The Kenwood Press
: 09/01/2013

Planting a fall harvest vegetable garden

Steve Albert

September is the time to plan and plant your fall and winter vegetable garden. The key to planting vegetables for fall and winter harvest is timing. Plant the fall vegetable garden so that the crops come to harvest on or about the average date of the first frost in fall. Plant the winter garden with cold January and February temperatures and crop protection in mind.

Crops for autumn and early winter harvest are cool weather crops - crops that like to get their start in warm soil and air, but yield best when they come to harvest when temperatures are cool.

Cool weather crops can be planted twice a year, first in early spring for harvest before summer heat arrives, and again in late summer for harvest in the cool of autumn. Some people call the autumn harvest of cool weather crops the second season.

Crops that can withstand a light frost - the first frost in autumn - are broccoli, Brussels sprouts, cabbage, carrots, chards, collards, radishes, and spinach. Crops that can withstand a heavy frost - usually the second or third frosts in autumn or early winter - are beets, cauliflower, endive, kohlrabi, lettuce, and peas. In the Sonoma Valley, almost all of these crops can be grown through the winter with some protection from sustained freezing weather (use a plant blanket or plastic sheeting tunnel to protect long-staying crops).

Fall planting time formula

Time the planting of fall harvest vegetables by determining the average first frost date in your garden. On average, the first frost in the Sonoma Valley over the past five years has come between mid-November and mid-December. We can use Dec. 1 as the average first frost date in Kenwood (some years it has been earlier and some years later).

With the date of the average first frost marked on your calendar, (1) count backwards the number of days required for the seed of that crop to germinate, (2) add the number of days it takes the crop to reach transplanting size, (3) add the number of days to maturity for the crop variety (you will find this on the seed packet; be sure to choose the quickest maturing variety of each crop for fall harvest), and, finally, (4) add an additional 14 days to adjust for daylight hours growing shorter in autumn. The total of these days counting back from the average frost date will give you the optimal planting date for sowing the seed of each crop.

If you are starting your fall and winter garden from transplants purchased at a local nursery or garden center, then you start your planning at step 3 above.

Planning the Fall Vegetable Garden

When you plan your fall and winter vegetable garden, keep in mind the size of each plant - the average height and width of each plant and the amount of space it will require, and the frost sensitivity of the crop. Is it frost-susceptible, meaning it will be killed or injured by temperatures below 32F degrees, or is it frost-tolerant, meaning it can withstand temperatures below 32F?

Crops that come to harvest in 30 to 60 days are quick maturing and will be in the garden for a short stay. Crops that require 60 to 80 days are moderate maturing, and crops that require 80 days or more are slow maturing or long staying in the garden. The more days a crop requires to reach harvest the more days you will need before the first frost, or you will need to choose crops that are frost and freeze tolerant.

Here is a quick guide to the number of days, the amount of space, and the frost-susceptibility (FS) or frost tolerance (FT) of potential fall and winter crops.

The short-staying or quick maturing (30-60 days) vegetables are beets (_ foot) FT; bush beans (1_ feet) FS; leaf lettuce (_ foot) FT; mustard (1_ feet) FT; radishes (_ feet) FT; spinach (_ foot) FT; summer squash (3 feet) FS; turnips (_ foot) FT; and turnip greens (_ foot) FT.

The moderate (60-80 days) maturing vegetables are broccoli (3 feet) FT; Chinese cabbage (1_ feet) FT; carrots (_ foot) FT; cucumbers (3 foot) FS; corn (6 feet) FS; green onions (_ feet) FT; kohlrabi (_ feet) FT; lima bush beans (1_ feet) FS; okra (6 feet) FS; parsley (1 foot) FT; peppers (3 feet) FS; and cherry tomatoes (4 feet) FS.

The slow maturing or long-staying (80 days or more) vegetables are: Brussels sprouts (2 feet) FT; bulb onions (1 foot) FT; cabbage (1_ feet) FT; cantaloupes (1 foot) FS; cauliflower (3 feet) FT; eggplant (3 feet) FS; garlic (1 foot) FT; Irish potatoes (2 feet) FS; pumpkins (2 feet) FS; sweet potatoes (2 feet) FS; tomatoes (4 feet) FS; watermelon (1 foot) FS; and winter squash (1 foot) FS.

