JSS Advantage - February 2010

Sale on seed-starting supplies
Johnny's has all the seed-starting supplies you need, and we have them available for immediate shipping. This month only, all seed-starting supplies are 10% off. Stock up for the rest of the season! Click here to learn more.

A quick crop of vegetables
Desperate for something green after a long, gloomy winter? Hungry for something fresh and home-grown? You don't have to wait for the outdoor gardening season; now is the perfect time to grow a crop of micro mix for sale or your own table. Micro mix, also called microgreens, is a mixture of tender gourmet vegetable seedlings cut at the first true leaf stage and blended together into a colorful confetti.

Commercial growers produce micro mix in heated greenhouses, using a combination of varieties that they select to create a signature product. Johnny's has dozens of varieties that can be grown for micro mix; the key is to choose varieties that germinate at the same time, and to keep seed costs in line with the prices you can charge for the finished product. You'll find a chart listing both fast-growing and slow-growing varieties in the catalog or on the website. Additionally, you can download instructions for commercial micro mix production there.

For personal use, growing micro mix is a fun and nutritious way to use up leftover seed or experiment with new flavors. The tiny plants are a vitamin-rich, flavorful addition to salads, sandwiches, and other dishes. You can grow a tray of mixed seedlings in a greenhouse, under grow lights, or even in a sunny window. Micro mix can consist of many kinds of vegetables, including amaranth, beets, broccoli, cabbage, pac choi, mizuna, arugula, mustards, kale, radishes, and any of the tender annual herbs such as basil, fennel, and cutting celery.

To grow micro mix at home, start with a seedling flat, a salad clamshell box, or other shallow container with drainage holes, with a solid tray below it to catch water. Fill with an inch or two of pre-moistened potting mix. Spread seeds across the entire surface of the flat, as thickly and evenly as possible. You may mix varieties together or plant them in separate sections in the tray. Press the seeds gently into the soil, then sift a thin layer of soil on top to lightly cover the seeds. Mist with a spray bottle, cover with an acrylic dome, and put the tray on a heat mat or in a warm place. As soon as the seeds start to germinate, remove the cover and provide strong light to the seedlings. Keep the soil moist by spraying or bottom-watering. Within one to two weeks, your seedlings should have their first set of true leaves, which means they are ready to harvest. Cut them with sharp scissors and enjoy.

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What to start in the hoophouse
When day length is less than 10 hours, as it is during the depths of winter in much of North America, most plants stop growing because of the lack of light. But in early to mid February, the days are long enough again for plant growth to resume. If you have a heated greenhouse or an unheated hoophouse, you can get an extra-early start to your season. Here are some ideas for plants to start now through April.

In an unheated hoophouse, you can start direct seeding cold-tolerant plants including beets, carrots, cilantro, radish, salad mix (mesclun), scallions, spinach, and turnips. By Feb. 15, it is generally safe to plant these anywhere in the U.S. inside a hoophouse. In very cold areas, you may also need a low tunnel inside the house to provide extra protection. At the same time, you can start transplants in a greenhouse or under grow lights for planting into the hoophouse in two to three weeks. Plants that are better transplanted than direct seeded include chard, Chinese cabbage, head lettuce, onions, and radicchio. Be sure to transplant in a timely manner to avoid stunting or premature bolting.

Choose varieties best suited for the weather you expect one to two months after planting. In the North, where cold weather will continue into April and May, choose cold-tolerant varieties. In the South, where the weather will be hot in a month or two, choose those marked as heat-tolerant, because they will be less likely to bolt.

Prepare your soil by removing any plant debris from last season, and spread compost or a fertilizer such as alfalfa pellets. Aerate the soil with a broadfork and hoe or rake the top inch or two to create a good texture for direct seeding. If the soil is frozen, put hoops on the bed and cover it with row cover. A sunny day will heat up the soil under the low tunnel and soon it will be warm enough to plant. You should also bring a hose into the hoophouse so that it warms up during the day and can be stretched to the water source for irrigation. You won't need much water in the cold days of February, and you may even have enough soil moisture without irrigating.

Once your beds are prepared, calculate how much of each crop you can use at the expected maturity date. If you have a farmers market or other place for early spring sales, plant optimistically. Hoophouse growers report that their products are immensely popular in early spring, when people are starved for fresh, local produce. If you won't have a market until May, you can still plant now for your own table, and schedule your market plantings for later.

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Succession planting in the greenhouse
Succession planting is one of the more challenging aspects of commercial vegetable production because there are no prescriptions or shortcuts. You have to work out your successions to fit your own marketing schedule, climate, and crops. And then you have to refine your plans every year, as you learn how specific varieties perform for you. Good record keeping and analysis are essential to successful succession planting. Here are some general rules to keep in mind for scheduling your greenhouse transplants.

Heat mat space and bench space are two limiting factors for transplant production, so try to plant only what you need. Check the germination rate on the seed packet to determine how many seeds will give you the required number of seedlings. Add 10-20% to account for possible losses. Avoid the temptation to plant far more than you need because, if all goes well, you will be faced with the even bigger temptation to grow more than you wanted just to keep from throwing out healthy seedlings.

Plants grow more slowly in the shorter days and cooler temperatures of late winter, even in a heated greenhouse. It's possible that plants seeded a week or two later will catch up with an earlier planting. Keep careful records about seeding dates to determine if this is the case.

Days to maturity printed in the catalog and on the seed packet can be used as a guideline for scheduling your successions. But it is highly accurate only when optimum temperatures are provided, so pay attention to recommended temperatures. Johnny's catalog includes detailed growing instructions for every crop.

You should know the earliest dates you can plant groups of crops, based on the average last frost date for your area. Count back the average days to maturity of a variety to determine when to seed the first succession. You should also figure out the latest date you can expect to have crops, and count back the days to maturity to determine when to seed your final succession. For example, you may be able to plant cold-tolerant crops such as broccoli in early April, two weeks before final frost. If your summers are extremely hot, you might have to set a date in June as the time when broccoli starts to decline. Count backward from both dates to determine your earliest and latest possible seeding dates.

Choose several varieties of each crop to provide a longer season. Start the season with a cold-tolerant variety, then switch to a heat-tolerant variety for summer harvests, then switch back to the cold-tolerant variety for fall.

With all these variables in mind, create a calendar of seeding dates to keep in the greenhouse. Get yourself in the habit of starting seeds on a specific day of the week. You will have a much better likelihood of sticking to your schedule, and having multiple successions of transplants to keep your crops producing all season.