Package of Johnny's Selected Seeds
Package of Johnny's Selected Seeds

Planning for opening day

By Lynn Byczynski

Whether you sell at a farmers market, roadside stand, or to wholesale accounts, you know how important the first market or delivery day can be. From a financial standpoint, you’ve been spending money for months on production, and it’s high time to start recouping some of those expenses. From a marketing standpoint, your offerings on opening day will set expectations for the season and start to build a customer base.

That’s why it’s important to have as much produce as possible to sell when your market opens. You need a critical mass of crops ready for harvest; without it, you might decide going to market is not worth the trouble. So if you’re going to plant anything to sell early in the season, you might as well plant as much as possible.

Figuring out when to plant so that you have a full table on opening day can be a complicated business. Johnny’s has created a Target Harvest Date calculator that allows you to input the date of your opening day or other big event, then shows you the date to plant various crops. However, this calculator is based on Days to Maturity for each vegetable, and that figure is obtained from the breeders who trial it in the field at a normal planting time. It does not take into account variables such as growing in a hoophouse or Quick Hoops™ tunnel when day length is shorter and temperatures lower than at the normal planting time.

If you use the Target Harvest Date calculator to figure production for an early market, you will need to make adjustments to the planting date to reflect conditions at your own farm. How much should you adjust the date? We wish we could provide specific information, but that simply has not been researched by anyone yet. Eliot Coleman has started collecting information for his farm in Maine, and he has found that crops grown over the winter can take two or even three times the published Days to Maturity. He addresses this aspect of his research in his book Winter Harvest Handbook, pages 48-50.

Pam Dawling, who writes about vegetable production for Growing for Market, has found that at her farm in Virginia, winter sowings are very slow, even in the hoophouse where they have enough warmth. For example, radishes planted in early September take 29 days. Those planted in late November take 77 days, and those planted at the end of January take 65 days.

From those two examples, you can see that Days to Maturity is affected by day length as much as temperature. The best advice we can give is to keep careful records about planting and harvest dates for every crop. Over time, you will have the data to be able to predict how much time to add to the published Days to Maturity for a crop, based on your day length and temperature.

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Succession planting

By Lynn Byczynski

Having high-quality vegetables for the longest possible season is a particularly challenging aspect of market gardening. You can stretch the harvest for each vegetable by planting several cultivars with different maturity dates or by planting the same cultivars repeatedly. In both cases, you have to consider:

  • The earliest date you can plant when cold weather limits you in spring.
  • The latest date you can plant and still get a crop to harvest before cold arrives in fall.
  • The date beyond which you won’t get good quality because of heat, rain, insects, or other negative pressures.
  • The days to maturity for each crop.
  • The length of the harvest period for each variety.

These factors vary widely across regions. In coastal California, for example, growers can plant broccoli every 10 days from the middle of April until the first of September, and harvest it every week from June through October. In the Southwest, in comparison, growers may get only one planting of broccoli to harvest before it gets too hot. In the South, growers may succession plant basil every three weeks from April through September, whereas growers in the North may get only one or two plantings of heat-loving basil.

Using season extension structures such as hoophouses and Quick Hoops™ tunnels complicates the calculations even further. A single crop such as lettuce may be planted several times in a hoophouse, then several times in the field, then again in the hoophouse.

The type of plant also affects decisions about succession planting. Pole beans will produce over a much longer period than bush beans. Cut-and-come-again salad mix can be harvested several times, unlike the single harvest you get from head lettuce. Indeterminate tomatoes keep producing on the same vines until they are stopped by cold or disease. Some growers plant tomatoes once a season whereas others make several successions to ensure highest yield.

Market demand also plays into succession planting. People might want lettuce every week of the year if it were available, but the demand for kale and kohlrabi might drop off considerably once tomatoes and basil are ready.

Every grower, then, has to figure out succession planting based on this abundance of factors and how they apply locally. Still, for beginners, there are some guidelines about how often you might want to plant IF weather did not limit seed starting or harvest:

Every 10 days to 2 weeks: arugula, beans, beets, broccoli, cauliflower, corn, green onions, greens, kale, kohlrabi, lettuce, muskmelons, radishes. Every three weeks: basil, cabbage, carrots, salad mix, spinach. Every 30 days: cucumbers, summer squash, tomatoes.

