May Zone 7/8
Azalea - after flowering, Bamboo, Boxwood, Buttonwood, Camellia, Cedar, Citrus, Cotoneaster, Crape Myrtle, Cryptomeria, Gardenia - as new buds appear,  
Hemlock, Juniper, Mountain Laurel - after flowers wither and new leaf buds appear, Pine - black/red, Pyracantha, Podacarpus, Sasanqua, Spruce, Tropicals, Willow, Yew.
Azalea - after flowering, Bald Cypress, Boxwood, Buttonwood, Cedar, Camellia, Cherry - 2/3 after flowering, Cotoneaster, Crabapple - after flowering, Cryptomeria, Elm, Gardenia, Hawthorn - after flowering season is over, Mountain Laurel, Persimmon, Pomegranate, Rhododendron, Sasanqua, Tropicals.

Trim
 
New Growth: Apple - trim after new shoots lengthen to 2-3 nodes leaving 1-2 nodes, Azalea - after flowering pinch/trim new growth until end of June, Bald  
Cypress, Beech - trim soft growth leaving 2 leaves, Birch - trim after soft growth elongates to 5-7 nodes leaving 1-2 nodes, Bamboo - trim close to the ground, Camellia - trim tips after leaves have hardened, Cedar - trim back new soft shoots continually, Citrus, Chamaecyparis - Hinoki - trim off  extending tips and clean out interior, Cotoneaster - trim all new growth leaving 2 pairs of leaves, Crabapple - trim new shoots, Crape Myrtle - trim hard after initial growth produces flowers on smaller branches, Cryptomeria - trim off tips of primary and secondary shoots continually, Cypress - trim new soft extended  
growth continuously, Elm - trim all new growth leaving 2 leaves, Fig (Ficus), Gardenia - trim shoots after they have lengthened to 3-5 nodes leaving 1 or 2 nodes, Gingko - pinch/trim new soft growth leaving 2 leaves, Hemlock, Hawthorn - cut terminals, Holly - all, Honey Locust - trim elongated shoots to 1 or 2 nodes, Hornbeam - trim new growth leaving 2 leaves, Juniper - trim off tips of primary and secondary shoots continually, Maples - all - pinch/trim soft new growth on all twigs, leaving 2-3 sets of leaves, Mountain Laurel - trim after new shoots harden leaving 2-3 leaves, Oak, Pines - Cork bark/red/white, Podacarpus -trim back soft shoots continually, Pomegranate - as new shoots lengthen trim to leave 1 or 2 nodes - after secondary buds lengthen pinch back growth through June, Redbud - trim tips after leaves harden, Sasanqua, Spruce, Sweetgum, Tropicals, Willow, Wisteria, Yew - pinch/trim soft shoots continually, Zelkova - trim new soft growth leaving 2 leaves, Willow, Yew - trim out new growth anytime during the growing season.

Leaf Prune: 
 
Make certain your trees are healthy and fertilize them at least 2 weeks before leaf pruning. Apple, Elm, Maple - all, Zelkova.
Apricot, Bald Cypress, Beech - as twigs harden - remove in 3 months, Boxwood, Camellia - as soon as shoots are woody, Cherry Crabapple, Cryptomeria,  
Cotoneaster, Elaeagnus, Elm, Fig (ficus), Gardenia, Hackberry, Holly - all - new growth only - old wood too brittle, Mountain Laurel - after shoots harden, Pear, Persimmon - when leaves harden - removes wires in autumn, Plum, Podacarpus, Pomegranate, Privet, Pyracantha, Quince - Japanese, Redbud - after shoots begin to harden, Sasanqua - as soon as shoots are woody, Tamarix, Tropicals, Wisteria.
Apple, Apricot, Bald Cypress, Bamboo, Beech, Boxwood, Buttonwood, Camellia, Cedar, Citrus, Chamaecyparis - Hinoki, Cotoneaster, Crabapple, Crape Myrtle, Cryptomeria, Elm, Fig (ficus), Gardenia, Gingko, Hawthorn, Hemlock, Holly - deciduous, Hornbeam, Maples, Nandina, Oak, Pear, Persimmon, Pine -  
red/white, Plum, Podacarpus, Quince, Rhododendron, Sasanqua, Tropicals, Willow, Wisteria, Yew, Zelkova.
A very active month for bonsai enthusiasts. Bonsai can be set up safely on display benches or shelves outdoors. As the days get warmer,, growth will increase. Water young, rapid growing trees frequently, however, water older trees sparingly to keep foliage in scale with the size of the bonsai. This is particularly true if you plan on showing your trees this month and in June. If the trees are in training, they should be fertilized at least twice during this month except for conifers. If the trees have been pruned to shape, fertilize only once to maintain health without rapid, lush growth. Please see section "Fertilize" above. Re-potting and first-time potting continues this month. More attention should be paid to pinching and trimming this month to prevent long internodes on trees such as maples, elms, beech, hornbeam and sweetgum. Rotate tender leafed trees (as above) between shade and sun to prevent sun scorch. Check your wiring often during the growing season (through July and even into August). Don't let the wire cut into the bark of your trees. It could cause permanent scars on your tender-bark trees such as azaleas, elms and maples. Insects will be more active this month. Be aware of these pests and use the appropriate insecticides when necessary. For safety and health reasons, follow manufacturer's label instructions explicitly. Don't take chances with the "more is better" reasoning. Junipers and cypress should be pinched heavily to promote dense growth.