A common question in late fall concerns the lack of berries on holly.

Most hollies, Ilex spp., whether evergreen or deciduous, have male and female flowers on separate plants. Hollies are dioecious. To obtain fruit set, the female requires a compatible male of the same or related species for proper pollination.

If a holly plant fails to produce berries, it is either a male, and will never produce berries, or it is an unfertilized female. There are several reasons why female hollies fail to produce berries, many of which are under the control of the gardener.

Lack of a compatible male plant:

A compatible male was not present within 100 yards, the range for bees to transfer pollen, while the female was in flower.

Lack of pollinators:

Insect pollinators, primarily honeybees, may have been too scarce because of loss of habitat or use of herbicides. There may have been reduced activity because of cold, rainy weather during full bloom, thus reducing flowers and preventing fruit set.

Immaturity:

Hollies may take three to five years or more to bloom if grown from seed. Those grown from cuttings may take up to two years to bloom.

Poor growing conditions:

Hollies need moist, well-drained, acidic soil, in part shade to full sun. Lack of flower and berry production may be because of extremely dry sites, unprotected sites with exposure to desiccating winds and winter sun, heavy shade, and-or poor soil drainage.

Improper fertilization:

Excess nitrogen fertilizer, applied directly to the plant or even to adjacent turf, could have caused an overabundance of foliage at the expense of flowers and berries. Too little nitrogen could have also been a problem.

Improper or heavy pruning:

This may cause failure to flower and hence fruit set. Prune out dead, diseased, or wayward branches at any time. Early summer is the best time to prune evergreen hollies, as they set buds the previous fall.

A hard pruning after mid-July can force new growth, which may not harden off enough before the killing winter cold. Deciduous hollies bloom on new wood and may be pruned in late winter. Prune no more than one-third of the shrub at any one time.

Uncooperative weather:

Severe drought and-or high temperatures may have caused flowers or berries to drop. An early autumn frost or a particularly hard winter may have damaged tissue that was not fully hardened off. A late frost in spring may have damaged flowers and prevented fruit set.

Improper labeling:

Your holly plant may not have been properly labeled at the nursery. Perhaps it is a male or is not compatible as a pollinator. To distinguish between male and female plants, examine the flowers. Male flowers have four stamens. They can be distinguished from female flowers which have a globose (spherical)-rounded pistil.

Spotted Lanternfly update:

Be on the lookout for spotted lanternfly egg masses. For information on what to look for and how to destroy the eggs: extension.psu.edu/spotted-lanternfly

If you see egg masses, scrape them off, double bag them and throw them away. You can also place the eggs into alcohol or hand sanitizer to kill them. In order to kill the eggs, it is critical that you “pop” the eggs if you are not double-bagging them or putting them in alcohol or hand sanitizer.

“Growing Green” is contributed by Diane Dorn, Lehigh County Extension Office Staff, and Master Gardeners. Information: Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-813-6613.