Raised Bed Greenhouse

I built this raised bed greenhouse in order to have a place to grow vegetables that is safe from chickens, cats, squirrels, and caterpillars.

I enjoy the aesthetics of how the material change breaks up the scale of the structure and the friendly, orderly lines of the gable roof.

Step 1: Materials List and Budget

This is a rough budget for the project to get an idea of cost.

Ideally, I would have built it out of a naturally rot-resistant wood like poplar or redwood.

As far as tools it's pretty basic: circular saw, a staple gun, level, scissors, shovel, an impact driver, and drill.

Step 2: Working Drawing

This is the drawing that I used to build it, it is modeled in SketchUp.

Verify the smaller measurements as you go based on your unique site conditions.

The height of the raised bed is ergonomic and reduces the need to bend over to reach the plants.

It contains approximately 2.5 cubic yards or 67 cubic feet of material.

To reduce the amount of soil I needed to fill it with, the first layer is rotting logs that I had laying around my yard. On top of the logs is about a foot deep layer of native soil mixed with cow manure from the local garden shop. Google hugelkultur if you want to learn more about this method of using logs to retain moisture and fertilize your garden.

Step 3: Raised Bed Greenhouse End

First I prepped the site by clearing an area for the structure to go.

My yard was not level, so I used urbanite as a foundation. I placed pieces of urbanite beneath all four corners and the center and checked that they were level by placing a level on a board that spanned them.

I built all the side panels first, and then screwed them together in place on the foundation.

Next, I climbed inside and laid weed barrier down for the bottom, I stapled it in place halfway up the side walls.

Over the weed barrier, I lined the inside walls with a layer of plastic to separate the wood from the dirt.

Check that everything is square and level again and adjust as needed, since it will help your roof turn out nice and straight.

After filling it with logs and soil, I finished framing the roof.

Step 4: Raised Bed Greenhouse Door Open

Once the framing is complete, stretch plastic over all the sides without the doors. Staple it down with a staple about every 4". I left a bit of overhang on the plastic to deter bugs from entering and to shed some water away from the wood when it rains. I also added a horizontal brace every 4' to help keep the structure rigid and square.

The two doors are hung with three hinges each. I added 45-degree braces at each corner to keep them square. I'm not totally confident about how durable the door situation is, so I'm gentle opening and closing the top. It does make a satisfying sound when they fall into place.

I used flyscreen for the two end panels to provide ventilation and airflow to the greenhouse. There is room for improvement here because aphids are still able to get through and proliferate on my kale. I later added a secondary layer of flyscreen at a 45-degree angle, but I won't know if it is enough to keep the aphids out until next year since they have already infiltrated the greenhouse.

There is also an opportunity to have more control over growing conditions by installing a ventilation fan and a temperature gauge and the greenhouse could easily be outfitted with an automatic watering system.

Step 5: ​Plant Your Plants!

Choose plants that have a short plant height at maturity and like lots of heat, sunshine and water retention.

I chose kale because it produces a lot and it is nice to have on hand when you only want a couple leaves to toss in your scrambled eggs for breakfast. The kale will quickly reach the top of the interior, so top it to keep the plants short.

I've also planted cabbage and romaine which is growing happily.

My long-term goal is to practice a no-till gardening method called KNF (Korean natural farming) to keep labor to a minimum. Also, to experiment with interplanting techniques to maximize the amount of food I can produce in this greenhouse.

It's been great having a dedicated place to grow delicate vegetables and reduce pests naturally.

It feels like having a living extension on my pantry!

Comments

[lolamatic]

Sorry if this was mentioned: Do you have any sense of the temperatures you're able to achieve and what the heat and humidity retention is like? Been thinking of something similar and wondering how well the 6 mil versus actual glass will work out.

[shalnachywyt]

If you're in a colder zone (7 or less) you might want to consider either glass or acrylic. I've used the flat acrylic that I got from Lowes and that works very well and doesn't break down as fast as 6 mil does. It's a bit expensive, but the idea was to build it once and never need to replace it. However, if you have a problem with high winds in your area (I do), you need to make sure that the places where you can open the frame is locked down tight whenever high winds are expected or your frame with end up in pieces. That has happened to me more than once. :( I've also considered using the clear corrugated roofing material to cover the frame, as I've seen that in other pics online.
I always suggest that folks do online research to see how others do cold frames to get ideas on how to build to suit one's own needs.

