Casual Experiments in Sequoia Seed Germination
(Information Provided is for Recreational Purposes Only--No Liability Assumed)
There are three Redwood species:
Coast Redwood (of Redwood Forest fame and lumber): Sequoia sempervirens
Dawn Redwood (Chinese native, deciduous and similar to Bald Cypress in appearance): Metasequoia glyptostroboides
Giant Redwood/Giant Sequoia (Big Trees of the Sierra Nevada interior, Yosemite and Sequoia Natl Park): Sequoiadendron giganteum
In the NYC/Philly Area, Metasequoia grows easily, Sequoiadendron grows grudgingly and S. sempervirens generally
will not survive our winters. S.s. is seen growing in coastal Maryland, Virginia and DE (borderline zone 8 areas).
There are some tricks to growing Sequoiadendron in the area, so this site is dedicated to those interested.
For those interested in growing the tree from seed, some advice can be offered. In general, growing from seed will produce offspring best suited to local conditions. The following, however, represents only the early trials of determining the best methodology for seed germination. See the summary for more current advice:
Quick and dirty experiments in the art of germinating Sequoiadendron giganteum seeds suggest that the best results are obtained by:
1) Choosing the largest, flattest and plumpest seeds.
2) Cold stratifying them in a refrigerated (40--45F), clean, sealed container of steam distilled water--allowing them to float on the water for 40 to 45 days. [See the summary for more current advice.]
3) Planting the seeds "pointy-side" down in wetted standard peat moss until germination (about one-week). This can be done in cups or containers in a dark room at room temperature. Do not expose the seeds to sunlight.
4) Use of sterilized soil will perhaps aid seedling survival.
The results obtained recently following these methods resulted in approximately 2/3rds of the seeds germinating.
The survival of the growing seedlings following germination was not great. In a stressful environment the seedlings exhibit a high mortality rate due to factors such as over-watering, heat-stress, animal attacks and fungal attacks. Seedlings require very loose soil, containing nearly entirely peat moss or similar for several months before transplantation can occur. Moisture retention should be about 50%, varying from 30 to 80%. After three months the seedlings respond to low-salt, slow-release fertilizer, but no noticeable effects occur before then. Soil pH should be low--around 6, and the seedlings can be watered with pH balanced mineral water (pH of about 6.5) to reduce mold problems. Use of various fungicides might help seedlings survive, but the best protection comes from keeping them away from other plants in a dry location. Seedlings respond well initially to warm colored fluorescent lighting (will be burned by cool colored lighting), but need outdoor conditions, including sunlight, circulating air and temperature changes, to grow well.
Test of Seed Appearance Variable (with followup on germination rates and times).
Test of Soil Constituents (with followup on seedlings from round 2).
Test of Stratification Timing (with more followup on seedlings from round 2).
The literature on Sequoiadendron germinating is not consistent. Advice ranges from warm stratification to cold, stratification periods lasting from weeks to months and other inconsistencies. It is hoped that some definitive results can be shown here to aid gardeners interested in this issue. During the winter and spring of 2002, casual experiments were performed to attempt to find some indications as to how to best germinate and grow Sequoiadendron giganteum from seeds. A difficult tree to grow in places outside of the west coast of the United States, growing a tree successfully requires a winnowing process whereby a large number of seedlings are started in the hopes that a few will survive the local environmental conditions. The low germination rates of these seeds makes the task yet more difficult, so increasing germination rates would increase the overall trial effectiveness.
Since a large number of experiments would normally be performed to determine the ideal method of germinating these seeds, the experimentation here was compressed. The results, therefore, are not scientifically valid, but can help indicate the direction of future research. Any method that produces a germination rate better than 50% should be considered suitable for breeding experiments, so the only future testing required of the indicated methods would be to verify that one can consistently obtain high germination rates consistently.
The experiments also followed the development of the resulting seedlings for 90 days. There is no indication that germination methods have much effect on seedling survival, so other experiments will need to be conducted to determine how to improve seedling survival. Outside California, seedlings that survive into maturity are likely to be mutant varieties of the species, either more cold or disease resistant. The discovery of random mutations in a seedling bed would therefore be of some interest to nurseries and gardeners. Indications of unusual needle color, size or shape, atypical growth rates, habit or form suggest a mutation is present. Of all the seedlings grown for this experiment, only three survived the long, hot 2002 summer here on the East Coast. One suspects, however, that the experiments themselves might have undermined seedling survival.
