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(pronounced ‘bone sigh’) is the practice of growing trees in pots. It combines both horticultural and artistic skills. A bonsai is intended to be a miniature representation of a full-grown, mature tree. Shape, harmony, proportion and scale are all carefully balanced to achieve this representation. The translation of the Japanese word ‘bonsai’ is literally ‘tree in a pot.’ There is good evidence that many cultures – Egyptian, Indian, Chinese, and Japanese – began practicing bonsai long ago, but the Japanese are credited with refining the art form. Virtually every country in the world has practitioners of this ancient art. Many public gardens and arboretums have bonsai displays, and most major cities have a local bonsai club. Contrary to what many think, bonsai is not a specific tree species. Bonsai can be created from many varieties of trees, shrubs and vines.
- A bonsai will grow best if it experiences the same or similar environmental conditions as it would in its native environment. This means that almost all bonsai must be grown outdoors.
- A few varieties of tropical plants can be grown as indoor bonsai, but even these will do best if grown outside during the warm season. Bonsai need the daily temperature variations, such as the intensity of the sun and seasonal variations in temperature to remain strong and vigorous.
- Bonsai can be brought indoors for display for a day or two, but this should be kept to a minimum.
A Quick Intro to Bonsai Care
Watering is the single most important factor in keeping your tree alive. More bonsai are lost due to improper watering than from all other causes combined. Conditions such as humidity, soil moisture retention, weather, and pot size all play a key factor. You should check to see if your bonsai needs water by gently probing you finger slightly below the soil surface. Do not water if the soil is still moist. Bonsai are grown in coarse and granular potting mix that allows for water to freely run through it. When bonsai are watered, most of the water will run out of the drainage holes, and only a small amount is retained in the pot. During the active growing period, watering is usually carried out once every day or two, but this will often vary. Water your bonsai with a watering can or with an attachment to your garden hose that delivers a gentle spray. Water until water runs from the bottom of the pot. This is best carried out in the morning, so the tree and soil are fully hydrated during the hottest part of the day.
Sunlight is critical for a tree’s good health. Sufficient light is also essential to maintain the inner growth of your bonsai. Without this, your bonsai will become leggy and sparse of foliage. For most conifers – spruce, pine, juniper, etc. – full sun is best. For many broadleaf, deciduous trees, full morning sun and partial afternoon sun is best. In general, trees with thick coarse leaves will tolerate more sun than those with thin, delicate leaves.
Fertilizer is important for your tree’s health, vigor, and its ability to withstand stress. Your tree should normally be fertilized during the active growing season – spring to fall. You may either use a time release or water-soluble fertilizer. A water-soluble fertilizer is usually applied every 2 to 4 weeks during the growing season, in a half-strength solution. Miracle-Gro or Miracid are commonly used, but check label directions for your type of tree. For temperate trees, it’s often beneficial to apply a 0-10-10 ratio during late summer and fall. This eliminates nitrogen, but provides a sufficient amount of phosphorus and potassium for trunk, root and future spring growth. Don’t feed after repotting (wait for 3-4 weeks) or if the tree is in a weak condition. Always pre-moisten the plant soil first.
A bonsai must be periodically repotted to maintain health. Trimming the roots is necessary to keep the root system in balance with the top growth. It also prevents the tree from becoming pot bound and stimulates new growth. This process is best done in spring, just as the plant is awaking from dormancy. Most require repotting every two to four years. In general, older trees require less frequent repotting and conifers require repotting less often than broadleaf deciduous trees. Do not fertilize for 3-4 weeks after repotting and do not let the roots go dry while repotting. Water well when finished.
Many insects will not harm your bonsai. In fact, some are beneficial and will prey on insects that will harm your bonsai. Your tree can be treated with commonly found insecticides and fungicides according to directions on the package. Insects such as aphids, spider mites, scale, and root aphids are a common problem corrected by sprays, soapy rinse, or a systemic. An infestation may also be treated non-chemically with water by using a pressure sprayer.
Trimming and pruning are the means by which a bonsai is kept miniature. This involves the systematic removal of vigorous growth in the spring. Lesser pruning is done throughout the growing season. It is essential to equalize the vigor in different portions of the tree. The ‘strong’ areas – usually the apex (top of the tree) and ends of the branches – are pruned more than ‘weak’ areas of the tree – the inner and lower branches. A technique called ‘Defoliating’ refers to the removal of leaves in order to force a second set of growth in the same season. This results in increased ramification (which is basically when a main branch splits and splits again until there is a system of smaller and smaller branches), a reduction in leaf size and internode length, and intensified autumn color. Be sure to only utilize this technique when the tree is healthy and vigorous. It can be detrimental otherwise.
Tropical and sub-tropical trees can be grown as indoor bonsai. As mentioned previously, a few hobbyists grow these indoors all year long with supplemental lighting, but even these will do best if grown outdoors during the warm season. Tropical and sub-tropical trees cannot typically tolerate temperatures below 40 – 50 degrees F. Give your bonsai as much light as possible when indoors. Inside light should be filtered sunlight from an east, south, or west window. It may be best to supplement with grow lights set on a timer for approximately 12 hours a day. Most homes have relatively low humidity during the winter; therefore it best to either mist the foliage or use a humidity tray to increase the humidity levels.
A dormant period is required for all temperate trees; otherwise the tree will eventually die when not given adequate rest. The type of winter protection needed will vary with the type of tree and severity of winter conditions in your area. In northern climates, winter protection from freeze-drying winds is necessary. Trees can typically be kept in an unheated garage, shed, breezeway, or cold frame. They should not be subjected to repeat cycles of freeze-thaw. Check the root system for moisture and water as necessary while in winter storage. Unless the root ball is frozen, they will periodically need water.