Satsuki azalea

In early summer, a satsuki azalea bonsai is a sea of flowers: hundreds of blooms in white, pink, red or purple, sometimes several colours on one tree. Botanically it is an azalea from Japan (Rhododendron indicum and cultivars bred from it). It takes pruning very well and is not as hard as its reputation. To be honest, though, it is more demanding than a typical beginner tree: it needs acidic soil, soft water and the right timing for pruning. Get those three right and you are well on your way.

Position: outdoors, sunny, a little shade in midsummer

The satsuki is evergreen and belongs outdoors. Indoors it gets too little light and barely flowers.

• Spring and autumn: plenty of sun, which builds strong buds.
• Midsummer: protection from the hot midday sun, for example morning sun and partial shade from noon.
• While flowering: keep it out of rain and harsh sun. Wet flowers quickly turn mushy and spotty.

Winter: light frost yes, hard frost no

A healthy satsuki can handle light frost. In a pot, though, the fine roots freeze quickly. From about −5 °C (23 °F), give it shelter, for example in a cold, bright room, a cold frame or a frost-free garage with a window. Not a warm living room: it needs its cool rest.

Soil: it has to be acidic

Azaleas need acidic, lime-free soil. Normal bonsai soil or potting compost won't do. The classic choice is kanuma, a soft, yellowish volcanic soil from Japan. It holds water well, still lets air reach the roots, and is slightly acidic. You can buy kanuma from bonsai suppliers.

The roots are very fine and dense, a bit like cotton wool. So never press the soil down hard.

Watering: evenly moist, with soft water

This is where most mistakes happen.

• The soil should always be slightly moist: never fully dry, but never standing in water either.
• Use rainwater or filtered water. Hard tap water contains lime. Over time it makes the soil less acidic, and the leaves turn yellow.
• If the root ball does dry out completely, stand the pot in a bucket of water for a few minutes until no more air bubbles rise.

More on this in watering bonsai.

Feeding

During the growing season, feed with azalea or rhododendron fertiliser, following the pack. Pause or use half the dose while it flowers. After flowering, feed normally again, because in summer the tree sets the buds for next year.

Caring for the flowers

• Pick off faded flowers, including the small green knob in the middle. Otherwise it turns into seeds, which costs the tree energy.
• On weak trees you can remove some of the buds early. Fewer flowers mean more energy for growth.

Pruning: right after flowering

This is the most important satsuki rule: prune straight after flowering, around June. In summer the tree already forms next year's flower buds. If you prune later, you cut off tomorrow's flowers.

• Satsuki tolerate even hard pruning and will bud again afterwards.
• They grow more strongly low down than at the top. So cut the lower branches back a little harder than the upper ones.
• Many new shoots often appear at each tip. Keep two at most and remove the rest.
• Unwanted shoots, for example straight out of the trunk, can be removed at any time.

You'll find suitable scissors in bonsai tools for beginners.

Wiring and repotting

• Wiring: best right after pruning in early summer. The wood of older branches is brittle and snaps easily, so bend gently.
• Repotting: every two to three years, ideally after flowering, into kanuma. Gently loosen the matted roots and trim only a little.

If the leaves still turn yellow, the bonsai doctor can help with yellow leaves. In dry summer air, also watch out for spider mites.

In Japan

Its Japanese name is satsuki (皐月). That is the name of the fifth month in the old Japanese lunar calendar, which falls roughly in our June. So the name says: this azalea flowers later than the others, after the big spring bloom, in May and June.

Satsuki have been bred in Japan for centuries. A book from around 1692 already described well over a hundred varieties. Today there are thousands, and one tree can carry flowers in several colours and patterns. No two years look the same, and that is a big part of their charm.

The soil has a Japanese home too: kanuma (鹿沼土, kanuma-tsuchi) comes from the area around the city of Kanuma in Tochigi Prefecture. The city is regarded as Japan's biggest satsuki growing area, and the satsuki is its official city flower. Every year from late May to early June, the Kanuma Satsuki Festival takes place, where enthusiasts from all over Japan show their finest satsuki bonsai in full bloom.

Toxic to pets

Yes. Azaleas are toxic to cats and dogs. They contain grayanotoxins, which can cause vomiting, diarrhoea, weakness and, in the worst case, heart problems. Place your satsuki where pets cannot chew on it, and if in doubt, see a vet right away.