The experimental variables considered were:
1) Seed form and condition.
2) Seed size.
3) Cold Stratification
4) Stratification media
5) Germination media
Seed form and condition:
Seeds vary in size, color and shape. One notices that some seeds are dried-out, wrinkled, blackened or otherwise misshapen. For the purposes of these experiments, only the healthiest looking seeds were selected. One could hypothetically conduct an experiment to test this variable by taking healthy looking seeds and germinating them in one lot, germinating unhealthy looking seeds in another lot and germinating seeds selected at random in a third lot. This will require hundreds of seeds roughly evenly divided between lots. The method to induce germination for all three lots will be identical. After a period of time deemed sufficient, the germination rates for all three lots can be calculated and compared. If identical, nearly identical or if the random lot results are significantly higher or lower than the other two lots then seed appearance is not a variable in germination rates and can be ignored. If the rates follow a trend: highest, middle, lowest where the random lot is in the middle (neither the highest nor lowest germination rate) then seed appearance is a variable in germination rates and should be considered. For the results to be statistically significant the seeds should be sourced from a variety of locations and the results should be analyzed using statistical methods for confidence.
Healthy seeds were segregated based on size. Normally only the largest seeds were used, but in one experiment only the smallest seeds were used.
Seeds were put into lots for germinating, either in a cold location or a warm location.
Since in many planting situations seeds are placed in special environments for germinating, a few stratification media were experimented with, including soil, water, water with minerals, water with minerals and acid and a gel.
When removed from the stratification media, seeds were planted in soils of various kinds for rooting. They remained in these soils for at least one month.
Once the seedlings started to grow, lots were selected to either receive fertilizer or not. As only one type of generic fertilizer was used, experiments might be conducted to see what type of fertilizer might be best, if any can be shown to have any effect at all. This would require several dozen seedlings of nearly the same age and grown under identical circumstances.
The materials and equipment used in these experiments were chosen for their ready availability to the plant enthusiast.
Cold stratification was performed either in a standard refrigerator or a cold room exposed to the outside during late winter/early spring.
Soils and fillers selected were all commonly available at garden shops. Shredded peat moss is the most commonly available. Sand added to soil was white sand suitable for children. None of the soils were sterilized. It may be advisable to perform experiments to see if sterilized soils perform better. In one experiment, germination was attempted in common garden soil and compost.
Germination was done in small plastic cups. Cups were carefully labeled to indicate their contents.
Water used was steam distilled.
Minerals added were derived from colloidal shales.
Acid was derived from common 5% acetic acid white vinegar.
Aloe Vera gel was as pure as could be obtained locally. It was sterile.
Results were tabulated on the spreadsheets shown below.
Growing Seedlings in Peat Moss:
This might be considered the most normal approach to growing seedlings. Peat moss with perlite was placed into plastic cups. The cups were numbered from 1 to 20. One large and healthy looking seed was put into each cup approximately 0.25" deep. The cups contained approximately 10 oz. of soil each. The soil of each cup was saturated with one of five solutions of colloidal minerals. Cups 1 through 10 were placed in a refrigerator at 40-45F, the rest were kept at room temperature of 65-70F. Cups 1 through 5, then 6 to 10, then 11 to 15, then 16 to 20 used increasing concentrations of minerals in the pattern 5%, 10%, 15%, 20% and 25%. Cups 1 through 5 and 11 through 15 were selected to receive fertilizer.
The dates of germination were recorded when the first indication of rooting occurred. These were compared with the planting date to determine the number of days to germination. After that, heights were recorded on days 30, 60 and 90 after the date of germination. Other notes were taken as needed. Since high levels of mold were noticed in the cups the pH was adjusted after some time. A few were eventually replanted and put outside. They did not survive the wet, rainy spring.