Two great resources to help you think about how to schedule crops:

“Teaching Direct Marketing and Small Farm Viability” which is available from the University of California-Santa Cruz. This resource can be purchased online or downloaded free. The chapter on CSA Crop Planning gives schedules for California.

The ATTRA publication, “Scheduling Vegetable Plantings for Continuous Harvest.”

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Overwintering crops

By Lynn Byczynski

Spring weather can be highly variable, too rainy or hot or cold, and you may not be able to start crops when you would like. Overwintering is a strategy that provides a bit of insurance. With certain crops, you can seed in fall under Quick Hoops™ tunnels or in a hoophouse. The plants will either germinate in fall and go dormant, or the seeds will sit dormant over the winter. But, when conditions are right, they will come to life and grow rapidly. Overwintered veggies can be several weeks to months ahead of spring-sown crops.

Spinach is one of the best-understood crops for overwintering. It germinates well in cool soil, 45-75°F/7-24°C, so it can be planted several times in autumn. Depending on the weather, some plantings may reach a harvestable size in fall and then go dormant until spring. Other plantings may not germinate in fall but wait until late winter to start growing. Spinach is hardy down to 20°F/-6.7°C, which means it can be grown in the field in the South or in a hoophouse under an inner layer of row cover in many other places. The short days of winter may cause the spinach plants to stop growing, but if the plants are mature before short days arrive, it’s possible to harvest spinach all winter. Cold makes spinach incredibly sweet and succulent. The best varieties for winter production are the smooth-leaf ‘Space’ and the semi-savoyed ‘Regiment’ and ‘Tyee’.

Many other cold-tolerant crops are good candidates for fall planting and overwintering. They include arugula, beets, carrots, lettuce, onions, peas, and scallions. Always look for the most cold-hardy varieties of each crop. Direct seed in fall and watch them to determine whether they germinate then or in late winter. If they germinate and grow quickly, they may be killed by winter cold; in that case, seed later next year.

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Be first and last to market

By Lynn Byczynski

Growing and selling over the longest possible season is a key to success on your market farm.Being the first to market with farm fresh products in the spring and having a variety of products available through winter will help differentiate your operation and build customer loyalty.


Extending CSA shares through 3-4 seasons lets you spread the workload and the risks by growing across multiple seasons. Bottom line: you'll make more money. At home, you'll own bragging rights with family, friends, and neighbors.


Sow spring vegetables in an unheated hoophouse as soon as your day length reaches 10 hours. In January, February and March, plant arugula, beets, carrots, chard, kale/collards, lettuce, radishes, salad mix, scallions, spinach, and salad turnips.


Start the cold-hardy vegetables listed above under Quick Hoops™ or caterpillar tunnels for a low-cost alternative to greenhouses, as soon as the soil can be worked.


After the last frost, plant summer crops on plastic mulch for maximum soil warming.


Use row cover to provide a protected environment that will get seedlings off to a good start.


Plant several successions of crops, counting back from the first frost date to calculate the final planting of the year.


Grow plenty of storage crops, including onions, garlic, winter squash, potatoes, leeks, storage cabbage, carrots, parsnips, kohlrabi, and sweet potatoes, to sell throughout the autumn and winter.


Plant cold-tolerant crops in the field and be ready to protect them with row cover as the frost date approaches.


Plant cold-hardy crops under Quick Hoops™, caterpillar tunnels, or hoophouses for fall harvest.

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Extend your season

By Lynn Byczynski

Protected cultivation — growing with products that moderate the weather — has become an essential component of most horticultural production. Hoophouses, low tunnels, row covers, and mulches are widely used on market farms because of the enormous benefits they offer. You can use these products to harvest earlier in spring and later in fall, extend and stagger the harvest of most crops, improve quality, protect against insect pests, and increase yields.

Most important, protected cultivation strategies can help you spread out your workload over a longer season. That means less stress and burnout in summer’s heat, more enjoyable farming in pleasant weather. The ultimate goal, of course, is to increase revenue. Most growers who have adopted these practices are amazed at how much income they can derive from these inexpensive structures and products.

Protected cultivation adds a level of complexity to a vegetable farm, but it’s a challenge that most growers enjoy. You need to adjust your thinking about many elements of farming. The frost-free date is less important, the day length more important. Large plantings may be replaced by numerous smaller plantings in various environments. You may even start to grow crops that never succeeded for you in the field.

