Gunnera is a genus of flowering plants found in tropical regions of the world. There are over 400 species, with many being used medicinally or ornamental. Some of these plants include the common garden weed, the coffee tree (Coffea arabica), and the elephant’s foot (Erythrina tesota). All gunneras have three main parts: leaves, flowers and fruit.
The most commonly grown gunnera varieties are the coffee tree (Coffea arabica) and the elephant’s foot (Erythrina tesota). These two species are both native to South America.
Both species produce large clusters of white flowers in spring followed by small yellow fruits in summer. The coffee tree produces its flowers from April through June while the elephant’s foot produces its flowers from July through September.
How To Grow Gunnera?
There are several ways to grow gunnera. One way is to simply plant them in pots. Another method is to grow them out of seed. A third option is growing them in soil and then transplanting into containers once they’re established. Each method has advantages and disadvantages depending on your location, climate, and other factors such as time of year when you want to harvest the gunnera fruits.
In all cases, it is important to use well-draining potting soil. It’s also beneficial to mix in some perlite or sand for maximum aeration.
The containers should be at least a few inches wide to avoid the roots from becoming water-logged. Because gunneras are very large plants, you’ll need a very large container before transplanting into the ground.
Grow From Seed
The first step is to gather some seeds. You can order gunnera seeds online.
Wait until the seed package has been delivered and then follow the instructions for preparing the soil and planting the seeds. You can either plant the whole seed or just nick it with your thumbnail and soak it in water for a few hours before planting it (this helps to expand the seedcoat and promotes faster germination).
The best time of year to plant gunnera seeds is in fall or winter. You can either plant them outside or in a container.
If you’re planting them outside, make sure to wait until the weather has cooled down and the risk of frost has passed. Spread an inch or two of mulch over where you want to plant the gunnera seeds. Plant the seeds 2-3 inches deep. Keep the soil moist but not water-logged. You may need to water it every day for the first week or two while the seeds are establishing roots.
If you’re planting the gunnera in a container, choose the container first. The containers should have good drainage and be at least a few inches wide.
Fill it with potting soil and plant the seeds according to the instructions listed below.
Care And Maintenance
Once your seeds are planted, keep the soil just moist (but not soggy!) and keep an eye on it until you see some sprouts coming out of the soil.
Gunnera seeds sprout quickly, some in just a few days. Continue to provide adequate water and keep the soil from drying out.
When your gunnera plants have at least two sets of true leaves you can plant them outside. Dig a hole twice as wide and just as deep as the roots.
You’ll want the top of the rootball to be level with the ground. If you’re planting more than one gunnera plant, space them 3-5 feet apart. Backfill the hole with the original soil and then add some mulch around the base of the plant. Like most plants, gunneras like a lot of water when they’re first established but prefer drier conditions after that.
Soil & Site
Gunneras can be grown in most types of soils except for really wet or dry ones. They also prefer acidic soils with a pH between 5 and 6.0.
Since they’re native to South America, they’ll grow very well in the landscape in zones 9b-11.
For people living in colder climates (zones 7 and below) it’s best to start your gunnera seeds indoors since they won’t reliably survive the winter outside.
The best type of containers to grow gunneras in are the hanging baskets since these have more surface area for the roots to absorb water and nutrients. You’ll need to transplant your seedling into a bigger container once it outgrows its current container.
You can also plant your gunnera directly in a hanging basket or even in the ground.
If you’re planting your gunnera in a container, it’s easiest to start with a container at least a few years old. You want one that has good drainage since gunneras like their soil on the dry side.
Mix in some compost or organic material to increase the organic content of the soil and help with drainage.
When planting your seeds, make sure you plant them at the same depth that they were in the seed starting container. Add a little bit of soil and gently pat it down.
Keep the soil lightly moist and don’t water too much since gunneras don’t like soggy soil. Overwatering is as bad as underwatering since it’ll cause the roots to rot.
You’ll also want to place the container in a sunny location. Even though gunneras like their soil on the dry side, they do like lots of sun!
Hanging containers will need to be hung from trees or poles since they won’t sit well on the ground. You’ll probably need to use a watering can to water it thoroughly and then keep an eye on it to be sure that the soil doesn’t dry out completely.
Once your gunnera plant is established (which should be within a few months), you can transplant it into the ground if you want, or even transfer it to another container.
Sources & references used in this article:
Soil seed banks associated with two invasive species, Gunnera tinctoria and Heracleum mantegazzianum. by M Gioria, B Osborne – Plant invasions: human perception …, 2008 – cabdirect.org
Tissue culture of Gunnera manlcata L. by SL Chen, XL Lv, XH Cui, C Wang, Q Zhang… – Bulletin of Botanical …, 2014 – cabdirect.org
Antenna pigments in some species of cycads (gymnosperms) and Gunnera (angiosperms) plants in which nostocacean cyanobacteria are symbionts. by B Czeczuga, A Semeniuk… – Current Topics in Plant …, 2011 – cabdirect.org
Control of weed Hedychium gardnerianum and Gunnera tinctoria in forest areas in the S. Miguel Island-Azores. by MLT Penacho, RS Amaral, A Malveiro… – XII Congresso da …, 2009 – cabdirect.org
Study on the seed germination characteristics of Gunnera manicata L.. by XL Lv, L Lu, YY Qian – Seed, 2012 – cabdirect.org
Isolation, characterization and biological activities of terpenoids from Gunnera perpensa by FK Mammo – 2018 – openscholar.dut.ac.za
Physiological Adaptations in Nitrogen-fixing Nostoc–Plant Symbiotic Associations by JC Meeks – Prokaryotic symbionts in plants, 2007 – Springer
The Nostoc-Gunnera Symbiosis by B Bergman – Cyanobacteria in symbiosis, 2002 – Springer
Regulation of cellular differentiation in filamentous cyanobacteria in free-living and plant-associated symbiotic growth states by JC Meeks, J Elhai – Microbiology and molecular biology reviews, 2002 – Am Soc Microbiol