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Garden Coach on Ways to Extend Your Vegetable Growing Season

October 10, 2009
Shiloh Thanking Bob for Building the Hoophouse

Shiloh Thanking Bob for Building the Hoophouse

It’s all the buzz right now — vegetable growing. Nearly all of my garden coaching clients are asking about them. And why not? This is the season when starts and seeds are appearing in nursery centers. It’s that time of year when gardeners are checking weather forecasts daily. The days are shorter and the warmth of summer is rapidly seeping away. Friends living in places like Colorado are already posting Facebook updates about picking up newspapers in the snow. Here in Seattle, the weather reporters warned that tonight we may have a mild freeze. This news means we will be switching out all remaining floating row cover in the garden for the more protective and heat building and heat retaining plastic hoop house covers.

If you’re growing edibles in your winter garden and need help retaining heat, read on for ways to extend your growing season. And, don’t delay. If cold temps are trickling (or racing) into your garden, one freeze can do in your crops. Protect them early and eat well all winter.

(Original post from March 27, 2009)

Gardening magazines are featuring edible gardening. Heck, even the Obamas are jumping on the bandwagon this year. Edible gardening is nothing new to me. I grew up pulling weeds around squash, hoeing acres of rows for greenbeans, and putting up freezers full of all sorts of vegetables on our farm year-after-year. I come from a family of farm folk, and though I’ve chosen a suburban home life, I continue to raise food year-round in Seattle.

Seattle is a great place to garden. Although the winter of 2008/09 brought us huge freezes that took out a lot of our consistent garden performers like Rosemary, Lavender and Flax, generally we have mild winters through which a wide array of plants will survive — including winter edibles. However, as great as gardening can be in Seattle, it does present some consistent challenges, particularly long, cool, wet springs.

Even the most seasoned edible gardener is going to need to rethink tried and true methods they’ve used in other areas of the country. For instance, the beefsteak tomato that you’ve grown up loving in the midwest may do nothing for you here; if you’re lucky you might get some big green tomatoes from it. Peppers can be difficult to get going, especially if we have an extra cool gardening season. So, what can you do to get past these trouble spots and have success in your garden? Well, besides taking care to select edible starts and seeds known to perform well in your area, creating heat-traps in your garden may make all the difference!

First Hoop House On Raised Bed

First Hoop House On Raised Bed

Maybe you don’t have room or budget for a greenhouse. Maybe you don’t have room for a coldframe. Instead, consider adding a simple hoophouse over your exisiting vegetable beds or plot. They are relatively inexpensive to build and can easily be dismantled when the growing season really kicks into high gear.

For several years, I’ve maintained one small raised bed in my west-facing front garden. Seasonally, we pull out the PVC hoops, a sheet of plastic and some clips to help warm up seedlings or protect them from winter (or spring) snows. Through the winter, this small bed has kept a nice crop of various things going for us — ranging from chard to lettuce to parsley to kale. In the cool spring, the hoop house has later served as a protective incubator for tomatoes too delicate to face the range of temperatures swinging back and forth in the early (or late) Seattle spring.

Closed Hoop House

Closed Hoop House

A hoop house is designed to trap heat in a specific garden bed area. Sunlight, even diffused sunlight, filters through the plastic sheeting, warming the air inside the tent as well as the soil and the plants growing inside. As plants transpire, the hoop house can also serve to trap the warmth and moisture released by the plants. This creates a great, inexpensive greenhouse in a specific area of your garden. But, be sure to check the soil and water regularly. Since you’re keeping the rain out and you’re heating up the environment, you’ll probably need to provide your bed with additional water regularly!

In our garden this year, we added a second, taller hoop house to a new edible section of our garden. Unlike the hoops on our raised bed, this new system is installed directly into the earth using rebar to stabilize the hoops. So, in this case the PVC is attached over the rebar. Honestly, this isn’t my preferred method.  PVC can leach toxins. My preferred method is to attach brackets to the outside of a raised wooden bed so that the PVC slips into the brackets outside the growing area. Regardless, we’re trying both methods this year and doing our best to keep the PVC away from our soil. I have seen other materials used for hoops, but none are as cost effective as the PVC.

