Forsythia are a stunning bonsai that are at their best this time of year due to the bright yellow flowers that signify the start of Spring. The flowers form before the leaves so you get the full advantage of being able to see the flowers without them being hidden underneath a full canopy of leaves. Forsythia are from the Oleaceae family, and the majority are hardy, easy to grow and are considered a shrub as opposed to a tree due to their shape and form. They have spring flowers that are golden yellow and bell shaped which form along the bare branches. There are several large flowered hybrids too so pick your variety well as the smaller flowering forms are better for bonsai. They are a deciduous shrub with a toothed leaf shape which varies in shape depending on the species.
In terms of pruning, thin out and cut back old flowering shoots to within a few centimetres of the old wood immediately after flowering and this will prevent elongated branch development and also promote flowering for next year.
Examples of hybrids include:-
- Forsythia ‘Arnold Dwarf’ (Ground cover form, insignificant yellow to green flowers)
- Forsythia ‘Beatrix Farrand’ (Large deep canary yellow flowers 2.5cm across)
- Forsythia X intermedia (Vigorous hybrid with range of cultivars and F. intermedia ‘Minigold’ is a good dwarf form while ‘Spectabilis’ is a large form with a profusion of flowers)
- Forsythia ‘Robusta’ (Strong growing shrub of hybrid origin)
- Forsythia ‘Tremonia’ (Compact small shrub with pale yellow flowers, broad petals and serrated at apex)
- Forsythia ‘Volunteer’ (Vigorous shrub with dark coloured shoots and clusters of yellow flowers)
- Forsythia Boucle d’Or (Slow growing dwarf less than 50cm tall, bright yellow flowers)
- Forsythia Maree d’Or (Good ground cover form, lemon yellow flowers and profuse to bloom with reddish autumn colour)
- Forsythia Melee d’Or (Upright habit, leaves toothed, red autumn colour)
Forsythia Species and Cultivars
F. europaea (pale yellow flowers)
- F. europaea ‘Fiesta’ (Lime yellow and cream coloured leaves)
F. giraldiana (Large loose shrub with graceful habit and 1st to flower of this species in late February)
- F. giraldiana ‘Golden Nugget’ (Large flowers up to 5cm across)
- F. giraldiana “Golden Times’ (Shy flowering and can scorch in hot sun, yellow leaves with creamy white margin)
F. ovata (Early flowering in March with ovate leaves)
- F. ovata ‘Tetragold’ (A Colchicine-induced, tetraploidal form raised in Holland. Dense habit with large flowers)
F. suspensa (Rambling shrub grows well with support and later flowering in late March to April with trifoliate leaves)
- f. atrocaulis (Young stems almost black-purple, large lemon flowers)
- var. fortunei (Largest most vigorous form)
- ‘Nymans’ (Large shrub with bronze-purple branches and large primrose flowers)
- Var. sieboldii (Slender pendulant form, good in shade and good as wall shrub)
F. viridissima (Erect and square stemmed shrub with lanceolate leaves and flowers in April)
- F. viridissima ‘Bronxensis’ (Dense compact form with masses of twiggy branches)
Here are a few examples of Forsythia as bonsai in various seasons to show the form and structure with and without leaves and flowers.
The flowers then are borne on mature wood but not ageing wood and can be used as ornamental shrubs, wall plants, hedges, trained shrubs and as bonsai. They are very hardy and adaptable but need to be pruned regulary to maintain a good shape and form as they can become bushy and ungainly in form. They tend to be very vigorous and can get congested in the crown and if this occurs the flowering performance declines so thin out old shoots after flowering.
Repot after flowering or prior to the start of winter subject to weather conditions and they grow prolific roots so re-pot every two years once an established root plate has been developed that is like a fibrous pad as they do have the tendency to become pot bound with circling roots if left for too long. They like to be well drained but a fertile soil.
If you are developing a Forsythia as a bonsai from a young plant you may need to sacrifice the flowering initially while you develop the structure and form. They can be grown from softwood cuttings in Summer or Hardwood cuttings in Autumn or Winter and are fairly easy to buy from garden centres if you want to start one off from scratch. They lend themselves to all sizes of bonsai in informal upright, slanting, semi-cascade, twin trunk, clump and multiple trunk styles.
They grow well being positioned in full sun but will tolerate shady positions, and require watering throughout the growing season but less during dormancy. Feed based on the trees development and throughout the growing season especially a fertiliser high in potassium to aid with flower production.
Sources of information:-
- Bricknell, C & Joyce, D (1996) Royal Horticultural Society (RFS) Pruning and Training A Fully Illustrated Plant by Plant Manual (Dorling Kindersley)
- Hillier, J & Coombes, A (2002) The Hillier Manual of Trees and Shrubs (David & Charles)
- The Royal Horticultural Society Plant Guides – Shrubs and Climbers (1996) (Dorling Kindersley)
- Tomlinson, H (1990) The Complete Book of Bonsai (Dorling Kindersley)