This chart shows the progress of the experiment:
Germinating Seeds After Stratification in Solutions of Colloidal Minerals
This experiment was inspired by the remarks made in several books and articles on sequoias that they grow near streams. This indicates that the seeds might be spread by water, perhaps in spring floods, and spend a considerable amount of time in very wet environments before the summer dry season. Likewise, it seemed easier to determine the progress towards germination if the seeds were always visible to inspection. Twenty cups were lettered and filled each with ten healthy looking seeds. Mineral solutions were prepaid consisting of 0%, 5%, 10%, 15% and 20% colloidal solution content. To determine the mineral content of each cup, multiply the percentage given by 34 mg/mL. A 100 mL solution at 10% would have 100 x 0.1 x 34 = 340 mg of minerals. A 0% solution was steam distilled water as is commonly available to gardeners. It should be noted that the mineral solutions were highly acidic, with pH's below 5. Steam distilled water is also acidic, resulting from the absorption of atmospheric gases, particularly carbon dioxide. The pH can be neutralized by the addition of solutions of potassium bicarbonate, but the typical gardener has no easy means to create such solutions. The main reason to neutralize the stratification medium is to avoid mold, but cold stratification also inhibits mold growth, and cold stratification in a sealed container further inhibits it. For this experiment the solutions were not neutralized.
Cups A through J (1 through 10) were put in a warm environment, while cups K through T (11 through 20) were put in a cold room exposed to winter conditions. The temperature in the room would vary from 20F to 50F over the course of the time spent there. It was thought that simulating the environment encountered by the seeds in the wild would aid germination. A-E and K-O were to receive no fertilizer when planted while F-J and P-T would receive fertilizer. A-E, F-J, K-O and P-T would be filled with the solutions of colloidal minerals in the pattern: 0%, 5%, 10%, 15% and 20%. The seeds were allowed to float on top of the liquid since they readily float on water. Stratification varied from 25 to 39 days with warm seeds planted into soil before cold seeds. The soil used was a combination of peat moss and perlite. The high levels of mold that developed in the cups encouraged planting. Mold was high in all cups except for the 0% cups. In some cases the mold destroyed the seeds, but in most cases the seeds seem unaffected. Seeds were transferred from the cup containing the media to a cup with the same label containing soil. The soil was kept wet until germination was noted. Cups containing soil were all kept in a warm, dark environment.
The first date of germination was recorded for each cup, and compared with the date put into media to obtain the number of days to first germination. The number of seeds per cup that eventually germinated was recorded, as was the heights of the surviving seedlings. Several seedlings were replanted and put outside where only three survived.
The following chart shows the progress of the experiment:
Tests Conducted on Small Seeds
Since all tests previously were conducted on larger seeds, it was thought practical to test smaller seeds. If one does not have to segregate large seeds from small ones the job of planting is made easier. It was also thought to be a good time to test the soil type the seeds were planted in. The difficulties that developed with mold in the previous experiments suggested that simply using steam distilled water was best for stratification. There was as yet no indication whether warm or cold stratification was better so the seeds were stratified warm in temperatures ranging from 65-70F. 60 small but healthy looking seeds were placed into a single container of steam distilled water. Several began germinating within 25 days, so the seeds were planted in soils soon thereafter. Three types of soil were selected: peat moss and perlite as used before, a silty shale soil common to East Coast gardeners and a compost-soil derived from leaves, sometimes called an organic soil. Twelve cups were created. Six contained peat moss. Four contained the shale soil ("Mix"); and two contained the organic soil ("Muck"). Five seeds each were planted into the cups. Dates of the first germination per cup were recorded and the number of days to first germination calculated. Half the cups were to receive fertilizer and half not. The total number of germinations per cup was recorded as were the seedling heights on days 30, 60 and 90 past first germination.
The following chart records the progress of the experiment:
Experiments using Acid Solutions and Aloe Vera Gel
The following experiments were conducted, but since they failed to induce significant germination rates they should be deemed dead-end methods. The first was inspired by the fact that gardeners use acids to help induce germination. There are several acids employed, but few are readily available. They also tend to be difficult to use. Only when they clearly demonstrate a significant advantage should they be considered for use. As a caveat, it may be that the experiment might have simply been conducted incorrectly and acids would be useful in aiding germination, but this is not indicated here. The second was a shot in the dark. Since the seeds tended to float on water for long periods of time it was wondered if full submersion might be better, particularly if it reduced mold. A high water-content gel (Aloe Vera), commonly available to gardeners was used to test this idea. Results indicate that the seeds probably need oxygen or carbon dioxide to properly germinate, so full submersion is an indication of a seed less likely to germinate. This can happen if seeds are floating in water and then sink as well.
