INTRODUCTION:  The common houseplants in the Euphorbiaceae include shrubs, herbs and cactus-like plants.  Most produce a milky sap which may be poisonous.  The flower clusters are usually subtended by colorful bracts.  In nature many euphorbs have leaves for a short time and lose them during long periods of drought.  Most also have a distinct rest period and can be damaged by watering or trying to stimulate growth when they are in rest. 
 The genus Acalypha is a semi-woody plant with bright, copper-colored leaves.  Its common name is the copper leaf.  Many cultivars have been developed and they vary in size, leaf color and leaf variegation.  Copper leaf is a popular landscape plant in warmer parts of the country but also common as a house plant. 
 Crotons are in the genus Codiaeum.  They are shrubs that have brightly colored leaves, often many colors in one leaf.  The leaves have many interesting shapes.  Variegated patterns include spots, stripes, streaks, blotches, etc.  Bright light is essential for rich color development in the leaves.  Some crotons are large and used as hedges or specimen plants in warm landscapes.  San Franciscos is another common name sometimes used for the crotons. 
 Poinsettia is in the species Euphorbia pulcherrima.  It is an excellent house plant and one that can be grown on and brought into flower year after year.  In nature most poinsettias become large shrubs.  If they are to be maintained in containers either choose a large container or practice pruning to keep the plants in bounds.  Poinsettias require short days, long nights to trigger flowering.  If protected from lights that would cause long days, short nights, most will come into color in time for Christmas.  To get color earlier they should be covered a few hours each day to shorten the length of day. 
 Other members of the genus Euphorbia are common as house plants.  Euphorbia splendens is the crown of thorns, a small, shrubby plant with heavy development of thorns.  It has clusters of small flowers which are especially interesting when they appear in the heavy thorny growth.  Crown of thorns has a distinct rest requirement and should not be watered when it is in rest.  Euphorbia grandidens is the bigtooth or staghorn euphorbia, a very distinctive plant. 
 Devil’s backbone is Pedilanthus tithymaloides.  It gets its name from the zigzag stems.  Dwarf and tall cultivars exist and there are several variations in the leaves.  This plant has succulent stems, variegated white, green and red leaves and bright red flowers.  When the flower buds appear the have the shape of a tine red bird sitting in the top of each stem.  Consequently, another common name for this plant is red bird or red bird cactus.    
General Care of Euphorbs:  


temperature: Average room temperature is good. Many plants in this family grow and flower best when it is cooler in winter, but most could not survive frost or freezing weather.
medium: A well-drained mix is best, for example, the media described for succulents above.
water: With a well-drained medium these plants can be watered as other plants would be watered, but let them dry a little between waterings.  Also recognize the rest period that often precedes the flowering period or that may follow the flowering period and water sparingly if at all during this time.
light: In nature these plants would be in bright light.  Therefore, for best growth put them in a well-lighted window, in direct sunlight if possible.
fertilization: Fertilize sparingly.  Most of these plants can easily outgrow their space.  If lower leaves turn yellow it is a good sign that they are running out of nitrogen and need more fertilizer.
pests and problems: Mites are among the most common pests of these plants, but aphids, mealy bugs, scale and white fly can also become problems.  If over watered the roots will likely rot.  If this happens, withhold water for a while and wait for the plants to develop new roots.
grooming: Remove old, discolored and disfigured leaves. Prune to keep them in bounds and make the plants denser in appearance.  Prune poinsettia back and repot in early spring if it is to be grown on to be flowered another time.
propagation: Stem cuttings is the most common means of propagation.  Most benefit from allowing the milky sap to dry in the air before being stuck in the rooting medium.

Virtual Garden's Directory of Foliage House Plants

Virtual Garden's Directory of Flowering House Plants