Clipped Open Makes Working Inside Easy

Clipped Open Makes Working Inside Easy

Because I use clips that hold the plastic tight to the hoops, I have less trouble opening and closing the plastic to work in the beds. It also makes it easy to open the hoophouse during the day to let in natural rain and warmish breezes. Opening the house more and more as warm days approach is critical to hardening off the plants inside, getting them ready to withstand days and nights of unprotected exposure. As well, gentle breezes help deter many edible garden problems like bortrytis from killing seedlings. Too, gentle spring rains, direct from the sky, provides the type of water plants prefer over processed tap water.

Back in January, I wrote about starting my seedlings indoors. Yesterday, almost two months to the day I started these seeds, I planted young starts into my hoop houses. These little kale, cauliflower, cabbage, lettuce, spinach, chard and snow peas have made the rounds in my home. Beginning in January they were seeded into sterile mixes and placed in a south-facing window with a furnace vent below them to provide air circulation and bottom heat. After germinating, they were moved into my cooler basement under shop lights where they would begin managing cooler temperatures but continue growing under supplemental light. Then, after transplanting them from sterile soil into larger pots with mixed worm castings and potting soil, the young plants moved into my coldframe to further harden off and grow for about another 3-4 weeks. Now, I have two hoop house beds filled with edibles that we’ll be harvesting in just a few weeks.

Oh, and I should mention that we are already harvesting a few crops. Several rainbow chard, dinosaur kale and lettuce plants plugged right through the cold, hard winter. Each experienced a bit of dieback in the cold, but the plants themselves perservered and as an annoucement of spring, they’re already providing tasty morsels for our table. Curious what else is on the way? Well, tomato seedlings and beets are growing like mad under lights, and more seeding is coming soon. Here’s the full list of what we’re planning…well, it was the beginning list. We’ve added few new things since making this list at the beginning of the year.

Odds are we’ll have more food than we know what to do with. Between the garden and the prepaid CSA program, I anticipate having a lot of food on hand by summer. I’ll be canning and freezing and eating! I also hope that some of what I grow will go to feed the hungry. Local food banks are happy to accept fresh foods from our gardens to help fill their distribution needs.

Need help constructing a hoop house? Get in touch to schedule a gardening consultation to learn more about how to build a hoop house or cold frame of your very own!


  1. Laura says:

    What a great post! Thank you for all the information; I’ve been thinking about building one for a while and you may just have given me the push to do so!

  2. Katy says:

    So, with a hoop house, do you keep it closed all the time? I’ve never figured that out.

  3. rhaglund says:

    I open it. I monitor how warm it is outside and how hard the rain is falling. A light rain on a not-to-cold day is a great time to open it to water the plants. Also, you can roll up the ends just a bit to allow a little venting if you just need some airflow.

  4. Katy says:

    So when do you take it off for good?

  5. rhaglund says:

    That depends on what I’m growing and what the weather is like. I’ll take the hoop off my brassicas earlier than I will the bed that will be coddling tomato seedlings. By July I sincerely hope the weather is warm/consistent enough that all hoops are stashed for the summer. Sorry, no silver bullet calender marker on this stuff…I wish there were one though!

  6. […] we headed out to the farmer’s market this morning, we opened our hoop houses to let the lettuce, spinach, kale, cauliflower, chard and cabbage drink in the heavenly downpour […]

  7. […] heat, extend the growing season, ramp up edible production rates, and provide other protections as illustrated here.  But, for some crops and during the warmer times of year, when flying pests are looking for […]

  8. […] much of the year, my food crops are covered in protective hoop houses. Thriving Fall […]

  9. […] of growing hardy crops through the 2009-2010 winter, but alas in mid December, despite having hoop houses in place, I failed to protect all my crops from a hard freeze. Radish & Radish Greens – 2010 […]

  10. […] you don’t have a greenhouse, rigging up a temporary hoop house can work nearly as […]

