Cover the soil under the elderberry bushes with a 2- to 3-inch layer of mulch, leaving a 3-inch space between the mulch and stems of the bush. Mulch prevents the soil from drying too quickly, as elderberries can't tolerate dry conditions.
Water elderberries one to two times a week so the top 6 inches of soil remains moist. Avoid overwatering and soggy soils, as overly wet soil causes elderberry roots to rot.
Prune elderberries in spring before fertilizing. Cut out damaged and dead canes at soil level. Remove any canes or stems that are more than 3 years old, as these no longer produce fruit.
Fertilize elderberry bushes in the spring as the first new growth appears. Sprinkle a 10-10-10 analysis fertilizer blend around the base of each bush. Apply 1/2 lb. of fertilizer per year of age up to a maximum of 4 lbs. per plant.
Weed the bed throughout the growing season as elderberries can't tolerate competition. Pull up weeds as soon as they sprout. Replenishing the mulch layer annually also prevents heavy weed growth.