In the acid experiments six containers of various solutions were prepared. Ten seeds were placed in the containers along with the solutions and allowed to stratify warm. The acid solution used was common white vinegar (5% acetic acid), and the colloidal added were the same as noted above. Acid was at 5% concentration by volume or 10%. Colloidals were at 0%, 5% or 10% as noted above. 5% acetic acid solution used at 10% by volume concentration results in a 0.5% acetic acid solution. The six containers were filled by alternating all possible combinations of acetic acid and colloidals (six combinations). The seeds were allowed to float. After 17 days in solution they were all replanted into peat moss soil in cups. The cups each held the seeds from one container. They were all to get fertilizer. Only seeds from one container germinated. It was felt that too much time was spent in the containers since the seeds began to sink after two weeks. Perhaps ten days in solution would have been better.
Here is a chart of the progress made in the Acid Tests:
Twenty large and healthy looking seeds were placed fully in two cups containing Aloe Vera Gel, ten seeds per cup. One cup was placed in a refrigerator for cold stratification (40-45F) and the other was kept at room temperature (65-70F). After 45 days the seeds were placed in soil (peat moss) in four cups, two to get fertilizer and two to not. Only one of the twenty seeds germinated. it was unclear why, but gas exchange with the atmosphere is indicated. It is possible that reducing the time spent in the gel might have allowed more to germinate, but there is no indication that this provides any advantages over stratifying them in distilled water.
The following chart shows the experimental results:
The results of the experiments conducted did not demonstrate any means to germinate Sequoiadendron seeds at a rate greater than 40%, however, it appears that good results can be obtained easily by refrigerated cold stratifying seeds by floating them in distilled water for 40 to 45 days and then planting them in peat moss. Germination should occur within two weeks of planting in peat moss. A trial run of that method after the conclusion of these experiments resulted in a germination rate of 66%. The seeds should be put in a clean, sealed container with the distilled water and allowed to float. There should be air in the container as well. Seeds that sink to the bottom can be fished out and immediately planted, but there is little reason to wait beyond 45 days for seeds to sink before planting.
Here is a chart of the overall results:
The chart tracks several variables. The "All" column indicates the value of a particular result for all seeds combined. It is difficult with the methods used to spot trends where two variables acted in concert. For example, if cold stratifying helped but colloidals hurt germination rated then one has to compare several results to see this. This mixing of variables makes the results scientifically invalid in the rigorous sense. However, it would be relatively easy to conduct experiments to isolate a particular variable. Discovering a "best practices" method, however, involves a great deal of work since one has to try many different methods and their attendant variables in order to come-up with a best method.
Effects of cold or warm on germination rates:
In the last five columns of the chart are shown the effects of cold or warm stratification on germination rates and other results. As can be seen from line two, cold stratification results in germination rates twice those of warm stratification. This indicates that one should cold stratify the seeds.
Effects of stratification media on germination rates:
While stratification in soil had the highest germination rate, the small number of seeds tested were not statistically significant. Other difficulties involved with stratification in soil, such as the space required, mold and watering issues indicates that stratification in a water-based liquid is the best method. Since it is simply easiest to use steam distilled water, the other methods tried did not warrant further consideration. Here are results on germination rates based on colloidal solution strength:
As shown, distilled water ("0") out-performed any other concentration. Even 20% ("20"), which had the closest results, was not better, so considering the hassle of creating such a solution there is no indication that anything but distilled water is needed. Had the germination date for 20% been much sooner, say 20 days instead of 62, this might have made it desirable, but this was not the case. Likewise, distilled water had the fewest problems with mold. Other media considered, acids and aloe vera, faired poorly and are not indicated.
Effects of soil on germination rates:
As seen with the small seed results, the best media is peat moss. Other media had very low germination rates or produced unhealthy seedlings that quickly died. Peat moss can be difficult to work with, but only something similar in terms of looseness and moisture retention is indicated. Seeds should be planted in peat moss without perlite to get the best moisture retention. [See the summary for more current advice.]
