Growing Rare Fruit From Seed

The information here was extracted with minor revisions from an article by John M. Riley that appeared in the 1981 CRFG Yearbook (vol. 13, 1981, pp.1-47). The full article contains important additional information on mechanisms of seed germination, propagation techniques, propagation media, container mixes and seed storage. See the back issue information for price and ordering information.

Seed Treatment Methods

Hot Water
This treatment consists of soaking the seed in hot water for a period of time. One procedure is to pour boiling water over the seed, using about four volumes of water to one volume of seed. The intent is a thermal shock which rapidly diminished to room temperature. Usually this is followed by moist cold storage. Most pathogens are destroyed at about 160° F (71° C). The treatment is a little tricky for home use, since most seed are killed at 178° F (81° C).
Sulfuric Acid Treatment
The acid attacks cellulose and is often recommended as a dramatic treatment for seed coat modification. For the home gardener, handling sulfuric acid may present some hazard.
Hydrogen Peroxide
This is commonly available in a 3% solution. It may be used in full strength for about 20 minute to disinfect seed and alter the seed coat. The peroxide may then be diluted in half with water and the seed soaked for up to 24 hours.
Sodium/Calcium Hypochlorite
This material is commonly available as ordinary laundry bleach. It effectively sterilizes and disinfects when used in a 10% solution. This can be prepared by added 1/4 cup bleach to 2 cups of water. Soak the seed for 20 minutes to sterilize and rinse thoroughly afterwards.
Alcohol and Other Solvents
Many volatile solvents, including grain alcohol have been mentioned as having an effect on seed germination. Quite possibly this results from softening waxy compounds in the seed coat which are not water soluble.
Gibberellin
Gibberellic acid promotes germination in many seeds. It also helps overcome the tendency for some seedling to become dwarfed and to grow slowly after the harsh treatment used to initiate germination. Seed may be soaked with concentration of 100 to 1,000 ppm for 24 hours.
Cytokinins
Natural growth hormones stimulate the germination of many kinds of seed by acting at the molecular level on biological processes. Many synthetic cytokinins are available from tissue culture supply houses, but since they must be kept at a low temperature to prevent decomposition, they are not available in garden supply centers. Soaking for three minutes in kinetin at concentration of 100 ppm has been recommended.
Ethylene
This gas occurs naturally in plants and has a number of biological effects, including the stimulation of seed germination. One of the chemicals available to gardener to generate ethylene is ethephon. Since gibberellins, cytokinins and ethylene are three dominant components in initiating germination, it is natural that they work best when applied together.
Potassium Nitrate
Many freshly harvested dormant seeds germinate better if soaked in a 0.2% potassium nitrate solution. Seeds should be soaked for no more than 24 hours and then rinsed well.
Thiourea
This has been used to stimulate germination of some dormant seeds, particularly those that do not germinate in darkness or at high temperatures. A water solution of 0.5 to 4% is recommended. Since thiourea is somewhat inhibitory to growth, the seeds should be soaked no longer than 24 hours and then rinsed well.
Vitamins
The most common vitamin supplement for plants is vitamin B1 (thiamine). Other vitamins of the B complex are also useful. Nicotinic acid (niacin) and ascorbic acid (vitamin C) have all been recommended.
Willow Tea
A tea made from willow bark contains a substance that enhances the actions of plant hormones and appears to stimulate germination. Soaking seed in willow tea for 24 to 48 hours is suggested.

Procedures

The table that follows summarizes specific information useful for growing rare fruit from seed. Rare fruits (mostly those tried in California) are listed by their botanical names. Common names can be connected to their botanical names through the CRFG Fruit List.

Storage Life, in months, (assuming proper treatment) is listed in column two. The storage type (next column) is categorized as follows:

WTM–WARM TROPICAL MOIST
Seed should be maintained above 70° F (21° C) and not allowed to dry out before planting.
TI–TROPICAL INTERMEDIATE
Seed should be dried to about 70% of harvest weight and stored a temperature of about 40° F (4° C).
TD–TEMPERATE DRY
Seed should be dried to below 50% of harvest weight and stored at room temperature or preferably 40° F (4° C).
CM–COOL MOIST
Store seed with sufficient moisture to prevent drying out at about 40° F (4° C).

