The following are some plants that are recommended for japanese gardens.  Note that not all are necessarily hardy, but do lend them selves to the form and function requried for a japanese garden.

Evergreen Trees

• Abies nordmanniana
• Cedrus atlantica
• Cedrus deodara (deodar cedar)
• Chamaecyparis obtusa (Hinoki cypress) Chamaecyparis pisifera (Sawara cypress) Cryptomeria, various kinds
• Juniperus, various kinds
• Picea abies
• Picea pungens
• Pinus patula
• Pinus pinea
• Pinus radiata
• Pittosporum tobira (Japanese pittosporum) Podocarpus, various kinds

Evergreen Shrubs

• Abelia grandiflora (glossy abelia) Ardisia crispa
• Aucuba japonica (gold-dust tree) Bamboos, various kinds
• Camellia japonica
• Camellia sasanqua
• Daphne odora
• Euonymus japonicus
• Fatsia japonica (syn. Aralia sieboldii) Hebe buxifolia
• Ilex cornuta (Chinese holly) Juniperus, various kinds
• Laurus nobilis (sweet bay)
• Ligustrum lucidum (glossy privet)
• Ligustrum ovalifolium (privet)
• Mahonia bealii
• Nandina domestica (heavenly bamboo) Osmanthus, various kinds
• Pieris japonica
• Raphiolepis umbellata (Yeddo hawthorn) Rhododendron (azalea), various kinds

Deciduous Trees

• Acer ginnala (Amur maple)
• Acer palmatum (Japanese maple)
• Acer palmatum dissectum (Threadleaf Japanese maple)
• Cercidiphyllum japonicum (Katsura tree) Cornus kousa (Japanese dogwood) Ginkgo biloba
• Koelreuteria paniculata (golden rain tree) Magnolia, various kinds
• Malus, various kinds (crab-apple) Prunus, various kinds (Japanese cherry) Punica granatum (pomegranate)
• Sophora japonica (Japanese pagoda tree) Zelkova serrata

Deciduous Shrubs

• Berberis thunbergii (Japanese barberry) Cercis chinensis
• Chaenomeles japonica (Japanese quince) Cotoneaster horizontalis wilsonii Enkianthus japonica
• Hydrangea macrophylla hortensia Paeonia suffruticosa (tree peony) Pyracantha, various kinds (firethorn) Rhododendron (azalea), various kinds

Vines

• Akebia quinata (five-leaf akebia)
• Clematis montana rubens
• Parthenocissus tricuspidata (Boston ivy) Wisteria, various kinds

Ground Covers and Perennials

• Hedera, various kinds (ivies) Iris kaempferi (Japanese iris)
• Primula japonica (Japanese primrose)Abies nordmanniana
• Cedrus atlantica
• Cedrus deodara (deodar cedar)
• Chamaecyparis obtusa (Hinoki cypress) Chamaecyparis pisifera (Sawara cypress) Cryptomeria, various kinds
• Juniperus, various kinds
• Picea abies
• Picea pungens
• Pinus patula
• Pinus pinea
• Pinus radiata
• Pittosporum tobira (Japanese pittosporum) Podocarpus,
  various kinds