How do I propagate blue elderberry?
Key Points
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Blue elderberry is a wild plant – no clonally propagated cultivars exist yet.
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Propagation from seed is more reliable and contributes to genetic diversity.
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Propagation from cuttings may be more difficult but increases consistency and predictability.
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Propagation from regionally-sourced planting stock will ensure locally-adapted plants.
Due to the conservation status of the Valley Elderberry Longhorn Beetle (VELB) and federal restrictions on certain pruning practices and removal of blue elderberry plants within the known range of the VELB, please read: Valley Elderberry Longhorn Beetle – What California Growers Need to Know
Where to source elderberry plants
Small quantities of potted blue elderberry plants can be readily purchased from many nurseries that stock California native plants. Commercial sources for blue elderberry plants in bulk are essentially limited to nurseries growing native plants for restoration projects. A contract grow for larger quantities of plants may be arranged by contacting the nursery many months in advance of the planned planting date.
For a list of possible nurseries that stock blue elderberry, check the Calscape website, or contact your local California Native Plant Society chapter.
Look out for different names for blue elderberry. Some other common names include California elderberry and Mexican elderberry. In addition, several outdated scientific names for this subspecies are still commonly found online and in nurseries due to recent taxonomic updates of the Sambucus genus.
Current scientific name for blue elderberry: Sambucus nigra ssp. caerulea
Other scientific names that may still be in use for blue elderberry:
- Sambucus cerulea
- Sambucus glauca
- Sambucus arizonica
- Sambucus neomexicana
- Sambucus mexicana
It may be difficult to find a source of plants to purchase that meet your needs and budget. Conservation and biodiversity-focused growers may choose to propagate their own plants to ensure a locally adapted ecotype. Foragers may choose to propagate a favorite tree for a more convenient harvest.
Growers can choose to propagate elderberries either from seeds or cuttings, keeping in mind that, California nursery experts have reported that propagation of blue elderberry from cuttings is much more difficult than from seeds, even though cuttings are often the recommended method for other elderberry subspecies. Planting from seed will produce genetically unique trees, which can result in high variability of tree performance in the field (link to field demo page), while cuttings result in genetically identical trees (clones), providing more consistency and predictability.
Advantages and disadvantages of propagating blue elderberry from seeds versus cuttings
|
Propagation method |
Advantages |
Disadvantages |
|
From seed |
Produce genetically unique trees that may contribute to the long-term resilience of wild blue elderberry populations (Dorner 2002) Cheaper and easier to obtain |
High variability and less predictability of growth habit, flower and berry quantity, quality, and harvest time |
|
From rooted cuttings (clones) |
Increased consistency and predictability |
Lower success rates – require starting with a larger number of cuttings |
Regardless of propagation method, blue elderberry growers should try to source planting stock from wild plants as close to their planting site as possible. Local ecotypes are adapted to local growing conditions, and may result in healthier plants with lower rates of loss. Additionally, there are concerns among the native plant restoration community that introducing non-local genetics may negatively impact the resilience of native plant communities (Dorner 2002).
Propagation methods
Seed propagation is a cost-effective method for larger-scale plantings, and is commonly used by California native plant restoration nurseries. Seeds must be treated before planting for successful germination. Without treatment, elderberry seeds can take 2-5 years to germinate. Cold stratification for 60-90 days at 41F significantly reduces germination time1 but germination rate may still be low. However, blue elderberry seeds are very small (117,000-259,000 seeds/lb)2, and each small berry contains three to five seeds3, so it is possible to easily collect a large number of seeds to ensure adequate numbers of seedlings.
Procedure:
- To remove seeds:
- Crush fresh ripe berries and cover with cool water.
- Soak, stirring and mashing occasionally, for up to 24 hours.
- Skim off fruit pulp and partially-filled seeds floating at the top (fully mature, viable seeds are heavier and will sink to the bottom).
- Strain and wash mature seeds at the bottom of the soaking container using a fine sieve.
- Dry seeds and store them, or move directly into the next step, cold stratification.
- To stratify:
- Spread seeds on a moist paper towel, fold, and store in a plastic bag in the refrigerator. Peat moss, vermiculite, perlite, coffee filters, or similar media can also be used.
- Keep seeds moist for the duration of the 60-90 day stratification period, and check periodically for signs of germination. If germination occurs, seeds should be sown as soon as possible.3
Elderberry seeds can be stored dry at 41 degrees F for several years prior to stratification, and may be viable for up to 16 years if stored properly.4 To improve the germination rate of stored seeds, soak seeds either in a 1% bleach solution for 1 week, or in hydrochloric acid for 10-15 minutes, prior to the 2- to 3-month cold stratification treatment described above. Hydrochloric acid solutions are also sold under the name muriatic acid, and are typically available at hardware stores. Be sure to read the labels thoroughly and use recommended personal protective equipment when handling corrosive acids. California native plant nursery managers have reported success with the bleach and hydrochloric acid treatments, while more typical methods to scarify seeds (i.e. to soften or break through the hard seed coat), such as mechanical abrasion or hot water soaks, are reported not to work as well for elderberry seeds.
Blue elderberry has been shown to be more difficult to propagate from cuttings as compared to European and American elderberry. Growers propagating blue elderberry should plan for relatively low rooting success from hardwood cuttings, but may have higher success rates if cuttings are taken during bloom, rather than during winter dormancy. Storing hardwood cuttings in the refrigerator (cold callusing) for 14-18 weeks prior to rooting may increase rooting success rates.1
Procedure:
- Make cuttings at least 10” long including at least 2 nodes from wood grown during the last growing season. “Heel cuttings” may be more successful.4 “Mallet cuttings” are also used for woody species which can be difficult to root.
- Treat the rooting end of cuttings with rooting compound and place in pots with a soilless medium such as perlite and peat moss or sand, potting soil, or a prepared bed in soil.
- Keep moist until rooting occurs, then carefully transplant into pots (young roots are extremely fragile).
Elderberries can also be propagated using semi-hardwood cuttings, softwood cuttings, digging suckers and root cuttings.4,5
References:
- Maughan T, Black BL, Rupp LA, Yost MA. 2018. Propagation techniques for Sambucus cerulea (blue elderberry). Native Plants Journal 19(2):80-88.
- McDonough TC, Regan DJ, Nelson AS. 2018. Propagation protocol for blue elderberry (Sambucus nigra L. ssp. cerulea (Raf.) Bolli). Native Plants Journal 19(3):254–259.
- Emery DE. 1988. Seed propagation of native California plants. Santa Barbara Botanic Garden.
- Stevens, M. 2001. Plant Guide for blue elderberry (Sambucus nigra L. ssp. cerulea (L.) R. Bolli. USDA-National Resources Conservation Service, National Plant Data Center, Baton Rouge, LA.
- Charlebois D, Byers PL, Finn CE, Thomas AL. 2010. Elderberry: Botany, Horticulture, Potential. Horticultural Reviews 37(4):214-280.