Best Current Advice for Growing Giant Sequoias by Seed
(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.
Here I attempt to summarize what has been figured out:
There are two viable approaches to growing GS by seed. Growing them by seed
helps with establishing trees that can withstand local conditions, largely because the other seedlings will die. Most of the
culling happens during the first summer and winter, though the trees remain fragile for years. Both methods begin the same way,
the first is to grow them in tubes and the second is to grow them in a seed bed outside.
The advantage of growing the seedlings in tubes is the flexibility of the method. The advantage of growing the seedlings in a seed bed outside is the simplicity.
First we deal with growing seeds in tubes:
1) Segregate seeds by size, discarding
only the most damaged seeds. Small seeds will germinate much faster. The following
is for medium to large size seeds. There is some indication that seedlings from
larger seeds have better long-term survival rates.
2) Cold stratify them in a refrigerated (35 to 45 deg F), clean, sealed container of steam distilled water--allowing them to float on the water for roughly 21 days (3 weeks) if they sink in large numbers or 28 days (4 weeks) if they don't. One should give the seeds room so they don't overlap while floating. The less handling the seeds get the better they will float for that length of time. Seeds that sink may have a reduced germination rate, but seeds that are in the "Red/Brown" phase after stratification will be viable and seeds that are still "Green" will not be viable. Floating seeds remain 33% viable despite embryo color indications.
3) Bring the seeds out of the cold and place them in a shallow dish where the seeds can be wetted with distilled water but not floating or sinking in it. Place the seed dish in a container to retain moisture and let stand warm until seeds begin to germinate in about one week to three weeks. Plant seeds as they begin to germinate. After several weeks the ungerminated seeds can be discarded.
4) Tubes should be made of a sturdy plastic like acrylic, 3" in diameter and 12-18" long. Split the tubes into halves lengthwise. Tape the halves back together into a cylinder with a sturdy tape like electrical tape--something that can withstand being outside. Duct, masking or cellophane tape generally won't work. Use a poly fill material in the bottom of the tubes to hold the soil in while allowing water to get out freely. This can be held in place with tape again, though the bottoms should not be blocked with tape. Fill the tubes to within a half inch of the top with soil. It will probably compress when wetted, so compress the soil manually and add more. Plan for three seeds per tube. If you sow seeds that have already germinated you can plant one seed per tube. Plan for survival rates over the summer of about 5%. Plan for winter survival rates of about 33%. This means that you will need around 60 germinations to get one seedling to survive a whole year.
5) Planting the seeds "pointy-side" down in damp but not wet leaf mold (available at most garden stores). Do not allow the soil to get saturated with water when planting the germinating seeds below the depth of the seeds. Soil below the seeds should be dry/moist but not wet. This all can be done in a sunless room at room temperature. Do not expose the seeds to sunlight. You can also use potting soil or combinations of potting soil, peat moss and sand. Do not use sand alone. You can also use silty/shale mineral soils, though the seeds must be planted pointy-side up. Mineral soils should be dried before placed in the container, then wetted on top when the seeds are planted. This will avoid excess soil moisture problems. Make sure that the soil remains moist enough on the surface to allow the seedling to push through.
6) Watering seedlings only once per week is indicated while the seedlings are still indoors. Soil should be clearly dry before watering or so well drained that it does not retain excess moisture. Seedlings that begin to flag are in need of water but overwatered seedlings will either wither or turn blue/purple and shrivel.
7) You can initially grow seedlings indoors under warm fluorescent lighting as long as it is very bright. Seedlings can be racked together outdoors in full sun after the last frost. Careful to protect the seedlings from animals and spray regularly with anti-fungal sprays such as Chlorothalinol (follow all directions). Water weekly if there is no rain.
8) Seedlings kept outside will need to be sprayed with Thiophanate-Methyl fungicides to prevent or halt botrytis damage. The soil may be drenched with such fungicides as well. No fungal sprays will stop all infections.
9) After the summer growing season a choice needs to be made. The surviving seedlings will need to either be planted or placed into protected winter storage as they cannot survive root temperatures below 25 degrees F. Seedlings planted into the ground after one growing season will, as noted, have about a 33% survival rate. This can be improved by letting seedlings winter in a more protected environment. The choice is between cold storage and warm. Dormant and cold seedlings in the winter can remain in the dark, but should be kept above 25 degrees F. Warm seedlings will need some light. Water cold seedlings every two weeks. Water warm seedlings every week with about 75% of normal water amounts.
Here is the advice for growing in seed beds:
1) You will need hundreds to thousands
of seeds. They can be purchased online for around $10. Don't buy seed packs
that sell only a handful of seeds as these are not good deals. When you get
the seeds, you will need to plan for the day they will go outside. Determine
the date of your last frost. Let's say for example that it's going to be May
1st. You will need to know what date is 50 days before the date of your last
frost. This would be around March 10th in our example. You will need to start
stratifying your seeds on that date. Before stratifying, rinse the seeds to
make sure that dirt and other contaminants do not mix with the seeds. Shake
the seeds vigorously in distilled water to remove dirt.
