Storage and Germination of Nuts of Several Species of Juglans

W. C. Muenscher and Babette I. Brown

Cornell University, Ithaca, N. Y.

While working on the general problem of the possible toxic effect of the roots of species of Walnut (Juglans) upon other plants we have had occasion to germinate the nuts to produce seedlings for experimental use.[1] The storage treatment employed previous to planting the nuts provided a successful method of supplying viable nuts. The simple treatment used, a modification of that suggested by Barton,(2) is briefly described and the results that may be obtained are indicated in a report of some germination data from the plantings of 1943.

The nuts were harvested after they had fallen from the trees and were stored in a cool place as soon as possible thereafter until the time when the husks were removed. Those harvested at Ithaca were put in cold storage at once; those harvested in California or Texas were delayed a few weeks during shipment. The husked nuts were stratified between layers of moist peat 2 cm. thick in two-or five-gallon crocks. The uppermost layer of nuts was covered with peat to a depth of about 10 cm. The nuts were placed in a cold room at 1 to 3° C. in late autumn and left until they were planted, between April 15 and June 2. Nearly all species used germinated well after about five to six months of cold storage.

Table 1 shows the results obtained from treated nuts of ten species of Juglans when they were planted in the open field, in soil in the greenhouse or in moist sphagnum in the greenhouse. While some variation in germination is observed, most of the species gave a good germination under all treatments. The field planted seeds were somewhat slower in appearing above the soil surface than those planted in the greenhouse. This delay may have been caused by the cold rainy weather soon after planting. The firmness of the soil, a clay loam, may also have retarded the emergence of the seedlings.

The germination percentages are based upon lots of 100 nuts except in a few species in which only 50 nuts were used. Differences in the percentage of germination obtained from various plantings of the same species are slight in most species. Even the larger differences in germination obtained in a few species cannot be considered significant but probably indicate variations in the quality of the original lots used.

Summary

Walnuts husked soon after harvest, before they are completely air-dried, and stored in moist peat at 1 to 3° C. for five to six months have their dormancy broken and remain viable for at least three months thereafter. This treatment is effective for all ten species tested. It is probably effective for all species of Juglans. This method of handling the nuts has the advantage over outdoor stratifying or autumn planting which often result in much damage or loss of nuts from the activities of rodents.

Table 1. Germination of nuts of Juglans spp. after stratifying in peat over winter, at 1-3°C.

Per cent germination

KindSourceDate entered in storagePlanted in soil in greenhouse April 15Planted in field April 24Planted in sphagnum June 2

nigra(Cornell) Ithaca, N. Y.Oct. 1 70 80 68

nigra(Cayuga) Ithaca, N. Y.Oct. 1 100 — 80

cinerea—Ithaca, N. Y.Oct. 1 60 44 8

regia(Sorrentina) Chico, Calif.Nov. 9 66 48 8

regia(Franquette) Chico, Calif.Nov. 9 80 36 —

regia—Chico, Calif.Nov. 9 75 46 —

Sieboldiana—Ithaca, N. Y.Oct. 1 100 40 —

honorei—Chico, Calif.Dec. 18 60 55 46

pyriformis—Riverside, Calif.Nov. 9 10 54 31

rupestris—Alpine, TexasOct. 1 40 83 50

major—Riverside, Calif.Nov. 9 90 92 66

californica—Pomona, Calif.Nov. 9 62 84 91

californicaquercina —Chico, Calif.Dec. 18 — 18 25

hindsii—Riverside, Calif.Nov. 9 50 56 52

References—

1. Brown, Babette I. Injurious Influence of Bark of Black Walnut Roots on Seedlings of Tomato and Alfalfa. Northern Nut Growers Association, 1942: 97-101. 1943.

2. Barton, Lela V. Seedling Production in Carya ovata. Juglans cinerea and Juglans nigra. Contr. Boyce Thompson Inst. 8: (1) 1-5. 1936