With a piece of graph paper and a calendar, you can quickly plan and plant your fall and winter vegetable garden.

Here are a few quick tips for fall vegetable garden planting:

Know the average date of the first autumn or winter frost in your area. You can get this date from a nearby garden center or nursery or from the local cooperative extension. Remember the average date is an average; frost may arrive sooner or later this year.

Always choose the fastest-maturing varieties of a crop for fall harvest.

The optimal number of days to harvest will be printed on the seed packet or in the grower's seed catalog. This number assumes long days and warm temperatures.

The optimal soil temperature for seed starting is 80F.

Crops always take longer to mature in the late summer and fall because the number of hours of sunlight is decreasing along with air and soil temperatures-so factor in 10 to 14 additional days for plants to mature as daylight hours grow shorter.

Cabbage-family crops are commonly seed started indoors then transplanted into the garden when they reach about 4 inches tall. Cabbage-family crops include cabbage, cauliflower, broccoli, Brussels sprouts, and collards.

As frost approaches, remove mulches from around plants; this will allow the soil to absorb radiant solar heat that can be released back into the garden at night.

Protect frost sensitive crops by covering them with a horticultural blanket when frost is near or placing them under plastic sheeting - placed over a wood or PVC hoop frame.

Autumn crops can easily be grown on or after the first heavy frost or during freezing weather, but they must be covered and protected. Place a simple plastic tunnel over the crop.
When to plant autumn-harvest crops

Here's a crop-by-crop guide for the number of days from sowing to harvest for the most popular autumn harvest crops: (these numbers may vary slightly by variety):

Beets: count back 74 days: 5 days to germination + 55 days to maturity + 14 days factoring for short days. Direct sow beets in the garden. Beets can survive a heavy frost.

Broccoli: count back 95 days: 5 days to germination + 21 days to transplant size +55 days to maturity + 14 days factoring for short days. Start broccoli indoors then transplant to the garden. Broccoli can withstand light but not heavy frost without protection.

Brussels sprouts: count back 120 days: 5 days to germination + 21 days to transplant size + 80 days to maturity + 14 days factoring for short days. Start Brussels sprouts indoors then transplant to the garden. Brussels sprouts can withstand light but not heavy frost without protection.

Cabbage: count back 99 days: 4 days to germination + 21 days to transplant size + 60 days to maturity + 14 days factoring for short days. Start cabbage indoors then transplant to the garden. Cabbage can withstand light but not heavy frost without protection.

Carrots: count back 85 days: 6 days to germination + 65 days to maturity + 14 days factoring for short days. Direct sow carrots. Carrots can withstand light but not heavy frost without protection.

Cauliflower: count back 90 days: 5 days to germination + 21 days to transplant size + 50 days to maturity + 14 days factoring for short days. Start cauliflower indoors then transplant to the garden. Cauliflower can survive heavy frost.

Chard: count back 69 days: 6 days to germination + 50 days to maturity +14 days factoring for short days. Direct seed chard. Chard can survive heavy frost.

Collards: count back 94 days: 4 days to germination + 21 days to transplant size + 55 days to maturity + 14 days factoring for short days. Start collard seed indoors. Collards can withstand a light frost but not heavy frost without protection.

Endive: count back 142 days: 12 days to germination + 21 days to transplant size + 95 days to maturity+ 14 days factoring for short days. Start endive seed indoors. Endive can survive heavy frost but does best with some protection.

Kohlrabi: count back 86 days; 7 days to germination + 65 days: days to maturity + 14 days factoring for short days. Direct seed kohlrabi. Kohlrabi can survive heavy frost.

Lettuce, leaf: count back 76 days: 3 days to germination + 14 days to reach transplant size + 45 to maturity + 14 days factoring for short days. Start lettuce indoors for best results then transplant to the garden. Lettuce can survive a light frost but not heavy frost without protection.

Peas: days: count back 70 days: 6 days to germination + 50 to maturity+ 14 days factoring for short days. Direct seed peas. Peas can survive heavy frost.

Radishes: count back 42 days: 3 days to germination + 25 days to maturity + 14 days factoring for short days. Direct seed radishes. Radishes can withstand a light but should be protected from heavy frost.

Spinach: count back 64 days: 5 days to germination + 45 days to maturity+ 14 days factoring for short days. Direct seed spinach. Spinach can withstand light but should be protected from heavy frost.