Dormancy Breaker, column four, indicates any special treatment to break dormancy. In each case the seed can profit from a 24-hour soaking before planting.

SC–SCARIFICATION
Seeds are made permeable to water by sanding, filing or nicking the seed coat.
R–SEED COAT REMOVAL
Carefully crack or remove outer seed coating.
SK–PRESOAK
Soak seed 24 hours before planting.
MC–MOIST CHILLING
After soaking 24 hours, pack the seed with moist sterile material and store for 30 to 60 days at 40° F (4° C).
ST–STRATIFY
Soak seed 24 hours and store moist for one or more seasons in the natural environment. Do not let seed dry out.
WMS–WARM MOIST STORAGE
After soaking 24 hours, store above 70° F (21° C). Plant soon.
CW–ALTERNATE COLD/MOIST TREATMENT
Soak seed for 24 hours and subject to periods of 40° F (4° C). Cycle several times if necessary.

Germination Period, column five, lists the time lapse between seedbed planting and emergence. Time required to break dormancy is not included. Times vary with cultivation and seed condition.

Hardiness (deg. F and C), column six. Values are approximate and are mostly taken from books which include the tropics, Florida and California. In a given situation, plant size, previous environment, health and chill factor can alter the response to a given temperature. There may also be significant differences in variants of the same species. The hardiness values listed are probably optimistic by about 5° F (2° C) for tropical fruit tree seedlings or young plants.

General Comments. A number following a symbol indicates the days of treatment required. A plus (+) after a number means the value may be exceeded. A temperature in parenthesis following the germination period indicates the minimum temperature (°F, °C) required for germination. The information on germination time is approximate and based largely on John Riley’s personal experience.

