the following is a detailed description of the new ‘ zentmyer ’ variety , which was taken from an approximately nine - year - old mature tree , with the exception as a rootstock for a specific scion when reference is made to root rot resistance and salinity tolerance . the tree is located in an experimental orchard in irvine , calif . and is grafted on a persea americana seedling used as a rootstock . the royal horticultural society ( r . h . s .) color chart is used herein for the color description of the rind , seed , bark , leaf , flower , flesh color and other interest of the ‘ zentmyer ’ avocado tree . growth habit .— vigorous , upright and spreading when compared to the rootstock ‘ thomas ’. vigor .— below are data on the vigor of ‘ hass ’ grafted onto the rootstock of ‘ zentmyer ’, as determined by trunk diameter measurements from trees planted in an orchard with phytophthora cinnamomi in escondido calif . size .— medium . the typical canopy size of a three year old top - worked ‘ thomas ’ is 388 cu . ft . by comparison the canopy size of a three year old top - worked ‘ zentmyer ’ is 397 cu . ft . the tree is 610 - 915 cm in height when fully grown at the orchard site in irvine , calif . color .— the color of the one year old branch is green ( rhs 144d ). smoothness .— the bark of a one year old branch is smooth . lenticels .— the lenticels of a one year old branch are conspicuous . color .— grayed - green ( rhs 197a and rhs 197d ). texture of bark .— corky . intensity of anthocyanin coloration .— weak . anthocyanin coloration .— grayed - orange ( rhs 166a ). color .— grayed - orange ( rhs 166a ). conspicuousness of lenticels .— medium . color of lenticels .— purple ( rhs 185b ). size of lenticels .— 1 . 0 mm long . concentration of lenticels .— +/− 26 lenticels per square cm . color of upper side .— grayed - orange ( rhs 174a ). glossiness of upper side .— medium . color of lower surface .— grayed - orange ( rhs 177a ). length .— 15 . 0 cm . width .— 6 . 0 cm . ratio length / width .— 2 . 5 . shape .— lanceolate . color of upper side .— green ( rhs 137a ). color of lower side .— green ( rhs 138b ). glossiness of upper side .— medium . prominence of veins on lower side .— prominent and in relief . color of veins .— yellow - green ( rhs 151a ). general shape and cross - section .— concave . reflexing of apex .— absent . color of petiole .— yellow - green ( rhs 144a ). anise aroma .— absent . margin .— undulation of margin is absent or very weak , and the leaf margin is entire . leaf apex shape .— acuminate . leaf base shape .— lanceolate . length of leaf petiole .— approximately 3 . 0 cm . diameter of leaf petiole .— approximately 3 . 5 mm . leaf arrangement .— upright . bud size .— approximately 5 mm in length and approximately 4 mm in diameter . bud shape .— ovoid . bud color .— yellow - green ( rhs 153a ). opening .— belongs to group “ a ”, male opening ( i . e . with mature stamens ) occurs in the afternoon , the flower closes over night , and female opening ( i . e . with mature pistil ) occurs the next morning ; the flower &# 39 ; s opening cycle lasts 20 - 24 hours . petals .— borne in two whorls of three perianth lobes . the petals possess entire margins and petal coloration is near yellow - green ( rhs n144b ). both the upper and lower petal surfaces are near yellow - green ( rhs n144b ). stamen .— there are commonly nine fertile stamens with each having two basal nectar glands that are greyed - oranged ( rhs 174a ) in color and three staminodia . the anthers are tetrathecal . pistil .— the single pistil with a slender style and small stigmatic surface has one carpel with one ovule . the ovary is superior . sepals .— there are 6 sepals which are approximately 7 mm in length and approximately 4 mm in width , and the color of both sepal surfaces is yellow - green ( rhs 151a ). pedicel .— commonly approximately 7 mm in length and approximately 1 . 9 mm in diameter . the coloration is near yellow - green ( rhs n144a ). peduncles .— approximately 2 . 0 cm in length and approximately 5 . 0 mm in diameter . the coloration is yellow - green ( rhs 151a ). number of flowers on inflorescence .— approximately 170 - 200 flowers per inflorescence . fragrance .— absent . bloom .— bloom period at riverside , calif . experiment station varies with cultural conditions . on average ‘ zentmyer ’ has been found to bloom from 1st of february through 20th of march . length .— 9 . 5 cm . width .— 5 . 5 cm . ratio length / width .— 1 . 7 . weight .— 146 . 1 grams . shape .— obovate , with an apex and base diameter of approximately 3 . 5 cm and a center diameter of approximately 5 . 5 cm . color of skin ( when ripe ).— yellow - green ( rhs 144a ) with some patches of purple ( rhs n79 ). texture of skin .— smooth . presence of longitudinal ridges .— absent . thickness of skin .— thin . adherence of skin to flesh .— strong . main color of flesh .— yellow - green ( rhs 154c ). color of intensely colored area of flesh next to skin .— green ( rhs 140a ). width of intensely colored area next to skin .— 3 . 0 mm . conspicuousness of fibers in flesh .— inconspicuous . length .— 5 . 6 cm . width .— 3 . 4 cm . weight .— 20 . 8 grams . shape ( in longitudinal section ).— elliptical . shape ( in cross section ).— circular . color of seed coat ( fresh ).— grayed - orange ( rhs 166b ). cotyledon color .— orange - white ( rhs 159b ). time of harvesting .— ‘ zentmyer ’ fruit ripen in september ( in riverside calif .). resistance to pests .— strong resistance to phytophthora cinnamomi . tolerance to salinity .— sensitive to salinity . market use .— the fruit of ‘ zentmyer ’ are not intended for market use , but rather the variety is used as a rootstock onto which commercial varieties , such as ‘ hass ’ are grafted .
a new and distinct variety of persea americana tree having a high tolerance under most conditions to phytophthora cinnamomi when used as a rootstock . however , it is severely damaged by salt and is not recommended for locations where salt is a problem . this variety does not yield well under non - root rot conditions in comparison to similar varieties , making it desirable for replant situations where root rot infested soils are a problem .