How to Care for Indoor Conifers and Evergreens
Follow our editor's journey in creating an indoor haven for conifer trees.
Up north plant lovers can visit just about any nursery or plant shop and find conifers that in my neighborhood will not make it through our northernwinters. Before what I call my pre-conifer knowledge, I tried Podocarpus macrophyllus and Araucaria columnaris as houseplants only to watch them succumb to the dry heat of forced air furnaces, wither and die.
Northern nurseries also sell, as a rule, Sciadopitys verticillata, Cedrus atlantica (blue Atlas cedar), Cedrus deodara ‘Eisregen’ and Pinus densiflora ‘Golden Ghost’ with little or no warning regarding winter hardiness, survivability and planting location. Sadly, the beauty of spring and summer might very well be followed by the brown and death of fall and winter. My home and gardens are in Adrian, Michigan, Zone 5.
Conifers as Houseplants: A Thought
At the ACS National Meeting this past summer in Charlotte, there were many plants at the live and silent auctions. I was mesmerized by them and I wondered how I might carry some back to my home in Zone 5 and help them thrive and grow. I knew they could not be planted outside and overwintered, but Ron Determann, Conservatory Director at the Atlanta Botanical Garden, provided a glimpse of conifers as houseplants in his presentation on Jurassic Araucaria and other Southern Hemisphere conifers. Then I had lunch with Tom Cox.
Tom and I talked about conifers south of Zone 5 and the successes he has been having with them in pots. He shared how the plants spent the spring, summer and fall outside and then were brought indoors for the winter. Tom described the growing medium he has used in order to provide the trees with the best footing: pea gravel, fish aquarium charcoal and soil.
I listened with great interest as Tom listed the ingredients of the mixture; charcoal at the bottom of the pot “to sweeten” the mixture, pea gravel and soil for a somewhat porous medium. I also had to give them room to grow.
I have visited the Orangerie on the grounds of the palace of Frederick the Great, Sans Souci, in Potsdam, just outside of Berlin in The Federal Republic of Germany. There, potted fruit trees and tropical trees of all kinds spend spring and summer outside. Then, when the cold weather approaches, these large trees are wheeled into the glassed hallways of the Orangerie to spend the winter. I have even seen potted plants on plant-dollies in private gardens throughout Germany that spend the winter in garages.
My plants are far smaller than those in Potsdam, but they are very significant to me. And, the principle is the same. Tender plants can winter indoors under the right conditions.
Gathering my Indoor Conifer Candidates
The auctions that evening in Charlotte netted me some interesting specimens of Sciadopitys verticillata, Cunninghamia lanceolata ‘Samurai’ and Cryptomeria japonica ‘Sekkan-sugi.' To them I added from my favorite local nursery Barrett’s Podocarpus macrophyllus var. ‘maki’ (two plants), Cryptomeria japonica ‘Black Dragon’ (two plants), two more Sciadopitys verticillata and three Araucaria columnaris.
The Podocarpus and Araucaria have spent their entire time with me indoors. All the others spent the spring and summer outdoors on a southwest facing deck. The plants were fertilized with Osmocote as per instructions on the packaging. In October, when outside temperatures began to get near freezing, the outdoor inhabitants were brought indoors.
Then I purchased at Christmas time a Picea pungens, one Picea glauca ‘Conica’ and finally Picea glauca ‘Jean’s Dilly.' I chose to expand my collection to include Zone 5 hardy conifers because I wanted to see what they would do in the house too. As you know, nurseries have for many years sold potted conifers during the holidays for those interested in having a real, live Christmas tree. My thought was that, if the trees survived the winter indoors, they could remain “houseplants” and I could pass on my research and guidelines to my friends at Barrett’s.
How to Set Up Conifer Trees Indoors
The environment I have provided my coniferous house guests is a room off the dining area. It gets eastern, northern and filtered western light. This light is of course far fewer foot candles than the plants would receive outside. They have maintained their color and their vitality for the most part. My Sciadopitys from North Carolina is pushing new growth. However, two of the trees have been stressed. Daytime temperatures never exceed 60°F - 65°F. Nighttime temperatures remain at 60°F or below.
One Cryptomeria and one Sciadopitys have suffered in their indoor “plant room." The Cryptomeria was within seven feet of a floor heating vent. All the vents in the plant room had been closed once the trees came in and the overall house temperature had been dialed down to 70°F.
That Black Dragon browned on the entire one side that faced into the house proper. A good one-third of the plant dried out and had to be removed. It had already started sending new branches out from the trunk where older branches had died. This plant was the most vibrant and healthy before coming into the house. It had pushed a great deal of new growth during the spring, summer and even into the fall.
As of this writing, the tree appears to be in total decline. Much of the new growth is turning brown. The other Cryptomeria japonica stands in front of the patio door. It receives eastern light and is doing quite well. It too is pushing new growth.
The Sciadopitys, that was across from the stressed and dying Cryptomeria, began to experience what I would call radical needle drop. (Tom Cox had admonished me to plant Sciadopitys outside.) My stressed Sciadopitys verticillata too was facing on one side into the house proper, but was more than ten feet from the heating vent that I believe caused the Cryptomeria to suffer.
I moved the Sciadopitys deeper into the plant room where the temperatures are no more than 60°F on a very sunny day. It appears to be rebounding. At least the needle drop has tapered off.
