Gardening terms, explained

The words you'll see on seed packets and planting charts, in plain language.

Last frost date: The date after which freezing nights usually stop in spring. Rainline Garden uses the typical (median) date: in half of years the last frost comes later, so tender crops wait longer.
First frost date: The date the first fall freeze usually arrives. Warm-season crops die at the first frost; cool-season crops keep going.
Frost-free season: The number of days between the last spring frost and the first fall frost. It's your growing season for tomatoes, squash and other tender crops.
Sow seeds (direct sow): Planting seeds straight into the garden soil where they'll grow, instead of starting them in pots.
Starts (transplants): Young plants grown in small pots, either by you indoors or bought at a nursery, then planted in the garden.
Start seeds indoors: Sowing seeds in trays inside, under lights or in a sunny window, weeks before it's warm enough outside. It gives slow crops like tomatoes and peppers a head start.
Hardening off: Getting indoor seedlings used to sun, wind and cool nights by setting them outside for a few hours a day, longer each day, for about a week before planting.
Cool-season crop: A crop that grows best in cool weather and handles light frost, like peas, lettuce, kale and carrots. Plant these in early spring and again for fall.
Warm-season crop: A crop that's killed by frost and needs warm soil, like tomatoes, beans, squash and basil. Plant these after the last frost once the soil warms.
Soil temperature: How warm the soil is a few inches down. In the Northwest it lags weeks behind the air, which is why warm crops wait. A soil thermometer costs about $10.
Bolting: When a leafy crop like spinach or lettuce suddenly sends up a flower stalk, usually in heat or long days. The leaves turn bitter, so harvest before it happens.
Thinning: Pulling out extra seedlings so the rest have room to grow. Carrots, beets and radishes need it.
Succession planting: Sowing a short row every two or three weeks instead of all at once, so you get a steady harvest.
Row cover: A light fabric laid over plants. It traps warmth, guards against light frost and keeps insects off.
Wall-o-water and cloches: Covers that sit over a single plant to keep it warm. A wall-o-water is a ring of water-filled tubes that soaks up heat by day and releases it at night.
Mulch: A layer of straw, leaves, compost or plastic on top of the soil. It holds moisture, smothers weeds and, if dark plastic, warms the soil.
Days to harvest: Roughly how long from planting outdoors until the first harvest. Seed packets list it; it's longer in cool summers.
Onion sets: Small dormant onion bulbs you plant instead of seeds. They're the easiest way to grow onions.
Seed potatoes: Potatoes grown to be planted, certified free of disease. Grocery-store potatoes are often treated to stop sprouting.
Curing: Drying a harvest so it stores well: winter squash in a warm room, onions and garlic in a shady, airy spot.
Cover crop: A crop like crimson clover or cereal rye sown in empty beds over winter to protect and feed the soil.
Hardneck and softneck garlic: Hardneck garlic has a stiff center stalk, bigger cloves and better cold tolerance. Softneck stores longer and can be braided.