The Sequoiadendron giganteum is only unique in its care requirements to other more common bonsai tree species in the water requirements. With the giant sequoia, constantly moist soil is preferred. Most species prefer a wet then dry, then wet then dry regimen. The sequoia prefers consistent moisture. An occasional soaking is good but an occasional drying is bad for the sequoias. Think moist not muddy.
Sequoias are ravenous feeders and will grow accordingly. It is a mistake to attempt to miniaturize the giant sequoia by withholding nourishment. Miniaturization must be done with bonsai techniques such as selective branch pruning. Sequoias are self pruning in the roots. It is only necessary to root prune when you are shifting the tree to a smaller pot. Feed your shallow potted sequoia with regularity during the growing season. Cut back some during extremes in temperatures. We recommend Giant Sequoia Bonsai Plant Food available from our website at www.giant-sequoia.com. Giant Sequoia Potting Soil is also available in our online store.
The giant sequoia is an outside tree. Direct sun for at least a portion of the day during the growing season will be necessary for vitality. Be careful when the temperatures get high. The sequoias will suck all of the moisture out of the container in a short time on a hot day. If the summer becomes blistering hot move the sequoias to a shadier spot so they don’t dry out. High temperatures (100° F+) are not harmful to the foliage but will cause the roots to wither. Try to keep the roots cool in the summer (90° F or less). It’s ok to move the sequoias into the house for a period of time if the outside is too hot. Just remember to move them back out for sun and air occasionally when the temperatures are more moderate. During the winters in cold climates the danger is not cold it is, once again, dehydration. The trees can dehydrate even though the temperatures are below freezing. The best thing to do is to construct a well-drained cold frame and place the shallow potted trees into it. Water the trees well before the winter freeze. Where possible you can bury the trees in snow. They will remain in perfect condition, just as they do in nature, buried in snow for the entire winter. That will insulate them from the drying cold winds and preserve them perfectly. If there is no snow or cold frame possibility you may need to take them into a garage or cellar occasionally to protect them from drying winter wind. It’s not a good idea to keep them long in a heated house in the wintertime. The dormant trees are not able to pick up moisture rapidly enough to replace moisture loss to a heated room. A dormant giant sequoia bonsai will die if kept in a heated house for too long in winter.
Remember to work towards keeping the tree in its natural proportions so that you don’t wind up with a tree that is not representative of the species. The diameter of the branching spread should be around 6 times the diameter of the trunk at its base upon completion. The tree height should be 7 to 9 times the trunk diameter and the branching should start about halfway up the trunk. The giant sequoia can live to be around 3000 years old in nature. To achieve perfection in a giant sequoia bonsai can take many years. Each year the trees take on more of the attributes of an aged tree. The flared trunk base and cinnamon colored bark can take years to form.