The conifers are mixed in with my subtropicals (jade trees, cacti, and euphorbia) and are lightly fertilized and kept lightly watered from unpurified well water. There is an elevated humidity level in the room from the plants themselves which are causing condensation on the windows on the inside. But that is a small price to pay for this experiment and for the lives of my conifer houseplants.
Successes (and Loss) in the Indoor Conifer Room
I have in the past had Norfolk Island pines and they never made it. But my three Araucaria have been pushing new growth. They seem to be flourishing in the more temperate plant room. I do fawn over the trees and I check on them several times during the day. I write in that room, a bit bundled up to be sure, but it is my room.
I have been warned about what the spring might bring. But once it is safe for them to move out onto my eastern and southern facing decks, they will enjoy the spring and summer outside. In the meantime I had been tickled by the blue Atlas cedar that had been pushing new growth for the past two months. Needle drop had been extremely minimal on it and then disaster struck. The plant went rapidly into decline and has had to be removed from the house.
By the way, my Cedrus deodara ‘Eisregen’ and Pinus densilfora ‘Golden Ghost’ (three of them) get wrapped in burlap late every fall. They are outside. The first year in my garden the largest Golden Ghost browned and I feared it was a total loss. However, it came back more beautiful than ever.
‘Eisregen’ never suffered winter burn, was wrapped for its first winter and has made it each winter since. Once the trees exit the house and enjoy their vernal equinox and summer solstice outside, I will post an update as to their successes and, hopefully, not too many failures, or as Barbie Colvin has stated: “...to see how they get through the heat of winter."
I am in awe at the prospect of overwintering and even growing conifers as houseplants. Many thanks, Tom, for the encouragement and the advice. The experiment continues.
Thumbnail photograph by Sigmund.
This article was originally published in the Winter 2011 issue of Conifer Quarterly. Join the American Conifer Society to access our extensive library of conifer-related articles and connect to a nationwide group of plant lovers! Become a member for only $40 a year and get discounts with our growing list of participating nurseries in our Nursery Discount Program.
Auracaria heterophylla is an excellent room temperature plant all year long as long as it gets the moisture it needs. It likes spraying, the more the better. On N Island it rains almost all the time. I find that most conifers suffers winter indoors due to low humidity, particularly water on branches as in nature (they seem to be poor at transporting water from roots to needles ... ). Of course as all plants indoors during winter they prefer a growing light. I am keeping a plethora of conifers indoors, most of them at 5C, 60% humidity and only natural light. I am also keeping Cryptomeria japonica and Auracaria auracana at 24°C 40% humidity with artificial light and a lot of spraying - all my media is a mixture of planting soil and leca. The plants are surprisingly doing well, better than at 5°C / 60% humidity ... I am pretty sure it is the spraying and subsequent absorption of water by the needles is the trick (I am not spraying to increase humidity - that would be ridiculous). Note that I am spraying a lot.
how do you keep your trees from getting really gigantic? In nature all of the trees you list quickly grow to 100 feet tall.
Your advice is excellent and most welcomed. My failures have come from plants drying out. I had the temps right, but not the spraying. May I quote you for Conifer Quarterly?
I should say that my project with Araucaria araucana and Cryptomeria japonica is just starting, the Araucaria is doing excellent while the Cryptomeria is doing decently — I think the temperature is too high for it. I should add that the conifers at 5°C would do better if they had a growing light, which is why one is on its way.
Don't feel bad about the heterophylla - they (the imported plants) slowly decline in every nursery I have seen. You have to get them when they are fresh from the supplier, once they are in decline it is hard to get them back as with most conifers in my experience. I suspect the original nurseries have sprinklers or keep them at very high humidity levels (80 to 100%)
Feel free to share my thoughts.
Some are indeed very tall plants, but remember that those plants are very tall in their natural niche. Even if you plant them in a great natural spot elsewhere they often don't reach half that size and grow much slower. In a pot the cannot become trees proper, the root system is not large enough . You can increase or decrease their max size by choosing pot size.
I just remembered that I should say that A. heterophylla can survive drier climates. I had mine for about a year in around 10-15C 50%-ish humidity and it was watered irregularly. It did not decline somewhat surprisingly, I attribute this to the low temperature. It didn't grow one mm, it went into some form of stasis. So the humidity and spraying I mentioned above are for good growing conditions for saplings, adults are obviously much more tolerant. The main tip has grown about 5cm in a few months, I say main because I bought this specimen due to it having 5 stems that all split from the main stem at the second node.
I moved the Cryptomeria into the moisture tent(80%) with much better results, so much so that I also moved the A.araucanas as well. It is kind of ironic since A.heterophylla does very well with only spraying and it comes from one of the rainiest areas in the world as far as I know the other species live in less rainy habitats.
I forgot after all this writing that you should never spay any plant with tap water, no matter where you live.It is too 'hard', too many potential salt solvents(a.k.a. minerals). Rainwater is water that has evaporated and then condensated up in the skies, few other natural liquids follow that cycle and so rainwater is very 'soft'. Roots are much more tolerants of salts. I know that for some unfathomable idea some parts of the US have introduced flouride in water(toothpastes...sugar dissolves readily, it can be flushed and brushed out after consumtion, instead we introduce cytotoxic compounds in our mouths). Flouride is very toxic to anything living, including humans. Sorry about the disgression, flouride is just one of those things for me.