Hāpu‘u Hawaiian Tree Fern Indoor Care Secrets

In my trials and tribulations growing the Hāpu‘u, I have learned some key tips for caring for your Hawaiian tree fern to make them happy and lush. Now I will share those secrets with you!

(Specific instructions below)

Yes that is snow outside my window, but look how happy my tree fern is!

I love Hāpu‘u. They are beautiful and majestic. Gentle yet strong fronds unfurling and reaching toward the sun. Being able to enjoy them everyday allows you to bring a little tropical fantasy into your life. I live in temperate zone 5 so there is no way for me to grow tree ferns outdoors. We get harsh winters, bitter freezes, and short growing seasons, therefore I am limited to indoor care. However caring for Hawaiian tree ferns in your home is very difficult. With air conditioning and heating making household air dry and limited sunshine indoors maintaining certain tropicals is a balancing act. They require specific water, heat, humidity, and food.

There is also a lot of false/bad information out there about tree ferns from individuals lumping them in with regular ferns. Unfortunately information specifically geared towards Hawaiian tree ferns is limited. I have found significantly more information on Australian tree ferns, some information on outdoor care of Hawaiian tree ferns in similar climates to their native areas, but very little on care indoors.

One of the first myths I want to rid you of is that tree ferns don't like too much water. Some ferns can't handle a lot of water, but Hawaiian tree ferns mostly come from very wet areas. They need water, especially consistent water. Perhaps the worst thing you can do to a Hawaiian tree fern is to let it dry out.

So, how do I keep my Hawaiian tree fern consistently moist?

• Peat
I keep my Hāpu‘u in a more peaty than loamy soil. I hand mix the soil for my tree ferns. To make sure that the soil will retain moisture well I generally mix mostly peat with some potting soil and some dried moss. You can also add some lava rock to create air pockets for the roots. This means that it retains humidity and moisture in the soil better. It is not as well draining as loam, but this is a good quality to have in soil geared towards the Hawaiian tree fern.
• Water reservoir
I also took my moisture a step further and converted a regular pot into a water reservoir pot. This is very easy to do and garden stores now sell adapters to convert pots in to reservoirs or you can buy pots pre-fitted. I purchased my reservoir kit from Gardener's Supply.

I don't know if you can tell yet, that I am serious about the water. ;)

• Hydro-Mats
I even go so far as to line my pots with hydro-mats to ensure my humidity levels stay up within the pot. These mats absorb water, hold it, then slowly release it back into the soil.
• Terra-Sorb
This is another good product for maintaining continuous moisture. Terra-sorb is basically little crystals that swell up into gel when wet so that the plant has access to more water throughout the soil. Just make sure you don't go overboard with the amount you put in the soil. Your tree fern still needs to be able to breath. Do not drown your plant in water absorbing gel. A small handful should suffice.
• Water from the top
Your tree fern will truly appreciate being watered over its trunk. A significant amount of the root is there. Since the Hāpu‘u is a fern, it has a shallower root system than many other plants. This is why it needs such consistent moisture. When you water from the top you are ensuring that the base receives water. This also makes the fur on the base wet which will hold even more moisture. Another tip is to water with warm water; I think it is more effective.
• Misting
Misting occasionally can also increase the humidity in the air around your tree fern or you could even go so far as to put a humidifier next to your tree fern. This is not necessary, but your tree fern would most likely love it. In the winter months misting can really make a difference. You can also just put out the standard tray of water and pebbles for surrounding humidity.

Not to be contradictory, but make sure your tree fern is moist, not wet. Do not drown your Hawaiian tree fern. They do not want to sit in water. In other words, they do want to drain.

Heat, Food, and Light

• Your tree fern will want moderate light. Be careful because the fronds can burn. They do not need significant light though and can do just fine with indirect sunlight in your house, however you will see the fronds fan out toward the window to optimize their photosynthesis.
• The Hāpu‘u likes moderately acidic soil and it likes to be fed. I like to feed mine every once in a while with some watered down coffee. You don't want to burn your tree fern with hot coffee or too much coffee(ie too high acidity). They do like to be fed though, so go ahead and give it a little fertilizer or coffee every so often. Feed it less in the winter since its growth will be down. Sometimes when you feed your tree fern it may mold since it is encased in fur. You can just wipe off the mold gently and it should be fine.

Here are two tree ferns that I am starting out. They are both on heating pads and will hopefully take off when the weather gets better. Unfortunately we got these in the dead of winter, so they are not at their growth peak and it is harder to get them started.

• Heating your fern
To encourage root growth I like to set my Hāpu‘u's pot onto a plant heating pad. This keeps the soil nice and warm, like it would enjoy at home in Hawai'i. The roots should grow deeper and the plant will grow faster. The deeper you can establish the roots the better. This will help you in stabilizing your tree fern for watering and overall health. This is especially important when you are establishing a new Hāpu‘u!!! As a rule of thumb I always have a new Hāpu‘u on heating pad so that I can ensure it takes off.

Troubleshooting.

• Brown and brittle frond tips
When I first started with tree ferns I had the issue that all of my fronds would come out beautifully but then each one would slowly crumple down from the tips. They would turn brown and shrivel up. This was a result of not giving the tree fern the appropriate amount of water. If you are able to keep the moisture level up this should not happen. When I corrected this problem the browning stopped. Any time however that I am not religious with my watering, I may lose parts of my fronds. I must be especially careful in the winter.
• Winter
In the winter your room will be both colder and drier, so growth will significantly decrease. This is normal. Your tree fern's growth should pick up as the weather warms up again and your Hāpu‘u will throw out more new fronds again.

Here is a new frond coming out of my established tree fern. It is just waiting to pop. You can also see a little mold, because I recently fertilized. I will scrape it off gently with a knife.

With these tips you can successfully grow a Hawaiian tree fern and enjoy a little Hawai'i in your life! Good Luck!!!

For some additional information, here is an article from the University of Hawai'i at Mānoa. It is more targeted toward growing Hawaiian tree ferns in Hawai'i and outdoors, but gives some great and substantial information about the Hawaiian tree fern.