CHARACTERISTICS OF RARE FRUIT PROPAGATION FROM SEED

Botanical nameStorage life (mos.)Storage typeDormancy breakerGermination daysHardiness°F (°C)
Actinidia
     chinensis12+TDSC/CW14-2110 (-12)
     arguta12+TDSC/CW14-21-25 (-32)
     kolomikta12+TDSC/CW14-21-40 (-40)
Aegle
     marmelo12+TISK/WMS14-2128 (-2)
Akebia
     quinata24+TDMC14-2125 (-4)
     trifoliata24+TDMC14-2125 (-4)
Amelanchier
     ainifoli8TDSC/MC14-21-50 (-45)
     canadensis8TDSC/MC14-21-30(-35)
     denticulatum8TDSC/MC14-21-10(-23)
Anacardium
     occidental1WTMSK14-2130 (-1)
Annona
     cherimola24+TDSK14-2126 (-3)
     purpurea12+TISK14-2128 (-2)
     reticulata12+TISK14-2128 (-2)
     squamosa12+TISK14-2128 (-2)
Antidesma
     bunius12+TISK14-2126 (-3)
     dallachyanum12+TISK14-2126 (-3)
     platyphyllum12+TISK14-2128 (-2)
Arbutus
     unedo12-24TDMC3015 (-10)
Artocarpus
     communis1WTMWMS7-2135 (3)
     integrifolia1WTMWMS7-2130 (-1)
     hypargyraeus1WTMWMS7-2130 (-1)
Asimina
     triloba12+CMSC/MC30-90-25 (-32)
Averrhoa
     bilimbi6TISK14-2128 (-2)
     carambola6TISK14-2128 (-2)
Billardia
     cymosa24+TDMC14-210 (-12)
     scandens24+TDMC14-210 (-12)
Blighia
     sapida3WTMWMS7-2130 (-1)
Carica
     goudotiana24+TDSK14-3028 (-2)
     monoica24+TDSK14-3028 (-2)
     papaya24+TDSK14-3030 (-1)
     pubescens24+TDSK14-3026 (-3)
     stipulata24+TDSK14-3028 (-2)
     toronchi24+TDSK14-3028 (-2)
Carissa
     carandas12+TISK1624 (-5)
     edulis12+TISK1626 (-3)
     macrocarpa12+TISK1626 (-3)
Carya
     illinoiensis36-48TIMC30-10 (-23)
Casimiroa
     edulis6TIR/SK14-2124 (-5)
     tetrameria6TIR/SK14-2128 (-2)
Castanea
     dentata8CMMC28-10 (-23)
     pumila8CMMC28-10 (-23)
Ceratonia
     siliqua60TDSC20-3020 (-8)
Cereus
     peruvianus36TDlight3-1426 (-3)
Chrysophyllum
     cainito6WTMWMS14-2128 (-2)
Citrus
     aurantifolia12TISK14-2128 (-2)
     aurantium12TISK14-2128 (-2)
     limon12TISK14-2128 (-2)
     maxima12TISK14-2128 (-2)
     mitis12TISK14-2120 (-8)
     paradisi12TISK14-2125 (-4)
     reticulata12TISK14-2125 (-4)
     sinensis12TISK14-2125 (-4)
Clausena
     lansium12TISK14-2125 (-4)
Coccolaba
     uvifera12TDWMS14-2130 (-1)
Coffea
     arabica6CMWMS14-2128 (-2)
     liberica6CMWMS14-2128 (-2)
Cornus
     amonum24+TDCW14-210 (-18)
     mas24+TDCW14-210 (-18)
Corylus
     americana12+CMCW10-30-15 (-26)
     avellana12+CMCW10-30-15 (-26)
Crateagus
     aestivalis24+TDSC/MC30-40-15 (-26)
     pubescens24+TDSC/MC30-40-15 (-26)
Cudrania
     tricuspidata36TDSC/ST14-21-20 (-29)
Cydonia
     oblonga8CMMC14-21-15 (-26)
Cyphomandra
     betacea24TDSK14-2128 (-2)
Diospyros
     digyna6WTMSK/WMS14-2128 (-2)
     discolor6WTMSK/WMS14-2128 (-2)
     kaki12+TISC/MC14-210 (-18)
     virginiana24-36TDSC/MC14-21-10 (-23)
Dovyalis
     abyssinica24+TISK14-2125 (-4)
     caffra24+TISK14-2128 (-2)
     hebecarpa24+TISK14-2128 (-2)
Elaeagnus
     multiflora24+TISK/MC14-21-10 (-23)
     philippensis12+TISK14-2125 (-4)
     pungaens24+TISK/MC14-210 (-18)
Eriobotrya
     japonica8 daysCMMC14-2112 (-11)
Eugenia
     aggregata6TISK14-2120 (-8)
     brasilliensis6TISK14-2128 (-2)
     luschnathiana6TISK14-2128 (-2)
     uniflora6TISK14-2128 (-2)
Euphoria
     longan1WTMWMS16-3024 (-4)
Feijoa
     sellowiana24+TIMC14-2114 (-10)
Feronia
     limonia12TISK14-2128 (-2)
Ficus
     carica24+TISK14-2125 (-4)
Flacourtia
     ramonchi12+TISK14-2128 (-2)
Fortunella
     japonica12TISK14-2110 (-12)
     margarita12TISK14-2110 (-12)
Garcinia
     mangostana1-2WTMSK/WMS14-2140 (4)
     xanthochymus2-4WTMSK/WMS14-2128 (-2)
Gaultheria
     shallon12TDMC300 (-18)
Gaylussacia
     frondosa24+TDCW10-300 (-18)
     resinosa24+TDCW10-300 (-18)
Gevuina
     avellana6CMWMS14-2110 (-12)
Harpyphyllum
     caffrum24+TIR14-2126 (-3)
Hibiscus
     sabariffa36TDSK14-2128 (-2)
Hovenia
     dulcis24+TDSC/MC14-30-10 (-23)
Inga
     paterno6TISK14-2128 (-2)
Litchi
     chinensis1WTMWMS16-3028 (-2)
Macadamia
     integrifolia24TISK14-3024 (-4)
     tetraphylla24TOSK14-3024 (-4)
Malphigia
     glabra6TISK14-2128 (-2)
Mammea
     americana2-4WTMSK/WMS14-2128 (-2)
Mangiferum
     indica2WTMR/SK14-2128 (-2)
Manilkara
     zapota24TDSK15-3028 (-2)
Melicoccus
     bijugatus3TISK14-2128 (-2)
Morus
     alba24+TISC/ST14-21-20 (-29)
     nigra24+TISC/ST14-210 (-18)
     rubra24+TISC/ST14-21-10 (-13)
Muntingia
     calibura12+TISK/WMS14-2128 (-2)
Musa
     balbisiana12TISK/WMS14-2128 (-2)
Myrciaria
     cauliflora6TISK14-2124 (-4)
Myrtus
     communis24+TDMC14-2125 (-4)
Passiflora
     alata3-6TISK14-2128 (-2)
     edulis3-6TISK14-2125 (-4)
     laurifolia3-6TISK14-2125 (-4)
     ligularis3-6TISK14-2128 (-2)
     molissima3-6TISK14-2125 (-4)
     quadrangularis3-6TISK14-2132 (0)
Persea
     americana 4 WTM WMS 14-21 22-28 (-6, -2)

