Vegetable Planting Calendar: Build It in 4 Steps

Step 1: Pick the two frost dates that run your calendar

A calendar made of months fails because the same month means different weather in different towns. Frost dates fix that. The last spring frost is the one that matters most, and the first fall frost closes the season.

Use the average last frost for the weather station nearest you. A University of New Hampshire Extension fact sheet puts the rule bluntly. The sheet says not to seed or transplant frost-sensitive plants before that date.

Write both dates at the top of a blank page. The rest of this article uses two made-up dates so you can see the sums. The last spring frost is April 15 and the first fall frost is October 15.

Step 2: Count each crop's weeks from the last frost

Extension services publish crop timing as weeks, because weeks hold up from year to year. The New Hampshire sheet lists them crop by crop. Broccoli takes 4 to 6 weeks from seed to transplant and is safe to set out 2 to 4 weeks before the last frost. Tomato takes 6 to 8 weeks and goes out 1 to 2 weeks after the last frost. Pepper takes 8 to 10 weeks and goes out 2 weeks after. Radish is seeded straight into the garden 2 to 4 weeks before the last frost. Bean is seeded after it.

With a last frost of April 15, those weeks become dates.

Here is the sum for broccoli. The set-out window runs from 4 weeks before April 15 (March 18) to 2 weeks before (April 1). Seeds start 4 to 6 weeks ahead of the set-out date, so the earliest start is 6 weeks before March 18 (February 4) and the latest is 4 weeks before April 1 (March 4).

Broccoli gets a shorter lead in a University of Illinois Extension article, 4 to 6 weeks before the average last frost. Two good sources can differ by a few weeks. Pick the middle of the range, and adjust after your first season.

A planting date is a count of weeks from a frost, and the month is just where that count lands.

The master chart in The Winter Plan lists 41 crops with their indoor, transplant and sow weeks counted from your own last-frost date, so you only fill in that one date.

Step 3: Lay out your vegetable planting calendar month by month

Now sort the dates under their months. This is the calendar most people go looking for, and you can write it in an evening.

May is empty on purpose. Spring planting is done and fall planting has not started. Use the gap for the garden itself, such as weeding, watering and harvesting.

Why one month's calendar fits only one frost date

Take a second gardener whose last spring frost is May 15, one month later. Every spring date moves by the same 30 days, and the months change with it.

Each of the four jobs lands in the next month, and the two calendars share almost no dates. A printed calendar with fixed months can serve only one of these gardeners.

Step 4: Count back from your first fall frost

Fall dates run the other way. You start from the first fall frost and subtract the days a crop needs.

A Kansas State University Extension guide lists days to first harvest. Broccoli needs 60 to 80 days after transplanting, bush beans 50 to 60 days, fall radish 35 to 60 days, and spinach 25 to 40 days. The guide also says to allow 4 to 8 weeks indoors for broccoli seedlings, and that all of its windows are approximate.

With a first frost of October 15, subtract those days.

Treat the later date as a last call, and plant earlier when you can. Kansas State lists bush beans as tender, so a bean sown on the last date has no days to spare before frost.

The same sum answers the July question. Broccoli transplants and bush beans both fit in July with an October 15 frost. A tomato set out on July 1 has 106 days before frost, which suits an early variety only, because Kansas State lists 52 to 120 days from transplant to first harvest.

Seed timing for warm-season crops follows the same count. A University of Georgia article advises, in general, to sow seeds six to eight weeks before transplanting. Its example is a last frost of April 15 and tomato seeds in late February or early March, which matches the table above.

Repeat sowings for a steady harvest

Some crops give their harvest all at once. The New Hampshire fact sheet marks broccoli, bean, corn, lettuce and basil as having a short harvest season, which you can prolong with several smaller sequence plantings. A Virginia Cooperative Extension publication says successive plantings of beans give a longer harvest period and increase your yield.

On the calendar, a repeat sowing is one more row of dates. The sources give no single gap, so the gap is your choice. Take bush beans and a three-week gap. The first sowing goes in on the April 15 last frost, and the last one must be on or before the August 16 limit from Step 4.

A seventh sowing would land on August 19, three days past the limit, so six sowings is the most that fit. Write each date under its month, and each bean row has its own harvest window.

A calendar will not fit every microclimate

If your state extension office publishes a planting calendar for your county, use it first. It was written by people who know your soil, and it costs nothing.

A month-by-month list also does not suit a year-round garden in a mild climate, where frost is not what sets your dates. Ask your county extension office for its sowing dates instead.

The Winter Plan is a fit when you want the weeks counted for you and a place to write the dates down. You would use its master chart when you pick crops in winter, its succession waves page when you plan repeat sowings, and the season calendar's day boxes as each month comes round. You still choose the crops and pencil in the dates yourself.