How can I have a stronger stem for my Flowering Maple plant (see photos)?

Abutilon
( Moonchimes Flowering Maple )

Fast growing, evergreen shrub reaching up to 6 feet. Leaves are oval, light to medium green, maple-like in appearance and up to 5 inches long. Grown for showy, pendent, bell-shaped flowers in yellow. Blooms all year long. This plant was a favorite of Victorians, growing well in bright conservatories and relocated outside in containers during warmer months. Whiteflies, spider mites, scale insects and and mealybugs may be a problem. May be grown outside year round in frost-free areas or against warm wall or protected space in marginal areas. Use in shrub border, container garden, houseplant, or as espalier.

Right now, the plant is about 3 feet high and the stock isn’t all that strong. A few photos.

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