While visiting home garden centers, and even some grocery stores in the holiday season, one might espy a small, symmetrical conifer being offered as an indoor Christmas tree, often already sparsely decorated, ready to go on the dining table or another prominent location in the home. These are usually Cook Pines (Araucaria columnaris) or Norfolk Island Pines (Araucaria heterophylla) and are sold by the thousands every November and December as living Christmas trees. Most are destined to die or be thrown out soon after the holidays, either due to ignorance or apathy. But with the proper care they can be kept healthy and made to last for many subsequent holiday seasons, almost becoming part of the family and a holiday tradition.
(Editor's Note: This article was originally published on December 17, 2007. We hope you enjoy it as we count down to Christmas.)
Though called a pine, this conifer is in another family, the Araucariaceae, with a few other notable species such as Araucaria bidwillii, the Bunya Bunya tree of Australia, or Araucaria araucana, the Monkey Puzzle Tree of South America. The Norfolk Island Pine or Star Pine (Araucaria heterophylla), originates from a tiny island off the east coast of Australia. The Cook Pine, (Araucaria columnaris) is a New Caledonian native. The climate on these islands is very controlled and it never freezes or gets very hot there. And though these are both touted as unique Christmas trees, they could never handle being snowed upon as they are both very cold sensitive species, suffering visibly as temperatures even begin to drop below freezing outdoors.
Cook and Norfolk Pines are very popular mostly due to their being very easy to grow (therefore very cheap) from both seed and cuttings, and they are ornamentally symmetrical (particularly the Norfolk Pines), making them look very different from your average conifer. The trees form nearly perfect pyramid silhouettes (more so the Norfolk Pines rather than the Cook Pines) with branches coming off the trunk usually in four directions and very regularly spaced from bottom to top. In a tropical climate trees can grow up to 200 feet tall (60+ meters), but rarely do that in less than ideal climates. I live in Southern California and trees over 50 feet tall are rare- either get blown over, suffer a freeze now and then, or seem to develop some other malady.
Araucaraia heterophylla adults
Araucaria columnaris adults
Cook Pines are usually the ones encountered in cultivation, though they are usually misidentified as Norfolk Island Pines. They look nearly identical as seedlings so for their differences count for little as indoor Christmas Trees. Adult trees differ quite a bit, however, with the Cook Pines often growing at a bit of an angle, having much more closely spaced branches than the other, and not all the foliage points straight up toward the sky as it does with Araucaria heterophylla.
A typical outdoor tree in southern California, about 30 feet tall; the look of a branch in an arid climate
Other than their temperature needs, these trees are pretty adaptable outdoors. They can survive along salty beaches, tolerate a wide variety of soil pHs, and will survive in shady areas as well as in full sun. But they do need consistent moisture in the soil as well as temps that do not get too hot or cold. Both species makes lousy desert trees as the low humidity combined with the high heat forces them to lose most of their needles, then die. Drought is another difficult situation for these conifers to overcome, and again, leaf loss and death are soon to follow. The good thing is these are survivors, and apparently dead trees will often grow back from the roots or stumps if water is sufficient and temperatures are warm. The roots are somewhat weak, allowing them to blow over easily in high winds. But this weak root system is an advantage when grown in containers as it means repotting these trees does not need to be done very often.
Look of Cook Pines in a tropical climate (Hawaii here)- much larger! Detail of fuller, thicker branches in the tropical climate
As indoor plants, these perform much better than just about any other conifer in cultivation. They grow slowly, particularly when confined to a container, need average watering only, tolerate periods of low light (though not indefinitely) and rarely need to be fertilized.
Indoor tree for sale with other holiday indoor plants on left; and two plants living their lives as indoor plants (middle photo by Johnny MTB and right photo by PDB_Evert)
Temperature range is ideally between 50F and 70F. Though they prefer daily direct sunlight, do not place them in a situation where the sun will heat the plant up too much (temps into the 80s and 90s will cause needle drop). As much bright light as possible, otherwise, is best. Sometimes, if kept in front of a window that has direct sunlight, they will begin to grow lopsided, so rotating the plant every few weeks is a good idea. Taking these trees outdoors when its warm for additional lighting, as well as humidity, is a very good idea (think about putting your tree in a large container on rollers so it can be moved easily).
outdoor palm burned by freeze down around 27F
Watering should be done as with most house plants- when the top of the soil is dry-ish about 1 inch down. But do not let this tree dry out or it will die. Try to use distilled or rain water, or set out water for a period to rid it of the excess salts. Or take it outdoors 3 or 4 times a year and heavily rinse the soil with repeated watering to leach out the accumulated salts in the soil. If using a catch basin under the pot, be sure these trees are not sitting in water for any length of time or root rot will occur.
