Colors are know to have an effect the moods of those that view them, red is a busy color that projects activity and vibrancy, it promotes movement and excitement.  The use of  any color  in the garden comes down to a personal one and many factors effect the way we respond to colors. Weather, time of day, what we have or have not eaten , our current mood and the surroundings we find the colors in effect the way we respond to what we see.  Red flowers tend to dominate softer colors taking away from the beauty of the softer colors but they also can lend a sense of flowing into the more neutral tones. Reds work well in a color scheme with whites and darker blues but keep in mind that foliage texture and color will have a large effect on our perceptions of red and it's mixing with other colors. An all red garden tends to get boring after a while but mix in a few nice bright whites and deep blues and the garden takes on a life that is more enjoyable and gives the garden vital interest throughout out many days of viewing. Staring at the same old red salvia's all summer does not appeal to me. I guess that is why I like perennials, the perennial garden changes and transforms it's self over the season and red flowers can find a place in the garden from early spring to fall, even in winter red berries are pleasing to the eye, best yet contrasted with fresh clean snow on a crisp  bright sunny day.

    Light is the primary factor effecting out interpatation of colors and our responses.  In very bright locations the softer colors may appear bland and washed out but reds stand out and say "look at me". The Interaction of a bright red color and intense sunlight effects our mood  in a positive way. cheerfulness and life, invigorates our senses  and our emotional state and even   making us happy and awake.  Red in shade or on a hazy cloudy day does not have the same effect, some red flowers way even appear drab or lifeless.  Color shades change with the intensity and amount of light, many if not most red flowers have hues that change during the coarse of the day.   One view I like -  is standing in a shady area and looking out to a sunny area with some nice bright red Peonies  or daylilies.  Other factors that effect the perception of colors are backgrounds.  A fence or a building, the sea or a body or water  the color of the sky.  All these things plus many more play a part in the way colors are presented to our brain and our interptaion of them.
      The glowing warm colors of  red flowers, are I think, best complemented by dark blues.  The color that stands up best as a offset is white. Many plants that have red flowers are genetically predispsioned to produce  some white flowering forms.  Those species that have red flowers tend to have albino forms.  I find it a good complement to grow the red flowering plant and the white flowering plant of the same species next to each other as a complement. Red flowers also look good as a focal point in a sea of other colors.  A bed of yellow flowering plants with a  taller single red  plant in the middle makes a memorable picture.  Reds in the garden work well in the front of softer colors causing the eye to fix ate at first on the red and then to flow slowly along the softer shades of yellow and pink.  red in the background of a planting takes the eyes right away to the back and hides those plantings in the foreground.   The strong colors of red are more loved by younger people and those that have a lot of activities and are overly intense . But for a more peaceful garden or location - nice soft colors and a lot of green mixed in with the occasional red tucked in a corner is calmer and has a calming effect on one's senses. The hotter colors like red look there best around the house with blues and whites placed at a distance making the landscape spread out giving the perspective of distance and volume.

    Well now that that is done lets get into the plants. But first we need to call a spade a spade. Red is not just one color, we have true reds and we have red - orange and orange - red, or even red - pink or red - purple. The names for red are many and many of use have diffrent forms of  color blindness and any way not every one sees the same thing.    The list below covers all those plants that one might call red.  orange flowers are for another list and so are the pink colored flowers.

Acer capillipes - A deciduous tree up to 60' tall with a spreading shape.  Lobed leaves that turn red and orange in the fall. full sun  Zones 6-9.

Acer henryi - Deciduous tree up to 20 feet tall  with three oval leaflets that turn bright red or orange in the fall.  full sun  Zones 6-8.

Acer rubrum 'Scanlon' - "Red Maple" or "Scarlet Maple" or "Swamp Maple" .  A upright growing deciduous tree  with dark green leaves that turn bright red in the fall when grown on acid or neutral soils. small red flowers in the spring before the leaves come out.  full sun. Zones 4-9.

Acer rubrum 'Schlesingeri' - Tree with a rounded shape and dark green leaves that in early fall turn deep red.  also has red flowers in spring on naked wood.  full sun. Zones 4-9

Acer rufinerve - A deciduous tree up to 60 feet with arching branches that have striped green and white bark.  Leaves turn a brilliant red and orange in late summer.  full sun.  Zones 6-9.

Acer saccharum 'Temple's Upright' - A columnar shaped tree to 50 feet tall with red  and orange leaves in the fall. full sun . Zones 4-8.

