How to Prune Rosemary for an Endless Harvest, According to Horticulturists

Rosemary is a perennial herb that can thrive year-round in warm USDA zones and adds fresh flavor to many dishes. To keep your plant healthy, regular pruning is essential. Light trimming during the growing season encourages new growth and a more abundant harvest. However, the best time for more thorough pruning is in the spring and summer. To help you prune rosemary the right way, we asked experts to share their top tips—and the most common mistakes to avoid.

When to Prune Rosemary

When it comes to pruning a rosemary plant, timing is everything. The best time to prune a rosemary plant is in the late spring or early summer, after the blooms begin to fade. "This will spur fresh growth, with follow-up pruning and harvesting supporting new growth throughout the summer," says Linda Langelo, a horticulture specialist at Colorado State University. Pruning rosemary too early can remove the flowers and produce new growth that could be damaged by a late frost. "Avoid pruning under 1 to 1 1/2 months before the first frost, as new growth can get damaged by the sudden cold," says Langelo.

How to Prune Rosemary

Again, it's best to wait until after the plant has bloomed. Make sure to use a pair of sharp, sterile pruners, says Langelo. The sharper the blades, the cleaner the cut—helping avoid damage and reducing the risk of disease.

While pruning, first remove any dead or diseased stems, along with any that are rubbing or crossing. Then prune to shape the plant. The proper shape after pruning should leave the rosemary with an open center, which creates a more compact form and encourages fuller growth, according to Langelo.

Step-by-Step Instructions

Damon Abdi, of the Hammond Research Station at Louisiana State University's agricultural center, shares his step-by-step instructions and tips for pruning rosemary:

1. Any time of year, remove dead, damaged, diseased, or dying branches.
2. Look to the interior of the plant and remove crossing branches to thin out growth and improve the airflow.
3. For harvesting, cut the top 3 to 6 inches of the stems throughout the season.
4. For shaping, cutting individual stems with pruners or shears encourages bushier growth. Cut just above a leaf node—two new branches with grow from that point.
5. Avoid cutting in the woody part of the plant, and always leave some green leaves to support continued growth.
6. Think long-term when trying to restore an overgrown rosemary bush. Don't prune too much at once. Instead, guide growth over several successful pruning sessions. Remember: You can always prune more, but you can't prune less after the fact.
   

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Rosemary Pruning Mistakes to Avoid

There are several common mistakes to avoid when pruning rosemary to ensure the plant stays healthy. Langelo and Abdi share their advice for what to look out for.

• Pruning too early or too late: Timing is critical. The biggest mistake is pruning too early or too late. "Trim when blooming has stopped," says Langelo. "This prevents over-pruning and overgrowth." Pruning too early can lead to overgrowth, while pruning in the winter can damage the plant. Since pruning encourages new growth, the new growth may be harmed by frost.
• Using the wrong tools: The type of branch you're removing should determine the tool. Use loppers for thicker, woody branches that are dead. For quick stem harvesting, use bypass pruners. When shaping, Abdi recommends using shears for a more efficient landscaping process.
• Using unsanitary tools: Dirty blades can spread disease between plants. Always sanitize pruners and shears with isopropyl alcohol to reduce this risk.
• Cutting back too much: Avoid cutting too far into the woody part of the plant, which can result in bare spots and sparse foliage. "I recommend pruning rosemary as well as pruning any plant; remove only a third of the plant," says Langelo.