorous, uniform and often disease resistant, but seed saved from them produces a random mix, so you must buy new seed each year. F1 is not genetically modified, which is a different process not sold to home gardeners. For beginners, F1 gives reliable results. For seed saving, choose open-pollinated.

How long seeds last

Seeds are alive and slowly running down. Stored cool and dry, onions, leeks and parsnips last about 1 year. Sweetcorn, peppers and beans last 2 to 3. Carrots, peas and beetroot 3 to 4. Tomatoes, cucumbers, squash, lettuce and brassicas keep 4 to 6 years. Old seed does not fail completely: it sprouts more slowly and in smaller numbers. Test an old packet by putting 10 seeds on damp kitchen paper in a sealed bag at room temperature for a week. If 7 come up, sow normally. If 4 come up, sow twice as thick. If 1 or 2 come up, compost the packet.

Storing seeds

The enemies of seed are warmth, moisture and light. Keep packets in a sealed jar or airtight box in the coolest, driest room of the house. A fridge works if the box is truly airtight, with a sachet of silica gel or a tablespoon of dry rice inside to absorb moisture. Never store seeds in a greenhouse or shed where temperatures swing. Label everything with the variety and year. A rule of thumb from seed banks: the temperature in degrees C plus the relative humidity in percent should add up to under 100. A 15 degree room at 50 percent humidity is fine.

Where to buy

Buy from specialist seed companies, local seed swaps and seed libraries rather than the supermarket rack, which often sits in a warm shop for a year. Small regional seed growers sell varieties already adapted to your climate, which matters far more than a famous name. In Portugal, look for national heritage varieties and Mediterranean-adapted lines. Start with 6 to 8 easy crops in year one: lettuce, radish, beans, courgette, tomato, chard, peas and herbs. A packet holds far more than one garden needs, so share with neighbours. Resist buying 40 packets. You will sow ten.

Next lesson: Starting Seeds and Taking Cuttings →

Related lessons

Starting Seeds and Taking Cuttings

Raise strong seedlings indoors and multiply plants for free