A General Bonsai Care Guide
Simply Put there are two main types of trees. Deciduous and Evergreen. Deciduous trees loose their leaves during the fall and evergreen keep their foliage all year round. You do get some species that are semi evergreen meaning they loose some leaves during the fall / winter. Usually they loose more leaves the colder it gets. Outdoor bonsai need to be placed outside all year round. They need the cold of winter to become dormant and have a rest period before spring. An outdoor bonsai placed inside will eventually die! Some species may require a little protection during the coldest months (January to April) These tend to be species with fleshy roots like Trident Maple. An unheated porch, greenhouse, garage are ok but not essential. If you don't have access to any of these, find a nice sheltered spot in the garden, an area with less wind and rain will do just as good. You can wrap the pot in something to insulate it a little if needed. We have used bubble wrap in the past but other things can be used. This can be removed once spring arrives and the last frosts are over. Be sure not to over protect an outdoor bonsai tree as this can be the same as bringing it inside causing the tree to wake up from dormancy early (Not good) Most outdoor bonsai trees sold in the U.K can withstand a degree of frost, how much depends on the species.
You should note that bonsai trees require much less water during the winter months. If your tree is sitting in wet soggy soil all of the time it can stress your bonsai and loss of vigour can result. You should remember that the drier the tree is kept during the winter months, the more cold / frost your tree will withstand. You should obviously never let the pot fully dry out. This leads us on to the next topic, watering.
When and how often should you water? The answer is simple. WHEN IT NEEDS IT. Here are a few things that can affect the watering needs of your bonsai trees. The position your bonsai is placed i.e full sun / shade, the temperature, the wind (warm or cold) and the soil medium your tree is planted in. You should never water your bonsai on a schedule because there are many factors to think about when watering. Instead of watering to a schedule you should make a schedule for checking if your bonsai needs water. We check our trees 2 or 3 times a day during the hottest months. We understand this is not always practical for people in full time work so during the growing season we recommend checking your trees in the morning (before work) and checking them again when you return. Water as and when needed. Generally most bonsai like to dry out a little between watering. There are exceptions, again look up the species you are working with for more detailed information on its watering needs. If you plan to be away from home for more than a day during the growing season it might make sense to move your trees into a shaded location until you return. Remember Trees placed in full sun during the hottest months can dry out very quick, especially trees planted into very small pots. You should make sure the pot never fully dries out. To test if your tree needs water you can use your finger to feel if it needs water. Another method is to stick a wooden chopstick into the soil then remove it and feel it. If its on the dry side you should water, if its still quite wet check again later and water once its dried a little. Oxygen / air flow around the roots is vital for bonsai trees to thrive and grow the fine root system needed to support the foliage. This is why sitting in soggy, wet, airless soil will eventually cause the decline in health and possibly death of your bonsai. When watering its good to think of it as filling the pot with water, then allowing the pot to fill with fresh oxygen as it dries. This formula will insure regular fresh water & oxygen around the roots (a good thing) All this isn't to say watering is easy. It can be very difficult to master and is often the last thing to be taught to students in Japan. The tips above and simple common sense should get you off onto the right path.
Probably one the most important thing's for successful bonsai cultivation is a good quality free draining soil that's open enough to allow the roots to breathe. A good quality soil is a must for the long term health of your bonsai tree. Garden centre / supermarket brought bonsai are often planted into a poor airless compacted media causing poor health, loss of vigour and eventually death. Airflow around the roots is vital for bonsai trees to thrive. Normal potting soil won't allow the roots to breath enough. A good quality gritty free draining mix is what you need! How free draining depends on the species you are working with. A good water retentive but free draining mix also gives you more control over the watering needs of your bonsai generally drying out easier than normal potting soil / compost between watering. Free draining soil insures the tree is not sitting in wet soggy soil permanently. As mentioned above most bonsai species like to dry out a little between watering.
Please Be Aware - So called bonsai soils found in most garden centres in similar packaging to most generic composts & soils is nothing like the soil we stock. These so called bonsai soils often have absolutely no free draining qualities meaning the soil breaks down and compact very fast. They also stay too wet which will eventually cause poor health and loss of vigour.
