Posted on: 16 Feb 2021 by Greenwood Bonsai Studio
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The Tree of a thousand stars, so called because of its numerous star shaped flowers, is a very popular species with beginners as it is one of the few indoor varieties that flowers. Their small leaves, the fact they often have naturally exposed twisty roots and their flaky bark combine well to make even young trees look convincingly old. The shoots and roots give off an unpleasant smell when trimmed. This is not an overpowering smell and is unnoticeable most of the time.
Key Points/ Defining features
– Small leaves
– Small white flowers
– Flaky bark even when young
– Often have exposed roots
Serissas are grown as indoors trees because they need to be kept fairly warm. A minimum of 15 degrees is advised, anything below 10 degrees and the tree will start to suffer. They should never get frosted, as they WILL die. Place close to a window to get plenty of light during the day, but ensure that they don’t get too cold at nighttime in winter.
In summer water daily. Serissas do have very thin leaves so if they do get too dry the leaves can go yellow and drop off very quickly. Therefore it is more important than with a lot of other species that you keep them well watered.
During winter months check your tree daily to make sure the soil surface is not dry. Watering routines can vary depending on the temperature of your house.
Feed May to September with low nitrogen feed. We would recommend a slow release granular feed such as phosmag. Sprinkle sparingly on the soil surface and replenish once completely dissolved. Alternatively you can use a liquid feed such as Maxicrop Bonsai Fertiliser.
New shoots on Serissa tend to grow fairly upright with pairs of leaves alternating along the branch. Keep pruning back to a pair of leaves. You will then get one, or sometimes two, new shoots growing in approximately the same direction. As new growth appears expect to see yellowing and dropping of old leaves. During summer and autumn you may get flowers growing on the tips of new shoots.
During the summer Serissas grow very quickly, to retain compact foliage masses you need to be almost constantly pinching out of pruning the new shoots. As they flower on the tips of new shoots many people incorrectly allow the new growth to get longer waiting to see the flowers. This practise leads to very leggy sparse trees. We prioritise keeping a good shape and pinch them back to prevent them from getting too sparse, subsequently we end up with trees flowering on shorter shoots later in the year. Constant pinching out also helps minimise weaker shoots dying off. Once shoots have gone woody but are still fairly thin they can be repositioned with training wire. They are relatively brittle and inflexible though so take care.
Avoid using garden centre “bonsai” compost that will generally not drain well enough.
Many newly imported bonsai from other retailers are often in inappropriate compost and should be re-potted at the next opportunity.
Use free draining bonsai soil e.g. our premixed compost or if you use Japanese soils they can be planted in neat Akadama.
For young Serissas re-pot every 1-2 years
For older trees just as needed.
Serissas should ideally be re-potted during winter to early spring, as they are least actively growing during those months.
You can tell a bonsai needs re-potting when the root system seems very dense and the roots have started to grow in a circle around the inside of the pot. You can see this by gently lifting the tree out of its pot. This should only be done during the re-potting season.
Other things to watch out for during the growing season are if your tree is drying out faster than usual or if its growth is less vigorous than usual.
Serissas do have old leaves go yellow and drop naturally as they grow. Many new owners worry whether they may be dropping more than they should. If that includes you, try watering more frequently and trimming more often.