In this video, Oregon State University’s Community and Urban Horticulturist, Weston Miller, demonstrates ways to extend the growing season by planting earlier, and growing later into the season. Though, in the examples he shows, apply to the USDA Plant Hardiness Zone 8 region, these principles can be applied to many other regions of the country. Some of the key points that he covers for extending the harvest:
- Using Row Cover Fabric
- unheated greenhouses-cold frames and high tunnels
- Cloches
- Increasing soil temperatures
Edited video transcript:
Today we’re going to talk about season extension, which is using various devices like the row cover fabric that you can see around me, cloches and cold frames, and unheated greenhouses, to extend the growing season. – We’re able to add on about 3 or 4 weeks to the early season, 3 or 4 weeks late in the season, giving us a longer overall season where we get to harvest more food and share that with our families.
With row cover fabric, it’s a spun polyester fabric and it’s used in two ways. One right here is called floating row cover. The idea [ the fabric] is just laid down on the ground, bricks or other devices are used to weight it down. There’s a little bit of slack, so as the plant grows, it will push the fabric up. Here we have peas that have germinated underneath the row cover fabric, and soon we will pull this material off and trellis the peas and they’re going to grow as you normally grow peas up on a garden trellis.
[folds back row cover fabric] The other way to use row cover fabric is to use bows or hoops to support the fabric. And under here we have chard that has been transplanted. And there are advantages to using the bows in that it keeps the fabric up off of the plant so that when the plants get a little bit bigger, nice big leafy chard or big heads of broccoli, that it’s not going to be weighted down on the plants at all. We also use this system for peppers, tomatoes, zucchini, and cucumbers, all of which we transplant underneath row cover fabric and keep it covered for the first four to six weeks of growth. The plants will grow very quickly because it is four to seven degrees warmer underneath the fabric so it’s an ideal situation for plants to grow readily. And then once the plant starts to flower, we remove the row cover fabric, and trellis them if they need to be trellised, and they will grow normally from there.
The other main advantage to using row cover fabric in this way is that when the fabric is weighted down all around, the plants growing underneath are protected. For example, leaf minor is a major pest of chard, and without using the row cover fabric, I couldn’t grow high quality, marketable chard because the unprotected chard would contain major blemishes.
Another technique in season extension, is using an unheated greenhouse [like this one shown in the video], called a cold frame, or high tunnel. The idea with these, it’s not a traditional greenhouse, there’s no mechanical heating or cooling, but two things can happen. One is, we use it to house our transplants for periods of time before they go into the field. And soon enough, we will pull all the flats out of here and expose the beds, so you can plant in the ground in cold frames, and high tunnels like this. And that again is going to provide you with a degree of frost protection and a whole lot warmer temperatures. So last year, we grew melons in this high tunnel, where normally in the Willamette Valley area, melons aren’t a great crop to grow. We grew some decent melons in the high tunnel. With cold frames like this, you can also plant very late into the season. For example (in the USDA plant hardiness zone 8 region http://planthardiness.ars.usda.gov/PHZMWeb/#), you can seed arugula in November, and even December, and get it germinated and growing. And before too long, it will be too warm to grow arugula through the course of the warm season in a tunnel like this, but it really allows for some winter growing, that in Oregon, would not be possible otherwise.
Lastly with season extension, there are devices like this which are called cloches, which are used to help increase the temperature around individual plants. So for example, this is called a wall-o-water, and it’s a plastic set of sleeves that’s filled with water. It sits rigidly once it’s filled with water, and that water is going to absorb the sun’s energy. Water has a high thermal mass, it’s going to radiate that energy out over time, and keep the temperature up inside so that the tomato that we transplanted is going to be able to get a really strong start. It’s also going to cut the wind and create really an ideal situation for this individual tomato plant to grow. These are called “hot caps” and it similarly is a device that’s used to cover an individual plant. It’s a plastic one here, it’s got a vent on the top, and you’ll want to keep it vented. And basically, you’re going to put it around an individual plant, and then cover the rim around with soil so that it doesn’t blow away, and keep it ventilated. You can see that water is already starting to condensate inside because it’s nice and warm.
With the dome that is covering your plants, you’re going to want to keep that on until the plants start to fill it in, and touch the surface on the top of it. With the wall-o-water, you can leave that on for the whole time, or you can leave it on until the plants get well established—until they’re starting to peek above the top of it. Then you can take those off, and the plants should resume normal growth.
With reference to all the season extension, there’s four things you want to keep in mind. One is temperature inside. Vegetable plants like it warm, but they don’t like it too warm. So you want to provide ventilation as much as possible. Air movement is going to be another really important factor. Vegetables, when the air is really still, they don’t grow strong stems. So particularly in a greenhouse scenario, you’re going to want to open the door so that the wind gets in there. Humidity is another thing. I would keep it as dry as possible because you want to minimize the potential for disease. Keeping it ventilated is going to be a great step towards doing that. And lastly, soil temperature is another thing that you’re going to want to monitor. And here is the great advantage of growing in protected situations, the soil temperature is going to be just a little bit warmer. That’s going to favor rapid growth of the vegetables, and it’s also going to favor the rapid growth of weeds and slugs as well, so you’re going to want to be very careful of those things.
With season extension, it’s lots of fun, and it’s a great way to extend your season, to get a larger harvest for you and your family.