Acer pseudoplatanus f. erythrocarpum - a string growing deciduous tree with a spreading habit and lobed dark green leaves. The fruit has bright red wings in the fall.

Aesculus x carnea 'Briotii' - "Ruby Horse Chestnut".  A deciduous tree growing up to 50 feet tall and 25 feet wide with panicles of red flowers in late spring.  foliage is a dark green and glossy. full sun and drought tolerant. zones 5-8.

Aesculus flava - "Yellow Buckeye". 40 foot tall tree with a spreading shape and glossy dark green leaves that have 5-7 oval shaped leaflets. Yellow flowers in spring and red leaves in fall. full sun. Zones 6-9

Ardisia crenata - "Coralberry" or "Spiceberry". Ever green upright growing shrub to 7 feet tall. star shaped white flowers in early summer followed with  long lasting bright red fruits. light shade, moist soils.  Zones 9-10.

Brachychiton acerifolius - "Flame Bottle Tree".  A deciduous tree that has bright scarlet flowers in late winter or spring. 65 feet tall and 45 feet wide. full sun.  zones 9-10.

Cornus alba 'Sibirica' - "Siberian Dogwood".  A deciduous upright multi branched shrub growing to 7 feet tall. Has bright red stems in the winter and spring, moist prominent of new growth. full sun. Zones 2-8.

Chaenomeles x superba 'Rowallane' - A spreading deciduous  low growing shrub to 6 feet tall.  Lots of large red flowers during spring. Full sun .  Zones 5-8.

Chaenomeles x superba 'Nicoline' - A spreading deciduous  low growing dense shrub to 6 feet tall. Many Scarlet  flowers during spring followed by yellow fruit. . Full sun .  Zones 5-8.

Euphorbia milii - "Crown-of-Thorns" A slow growing, more or less evergreen, spiny shrub, growing to 12 feet tall.  Plants have bright red bracts during flowering. full sun. Zones 9-10.

 fuchsias -------

Illex  ciliospinosa,  aquipernyi,  xaltaclerensis 'Begica',  fargesii v. brevifolia,  x altaclerensis 'Balearice',  x merserveae 'Blue Princess',  aquifolium.  These  are some of  the hollies that produce red fruits on female trees, one needs both a male and a female tree to get fruit.  Plants are evergreens  and some are tree sand others are large shrubs.  Plants respond well to pruning.  Zones 5-8

Liquidandor styraciflua - "American Sweet Gum"   a spreading to conical shaped deciduous tree with corky ridged twigs and dark green leaves that turn a brillant red or orange in the fall sometimes even purple.  Full sun and moist soils.  Zones 6-9.

Nandina domestica 'firepower' - evergreen to semi evergreen bamboo like 5 foot shrub with purplish red leaflets when young and in the fall and winter. Orange -red fruits to from white flowers. full sun moist soil.  Zones 7-10.

Nothofagus procera - conical shaped tree growing to 80 feet with dark green leaves that turn red or orange in the fall. fast growing zones 8-9.

Nyssa sinensis - "Chinese Sow Gum". A deciduous tree has long narrow leaves that are purple in the spring and dark green in summer and turn a brilliant scarlet in fall.  Full sun. Moist soil.  Zones 7-9.

Nyssa sylvatica - "Black Gum" or "Sour Gum" or "Black Tupelo". A broad based conical shaped tree up to fifty feet. Oval glossy dark to mid green leaves that turn bright red or orange or yellow in the fall. Full sun. Moist soil. Zones 5-9.

Nothofagus obliqua  - a slender elegant deciduous  tree growing to 80 feet with dark green leaves that turn red or orange in the fall. fast growing zones 8-9.

Parthenocissus tricuspidata - "Boston Ivy" or "Japanese ivy".  A vigorous growing deciduous vine up to 70 feet tall..  Woody stems have tendrils  and leaves that turn a brilliant crimson red in the fall. light shade.  Zones 5-9.

Parthenocissus tricuspidata 'Lowii' - "low's Japanese Creeper".  A vigorous growing deciduous vine up to 70 feet tall..  Woody stems have tendrils  and leaves that are deeply cut and crinkled. foliage turns a brilliant crimson red in the fall. light shade.  Zones 5-9.

Potentilla 'Red Ace' - A bushy deciduous dense shrub. Bright vermilion flowers in late spring to late summer.  light shade.  Zones 3-8.