[lolamatic]

Hi shalnachywyt, these are indeed options I've been weighing as I look into making my own. The plan is to use a ridig sheet not the 6 or 8 mil plastic. The corrugated roofing had moved to the top of the list but then i started reading reviews and the longevity of what i have available in my bigbox stores may not be great. I'll figure it out soon enough thanks

[shalnachywyt]

I have corrugated roofing on the canopy over my deck. It's at least 10 years old and haven't had any problems with it other than some black mold(?) on the underside where leaks sometimes occur during very heavy rains because of the way it was constructed by this completely clueless builder (ha ha). Anyhow, because it's basically out in the open with plenty of air circulation, I don't really consider it a problem. You've got me concerned and I'll have to do some research on longevity. Thanks for the update.

[Kerico]

I haven't tried measuring the temperature/humidity relative to outside yet. I have a hygrometer in the soil and I've been watering every four to five days. It seems to retain water better than the rest of the garden. This would look great with actual glass, but you would probably need to double up on the wood to hold the extra weight, and the doors would probably have to be 4' instead of 8'.

[lolamatic]

Yes, would definitely require some design adjustments. Thanks for the info and here's to a plentiful harvest!

[dennisgun]

Did you give any consideration to using straw bales as your “soil” source ? I am nearing the end of the season of my first straw bale garden and I’ve been impressed with decomposed straw as a plant medium, however as it is breaking down it is beginning to slump and want to fall apart. If I had your skill set and energy and could start over, I would have enclosed the bales in your greenhouse and been able to avoid staking up of bales and have a year round garden.

[Kerico]

I use straw in the garden as a mulch around all my plants, it helps the soil retain moisture and breaks down quickly into humus. It would probably work great to fill the bottom half with straw and the top half with soil.

[dennisgun]

The thing about straw bale gardening is that you “season” the bales at least a month before planting. Seasoning meaning you fertilize and water the bales to promote it’s decomposition, meaning you do not need soil, the straw becomes the soil. The advantage is you have a relatively weed free environment except for an occasional sprout of wheat or oats or whatever the straw bale was composed of. When I realized how the seasoned straw replaces soil, it was an immediate answer to the poor topsoil I was dealing with. Joel Karsten, from my perspective is the guru of this technique. Below is a picture of my straw bale garden today 8/13/2019. Thank you again for your instructable !

[Kerico]

I've seen this in a neighbor's back yard, a great solution for poor topsoil!

[shalnachywyt]

Oy! I've been using straw bales as mulch in my garden for at least 10 years. Unfortunately, this year, where ever Lowes was getting their straw bales from, the farmer obviously doesn't understand that straw is what's left over after the wheat seeds have been harvested. The result was that instead of mulch, I ended up with wheat growing in my beds. What a mess! It took me forever to yank out the growing wheat, which sprouts and grows very quickly in my zone 6b/7a garden. I've decided to use pine straw instead for a few years.
When done properly, yes, whatever you're using as mulch does rot down into soil. However, I've noticed that if I don't, at least, turn over the bed with a fork, the rain packs the soil down so hard that it is almost impossible to plant anything in it.

[EdM63]

I've been trying to figure out how to keep the deer, rabbits, and chipmunks out of my garden, and this would be an awesome addition!

[wolfwings]

When I was growing lots of roses, I noticed lots of aphids also liked them.

I find that if you go to a plant store you can get lots of ladybugs. They love the taste of aphids and will eat them all up, and are very inexpensive.

[rozzieozzie]

I love this idea, thank you for your ingenuity! My sister has been talking about getting a greenhouse, so I'll have to show her this one. I have a feeling we will be building one next spring!

[Kerico]

Awesome! Would love to see how it turns out.

[shalnachywyt]

You've given me some ideas on how to fix a bed that was meant for herbs by turning it into a winter greenhouse. I, however, would not use wood, but composite lumber or concrete since neither rots. Otherwise, fantastic project!

[Kerico]

I'd love to re-build this project out of a rot-resistant wood like poplar or redwood, unfortunately, it was out of my price range at the time of the build.

[shalnachywyt]

Your bed is considerably larger than the one I have planned.

[Kerico]

It took a lot of soil to fill it, you could do half logs/half soil like I did or half straw/half soil. Or the design could easily be 3'x8'.

[shalnachywyt]

What zone are you in? I'm allegedly in Zone 7a, but I think practically I'm in Zone 6b.