Feeding / Fertilizing
Feeding is also very important to maintain your bonsai over a long period of time. How you feed depends on what stage you're at with or what you're planning to achieve with your bonsai / material. Needless to say you don't want to go feeding a 'nearly finished' / 'fully ramified' bonsai like crazy or you're sure to ruin the hard work that's already been put in. A bonsai in development that requires lots of growth can be fed well. There are many feeding programs that can be used. You should note if you are using a heavy feeding program to promote lots of growth you should probably water more often to reduce salt build up from the feed and reduce the risk of root burn, feeding heavy should be coupled with heavier watering too, not to mention a very free draining open soil mix. There are two main types of feed / fertiliser available. 1 Slow release organic feeds, these generally come in pellet or cake form. 2 liquid feeds. Some people say that slow release feed gives you more control and reduces the risks of burning your fine root system (This can happen if liquid feeds are not diluted correctly and salt builds up) Generally you should feed your trees during the growing season (March to September ish) Some evergreens may benefit from a light application of feed during the winter months. In Japan some people like to feed white pines during the fall and early winter to strength the next seasons buds / candles. Feeding White Pines well during the spring & summer can produce long needles and distort branches (not desirable for a nearly finished tree) Again this isn't a problem if you have a tree that needs lots of growth or if you want to promote thickening of branches. Smaller foliage / needles shouldn't be forced though. You should never under water or under feed to try and achieve leaf / needle reduction. A well ramified tree will have smaller leaves / foliage. Another way of insuring the kind of growth you want is to make sure you're using a suitable pot, container for your needs. It's no use using a tiny bonsai pot if you want to promote lots of heavy new growth. a smaller pot will only slow down the amount of growth. Needless to say ugly, large and unsightly training pots / containers are needed for trees in development. The extra room in the pot will encourage the roots to grow well and in turn will encourage the foliage mass to grow vigorously. It's always tempting for the newcomer to stick an unfinished / unramified tree into a lovely little bonsai pot but this will only slow your progress.
Please Note : You should NEVER feed a sickly or stressed bonsai tree. If you do you run the risk of killing it. If you're tree isn't doing very well or if you notice any problems stop feeding immediately, find out the cause and wait until normal growth resumes before starting a new feeding plan.
Also Note : Healthy bonsai trees are less susceptible to health problems and attacks from bugs.
Repotting is a very important part of keeping bonsai. As your tree grows so do the roots. If you don't repot your bonsai it will eventually become pot bound and the health of the tree will slowly deteriorate and lack of vigour or even death can result. This isn't to say that some species don't prefer to be a little pot bound but there are limits. All trees need repotting at some stage. Check what species you're working with for more detailed information on its repotting needs. Root pruning and a fresh pot of soil will insure your tree stays in peak health. Generally you should repot in early spring just as the tree is waking up from dormancy. Repotting also gives you a chance to have a look at and inspect the root system to see if there are any problems. Only repot if the tree needs to be repotted, don't do it for the sake of it. When buying a new tree we recommend keeping it a season before jumping in and repotting unless it's completely necessary. Get to know and understand the tree and its needs first. See how it grows and learn its watering and feeding needs. Obviously if a tree is in poor health or is very very pot bound repotting is sometimes the only way forward. In these cases repotting should be done at the nearest possible opportunity.
Where should you place your bonsai tree? All outdoor bonsai trees need to be exposed to natural light, some more than others. Evergreens like Pines and Junipers need plenty of sun during the growing season so a very sunny spot will do these species well. More delicate species such as Japanese Maples can be more tender and are more susceptible to leaf damage during the hottest months, therefore some species should be placed into light shade during the hottest part of the day. Remember wind can also dry out the foliage and pot very quickly if you're not careful. This is another reason to check the watering needs as often as possible especially during the hottest months. Evergreens should be exposed to plenty sun light even during the winter months as they do still photosynthesis. You should note if the pot / soil is frozen the roots won't be able to take up as much water as normal and on very sunny / windy winter days the foliage can dry out very quickly and the roots won't be able to replace lost moisture. Care should be given to prevent this happening and move into a sheltered spot when needed. Deciduous bonsai trees do not need sun light once the leaves have fallen. Once new growth appears in the spring normal light requirements will be resumed. It is important to leave enough space between your trees to allow enough air and light circulate around them. Fresh air around the foliage is very important. Obviously in very strong winds your bonsai should be moved into a sheltered location to prevent the drying of the foliage or the tree being blown over causing even more damage to the tree or pot. If your trees are placed against a wall or fence make sure you rotate the pot so the tree receives even amounts of sun light.