Quercus alba - "White Oak". A out spreading tree with deciduous deeply lobed glossy dark green leaves with rounded edges. Leaves turn red to reddish purple in the fall. full sun. drought tolerant. Zones 4-9

Quercus coccinea - "Scarlet Oak".  a roundish shaped oak with deciduous  glossy leaves that turn bright red. leaves remain on the tree for many weeks. full sun. Zones 5-9

Quercus ellipsoidalis - A deciduous tree with deep lobes and sharp points that has glossy dark green leaves that turn dark purplish red and red in the fall. full sun. Zones 4-7.

Quercus palustris - "Pin Oak" or "Swamp Oak".  fast growing  tree with deciduous leaves that are deeply lobed and turn a bright  scarlet or red brown in the fall. 60 feet tall. zones 5-8.  full sun and drought tolerant.

Quercus rubra - "Red Oak". fast growing deciduous tree with spreading branch structure and large  deeply lobed leaves that turn reddish or yellowish  in the fall. 70 feet tall. zones 4-8. full sun.

Salvia fulgens - A evergreen sub shrub growing to 3 feet.  Racemes of tubular shaped scarlet flowers in late summer. full sun, drought tolerant.  Zones 9-10.

Sorbus aucuparia - "European Mountain Ash".  a 30 foot tall deciduous tree with compound leaves. a nice soft texture to the garden.  Leaves turn red or yellow in the fall and  have large clusters of red fruit that birds love. full sun. Zones 4-7.

Sorbus commixta - "Japanese Mountain Ash". a spreading tree to 65 feet with compound leaves that have 6-8 pairs of leaflets.  leaves turn deep red or orange in the fall.  White flowers in spring followed by large clusters of red fruits in the late summer. full sun.  Zones 6-8

Sorbus hupehensis "Rosea' - Another deciduous tree with a spreading shape growing to 65 feet. $-8 pairs of leaflets that are  blue-green and turn orangeade in the fall.  tree also has long lasting pinkish red fruits in late summer. full sun. Zones 6-8

Stewartia monadelpha -  a deciduous tree up to 40 feet tall. Has peeling bark and dark green leaves that turn red or orange in the fall. full sun and acid soils.  Zones 7-9.

Vitis coignetiae - "Crimson Glory Vine".  Up to 50  feet long, this vine with tendrils  has very showy  reddish leaves in the fall. Light shade.  Zones 5-9.
 
 

Achillea x 'Fanal' - Cherry red flowers have gold centers nice contrast in the blooms.  Plants grow 30" tall.
Achillea x 'Fireland' - Brick red flowers when new that fad to a creamy yellow with age.  Plants grow 36" tall
Achillea x '
Armeria maritima 'Dusseldorf Pride' - Not really red- but a lavender red. Plants flower at 6-12" tall over hummocks of grassy like leaves starting in mid spring.
Dicentra formosa 'Bountiful' - "Bleeding Heart". One of the darker shades of this plant, reddish purple flowers over fern like foilage. grow in part shade in moist rich soil.
Dryopteris erythrosora - "Japanese Sword Fern".
Epimedium x rubrum - "Barronwort".  Plants have red veined and mottled foliage in May and June. grow in a shady place, will take root compition. Rosy red flowers with milky yellow centers.  Zones 4-8.
Euphorbia amygdaloides 'Rebra'
Euphorbia griffithii 'Dixter'
Euphorbia griffithii 'Fireglow'
Fragaria x 'Lipstick' - Rose-red/ ornge flowers over strawberry type short 3-7" tall creeping plants. Full sun, use as a ground cover. Blooms on and off threw out the summer.
Helleborus - There are many of these plants that have red flowers that bloom in late winter and early spring. I do know of any common cultivars that you can get with out going way out of your way.  "Queen Of The Night" "Philip Ballard" "Atrorubens"
Imperata cylindrica 'Red Baron' - "Japanese Blood Grass"
Bergenia cordifolia 'Rotblum' - Red flowers over large bronze leaves in winter-early spring. Plants grow 10" tall.
Bergenia x 'Ballawlay'
Bergenia x schmidtii - A soft red that blooms very early.
Monarda x 'Gardenveiw Scarlet' - Fire engine red flowers on 30" tale stems,  Mildew resistant.
Monarda x 'Squaw' - A nice red, mildew resistant, growing 30" tall.
Phelypaea tournefortii - A parisite on Achillea and Tanacetum. Flowers in late June with red flowers and black throats. Zones 5-8. Not realy know in cultivation but worth a try if you can get the seeds, sow directly on the host plant.
Pulmonaria rubra - Clump forming plants that have reddish flowers early in spring. Will grow in moist soil.
Pulsatilla vulgaris 'Rubra' - A few diffrent shades of red on this spring blooming plant. flowers have yellow stamens.  Plants have fuzzy stems and leaves and grow 6-8" tall.  they need a chalky soil and do not like to have wet feet.. Zones 5-7
Sedum x 'Autumn Joy' - Plants have large flat flower heads in fall that turn from light rust red to dried blood red in late fall. flowers persist in their color into mid winter. Good easy plant for full sun or semi shade. Plants grow 15" tall.
Vinca minor 'Atropurpurea' - "Lesser Periwinkle".  Has deep purplish red flowers in spring .  Plant in shade or sun.  a spreading ground cover. Zones (4)5-8
 
