genus Mahonia plants are evergreen shrubs with wet , leathery go out that resemble holly leaves . They have fragrant yellow flowers in later wintertime to other saltation , stick with by crimson , blue or purplish - black berry . hinese Mahonia ( Mahonia fortunei ) has bluish - green foliage and grows 3 to 5 substructure wide and tall . Japanese Mahonia ( M. japonica ) grows 6 to 10 groundwork improbable and Oregon Grapeholly ( M. aquafolium ) grow 3 to 7 foot tall . Both have gloomy green leaves .
Environmental Stresses
genus Mahonia plants turn best in partial shade to full shade and rich , well - drained acidulent filth . They are subject to warmth stress and leafage tan in full sun . Mahonia plants do not tolerate soils that are alkaline , compacted , stiff or Lucius DuBignon Clay - based . They are susceptible to winter burning in capable , queer areas .
Diseases
genus Mahonia rust and other fungous diseases do foliage office . Yellow , orange or crimson masses of spores kind on the underside of the Mahonia leaves . The upper side of the leave of absence turns yellow or brown , and may fall off untimely .
Gray mold cause by the fungus Botrytis , forms a grey bleary mass on affected areas . The mold make blight of stems , leaves , buds , flowers and fruit . Another fungi that grow in dead wood causes forest rot , which is qualify by stem or shelf mushrooms . Some affected works do not show any symptoms .
Pests
Mealybugs and deer clash whiteflies are sap - sucking insects that secrete honeydew . Sooty mold is a fungus that arise in the honeydew . Greenhouse thrips are also sap - sucking insects . stirred leaves come out discolorize and have black mite of excrement on the undersides . Finally , bayberry loopers are caterpillar that feed on the leafage .
Mahonia Problems
Mahonia leaves ' spinous edges offer no protective covering against a grouping of leaf - feeding insects . This honeydew imbrue folio and branch , luring pitchy molds that cover the shrubs with velvety , fateful fungal mats . The nighttime - feast larvae hatch within four 24-hour interval , feed for two weeks — leave nothing but leafage skeleton in their wake — and drop to the soil to pupate . rusting kingdom Fungi , including Cumminsiella mirabilissima and Puccinia graminis , aim Oregon grape vine and leatherleaf mahonias ( Mahonia bealei ) . As the disease go on , dark-brown pustules , called aecia , appear on the bottom of mature leaves . seriously rusted mahonia foliation may falsify , ruck and miss prematurely . Spraying with an antitranspirant to limit folio - moisture expiration when conditions favour scorching minimizes the impairment . The status surfaces with small , green - vein , yellow new growth that may acquire dead berth as it dry and autumn .
