Peony News 6: 17-19. (1918)
A METHOD OF HASTENING GERMINATION OF HARD-COATED SEEDS
A. P. Saunders
In the February number of the Garden Magazine there appeared a paragraph by M. G. Kains on the above theme. The earlier part of the communication reads as follows:
"Many seeds such as Canna, Kentucky Coffee Tree, hardy Locust, and to a less extent Sweet Pea, are very slow to germinate because of the bony coverings around their kernels. Many a Moonflower, Wild Cucumber, and Abyssinian Banana seed have I filed, cut, or soaked in boiling water, to hasten germination. While the holes admit water, the process is too slow; and while the hot water is a quick and easy way of treating a lot of seed at a time, it does not prove as effective as could be desired. A year or so ago, a friend who had heard of the use of sulphuric acid for the treatment of cotton, alfalfa, and clover seeds, tried some experiments with the boniest seeds he could get at the time—those of the Kentucky Coffee Tree. These seeds had lain beneath the parent tree from the previous fall, more or less covered and thus kept moist by leaves and leaf mold. Not one had shown the slightest inclination to swell, much less to sprout. They were placed in a convenient sized beaker glass and covered with concentrated sulphuric acid (specific gravity 1.84, the strongest obtainable). They were left in contact with the acid for one hour, when the acid was drained off and the seed washed free from acid with water. Next they were planted (July 15) in flower pots filled with ordinary good soil and the pots plunged rim deep in a shady moist place. Untreated seeds were similarly planted, but up to the time that the photograph of the successful ones was taken, forty-one days later (August 25) not one had sprouted. Considering the extreme slowness of this plant, the growth of about six inches of stem and a spread of nearly a foot is surely remarkable."
The photograph referred to shows a healthy looking young plant with four well-developed compound leaves.
The application of this method to peony seed suggested itself at once, and on April 14 I started the following experiments: (1) 20 seeds of tree peony (Japanese seed, rather old) were soaked in sulphuric acid for one hour, then planted; after one month this lot showed 7 rotted, the rest still sound but showing no signs of germinating. (2) 20 tree peony seed, fresh, i. e. last autumn's, also in acid one hour; after one month 1 rotted, the rest sound and showing no signs of germinating, but the shells are quite soft, and can be rubbed off. (3) 20 herbaceous peony seed of last autumn, one hour in acid; after one month, one was rotted, two splitting open and sprouting, the rest sound and unchanged. (4) 20 herbaceous peony seed of last autumn, another variety, one hour in acid, after one month two splitting open and sprouting, the rest sound and unchanged. (5) 20 herbaceous peony seed of last autumn, two hours in acid; after one month, one sprouted, the sprout already half an inch long, four others splitting and sprouting, two rotted, the rest sound and still unchanged.
Of course these first sprouts are roots, not leaves. The sequence of events with ordinary dry peony seed, as those well know who have worked with it, is this: if sown, let us say, in the autumn of 1917, growth begins about August, 1918, and consists in the sending down of a root to a depth of two or three inches; and then nothing more that year. In the spring of 1919 leaf growth begins. It will therefore be interesting to watch these seeds, which are beginning their root growth three months earlier than normal, and to observe whether they will decide to start leaf growth this summer, or to wait over until next spring. Meanwhile it is evident that the treatment with sulphuric acid is effective in bringing about speedy germination, though there seems to be some danger to the kernel, to judge from the rapid rotting of some of the tested seeds.
Perhaps some of our members will be interested to try experiments of their own. If so, it may be worth adding that the seed should be carefully washed after treatment with the strong acid. In the tests I have made, it was soaked for a few minutes after washing, in water containing a little ammonia to free it from the last traces of acid.
The blackish outer coating of the seed can be rubbed off after the acid treatment, leaving the seed of a uniform brown color. In the case of seed treated for two hours, the shell was so much reduced in thickness that it could be easily broken between the fingers.
It is of no use to follow the matter to its logical conclusion, and crack the shells open and plant the unprotected kernels in the soil. I have done this, and they all immediately decayed and filled the soil with mould.