When To Plant Rosemary In Oregon

If you’re wondering when to plant rosemary in Oregon, you’ve come to the right place. Oregon’s ideal planting season for this herb depends heavily on your local climate, but timing it right is the key to success.

Rosemary is a wonderful, fragrant perennial herb that can thrive in Oregon gardens for years. It loves sun and well-drained soil. Getting the planting date correct helps your rosemary establish strong roots before winter or summer stress hits.

For most Oregon gardeners, the best time to plant rosemary is in the late spring, after the danger of frost has passed. This typically means from mid-May to early June. The soil has warmed up by then, which rosemary prefers.

In warmer regions like the Rogue Valley or along the coast where frosts are mild, you can often plant as early as late April. In colder, higher elevation areas like Central Oregon, waiting until early June is safer. A fall planting is also possible in western Oregon if done by early September, giving the plant time to settle before cool, wet weather.

Understanding Oregon’s Climate Zones

Oregon’s climate isn’t one-size-fits-all. It ranges from wet maritime zones to dry high deserts. Your planting schedule depends on which zone you garden in.

Western Valleys (Willamette, Umpqua): Plant from mid-May. Fall planting by early September works well here too.
Oregon Coast: Mild year-round. You can plant from late April to May, taking advantage of the long, frost-free season.
Southern Oregon (Medford, Grants Pass): Warmest regions. Aim for late April to early May.
Central and Eastern Oregon (Bend, Ontario): Short growing season, cold winters. Wait until early June and choose a very protected, sunny site.

Choosing the Right Rosemary Variety

Selecting a hardy variety is crucial, especially for colder areas. Not all rosemary is created equal when it comes to surviving an Oregon winter.

‘Arp’: The most cold-hardy, often surviving down to -10°F. Excellent for inland valleys.
‘Hill Hardy’: Another reliable choice for colder zones, with a upright growth habit.
‘Tuscan Blue’: Beautiful flavor and flowers, but best for western Oregon where winters are milder.
Prostrate Rosemary: Great for trailing over walls or containers. Needs winter protection in cold areas.

Step-by-Step Planting Guide

Once your timing is right, follow these steps to give your rosemary the best start.

1. Select the Perfect Spot

Rosemary demands full sun—at least 6-8 hours of direct light daily. It also needs excellent drainage. Avoid low spots where water collects. South or west-facing slopes or walls are ideal.

2. Prepare the Soil

This is the most important step for Oregon’s often heavy clay soils. Rosemary will not tolerate wet feet.

Dig a hole twice as wide as the root ball but no deeper.
Mix the native soil with a generous amount of coarse sand or fine gravel (up to 50%) and some compost. This creates the fast-draining conditions rosemary loves.
For heavy clay, consider planting in a raised mound or a raised bed filled with a sandy soil mix.

3. Planting Your Rosemary

Water the plant in its nursery pot thoroughly an hour before planting.
Gently remove it from the pot and loosen the roots slightly if they are pot-bound.
Place it in the hole so the top of the root ball is level with or slightly above the soil surface. Planting too deep can cause stem rot.
Backfill with your prepared soil mix and firm it gently.
Water deeply to settle the soil around the roots.

4. Initial Care and Spacing

Space plants 2 to 3 feet apart. After planting, add a thin layer of gravel or small stones as mulch. This keeps the foliage dry and helps retain heat. Water regularly for the first season to establish roots, then taper off.

Growing Rosemary in Containers

In areas with poor soil or harsh winters, containers are a fantastic option. You can control the soil and move the plant to shelter.

Use a pot with large drainage holes that is at least 12-16 inches wide.
Fill with a cactus/succulent potting mix or make your own with regular potting soil and 30% perlite or pumice.
Container plants need more frequent watering than in-ground ones, but always let the soil dry out between waterings.
In winter, move pots to a protected location, like a garage or against a house wall, in colder parts of the state.

Common Mistakes to Avoid

Even experienced gardeners can make a few errors with rosemary in Oregon’s unique climate.

Overwatering: This is the number one killer. Rosemary is drought-tolerant. Soggy soil leads to root rot.
Poor Drainage: Not amending heavy clay soil is a recipe for failure.
Planting Too Early: A late frost can damage or kill young, tender plants.
Over-fertilizing: Rosemary isn’t a heavy feeder. Too much fertilizer leads to weak, leggy growth and less flavor.
Not Providing Winter Protection: In cold zones, a layer of dry mulch (like straw) around the base after the ground freezes can help.

Seasonal Care Calendar

Here’s a quick guide to year-round rosemary care in Oregon.

Spring (Late Apr-Jun): Plant after frost danger. Prune lightly to shape.
Summer (Jul-Aug): Water only during extended dry periods. Harvest stems as needed.
Fall (Sep-Oct): Do a light harvest. Stop fertilizing. Plant new rosemary by early Sep in mild areas.
Winter (Nov-Mar): Protect in-ground plants in cold zones with mulch. Shield from winter wetness if possible. Water container plants sparingly.

FAQ: Rosemary in Oregon

Can rosemary survive Oregon winters?

Yes, many hardy varieties can, especially in western Oregon. In eastern Oregon, it needs significant winter protection or should be grown in a pot and brought indoors.

What is the best month to plant rosemary in the Willamette Valley?

Mid to late May is generally safe. You can also plant in early September for fall establishment.

Why is my rosemary plant turning brown?

Browning is usually a sign of root rot from overwatering or poor drainage, especially during Oregon’s wet winters. Cold damage can also cause browning.

How often should I water rosemary in Oregon?

Once established, it often needs no supplemental water in western Oregon, except in summer drought. In eastern Oregon, water deeply but infrequently, allowing soil to dry completely. Always err on the side of underwatering.

Can I grow rosemary from seed in Oregon?

It’s possible but very slow and germination is unreliable. It’s much easier and faster to start with a small nursery plant or take cuttings from an existing plant.

By following these guidelines for when to plant rosemary in Oregon, you’ll set your herb up for a long and productive life. With its sun-loving nature and need for good drainage kept in mind, you’ll be able to enjoy fresh rosemary for cooking, fragrance, and garden beauty throughout the year. Remember, patience in the spring leads to a hardy plant that can handle our variable Oregon weather.