I recently bought a gunnera manicata also known as: giant rhubarb (it’s not actually related to rhubarb but the leaf shape is similar) or dinosaur food. As with all things I purchase for my garden: I did a lot of research. It started years ago when I saw photos of this plant. I have always had it in the back of my mind, but I was too busy converting my backyard into a perennial food forest to make time for this.
The plant requires a ton of water. If you look at the surface area of its giant 4-10 foot leaves you can see how it would need a steady flow of water to keep the transpiration rate up. These wilt in high heat. I’m just hoping to create enough of a boggy home to keep it alive.
I ended up ordering from Joy Nurseries (I was extremely happy with the plant and the shipping: which was within a couple of days. I will definitely use them again!) and this is their description:
I lifted the two photos above from Wikipedia because I don’t have a mature picture of this plant… Yet!
At approximately 150 million years old, I can imagine an herbivore from the beginning of the Jurassic period munching on these leaves! And now, with these impressive photos, you can see why I have made space for a small “defiance garden”: Where I defy mother nature and dare her to stop me!
I don’t usually create this type of garden because they are super difficult to maintain. But. I’m in love with the idea of this plant, so here it is. I occasionally will add something that I am totally OK with nursing along and creating special conditions that are not natural for my zone or microclimate. I am stubborn. I’ve grown cantaloupe in the colorado foothills by planting water bottles next to the plants (to absorb and radiate heat when the temperature drops at night.)
Sometimes, my defiance gardens succeed! But they are never a plant and forget situation! I’m expecting to have to water this plant daily in our summer heat.
If you want to try to create your own defiance garden it will probably only be able to sustain one kind of broken rule for your area. I don’t plant things like peonies down here because that breaks two rules: 1. to bloom a peony needs full sun and 2. it’s too hot down here and they don’t get enough chill hours to properly break dormancy.
As far as I can tell, the Gunnera just doesn’t like heat (even though it requires zone 8-10). I can provide every other requirement that this bad boy needs, so I am only pushing one growing rule with it. They do really well in England and probably would do well on the American northern west coast. Neither of those places are anything like South Texas. So, we’ll see if I can provide enough things that it needs that I don’t kill it straight off!
In all honesty my gunnera is probably going to fail here because it doesn’t like our temperatures. So, San Antonio is a poor place to choose to plant it. But, I saw a review on DavesGarden.com (a truly stellar site for all sorts of plant information and sellers) that someone had successfully grown it down here in full shade.
I have a giant empty side yard. The fence is set way back and we just don’t do anything outside in that area. It’s on the north side of the house and it doesn’t drain well. I am attempting to grow the G. Manicata there.
I figure I have the perfect spot, to at least attempt, to grow this monster plant. I’ll show you how I chose to plant this thing and we’ll see how it does. The first thing to do (if you do not have a natural bog or ability to plant on the side of a water feature) to create a bog for any water loving plant, is find a low spot in a shaded area.
I would not try this if you don’t already have an area that holds a good deal of moisture on its own. This is also not going to do well under a tree because then there will be water competition and trees always win those. I have a low spot, that I had intended to put a French drain in, but hadn’t gotten around to doing it yet. It does drain… eventually, but every rain storm makes a big soggy mess out there.
I have seen some videos of people planting Gunnera Manicata but nothing that matches my exact conditions. So this is what I did to make the most of my soggy, shaded, side yard.
I’m big into soil prepping, especially if I have a feature plant and I want it to preform well for me. I dig huge holes for pretty much anything that comes in a pot.
Our native soil is really hard to work with. It’s like potters clay and full of limestone rocks. It’s also so basic that even our water from our aquifer will kill acid loving plants. Everything that needs acidic to neutral soil needs to be in a pot and my daily watering usually also includes dumping some of my morning’s coffee grounds on the soil in the pot.
I also put coffee grounds on anything with chlorosis (dark veining on yellowing leaves. It’s an iron deficiency and is very common in basic soil.) It works well, but needs constant reapplication. Soil ammendment down here is always necessary.
I would love my grandmother’s deep black Kansas soil, but this is what I have to work with. My soil is a very rich soil that usually only needs compost, iron and some regular applications of nitrogen. But it’s Hell to dig through!
I’ve also learned over the years that you can’t replace all of the soil in a hole because it will act like a pot. The roots grow fantastically until they hit the native dirt and then they turn around and grow back through the softer, amended soil until you end up with a circular mass of roots (this is called: being “root bound”). It will eventually restrict the plant’s growth and a root bound plant is going to be less vigorous and preform more poorly than a plant that creates a healthy root structure without restriction. To amend, and still encourage healthy roots, your amended soil needs to be at most a 50/50 mixture of the native soil and the soil/compost that you are adding.