2) Cold stratify them in a refrigerated (35 to 45 deg F), clean, sealed container of steam distilled water--allowing them to float on the water for roughly 21 days (3 weeks) if they sink in large numbers or 28 days (4 weeks) if they don't. One should give the seeds room so they don't overlap while floating. The less handling the seeds get the better they will float for that length of time.
3) You will need to prepare the seed bed for the time after the stratification. This will be before 28 days after the start of stratification, or around the 8th of April in our example.
4) Seed beds should be spotted where the final tree is expected to grow unless you plan to transplant the tree after a few years. Regardless, the spot should be where the seedlings can expect reasonable soil moisture levels without ponding. They will also need at least 5 to 6 hours of sun per day. The more sun the better. A seed bed in this case should be prepared in advance as follows. An area of approximately 16 to 25 square feet will be needed (4'x4' to 5'x5'). The grass or weeds in the area need to be removed. The area should be covered with 5" of organic top soil. The top soil should be covered with 3" of leaf mold, which is thoroughly composted leaves. You can make your own by shredding tree leaves the previous fall and letting them bed over the winter. The final mound should be around 3-6" taller than the surrounding soil. Adjust quantities to bring this about. The surface should be smooth and flat. Surround the area with guards/curbing to keep weeds out. Save some of the compost for the purpose of sowing and covering the seeds. It is important to have a raised bed with soil that will become moist but not waterlogged. In the winter, the freeze-thaw cycle will tend to rip seedlings out of the ground and kill them. This is best prevented by having a raised bed of well-drained soil. Well-drained soil will not freeze solid in a hoary frost that kills small plants. Mulch can also help prevent soil freezing cycles, but should only be applied late in the season and removed early in the spring. If a seedling is ripped out of the ground you can try to replant it while it is still dormant, but the odds will be against it.
5) Once stratification has been completed, the seeds are ready for planting. They will germinate in another couple of weeks. It is best if they germinate early in the season, but delaying things a few weeks will not hurt matters too badly. The main issue is soil moisture levels before germination. The leaf mold should not be allowed to dry out completely, as this will lower germination rates. Thus, delaying sowing until the dry summer months begin is not advised. Likewise, the seedlings benefit from a longer growing season. Get the seeds out of the jar. They can be spread evenly on the ground of the seed bed or mixed with dried leaf mold to make an even mixture for spreading. Once the plain seeds are on the bed, cover them with another 0.25" of moist leaf mold. A seed/mold mixture should be filled in as needed with more mold to make sure the seeds are properly covered. Pat the covered seeds down to set them in place. Make sure the top layer is moist.
6) The bed should receive enough moisture from the mold to complete the germination process. Rain will not hurt things. Don't let the bed get completely dry. There should be many seedlings. Raised screening can protect them from insects, birds and small mammals.
7) Seedlings should continue germinating for a few weeks. Make sure the bed does not completely dry out, but rain is the most critical component. Once germinations cease, only water if it stays very dry. Be careful to protect the seedlings from animals and spray regularly with anti-fungal sprays such as Chlorothalinol (follow all directions). Water weekly if there is no rain.
8) Seedlings will need to be sprayed with Thiophanate-Methyl fungicides to prevent or halt botrytis damage. The soil may be drenched with such fungicides as well. Initially seedlings will fail because of bad genetics, insect damage or other incidental causes. Loses will be high. Towards the end of the summer, when it is very hot and humid fungal infections will be the worst enemy.
9) That is really it as the seedlings will die off or otherwise take care of themselves. They may need sturdy protection in the winter to keep animals out, but otherwise they will be able to handle the cold (or not). You will only know which survived when the growing season begins again in spring. Transplanting a seedling is not recommended until it is about a foot high, though by then the root system will be very extensive. It is best, therefore, to place the bed in a location where the tree can grow fully. Growth rates will accelerate over the first couple of years. Don't expect a large tree for about ten years.
This advice should only be considered valid for Sequoiadendron giganteum seeds and no other species. For example, the author would not recommend stratifying P. aristata seeds at all, but simply sow them in moist mineral soil. Some species, such as P. jeffreyi have variable germination requirements based on the climate of the location of the parent tree.
Exotic Tree Home Page
Giant Sequoia Growing in NJ, NY and PA
More GS Photos in NYC/Philly Area
Photos of Area GS from Middle 2004
Photos of Area GS from Late 2004
Photos of GS Diseases
More Photos of GS Diseases
Conifer Winter Bronzing Photos
GS Photos from Other Photographers
Some Other Exotic Tree Species
Bald Cypress and Dawn Redwood Bark Photos
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