North American Fruit Explorers mailing list at ibiblio

[Christopher McGuire <cmmcguire@students.wisc.edu>]

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Hello,

I am very interested in growing and breeding the maypop for its edible fruit
(Passiflora incarnata).  The maypop is a perennial vine native to the
southeastern U.S. and is related to the more tropical passionfruit.  It bears 
a
truly delicious fruit.  

I have spoken to Lon Rombaugh about starting a NAFEX interest group for the
maypop.  I am writing this email to learn whether others of you are interested
in the maypop and to hear what your experiences have been.  Below I have
included a brief description of maypops gleaned from my own experience, my
reading, and my conversations with other growers.  I hope to hear from some of
you.

Regards,
Chris

******************************************************************************

History and current interest

Archaeological evidence and early historical accounts indicate that American
Indians frequently consumed wild and / or cultivated maypop fruits. 
European-Americans have also gathered maypops from the wild and occasionally
cultivated the plants.  Currently, a number of individuals are growing and
breeding maypops, and the fruits are sometimes marketed locally in the
southeastern U.S.  In addition to being a fruit crop, maypops are also grown
for their large, sweet-scented, ornamental flowers.  The plants also contain
chemicals with a sedative, tranquilizing effect, and there is a small
commercial industry growing plants for medicinal use.

Range

The maypop’s wild range is bordered by eastern Texas in the southwest, Kansas
in the northwest, Delaware in the northeast, and central Florida in the
southeast.  In cultivation, it sometimes overwinters in much colder areas,
including Michigan and New York State.  In some northern areas, however, 
plants
may overwinter but fail to ripen fruit because of the short, cool growing
season. 

Propagation

Maypops are easily propagated by root or rhizome division and stem cuttings. 
Seeds retain viability over winter in a refrigerator.  Seed germination can be
slow and uneven, but is hastened greatly by high heat.

Growth, flowering, and fruiting

Maypop plants are herbaceous and only the belowground parts overwinter. 
Seedlings and overwintering plants emerge when the soil is thoroughly warmed 
in
the spring.  Vines are extremely vigorous and sometimes highly branched 
trellising them can be a challenge.  The plants spread great distances
belowground as well, sending up new shoots yards away from the original 
plant. 


Plants will flower and fruit in their first year’s growth from seed as well as
in subsequent years.  The vines are indeterminate and flowers are produced at
many nodes on a stem, and the flowering season can therefore last several
months.  Flowers are attractive to many insects, but are usually best
pollinated by carpenter bees or large bumble bees.  Plants are usually
(always?) self-incompatible.  

Fruits mature about 8 weeks after the flowers open.  The fruits fall off the
plant when ripe and are usually harvested off the ground.  Ripe fruits are
oblong or round, several inches long, green or yellow, and often very
aromatic.  The rind is thin, and the interior of the fruit consists of many
large seeds each surrounded by a juicy aril.  The rind and seeds are not very
edible.  The juice in the arils, however, is very aromatic, sweet or slightly
tart, and delicious.  It can be drunk fresh, or made into jelly, wine, or
various other desserts.  

Pests

Many insects and viruses attack maypops, but generally their importance as 
crop
pests is unknown.  Blister beetles and fritillary butterfly larvae are
sometimes problems in cultivated plantings.

Weediness

Because of their rapid growth and underground spreading, maypops can be
invasive.  They are serious agricultural weeds in peanut fields of the
southeastern U.S.

Breeding and hybridization

Maypops are well suited for breeding work, because they have a short life 
cycle
and their large flowers are easily manipulated for controlled pollinations.  
In
addition, their large geographic range suggests that there is much genetic
variation that can be used in breeding.  However, very little maypop breeding
has been done.  Some attempts have been made to hybridize maypops with their
close relative Passiflora edulis, the tropical and sub-tropical passionfruit. 
The passionfruit is an important commercial fruit, and breeders have hoped to
combine its desirable commercial traits with the greater cold-hardiness of the
maypop.  Hybrids are frequently sterile, although the sterility can be partly
overcome by creating polyploid hybrids.  Several ornamental tetraploid hybrid
cultivars have been named, but to my knowledge none are widely grown for their
fruit.

Future work

There is a great deal of work to be done on growing, breeding, and utilizing
maypops.  I am currently collecting maypop germplasm to evaluate genetic
variation in fruit traits and eventually to select or breed varieties with
desirable fruit.  Mr. Patrick Worley of California is engaged in a similar
project.  A number of other individuals are growing and breeding maypops.