These plants ready for holiday sale are being watered daily and look lush
Fertilization should only be done during the warmer months, even indoors. Never fertilize around the holiday season (unless that’s the warm time of the year)- can be toxic to the comatose root system in winter.
Lack of humidity is the single toughest factor to overcome when keeping these as house plants. Cook and Norfolk Island Pines live normally in a climate with 50% or greater humidity and dry air situations will cause leaf loss. Frequent misting is essential to keeping these trees looking lush indoors. A humidifier would be even better, but may not be good for the rest of the house (mold on the walls, books etc.). Reportedly this is a tree that appreciates cool misting, not warm misting, so, if using a humidifier, it is best not to use one that warms up the mist to a steam.
This plant is ready for sale for indoor use, but is being kept outdoors in the mean time to keep up the humidity
Regular pruning should be kept to dead branch removal and no more. Pruning off any branch tips will cause asymmetrical growth of the tree- a pruned branch tip will not grow anymore, so only dead material should be removed. However, every few years, should the tree be getting too tall, there will often be a secondary trunk/stem that can be encouraged to replace the main one but cutting the main one off near its base. To speed up the growth of the secondary trunk, moving the tree outdoors in a semi-shady area will help it to recover faster. This may seem drastic, but in this way one can keep the same small tree as a house plant for dozens of years.
Here is a tree for sale during the holidays showing 3 stems. For a more typical Christmas tree look, one might trim 1 or 2 of these away for now, but let it regrow so by the time the main trunk is too tall, it can be cut back and the new stem will be ready to replace it.
Repotting should be done only when needed, since the roots are delicate, and damage to them will set the tree back a long time. Water the tree well before repotting in an effort to keep the rootball intact. Then move to a new, clean pot, perferably the same size or only a bit larger. Overpotted trees will be prone to rot. And too large a pot will eventually allow a rootball to form that will be too large to deal with the next time repotting needs to be done. These trees do not become rootbound that quickly unless grown outdoors much of the year and bright light and given lots of water and fertilizer. These larger trees will be healthy, but may become unmanagable as indoor plants.
This is my tree and it's about time to repot. Learn from my experience and do not plant these in clay pots- the soil dries out far too fast. This tree has two trunks. I eventually trimmed one back, it is growing back already
At Christmastime, if decorated, still try to keep it watered well, even if that means moving aside decorations to do so. Also, lights on the tree will decrease humidity further, necessitating even more frequent misting than done already. Norfolk Island Pines do not have strong branches, particularly as small trees, so be sure not to put too many ornaments on them or branch damage will occur. And remove them as soon as possible to avoid permanent drooping of the branches.
5-gallon plant for sale showing small, fairly weak branches- these can support small, light ornaments and very tiny lights, but anything heavier will pull down the branches
As many people are safety conscious these days, this is one of the safer house plants available. The needles are soft and relatively harmless. There are not toxic principles to any part of this tree other than possibly its cones (never will be a problem with indoor plants as they won’t cone) and a mild dermatitis from the saps on particularly sensitive animal species (though not a human dermatologic concern that I know of). Multiple web sites including ones sponsored by the University of California Davis, Oklahoma State University, Home and Gardens Education Center and the Children’s Safety Organization of Canada all list this is a safe and non-toxic house plant.
The soft fronds of this plant are among the least sharp and stiff of all potential Christmas trees
If one simply takes a little care and time with their indoor Christmas tree, one can develop a long relationship with these harmless little house plants, using them as holiday decorations year after year. And if one lives in a zone 9b or above, one can eventually even plant these trees outdoors and enjoy them as big trees for many more years to come.
About Geoff Stein
Veterinarian and Exotic Plant Lover... and obsessive, compulsive collector of all oddball tropical and desert plants.