March 23, 2019
When should I prune my pomegranate tree and how much wood should be removed during pruning?
- Extension Master Gardener Trainees in Valencia and Bernalillo Counties
Pomegranates (Punica granatum) are monoecious plants. Monoecious is a flowering term that means it has both male (pollen-forming) and female (ovary- and fruit-forming) reproductive organs on the same plant. The individual flowers can be perfect, meaning both male and female parts are found together in a single flower. Other flowers found on the same shrub can be imperfect, meaning they are single-sex. The imperfect flowers on pomegranates are male only, so they produce pollen and then fall to the ground. That should make many pomegranate growers breathe a sigh of relief because it’s common to find dozens of the bright red blossoms littering the ground, blame the wind, and then worry that you won’t get any fruit this year. Those male flowers were never meant to stay on the stems or become fruit. According to pomegranate informational sources online, the male flowers are more vase-shaped and the perfect flowers tend to be urn-shaped. Wait just a minute there, isn’t an urn a type of vase? insert eye-roll emoji Other sources describe the imperfect or “barren” flowers as being smaller and shorter than the big, bell-shaped, perfect (aka fruitful) flowers.
On most pomegranates, the perfect flowers can self pollinate, but they can also cross pollinate with another flower from that same plant or cross pollinate with a flower from a different plant. Hummingbirds as well as many insect pollinators are drawn to the bright red blossoms. Pomegranates can be single- or double-flowering. The double-flowering cultivars have showier blossoms, but may not produce as much fruit.
OK, I’ll stop beating around the shrub and get to the question at hand. The key to knowing when to prune any plant is knowing your plant’s flowering behavior. When does it flower? Does it flower on old wood, meaning growth from last year or years prior? Or does it flower on new wood?
One general rule is that plants that flower before they leaf out are likely blooming on old wood. Think redbuds, lilacs, wisteria, apricots, peaches, cherries, plums, and forsythia. These are species that set flowering buds in the previous season, but the bud stays dormant until early spring. This means that if you prune them in late summer, fall, or winter, you are pruning off spring flowers.
Other plants blossom on new wood or new growth. Annual flowers are a great example of this. The sunflower sprouts, grows like crazy, and then flowers on current season stalks. Rose of Sharon, crepe myrtles, chaste trees (aka vitex), butterfly bushes, and many roses are examples of trees and shrubs that bloom on new growth, and those flowers open up during the summer. Pomegranates are in this new wood group.
In their natural form, pomegranates tend to be multi-stemmed and bushy and don’t need much pruning, certainly not annually. With lots of work and continual care throughout each year, you can train a pomegranate to be more tree-like, but the shrub form is its natural state, so why not “just grow with it”?
That being said, it’s always a good time to remove dead or damaged branches, and you can prune out twiggy interior branches in the late winter or early spring, leaving larger, woodier stems alone. Be careful because stems can be thorny.
The blooming period is relatively long for pomegranates (April–June), but later-blooming flowers may not have time to develop into fully ripe fruit. Fruit ripening takes around 6–7 months for most pomegranates, so flowers blooming in April and May should be ready between Halloween and Thanksgiving.
Old photos of the pomegranate in my yard in Las Cruces from a few years ago show it covered in blooms in mid-April, but I do not remember what cultivar it is and we never saw fruit developing. I thought we planted it in too much shade, but never got around to transplanting.
One exciting thing about pomegranates is that besides being drought- and heat-tolerant they have higher salt tolerance than many fruiting species. Of course, less stress helps ensure a good harvest, so adequate fresh water is needed for most commercial growing operations. But research is underway on growing poms in saline and sodic soils as well as with brackish groundwater, treated effluent, and greywater.
For more info on pomegranate cultivar research for growing them in colder parts of New Mexico and why your pomegranate fruits might burst before they’re fully ripe, visit Desert Blooms and search “poms.”
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!