Conifers as houseplants is a tricky subject. Most conifers, with the exception of a small minority, don’t make good houseplants, but you can keep certain conifer trees inside if you provide the right conditions. Some coniferous houseplants can be grown indoors year-round, and some will only tolerate short periods before they need to go back outdoors.
Indoor Conifer Plants
By far, the easiest of the coniferous houseplants to grow indoors is the Norfolk Island pine or Araucaria heterophylla. These plants have a minimum temperature requirement of about 45 degrees F. (7 C.). Place your Norfolk Island Pine in a window that has plenty of bright, indirect light at a minimum, but some direct sun indoors is very beneficial.
Be sure to provide excellent drainage and avoid excessively dry or excessively wet conditions; otherwise, the lower branches will drop off. Plants will do best in humidity of 50 percent or above. Place the plant away from any heating vents, as this can damage the plant and also encourage spider mites. Fertilize throughout the growing season and avoid fertilizing during the winter months when growth has slowed or stopped.
There are some conifer trees that can be kept only temporarily indoors. If you are buying a live Christmas tree for the holidays, for instance, know that it is possible to keep it indoors, but certain needs have to be met and it can only stay indoors temporarily. You must keep the root ball moist for it to survive. Warmer indoor temperatures pose a challenge because they may break the tree’s dormancy and tender growth will be susceptible to cold damage once you place it back outdoors.
If you have a live Christmas tree that you plan on planting outdoors afterward, regardless of what type you have, you should keep it indoors for no longer than two weeks. This will help the tree not break dormancy and have the new growth exposed to killing winter temperatures.
Dwarf Alberta spruce are also commonly sold around the holidays as smaller, potted living Christmas trees. Give your spruce full sun indoors and never allow the soil to go completely dry. You may wish to move your potted plant outdoors once the temperatures warm up.
Another more commonly grown indoor conifer plant includes Japanese juniper bonsai. Give your juniper about half a day of direct sun, but avoid hot, midday sun. Avoid placing your bonsai near any heating vent and be careful with watering. Only allow the top half inch (1 cm.) of the soil to dry out before watering. This plant can be grown year-round indoors but will benefit from being outdoors in the warmer months.
Many people don’t consider growing conifers as houseplants and with good reason! Most of them do not make good houseplants. Norfolk Island pine is the best choice to grow indoors year-round, as well as Japanese spruce bonsai. Most others that typically grow in colder climates can only survive short periods indoors.