Christmas is only days away, and no, I haven't finished my shopping yet. But I do have my tree decorated, sitting on my table in my studio apartment. Every year, one of my friends sends me a hand-knit mitten in a Christmas card, and every year, I add that to the other beautiful mittens I use to decorate for the holidays. I have a smattering of decorations with various stories, as well, but my collection is definitely not enough to adorn a full-size Christmas tree! But, being The Indoor Garden(er), I thought: “Why get a cut Christmas tree... when I can grow my own year-round?”
I have had this Norfolk Island Pine, Araucaria heterophylla, for a little more than a year—I got it last year to be my Christmas tree. (I also bought an Italian Stone Pine, Pinus pinea, but, well, it died immediately.) I didn't know much about the plant until I brought it home, and I now understand fully why NIP is such a common alternative to cutting down an entire tree just for a single holiday.
If you have been to any garden centre in the past month or so, they were probably selling cut trees and even potted “living Christmas trees,” mostly various types of spruce, cypress, fir, and pine. Most of those potted living Christmas trees will die, I'd wager (just as my Italian Stone Pine did)—the buyer has to gently introduce the dormant tree to the household environment, take care not to keep it warm once it's there, and shove it back outside as fast as possible so it doesn't start thinking it's time to grow. If the tree “wakes up” and thinks it's a good time to start growing again, it will be sorely disappointed when it can't get enough light indoors, or the new growth will die after being put back out in the cold. (Ignoring people who live in year-round planting zones, in which some of these trees might die because of summer heat, of course.) FigTree previously posted a nice piece on how to prepare for, select, and care for a living Christmas tree that will be later planted outside.
Those of us without outdoor space to acclimate a tree and eventually plant it have to find other alternatives if we would like to have a living Christmas tree. Norfolk Island Pine (which is not a pine [trees in the genus Pinus]) is native to (you guessed it!) Norfolk Island, a tiny island in the Pacific Ocean near Australia. Having adapted to life on the coast, the plant is salt-tolerant, which is nice for people who want to grow a tree but are on municipal water systems, which use salts to ensure drinking water quality. Other such holiday trees may or may not be tolerant—many pine and spruce are sensitive to salt damage, but there are those that can handle it, as well.
Norfolk Island is a subtropical region—that means it's pretty hot year-round, but it also doesn't vary much throughout the year. So, Norfolk Island Pine is well-suited to being grown indoors year-round, because a comfortable human temperature is perfect for the tree. (It is also grown outdoors year-round in parts of California, Texas, and Florida, among other places.) Norfolk Island is very humid, and that's where some issues with Norfolk Island Pine may arise—not many households have greenhouse-like humidity, which NIP would like. When NIP isn't in his little sauna, his lower branches and needles start drying out and dropping off, a problem that is more pronounced in winter as the humidity decreases because of household heating. A pebble tray of water might help, or a humidifier, or the indoor gardener can just learn to be okay with the bottom fourth of the tree being more naked than it would be in nature.
I do decorate the tree for the holidays, but I don't use lights. The usual incandescent light bulbs may cause heat damage and drying, but LEDs might be okay for this plant. Be careful not to overdecorate—a Norfolk Island Pine may be top-heavy, and if the soil starts getting a little dry, it could tip over. Also, if a branch breaks off because of a heavy ornament (or any other reason), it won't grow back, so says the Internets. I haven't trimmed the tree at all in the year I've had it, except to remove dried-out branches, so I have no personal experience with its inability to regrow.
Outdoors, a Norfolk Island Pine can grow 50 to 100 feet tall, or even more. Indoors, it will likely take decades for a newly purchased foot-tall NIP to get tall enough to even hit the ceiling. The tree should be kept in a good light situation, but it can survive in a bit of shade. It can grow under lights, as well, but it might grow faster in a shop-light setup and outgrow the space pretty quickly! If in a window, it can be rotated to keep even growth. Overwatering is slightly less of an issue than underwatering—ensure that your NIP is watered well and frequently, but also don't let it sit rotting in a tray of water. Lower leaves and branches drying out is a sign of underwatering; yellowing leaves may be a sign of overwatering.
A bit of attention and a couple decorations make this year's holiday one I can enjoy all year with my little NIP!