Site Selection, Preparation & Planting

• Preferred Growing Conditions 

• Natural Habitat

• Planting Considerations

• Planting Design

• Irrigation

• Weed Control

Preferred Growing Conditions 

Blue elderberry thrives in full sun, part sun, and full shade. 

It prefers soils with moderate to good drainage and pH 6-7, but will tolerate many soil types and conditions¹. (Calscape: Blue elderberry accessed 2019)  It can tolerate standing water during winter dormancy². 

Natural Habitat

In natural areas, elderberries are most often found at forest edges or in sunny openings of moist areas (at the bottom of slopes or canyons, riparian forests, stream banks) as well as in drier, more open habitats with access to moisture,³ whether from deep in the soil profile or from seepage from nearby water bodies or irrigation ditches. Once established, blue elderberry also grows well in drier conditions but may go dormant in late summer or early fall as soil moisture levels wane, and green up again with winter rains. In most areas, however, blue elderberry typically goes dormant in winter.¹

Blue elderberry occurs naturally at elevations from 3-3000m,³ and can tolerate frost down to 5 degrees F, making it a suitable crop for a broad swath of California’s topography: southern coastal regions, central valley, and foothills.⁴ It does not appear to be as common directly on the coast in northern California, but occurs somewhat inland. A growing season of at least 85 frost-free days is required for full ripening of berries.⁵ 

Growth Form 

In ideal growing conditions with sufficient space, individual blue elderberry trees can grow up to 20-30 feet wide and 20-30 feet tall.  Most grow as large shrubs, with many straight canes sprouting from the base around a thicker, central trunk.^1,5 Berry clusters borne at the tips of long, flexible canes cause the canes to bend towards the ground. Left unpruned, this tendency often results in the tree taking on a rounded mound-like shape.  

When to plant 

Fall  and winter are the best times for planting perennials in CA, when cooler wetter conditions help plants establish before the heat of summer sets in. However, planting in spring can be quite successful as long as irrigation water is available.^{2, 4} For more information, see the Sacramento Valley Field Demonstration ). 

Choosing a planting site

In California, native plant hedgerows are often planted in non-cropped areas along roads, canals, fences, and field borders, or in weedy areas which need regular management.^{2, 4}  These are ideal planting sites for Central Valley growers, due to federal restrictions on plant removal and pruning for Valley Elderberry Longhorn Beetle (VELB)  .  Additionally, this strategy allows for elderberry production and habitat without sacrificing crop land already in production. 

The planting site should be easily accessible to equipment for planting and maintenance, and needs access to water for irrigating young plants for at least 3 years.^{2, 4} To avoid damage to elderberries, beneficial insects, and pollinators from herbicide and pesticide drift, choose a site that has a sufficient buffer from areas that are sprayed.⁴

Site preparation

Based on results from a 2018/2019 Sacramento Valley field demonstration in which planting occurred during spring, we recommend tillage of spring planting sites for maximum vigor and improved consistency of growth among plants. California native plants are commonly planted without tillage, but no-till plantings are best reserved for fall and winter when the soil is more consistently moist and easier for young roots to penetrate.  

Planting Design

Plant spacing considerations

The ideal spacing between elderberry plants depends on the grower’s goals and management plan, with different advantages and disadvantages accruing from wider versus closer spacing.

*For information on elderberry pruning restrictions in the Central Valley, see page on Elderberry and the Endangered Species Act

Single-species versus multi-species hedgerow design

Single-species, 100% blue elderberry:

• Minimum bush spacing: 4-8 ft apart
• For maximum bush size: a minimum of 15 ft or more apart for bushes to spread to their maximum width of 20-30 ft.
• Greater than 20 ft apart for better ladder accessibility between bushes

Single line, multi-species with elderberry and other large trees/shrubs:

• Follow spacing guidelines for single-species hedgerow above

Multi-species hedgerow:

• Space elderberry at 10-15 ft apart or more, and interplant with smaller shrubs, forbs, and grasses. Smaller plants installed in line with elderberries will likely be shaded out in a few years. Spreading species, such as yarrow, can migrate out of shady areas over time as trees and shrubs increase in size.
• If your planting site is wide enough, utilize separate planting rows, reserving one or two rows for elderberry and other large shrubs, and other rows for smaller plants, maintaining at least 10 ft distance between rows of large trees/shrubs and rows of smaller plants. If large trees/shrubs are planted closely together within their row, they will stay smaller, allowing relatively close spacing of smaller plants near them. However, if large trees/shrubs are widely spaced and allowed to grow larger, then smaller plants will need to be planted farther away. Consider the likely final size of all plants when designing the hedgerow.

For more guidance on planting design, species selection, establishment and maintenance of multi-species hedgerows, see Establishing Hedgerows on Farms in California

Irrigation

Make sure the planting site has access to water for irrigation, and install main irrigation lines and headers prior to planting. If using drip tubing with in-line emitters, place it down as well, to avoid crushing plants later. For tubing with emitters added manually, it may be easier to wait and install them directly next to plants after planting, taking care not to crush plants.

Irrigation requirements for blue elderberry:

During establishment phase:

• Irrigate once every 1-2 weeks for the first 3 years. Once per week is recommended for fastest growth in most parts of the Central Valley, especially in the first year. Sandy soils may require more frequent irrigation. Elderberry can thrive with less frequent than weekly irrigation in soils with high water-holding capacity.