Pistachia
     vera2-3TIR/SK14-2110 (-12)
Pometia
     pinnata6WTMWMS14-2128 (-2)
Poncirus
     trifoliata12-24TISK14-210 (-18)
Pouteria
     campechiana6WTMWMS14-2130 (-1)
     sapota6WTMWMS14-2130 (-1)
     viride6WTMWMS14-2130 (-1)
Prunus
     salicifolia24TISK14-2120 (-7)
Psidium
     cattleianum12+TISK14-2125 (-4)
     guajava12TISK14-2128 (-2)
Punica
     granatum36TIMC14-3012 (-11)
Rhodomyrtus
     tomentosa12TISK14-2126 (-3)
Ribes
     hirtellum 48+ TD MC 30 -30 (-35
     nigrum48+TDMC30-30 (-35)
     rubrum48+TDMC30-30 (-35)
     sativum48+TDMC30-30 (-35)
     uva-crispa 48+ TD MC 30 -30 (-35)

Rollinia
     deliciosa--TISK14-2128 (-2)
Sambucus
     caerulea24+TISC/MC30-20 (-28)
     canadensis24+TISC/MC30-20 (-28)
     racemosa24+TISC/MC30-20 (-28)
Sandoricum
     koetjape36TDSK14-2126 (-3)
Shepherdia
     argentea42+TDSC/MC30-60-20 (-28)
Simmondsia
     chinensis12+TDSK5-7 (78/176; F, 26/176; C)15 (-10)
Solanum
     quitoense24TDSK14-2128 (-2)
     topiru24TDSK14-2128 (-2)
Sorbus
     aucuparia24TDMC10-30-20 (-28)
     domestica24TDMC10-30-10 (-23)
     terminalis24TDMC10-30-10 (-23)
Synsepalum
     dulcificum1WTMWMS7-2130 (-1)
Syzygium
     aromaticum2-6TISK14-2132 (0)
     cumini2-6TISK14-2128 (-2)
     jamabos2-6TISK14-2128 (-2)
     malaccense2-6TISK14-2128 (-2)
     paniculatum2-6TISK14-2128 (-2)
Tamarindus
     indica6TISK14-2128 (-2)
Theobroma
     cacao1WTMSK7-14 (80/176; F, 27/176; C)30 (-1)
Ugni
     molinae24+TISK14-2110 (-12)
Vaccinium
     angustifolium120TIMC30-20 (-28)
     ashei120TIMC30-10 (-23)
     corymbosum120TIMC30-20 (-28)
Vitis
     labrusca24+CMMC20-30-20 (-28)
     rotundifolia24+CMMC20-30-5 (-21)
     vinifera24+CMMC20-30-5 (-21)
Ziziphus
     jujuba12-24TDR/SK14-21-20 (-28)
     mauritiana12-24TDR/SK14-2120 (-7)