 

Bald Eagle
Baltimore Oriole
Canadian Goose - Tetraploid growing 30" tall with crimson flowers that have a bright yellow throat.  Plants bloom in mid to late season.
Charles Johnston
Cherry Festival
Chicago Apache - Tetraploid with velvety scarlet flowers on 27" tall scapes blooming in mid season.
Chicago Aztec
Chicago Comanche
College Try - A diploid with red flowers that have a darker red halo. Plants grow 28" tall and bloom in Midseson.
Crimson Shadows - Tetraploid with crimson red flowers that have a purple red eye zone.  Plants grow 25" tall and bloom mid to late season.
Ed Murray
Firestorm
Fly Catcher
Grouse
Hemlock
James Marsh
Justin Miller - A diploid with red flowers that have a chartreuse throat and has a creamy edge.  Plants are 19" tall and bloom in early to mid season
Little Dandy -  A diploid growing 16" tall with dark red flowers and a green throat. Blooms in mid season.
Little Zinger - A diploid with red flowers that have a green throat.  Plants grow 20" tall and bloom early to mid season.
Lord Camden
Mallard - Tetraploid with vivid red flowers on 26" tall scapes blooming in mid season.
Mexican Maiden
Mockingbird
Mountain Laurel
Oriental Gem
Over There - A diploid that has bright red flowers that have a darker red halo.  Plants grow 28" tall and bloom early to mid season.
Painted Trillium
Pocket Change
Red Reward
Red Pinnochio - Tetraploid with crimson red flowers growing 24" tall and blooming in mid to late season.
Red Poll
Red Razzmatazz
Red Ripples
Renegade Red
Rooten Tooten Red
Ruffled Ruby - Tetraploid with rosy ruby red flowers. Plant grow 26" tall and bloom in mid season.
Scarlet Apache
Scarlet Oak
Scarlet Tanager
Screech Owl -  A tetraploid with  two tone light red flowers that have yellow edges. Plants grow 33" tall and bloom in mid season.
Siloam Cherry Chimes
Siloam Pocket Size  - A diploid growing 20" tall with rose red flowers and a rose halo.
Spider Man
Sultans Ruby
Summer Tanager
Viro
Wayside America - Tetraploid with red flowers that have a green throat.  Plants bloom mid to late season on 28" tall scapes.
Wayside Plains Indian - Tetraploid that has crimson flowers that have a green throat.  scapes grow 30" tall and flowers bloom late.
Wayside Red Regal - Tetraploid with red flowers that have green throat. Plants grow 30" tall and bloom in mid season.
Wine Bubbles - Tetraploid with round deep wine red flowers that have creamy midribs.  Plants grow 28" tall and bloom in mid season.
Wren
 
 

Best Man - Deep red double blooming in late season.
David Harum - A bomb type flower that is a clear red and makes a good cut flower. Midseson bloomer.
Edwin C. Bills - A double with large red flowers in mid season.
Harry L. Smith - semi-double deep cranberry red blooming in mid season.
Kansas -  A showy double bright red blooming early.
Karl Rosenfield - A good cut flower with double red flowers in mid season.
Lee - A cranderry red double blooming in mid season.
Lora Dexheimer - Watermelon red blooming in midseason with double flowers.
Philippe Riviore - A late blooming double with crimson flowers.
Richard Carvel - A red double that makes a good cut flower blooming early in the season.