  11. […] So, if you’ve got onions to place, seeds to sow, soil to test, berries to prune or weeds to pull, there’s no time like this very moment to get out there and get started. Even if your soil is frozen, sowing seeds now indoors or in a protected outdoor spot, will mean your garden will be well on its way by the time the Spring thaw comes. Find ideas for inexpensive season extenders here. […]

  12. Chris says:

    Hi what type of clip do you use to keep the plastic sheeting tight against the
    PVC piping? Also…what type of plastic sheeting do you use? I’m going to
    try this method for growing tomato plants (already have blossoms) in containers
    and building a hoop house around those containers to trap in some heat.
    I live in San Diego County, and it’s now starting to get a lot colder during
    the nights…Thanks in advance!

  13. Chris, Thanks for writing in. Many nurseries carry pre-cut plastic cuff clips that will hold the sheeting in place. Or try shopping online with greenhouse supply vendors. If not, buy a larger size length of PVC and cut your own clips. Just be sure the larger size you buy will fit over your hoop size.

    As for the plastic, I use the heaviest mil semi-opaque sheet plastic available at hardware or “box stores”. Usually, it is available in roll form, so I then just cut it to length.

    Good luck!

  14. Chris says:

    Thanks very much for all this information!
    Looking forward to good tomatoes in the winter months,
    hope it all works, experimentation is always good!

  15. Good luck Chris. May your winter tomatoes be red & flavorful!

  16. […] heat, extend the growing season, ramp up edible production rates, and provide other protections as illustrated here.  But, for some crops and during the warmer times of year, when flying pests are looking for […]

  17. […] we headed out to the farmer’s market this morning, we opened our hoop houses to let the lettuce, spinach, kale, cauliflower, chard and cabbage drink in the heavenly downpour […]

  18. […] of growing hardy crops through the 2009-2010 winter, but alas in mid December, despite having hoop houses in place, I failed to protect all my crops from a hard […]

  19. […] During much of the year, my food crops are covered in protective hoop houses. […]

  20. […] the first of your basil. Thin seedlings to give plants room to mature, and set them outdoors (after hardening them off) once the weather is consistently warm enough to support tomatoes and like […]

  21. Hugh says:

    I built hoop houses for the first time this year. Not only to extend the growing season, as mine is short here in Colorado, but to protect from excessive rain and hail. Last year we had one hail storm that destroyed every tomato plant we had. So far this year we’ve had a lot of rain…a little too much rain…and the ground is over saturated. So I’ve kept my plastic up most of the growing season thus far. What I’d like to ask, is can I damage the plants if I keep the plastic sheeting up while I’m gone on vacation? Meaning if we have a break in all this wetness while I’m gone and the temperatures exceed 90 degrees, am I taking the chance of coming home to dead vegetables? I have all of the boxes on sprinkler systems, so they’ll be getting enough water, but I want to protect them while away. Any suggestions?

  22. Hugh, thanks for writing in. I’d like to take some of that rain off your hands this season! Alas, that’s not going to happen. As to your question…if you’re gone and the weather takes a turn for the hot, you absolutely have a chance to fry your plants under those hoops. If temperatures aren’t dropping into freezing and you have a watering system in place while you’re away, you could try venting the hoops significantly to help. Essentially, clip the ends of the hoops open and clip the bottoms open. This will increase airflow, but if you leave the top of the plants covered, they’ll likely be protected from any heavy rains/hail. And, heat won’t build as much and become trapped, frying your plants. Without seeing your site and knowing exactly what’s going on, it’s hard to be absolutely certain what might work. That being said, we’ve been approaching the 90s here in Seattle over the last several days, and we’ve got our hoops set up like this. I hesitate to completely remove the top-protection plastic because you just never know when a heavy rain might hit or temperatures in the PacNW might take a surprise turn back to the cold. Hope this helps!

    You might also read this timeline piece on tomatoes. While it is written with a different set of goals in mind, it does look at keeping hoops from overheating: http://gardenmentors.com/garden-help/grow-your-own-food/how-to-grow-front-yard-tomatoes-that-ripen-even-in-a-record-cold-summer/

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