At Johnny’s research farm in Albion, Maine, we are constantly trialing products and varieties to find the best combinations for protected cultivation. You’ll find the products you need on the web and in the catalog. Below, we present 10 ideas for using protected cultivation. These are just suggestions for getting started; as you explore alternatives to field production on your own farm, you are likely to discover new ways to improve your crops, increase your income, and enjoy yourself more.

Top 10 ways to extend your season and increase your profits

  1. Plant cold-loving crops in a high tunnel in January and February, and cover with row cover on hoops.
  2. Seed leeks in a cold frame in January or February, and transplant them in a low tunnel as soon as the soil can be worked.
  3. Plant cool-weather crops in a low tunnel two to three weeks before you plant them unprotected in the field
  4. Plant cucumbers and tomatoes in a high tunnel a month before field planting.
  5. Plant eggplant in low tunnels covered with lightweight row cover to protect against flea beetles
  6. Put shade cloth on hoops in summer and plant heat-tolerant lettuces.
  7. Put shade cloth on the soil for a week before planting fall crops, to improve germination while the weather is still hot.
  8. Keep heavy row cover at hand in case of an early frost.
  9. Plant spinach and carrots in the hoophouse, in enough quantity to harvest throughout the winter.
  10. Plant spinach in low tunnels to overwinter; it will resume growth in early spring and be the first crop of the new season.

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How day length affects vegetable production

By Lynn Byczynski

The two primary environmental factors that affect plant growth are temperature and day length. Temperature is easy enough to understand: Every plant species has a temperature range in which it will grow, and optimum temperatures in which it will thrive. Day length is a little more complicated, especially in combination with temperature. Understanding the relationship between the two can lead to more successful season extension and variety selection.

The first thing to know is that the term day length is a misnomer. Scientific research has confirmed that it's actually the length of the dark periods, not the length of daylight periods, that controls plant growth. This fact was discovered long after day length became a widely used term in horticulture, and the name has stuck. Understanding the importance of dark periods can come in handy for the grower, though, because it can be used to trick plants about day length and force them into bloom outside their normal season. More on that later.

Many plant species have day length triggers that determine when they grow vegetatively and when they bloom. They may be long-day plants or short-day plants. Some plants don't react to day length; they are called day-neutral.

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Figuring day length


Day length is a function of latitude all places on the same latitude have the same amount of daylight on any given day. Day is equal to night 12 hours each at the two equinoxes, which mark the beginning of spring and the beginning of fall. The winter solstice marks the shortest day (longest night), and the summer solstice marks the longest day (shortest night) of the year. In the winter, days are longer the closer you get to the equator and in the summer, days are longer the farther you get from the equator. Compare day length in Maine and Florida in summer and winter:

Location Day length at summer solstice Day length at winter solstice
Portland, Maine 15 hrs., 26 min. 8 hrs., 55 min.
Miami, Florida 13 hrs., 45 min. 10 hrs., 32 min.

Most plants don't grow when day length is less than 10 hours. Even if the temperature is kept within the optimum range in a climate-controlled greenhouse, most plants will just sit dormant until the magic 10 hours of light per day arrives. See the chart below for examples of the period when day length is less than 10 hours.

 Location Dates when day length is less than 10 hours
 Atlanta, Georgia December 8 to  January 4
 Washington, D.C. November 19 to January 26
 New York, New York November 14 to January 30
 Portland, Maine November 8 to February 4

Because most plants don't grow with less than 10 hours of daylight, winter greenhouse production requires supplemental lighting as well as supplemental heat. Lights can be turned on shortly before sunset to extend the length of the day. Or they can be turned on in the middle of the night for a short period of time, a procedure called night-interruption lighting.

This brings us back to the fact that it's the dark period that's important to plants: The short days of winter have long nights. If a grower breaks up those long nights by turning on lights in the middle of the night, some plants will act as though the night is short (and therefore the day is long) and behave just as they would in the middle of summer. Many bedding plant and cut-flower greenhouses use night-interruption lighting to force flowers to bloom in winter.