Effects of seed size on germination rates:
Germination rates for small v. large seeds were similar, but small seeds seemed less likely to survive past 30 days. They seem to develop quickly and then succumb to environmental stress. The great advantage of small seeds is their tendency to germinate quickly, in as little as 19 days. Whereas large seeds germinate in about 40 to 50 days, small seeds germinate in about 20 to 30 days. In a typical seed lot there are more small seeds than large, but the number of healthy looking ones is about the same. At this time the use of larger seeds is indicated, though more tests might demonstrate no particular advantage.
Indications on the number of days required to stratify seeds:
Seeds tend to begin to sink in distilled water after 40 days. This suggests that 40 days of cold stratification is ideal, though one can go as long as 45 to 50 days. Seeds may begin to germinate before this time and sprout while in water. This is not likely if the water is cold. Seeds can be planted and survive if they sprout in this manner. [See the summary for more current advice.]
Results on the number of days to germination:
Large, healthy looking seeds germinate in about 40 to 60 days. There is no indication that cold or warm stratification influences the number of days required, but small seeds germinate much sooner than large ones.
How to plant seeds: [See the summary for more current advice.]
Obtain peat moss and place the soil in a long tube container. One must consider the time desired before repotting is needed. The longer the tube the longer one can go before repotting. The roots grow two to three times the length of the plant's height. They tend to grow straight down at first with little lateral branching. Seedlings do poorly at first if the soil is compacted or if there are layers of different kinds of soil. Polyester fiber-fill can be used with peat moss for early stage growth. Make sure that initially the soil is wet. There should be some way for the soil to dry over time, so a weep-hole at the bottom might help. Seeds should be planted pointy-side down to the height of the seed. They should be surrounded by soil but the top still visible at soil level. The following diagram displays which end goes down:
Effects on growth of fertilizer:
There is no indication that low levels of generic fertilizer affect growth rates 90 days after germination. Seedlings were almost invariably 1.3" after 30 days, 1.75" at 60 days and 2.2" at 90 days. Branching begins around day 60. This slows vertical growth in favor of lateral growth. The trunk begins to harden around four to five months. This helps the plants survive fungal attacks better, but they are still vulnerable. Not enough seedlings survived to indicate much about how germination methods affect seedling survival, but it is unlikely that this is an important consideration. It is more important for seedlings to avoid stressful environments. [See the summary for more current advice.]
Notes on individual tests:
It was difficult to maintain adequate moisture levels in cups left out in the warmth. In the refrigerator cups tended to remain very wet, probably due to decreased rates of evaporation. Mold tended to be worst in cups with the greatest colloidal concentrations. Cup 7 survived the longest, succumbing to a fungal attack that tends to turn needles orange. While good for rooting, peat moss retains less water than other soils and so requires frequent waterings outside. Overall, stratifying in soil requires more work for less gain than others tried.
This test involved the greatest number of seeds used. It was difficult to obtain enough seeds to find 200 to meet the requirements of this experiment, but this was done. Four of the twenty cups had such severe mold that they were disposed of prior to planting seeds in soil. The difficulty of extracting seeds from the mold, which involved wearing a face mask, tweezers and a great deal of time indicated that using distilled water was the best way to go. The worst mold was found in the warm stratified cups with 5% and 10% concentrations. A great many seedlings were produced. Many were replanted in large containers and put outside. Few survived. Most succumb to a fungus that rapidly turns seedlings black and dry, starting with a spot on the stem. Others simply wilted or were over-watered. While this suggests that seedlings should remain indoors for their first year, they seem to develop abnormally if they do not get true sunlight, wind and temperature swings. They will develop thin, weak "trunks", spindly foliage and poor color.
This experiment would have been better perhaps if soil considerations were dealt with in another series of tests. The use of heavy soils greatly reduced the germination rates of seeds, perhaps because the embryos could not escape the seed itself or perhaps because moisture/gas conditions were less than ideal. Small seeds tend to be difficult to handle.
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Germination Trials for growing by seed:
Summary of Tips for Growing GS from Seeds
Germination Trials I
Germination Trials II
Germination Trials III
Germination Trials IV