After establishment:

• In many parts of California, irrigation after the first 3 years will not be necessary, unless winters are unusually dry.
• In the San Joaquin Valley and other inland regions farther south, intermittent summer irrigation may be necessary if the area lacks a source of subsoil moisture, such as seepage from nearby streams, ditches, or irrigated crop fields, or a high water table.

In general, eliminating summer irrigation of California native plants once they are established is recommended as warm, wet conditions can kill or shorten the lives of many species.⁶ This consideration is worth noting when planting blue elderberry in multi-species hedgerows with other natives. 

Irrigation requirements for American elderberry:

American elderberry has a shallow, mat-like root system and is not considered very drought tolerant. Some researchers note that, if grown in Mediterranean climates, American elderberry will most likely require frequent summer irrigation for high-quality fruit production.⁷ California Central Valley growers should consider this carefully, especially if planting American elderberry with California native plants. (Here is more information on the Sacramento Valley field demonstration results.)

Irrigation methods  

Drip irrigation is recommended because it is efficient, reduces flooding damage to plants, and reduces weed pressure. Polyethylene irrigation tubing with one or two 0.5–1 gallon per hour emitters installed at each plant, as opposed to drip tape with in-line emitters, is recommended because of durability and the ability to place water directly at the base of plants only. Drip tube with in-line emitters is more durable than drip tape, but the inline emitters will place more water between plants, which will result in more weed pressure. Make sure that emitters are as close to plants as possible to ensure that young roots do not dry out, and water new plants thoroughly as soon as possible after planting. Pre-irrigating just prior to planting is ideal so there is soil moisture available immediately for new plants (Earnshaw 2018). 

Flood and sprinkler irrigation can be effective for elderberries, but will result in higher weed pressure. If using flood irrigation, take care not to include other plants in your hedgerow that do not tolerate standing water. ^{2, 4}

Weed Control

Proper weed control will decrease plant loss, increase the rate of growth during establishment, and may increase plant longevity and health after establishment. Existing weed infestations on the planting site should be eliminated prior to planting to reduce weeding labor during establishment. Weeds should be carefully and consistently removed during establishment to minimize growth stunting and plant loss due to weed competition. Weeds will eventually be shaded out as elderberries mature.

Caption: High weed pressure in the first year at one field trial site appears to have contributed to a 3-fold increase in blue elderberry seedling death during the rainy season, compared to losses during the summer growing season.

Mulch

Installing an effective weed barrier is recommended to help young plants outcompete weeds and conserve soil moisture. Spread organic mulch such as compost, woodchips, straw, and similar materials at a minimum of 2–3” deep to control weeds (although weed control will be more effective with even deeper mulch). A layer of plain cardboard placed underneath a layer of organic mulch can act as an additional weed barrier.

Mulch materials:

• compost
• woodchips
• straw
• rice hulls
• almond hulls
• cardboard
• plastic mulch
• landscape fabric (Earnshaw 2018)
• Living mulch – low-growing, spreading groundcover

Organic mulches, especially those that decompose more rapidly, lose their effectiveness more quickly than plastic mulches and may require significant weeding or re-mulching within a year. The drawback of using inorganic materials such as weed mats or plastic mulches is that the scraps of degraded material can significantly litter the area once these materials have lost their usefulness. 

Lighter mulches may blow away in the wind, and some, like straw, have even been known to catch fire and burn the hedgerow. Growers should consider their planting site and choose a material that suits their location.

Weed seeds will eventually germinate in or on top of any type of mulch. Whichever material is used, controlling weeds within and next to the hedgerow prior to seed production will significantly reduce the need for future weed control labor.  

Keep irrigation lines on top of mulch to make identifying and fixing leaks easier.

Tree protection tubes

Installing plastic tree protection tubes at planting time can reduce damage from vertebrate pests such as rabbits and deer, and herbicide drift. Tree tubes and/or flags can also protect plants from damage while weeding and walking in the area, simply by making the plant locations more obvious. However, while very commonly used, plastic tree tubes can also have negative tradeoffs. For example, temperatures can get extremely high inside the tubes, which might stunt plant growth, and they can reduce basal shoot growth. In the Sacramento Valley Field Demonstration, elderberries with tubes left on through the entire first growing season had substantially fewer basal shoots than those that had tubes removed as soon as leaves of the young plant were pressing up against the tube. A higher number of basal shoots appears to increase total berry yield in the second season. In addition, some restoration professionals have found that birds can sometimes get trapped in tubes if attracted by spiders and other insects living there.

References:

1. California Native Plant Society (CNPS), Calscape website: Blue Elderberry.  https://calscape.org/Sambucus-nigra-ssp.-caerulea-(Blue-Elderberry).
2. Long R, Anderson J. 2010.  Establishing Hedgerows on Farms in California.  University of California Agriculture and Natural Resources Pub. 8390
3. 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.
4. Earnshaw S. 2018. Hedgerows and Farmscaping for California Agriculture: A Resource Guide for Farmers. Community Alliance with Family Farmers, Davis, CA.
5. Maughan T, Black BL, Rupp LA, Yost MA. 2018. Propagation techniques for Sambucus cerulea (blue elderberry). Native Plants Journal 19(2):80-88.
6. California Native Plant Society (CNPS), Calscape website.  Calscape California Native Plant Gardening Guide: The Nature Restoration Approach. https://calscape.org/planting-guide.php.
7. Charlebois D, Byers PL, Finn CE, Thomas AL. 2010. Elderberry: Botany, Horticulture, Potential. Horticultural Reviews 37(4):214-280.