Even for growers who don't use supplemental lighting, the facts about day length are pertinent. Here are some examples of why day length may be a factor in gardening success:

  • Cauliflower starts to develop a head when days get shorter. That happens sooner in northern than in southern regions, which means cauliflower will produce sooner in Maine than in Virginia. Cooler temperatures during head development also lead to better flavor. So cauliflower is an easier crop in the north than the south.
  • Basil doesn't grow during the short days of winter, even in a tropical greenhouse. Supplemental lighting and heat are required to get good winter yields, and in most places the energy costs are not justified by the income from a basil crop.
  • Flower growers are especially subject to the rules of day length because many of the most popular cut flowers have day length triggers. Rudbeckia, for example, grows vegetatively in short days and flowers under long days. If you plant them in early spring, they will grow big, healthy plants and send up bountiful long stems as the days get longer in summer. But if you plant them in late summer hoping for a fall crop, you will get few flowers on very short stems because the day length is too short to trigger blooming.

Many other facets of food and flower production are affected by day length, temperature, or a combination of the two. If you have ever wondered why certain crops don't grow as well for you as they do in other parts of the country, day length may be a contributing factor. If you aren't attuned to the day length in your location, get a sunrise/sunset calculator and mark your calendar with the dates when you have 10 hours of daylight, 11 hours, 12 hours, and so on. Over time, you will begin to notice correlations between day length and your garden's activity.

Lynn Byczynski is the editor of Growing for Market and the author of Market Farming Success.

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Forum onion sets

Onions are one of the most popular vegetables, so most fresh market growers try to have them available for the longest season possible. 'Forum' onions, grown from sets, can be an important component of an onion program.

Planted before the last frost, 'Forum' sets will produce a bulb 90 days later. This onion fills the gap between last year's storage onions and this year's seed-grown onions. If properly cured, it will store for about three months. However, it will not store longer, so should be planted only in the quantity that can be sold within three months of harvest.

'Forum' provides an opportunity to sell when supplies are low and prices are high. For CSA growers, it adds to the diversity of the offering earlier in the season than usual. Although sets cost more than seed, these onions also have higher income potential if harvested and sold when market prices are high in early and mid summer.

'Forum' is a medium-sized, flattened round, yellow onion. It is a long-day onion and will not grow well below 37 latitude. For this reason, it should not be grown in North Carolina, South Carolina, Georgia, Florida, Tennessee, Alabama, Arkansas, Mississippi, Louisiana, Oklahoma, Texas, New Mexico, Arizona, and far southern California.

Onion sets are shipped 3 to 4 weeks before the last frost date in each region, if the weather allows. Shipments will be delayed if it is very cold, just as they are for seed potatoes. Upon arrival, onion sets should be taken out of the box for ventilation, and kept dry and cool but not freezing. Moisture and heat will cause the sets to sprout prematurely. The more air flow, the better. Hanging the bag of sets up in a garage that does not freeze is very good. Hanging the bag with a fan on it is ideal. Large quantities of onion sets can be set on a pallet with a fan.

'Forum' should be planted as early as the soil can be worked in the spring, ideally before the last frost date. Planting in cool soil encourages root development. As the soil warms, shoot development is promoted, and the plant already has a good root system to feed the growing top. Yield will be compromised if 'Forum' is planted late into warm soil.

Sets can be planted individually or in a shallow trench. The football-shaped sets should be planted root-end down, but if planted in a trench or mechanically, the sets will fall on their sides and right themselves as they grow. Either way, the sets should be covered with 1" to 2" of soil, so that the growing point will not freeze.

Onion sets should be planted 2" apart in the row. The onions will jostle each other in the row as they bulb. Or, sets can be planted closer than 2" and then thinned for bunched green onions or partially-bulbed grilling onions.

Forum will bulb up roughly ninety days from when it was planted. For many growers, this will mean that they can have a green-top (uncured) bulb onion by around the Fourth of July, and a dried onion a few weeks later (as long as the curing process takes). Considering that most cooking onions in northern areas are not bulbed and cured until September or October, this is very early!

'Forum' sets will be available for shipping beginning in mid-March. Order today because this great new onion is likely to sell fast!

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Grow a rainbow mix of cherry tomatoesrainbow tomatoes

A colorful mixture of cherry tomato varieties is a popular item at farmers markets, farm stands, and supermarkets. Creating a rainbow mix elevates the humble cherry tomato to gourmet status and calls out for a taste comparison. Customers who buy a cherry tomato mix once will be back for more because these varieties really do offer different flavors as well as colors, and all of them are delicious.

At Johnny's research farm, we grew a mix of cherry tomato varieties that are all about the same size and ready to harvest simultaneously. The varieties we chose for our suggested mix are 'Black Cherry', 'White Cherry', 'Favorita', 'Sun Cherry', and 'Sun Gold'. All are indeterminate varieties and range 58 to 65 days to first harvest. All the fruits are about 1 1/4" in diameter, however, any selection of cherry or grape tomato varieties can be put in a mix.