On the other hand, some plants have the kind of root system that you will want to control because otherwise they become invasive (and if you fail at restricting things like running bamboo you will have nothing but bamboo, as will ALL of your extremely unhappy neighbors!)
Gunnera Manicata is a monster. It has the kind of root system that can support its 4-10 FOOT leaves. It is invasive in some areas, and planting is extremely discouraged in places like Ireland. I’m not really sure where I’m going to fall in the realm of invasive or complete failure with this plant, so, I built in some options that I can easily change in my planting hole. I also did NOT plant it up against any structure. I’ve seen what this looks like above ground and I assume I’m going to deal with something similar below ground.
First thing of business is digging a suitable hole. I could have gone bigger but I really didn’t feel like putting more work into this. Here’s my hole I dug out in my swampy side yard.
The next part of this is trying to slow, but not stop, the water drainage even further. I have seen 1 year landscape fabric last years under soil so I didn’t try too hard with this. I shucked a Sunday newspaper of its plastic bag ripped it open and placed it in the bottom of the hole.
Next I built a micro hugelkultur underneath the plant. I happened to have some well composted mulch that had sat unopened for a while in our backyard. I also opened my compost trash cans (having special ratios or even oxygen is not needed to break down plant materials. I keep rodents and other things out of my compost while keeping constant moisture levels by using my metal trash bins.) These were started a couple of years ago with rabbit bedding and kitchen scraps. I lined them with plastic trash bags because I use this on my vegetable garden and I have no idea what metals they used in the cans. It’s beautiful dirt now!
For a mini hugelkultur you need a source of rotted wood at the base of the hole to absorb and hold water. It will act like a sponge, keeping your planting supplied with moisture. I use a modified hugelkultur in my raised beds. You can learn about them here: Modified Hugelkultur Raised Bed 1
Modified Hugelkultur Raised Bed 2
Since this is a monster plant, I am purposefully creating a “pot like” environment. This is to keep the roots under control, for a while. I line my pots with newspapers.
In the ground, these newspapers absorb water, like wood mulch does, but stop the roots from spreading so quickly that I have no control. I have left myself an option to open the area around the hole by shoving my spade perpendicular to the newspaper lining, cutting through the future soggy newspaper and giving the roots free access to the surrounding soil. Until then, it will keep the water I add to the planting hole draining down, and then out, keeping as much moisture in the hole’s soil as possible.
And since I am trying to create a bog: it is a plus that I am draining soil slowly. This very set up would kill most plants. If I had full sun here it might bake the native soil’s moisture out enough to have plants survive, but this already floods so much and has so little sun that everything I’ve put out here has struggled.
Gardening usually means working with what you are given. I’ve already got a wet area: I’m just creating a small section of constantly wet bog, instead of the rain garden that I have been given.
Next I fill the hole back in with a mixture of 50% native soil and 50% compost.
The reason I am taking so much care with this hole is because I am changing the native conditions. If I wanted to plant regular garden plants in here I would have put in the French drain (which would have been even more work!) If I had a normal slope and drainage on this side nothing I could do would be enough to qualify this as a bog garden. Gardening is always full of goals, this was the simplest answer to my mushy wet area. I used the lack of drainage to my benefit.
I filled the hole in and created a small area to place the plant. Then I ran the hose until I filled the hole full of water and then lowered the pressure to a dribble. I let that run for about a half hour. It was definitely soggy at the end of all that!
I accomplished these things with cardboard and a gallon milk jug. I was very aware of the problem of dehydration with this plant while I had it indoors. I was having to mist the leaves and base of the plant several times a day as the leaves would shrivel up and die without constant moisture. Because I hate the process of hardening off plants (getting them used to the sun and wind of the outdoors) I always protect mine with milk jugs. Just cut an x across the base of the milk jug and fold the corners out.
Plant your plant, cover the surrounding soil with cardboard and water in. Carefully place the milk jug over your plant and anchor with landscaping pins or whatever you want to use to keep the jug from blowing away. Add some rocks to anchor the cardboard and water in again.
This was a lot of work, so make sure you check on your plant at least once a day.
Mine is super happy in these conditions and is sending up new leaves!
Here it is a couple of weeks later:
I’m very happy with the results! I hope you enjoyed my bog tutorial! If you would like to know more about beginner gardening, I have a 4 part series that I repost at least once a year. It’s everything you need to know to grow!
Everything You Need To Know To Grow Part 1
Everything You Need To Know To Grow Part 2
Everything You Need To Know To Grow Part 3
Everything You Need To Know To Grow Part 4