Pine trees are coniferous evergreens that are native to the Northern Hemisphere. They are medium to fast growing trees that thrive in sunny, well-drained locations with acidic soils. Pine trees prefer warmer temperatures, though some species are cold hardy. The process of keeping a pine tree indoors involves raising the tree outside of its natural environment while maintaining a healthy but unnatural size. These indoor bonsai pines, like their natural sized counterparts, require a balanced level of nutrients, water and care to produce proportionate sized foliage and cones.
Keep the pine tree in a well-drained container with nutrient-rich soil. Choose a container with several drainage holes. Ensure that the container is just slightly larger than the plant's root system to control the growth of the tree. Plant the pine tree with nutrient rich soil that has been mixed with an equal amount of organic compost.
Position the pine tree in a warm location that receives at least eight hours of sunlight each day. Select a position that is away from direct temperature variations, such as a heating vent or air conditioner.
Irrigate the pine tree often but avoid overwatering. Water the pine tree thoroughly until the water flows from the container's drainage system. Use a watering can filled with tepid water and irrigate with a slow, steady flow. Check the soil's moisture levels before watering. Place your finger approximately two inches deep into the soil near the root system. Water the pine tree when the soil feels dry. Avoid long periods of drought to avoid stressing the pine tree.
Feed the pine bonsai with a well-balanced, slow release fertilizer. Apply the fertilizer in the early spring, just before the onset of the growing season. Select a fertilizer with lower levels of nitrogen, such as a 10-10-10 or 20-20-20 combination. Use a 0-10-10 combination for very small pine trees.
Hard prune the pine tree only once each year. Complete this pruning process during its dormancy periods in the winter months. Use sharp, sterile scissors or shears to prune the branches and foliage. Make angular cuts to branches leaving a small stub at the trunk, as opposed to a flush cut. Prune the pine tree from the top to the bottom, most vigorous to least vigorous. Complete the pruning conservatively, reducing the pine tree slowly over several seasons.