The tomatoes were grown in a high tunnel with drip irrigation underneath ground cloth to eliminate weeds. Plants were spaced 12"to 14" in the row and pruned to create two vines. Suckers were pruned off the plants as they grew. String was tied to the high-tunnel purlins, and the vines were trained onto the string utilizing tomato clips. If you plan to keep any indeterminate tomatoes all season in a high tunnel, you should leave extra string after attaching it to the purlin. Tomato plants can get so tall you will need to let the strings down late in the season to harvest the fruits - unless you want to pick from a ladder.

In the Johnny's trial, the high tunnel tomatoes had few pest or disease problems. Nor was pollination an issue; just walking through the high tunnel vibrates the plants enough for them to pollinate themselves. The variety 'Sun Gold' is prone to cracking if it gets too much moisture, so we put a valve on the drip line to those plants and reduced the amount of water they received relative to the other varieties.

Labor is the biggest issue with cherry tomatoes. They need to be picked every day or two for maximum yield, which makes them time-consuming, pound for pound, compared to regular tomatoes. But, they are certainly an eye-catching produce item that pulls in customers.

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Trellising hoophouse tomatoes

By Lynn Byczynski

Tomatoes are one of the most popular crops for hoophouse production because they can be ready for harvest a month before field crops - at a time when prices are highest. Tomatoes grow robustly and often for a longer time in the protected conditions of a hoophouse. As a result, the plants can get much taller than field-grown tomatoes. Indeterminate varieties are particularly high-yielding in a hoophouse, but they do require more maintenance. A plant with five or six fruiting clusters can exert 10–12 lb. of downward pull on its trellis, so pruning is essential and the support system needs to be both tall and strong.

This is usually accomplished in one of two ways:

The stake-and-weave system, also known as Florida weave or basket weave. Instead of putting a stake beside every tomato plant, stakes can be placed between every two or three plants. Strong T-posts should be driven into the soil at each end of the row. When the plants are about 12" tall, twine is tied to the T-post, then looped around each stake down the row. At the end of the row, the twine is looped around the other T-post, then passed down the other side to catch the plant between the two strings. Additional strings should be added as the plants grow, about 12" apart. Because hoophouse tomatoes get so tall and heavy, stakes should be at least 6' above the ground and driven into the soil securely.

The hanging string system. Tall, strong posts should be driven into the ground every 20', with a strong wire stretched tightly between the posts. A length of twine is then tied to the wire above each tomato plant, and loosely tied to the base of the plant. Plants should be trained to one or two leaders (vines). The one-leader system results in a smaller yield, but better flavored fruits. As the vines grow, they can be wrapped around the twine or attached with tomato clips. Again, the posts should be at least 6' above the ground.

When the crop is going to be left growing for six months or more, the vines will exceed this height. The usual strategy is to leave additional twine so that the plants can be lowered when they get too tall. See the description of "leaning and lowering" in the Florida Greenhouse Vegetable Publication cited below.


Tomato Production in Hoophouses by Eric Sideman, Maine Organic Farmers and Gardeners Association.

Production of Tomatoes Within a High Tunnel by Lewis W. Jett.

Production of Greenhouse Tomatoes — Florida Vegetable Greenhouse Production Handbook by G.J. Hochmuth.

Lynn Byczynski is the editor of Growing for Market and the publisher of The Hoophouse Handbook.

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the author:
Lynn Byczynski was growing organic vegetables and cut flowers for market when she decided to create a magazine that would help market gardeners nationwide share experiences and information. Her first issue of Growing for Market appeared in January 1992 and it has been published continuously since then. GFM is renowned in the market gardening world for realistic articles that give growers practical, how-to information about growing and selling produce and flowers. Lynn is now partnering with Johnny's to provide similarly useful information for the website and other publications.

Lynn, her husband Dan Nagengast, and their two children have grown vegetables and cut flowers since 1988, selling through a CSA, at farmers markets, to chefs, grocery stores, and florists. They currently grow cut flowers and hoophouse tomatoes on about 2 acres of their 20-acre farm near Lawrence, Kansas.

Lynn is also the author of several books about market farming:
The Flower Farmer: An Organic Grower's Guide to Raising and Selling Cut Flowers; The Hoophouse Handbook; Market Farming Success
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