Elderberry

Nitrogen as growth begins

As the buds break and growth begins, spread 1 to 2 pounds of actual nitrogen per 1000 square feet over the root zone of a mature bearing planting. Do not feed nitrogen at planting time; a new plant gets at most a light dose about 4 to 8 weeks after it goes in. Retest the soil every two to three years and add phosphorus or potassium only if the test calls for it, keeping pH between 5.5 and 6.5. Elderberry pushes its whole fruiting frame out of the crown each spring, so the nitrogen has to be there as the shoots extend; applied later it feeds soft growth that will not harden before frost instead of the cymes.

Dormant-prune elderberry well before bud breakJan – Mar

Any time the canes are fully dormant and well before bud break, cut out every dead, diseased or damaged stem, remove most wood that is three years old or older, and tip weak canes back to strong wood; leave five to eight strong canes on a mature bush. American cultivars can instead be cut entirely to the ground, which trades a little total yield for one uniform crop on new wood. Gather the prunings and burn or bin them rather than composting them in place. American elderberry fruits on wood at least a year old and also on new shoots thrown from the crown, so clearing spent old wood keeps light and air moving through the bush and pushes the vigorous new canes that carry the biggest cymes. Eriophyid mites overwinter under the buds and bud scales of those canes, so hauling the prunings away removes next year's mite population with them.

⚠ European elderberries (Sambucus nigra types such as Samdal, Haschberg, Korsor and Marge) fruit on the previous year's growth - cutting those to the ground removes the crop. Use the selective method on them.

Cut out borer-infested canes after harvest

With the fruit off, walk the planting and cut out any cane that is wilting at the tip, hollow, or showing frass at an entry hole. Burn the infested canes or take them off site - do not leave them in a brush pile or the compost. While you are there, pull out any wild elderberry growing near the planting. Pruning and burning infested canes is the only post-harvest control the Missouri guide lists for elder shoot borer moth: by now the larvae are living inside the wood where no spray can reach them, and they will overwinter there to emerge into next year's crop. (The guide does list a chemical option for this pest - Altacor 35WG - but only as a summer spray, which has to go on earlier, before the larvae are sealed in the cane. Once you are at post-harvest, sanitation is what is left.) Nearby wild elderberry acts as a reservoir that reinfests the planting every season.

Scout the cymes at bloom, but do not spray insecticide

Walk the planting while the cymes are open and record what is building: sawfly larvae stripping foliage, eastern flower thrips in the florets, stink bugs and Jessie's bug at the shoot tips, and adult elder borer beetles, which emerge exactly now. Write down what you find and what it is doing, then hold every insecticide until the petals have dropped. Elderberry is primarily wind-pollinated, so a bloom spray buys you almost nothing in fruit set while still poisoning the bees and other insects working the flowers. Missouri Extension is explicit that insecticides are not to be applied during bloom, and the pests you see now are all still treatable at petal fall a few days later.

⚠ Do not apply insecticides during bloom. Only spray a pest you have actually identified - scouting, not the calendar, decides whether an application is needed at all.

Horticultural oil at green tip for eriophyid mites

From dormancy through green tip, before any leaves unfurl, spray horticultural oil (Damoil) and wet the canes and buds thoroughly. If you missed the window, the organic pre-bloom options are insecticidal soap (M-Pede), neem oil (Trilogy) or pyrethrins (PyGanic) - but they must go on before the leaves curl. Eriophyid mites spend the winter tucked under the buds and bud scales, and oil smothers them while they are still exposed there. Once they move into the expanding leaves and cause the inward leaflet curl and puckering, they are sealed inside the folded tissue and no rescue spray reaches them; heavy infestations go on to destroy florets and young fruit.

⚠ Neem oil (Trilogy) carries a 1-day pre-harvest interval; PyGanic is capped at 10 applications per season. Apply before leaf curl occurs - the label is a legal document, so check that your product is labeled for elderberry.

Elder borer beetle at petal fall

Once the petals have actually dropped, and only if you found elder borer beetles while scouting at bloom, spray bifenthrin (Brigade WSP). Check again about ten days after petal fall and repeat only if adults are still present. The same timing covers sawfly, thrips, stink bugs and Jessie's bug if scouting turned them up. Adult elder borer beetles emerge during bloom and lay their eggs at the base of the plant; the larvae then tunnel into the canes and roots where nothing can reach them. Petal fall is the first moment you can hit the adults without spraying open flowers, and it is the last moment before the eggs are laid.

⚠ Bifenthrin (Brigade) has a 1-day pre-harvest interval, a 12-hour restricted-entry interval, and a season cap of 80 oz of product per acre. It is highly toxic to bees - confirm the petals are down, not merely fading, before you spray.

Spotted wing drosophila from first color

From the moment berries begin to color until the last pick, hang a vinegar trap and check it. If you catch spotted wing drosophila, spray spinosad (Entrust, an organic option) or spinetoram (Delegate), and pick up and destroy any fallen fruit. Alternate to a different chemistry rather than following one of these with the other. Unlike ordinary vinegar flies that need already-damaged fruit, SWD females have a serrated ovipositor that saws into sound ripening berries and lays eggs inside them. By the time the fruit looks soft or leaking, the larvae are already in it, so the spray has to be in place before the berries are attractive.

⚠ Entrust: 1-day PHI, no more than 2 consecutive applications. Delegate: 1-day PHI, no more than 3 applications a year with at least 7 days between them. Both are IRAC group 5, so rotating from one to the other is not a rotation and breeds resistance.

Clip whole cymes and chill them fast

Harvest when every berry in the cyme is fully colored to a deep purple-black, clipping the entire cluster rather than picking berries off it. Go over the planting at weekly intervals and pick early in the day. Get the fruit to 32-40F as soon as you come in, then freeze the whole cymes and knock the berries loose by hand-shattering them or running them through a de-stemmer. Fresh elderberries tear and bleed juice if you strip them off the stem, but they snap off cleanly once frozen. The fruit is highly perishable and ripens in the heat of summer, and the anthocyanins that make it worth growing are fragile - long storage and repeated freeze-thaw cycles destroy them.

⚠ Never harvest from roadside or railway wild stands - those crews often spray herbicide just before the berries are ready. Elderberry ripens over 6 to 8 weeks depending on cultivar, and a bush cut to the ground the previous winter ripens over 2 to 3 weeks while one with mixed-age shoots takes 3 to 4.