When to Plant

In a container you have one plant. Seven of our 26 fruit crops will never set fruit alone, no matter the pot — and that is the question to settle before you buy anything.

Extension services do not agree on how long hardening off takes — the range runs seven to fourteen days. Here is what each one says, why the temperature matters more than the count, and the two crops that invert the whole thing in opposite directions.

When to plant garlic by zone: about 1–2 weeks after your first killing frost. Late September into October in zones 3–6, into November in 7–8, and later in the South.

New Hampshire Extension gives the number nobody else does — five gallons of soil per plant. That turns the vague advice into arithmetic you can do with buckets you already own. Depth, hilling, and when to tip it out.

Five gallons is real advice — for a compact tomato. Seven out of ten tomato varieties are not compact, and that mismatch is why container tomatoes stall in July. Pot size, how to tell what you bought, and 33 varieties that actually fit.

Everybody says buckets are too shallow. They are not — a bucket meets the depth Maryland Extension's deepest class asks for. The real limits are width and weight.

Look up your USDA hardiness zone in one click, then find out what the number is actually for: 53 perennial crops and the coldest zone each one survives. Plus the one thing your zone will never tell you.

Maryland Extension publishes container sizes twice, in two different systems, and the two answers straddle the five-gallon line. A bucket is right for beans, carrots, chard, cherry tomatoes and cabbage. For tomatoes and peppers it is the floor, not the answer.

Your hardiness zone describes your coldest winter night, not when spring freezes stop. Here is what actually sets your tomato date, and how far apart two gardens in the same state really are.

Every seed-starting date is counted back from one date: your last spring frost. Here is that date for 28 US metros, the weeks to count back for 20 crops, and what to do if you started early.

You can sow carrots at 40°F. They germinate best at 55 to 65°F and take two to three weeks to show. The gap between those numbers is where most carrot rows are lost.

Every guide says give seedlings adequate light. Minnesota gives the number — the lamp goes two to four inches above the leaves — and names lack of light as the cause of leggy stems.

Onions are the hardiest thing you grow, and you can still plant them too early — cold doesn't kill them, it makes them bolt. Meanwhile bulbing starts on day length, not on your date.

Potatoes go in before the last frost, because a frost costs them two weeks rather than the crop. What they actually wait for is soil at 50°F — not a date, and not your zone.

A sprouting sweet potato is not spoiled, it is starting. Those shoots are slips, and they are how the crop is grown — with or without roots on them. Here is how to raise them.

Potting up and planting out are months apart and wait on different things. The one people delay is the one that wants doing sooner — as soon as the first true leaves appear.