Enhance your chance of success by considering a few key guidelines.
For the dedicated and the dabbling horticulturists in the Pacific Northwest (Oregon, Washington, Idaho, and western Montana), autumn presents a convenient window of opportunity for establishing resilient lavender plants. While spring planting is common, taking advantage of the cooler temperatures and increased moisture of fall can lead to stronger root systems and earlier establishment, provided a few key conditions are met. We’ll explore the nuances of autumn planting for Lavandula angustifolia (English lavender) and Lavandula x intermedia (lavandin) in our region, with mention of a few other species.
Timing is Key: Balancing Warmth and Winter’s Approach
The optimal timing for planting lavender starts in the fall hinges on the availability of sufficient time for root development before the ground freezes solid. In the Pacific Northwest, this generally falls between mid-September and late October. Planting too early, while the soil is still warm and dry, can stress the young plants. Planting too late risks failure to establish enough roots to withstand winter’s freeze-thaw cycles, which can heave plants out of the ground. Aim for a period when the intense summer heat has subsided, and consistent rainfall has begun to moisten the soil, but before hard frosts are consistently occurring.
Navigating Precipitation and Winter Freezes
Our region’s variable autumn and winter weather necessitates careful planning. While increased precipitation in the fall is generally beneficial for root establishment, excessively wet soils, particularly during prolonged periods of rain, can lead to root rot, especially in heavier clay soils common in some areas. Ensure excellent drainage in your planting beds. Do not plant where you know that water tends to pool during the winter. Incorporating amendments like sharp sand or pea gravel can significantly improve drainage.
Winter freezes pose another consideration. While established lavender is generally quite hardy, newly planted lavender is more vulnerable. Mulching around the base of the plants with straw or wood chips after the ground begins to cool can provide insulation and help prevent frost heave.
Cultivar Considerations
- Lavandula angustifolia (“English Lavender”): Generally more tolerant of colder temperatures and wetter conditions than lavandins, many angustifolia cultivars thrive in the Pacific Northwest. Consider some of the highly reliable and cold-tolerant traditional cultivars like ‘Hidcote’, ‘Maillette’, and ‘Munstead’, as well as some of the more recent introductions that remain quite hardy in our region, such as “Betty’s Blue’, ‘Buena Vista’, ‘Folgate’, ‘Hidcote Pink’, ‘Melissa’, ‘Miss Katherine’. ‘Sharon Roberts’, and ‘Royal Velvet’. By planting a variety of available and regionally hardy L. angustifolia cultivars, you will extend the lavender bloom time, and diversify the flower color and texture palette in your garden. For locations with the harshest winter conditions, local experience points to a few reliable performers, including ‘Croxton’s Wild’, ‘Cynthia Johnson’, ‘Imperial Gem’, ‘Melissa Lilac’, and ‘Violet Intrigue’. Autumn planting allows these cultivars to establish a strong root system before the demands of rapid spring growth confront the fledgling plants.
- Lavandula x intermedia (lavandin): Known for their larger size and more intense fragrance, lavandins such as ‘Abrialli’, ‘Edelweiss’, ‘Gros Bleu’, ’Grosso’, ‘Provence’, and ‘Super’ can also be successfully planted in the fall in milder areas of our region, and may even survive in some Zone 5 locations. However, compared to the L. angustifolia cultivars, they tend to be slightly less cold-hardy and more susceptible to root rot in overly wet conditions. Choose well-drained sites and consider planting slightly earlier in the fall to maximize root establishment. Gardeners in colder inland areas might find spring planting of lavandin cultivars to be a safer option. Among the lavandins, a few cultivars like ’Phenomenal’ and ‘Sensational’ standout for their remarkable cold hardiness, rivaling some L. angustifolia cultivars. These lavandin cultivars, along with one of the newest introductions, ‘Bridget Chloe’, are also noted for their resistance to heat and humidity, and have strong, upright growth habits.
- Lavandula x chaytorae: This lavender species is a hybrid (like the L. x intermedia group), and has inherited much of the hardiness of the angustifolia cultivars. The size and form of the mature plants, however, are more reminiscent of the lavandins with their long flower spikes and stems. They are notable for their attractive silvery foliage year-round, which makes them valuable for contrast in garden and border plantings. Increasing in popularity, several L. x chaytorae cultivars are readily available in the Pacific Northwest. ‘Richard Grey’ stands out in this group as a smaller, compact cultivar that is hardy in some of our drier, colder winter regions.
- Lavandula stoechas (“Spanish Lavender”): Sporting unique “rabbit ear” flowers, “Spanish lavenders” are generally the least cold-hardy of all. They are highly susceptible to frost and should be grown as annuals or tender perennials. They can be protected or overwintered indoors, and can also be grown in pots in most of the Pacific Northwest. Even in areas with comparatively mild winter conditions, L. stoechas cultivars are susceptible to loss of portions of individual plants or perishing altogether. One of the hardiest cultivars in this group is L. stoechas ‘Otto Quast’ which is known to survive mild winters and to re-seed itself in Oregon’s North Willamette Valley.
- Lavandula dentata (sometimes confusingly called “French Lavender”): This species of lavender is also quite tender and will not survive a typical Pacific Northwest winter. The novelty of their light green, tooth-edge leaves and continual blooms in the summer is attention grabbling, but like Spanish lavender, they are best treated as annuals or tender perennials, or grown as container plants that are brought indoors for the winter.
Technical Aspects of Autumn Planting
- Plant Spacing: Follow recommended spacing guidelines for the specific cultivar you are planting (generally 18-48 inches for L. angustifolia cultivars depending on the size of the mature plants, and 36-60 inches for L. x intermedia cultivars). Adequate space allows for good air circulation, which is crucial in our often-damp climate, helping to prevent fungal diseases. Good spacing also reduces interdigitation of the flower stalks, and makes harvesting your lavender easier.
- Planting Depth: Plant your lavender starts at the same depth they were in their nursery pots. Avoid planting too deeply, as this can increase the chance of root rot.
- Fertilizers: Generally, it is best to avoid applying high-nitrogen fertilizers at the time of autumn planting as excess nitrogen will push unwanted foliage growth. The focus should be on root development, not top growth. Provide a light application of a balanced, slow-release fertilizer or natural soil amendments like well-composted manure, bat guano, bone meal, kelp meal, and composted fruits and vegetables. These amendments can be worked into the planting hole or applied as a top-dress to provide essential nutrients without pushing excessive foliage growth, strengthening the young plants that are more vulnerable to winter damage.
Sub-regional Safety and Risk for Autumn Planting
The Pacific Northwest is a region of diverse microclimates, and the success of autumn planting can vary significantly depending on your specific location.
Safest Areas for Autumn Planting:
- Puget Sound Lowlands (Western Washington): Characterized by mild, wet winters, this region’s extended fall season provides a long window for plants to establish roots before any severe freezing. The mild temperatures are generally forgiving.
- Willamette Valley (Western Oregon): Similar to the Puget Sound area, the Willamette Valley’s relatively temperate climate, with its mild winters and consistent rainfall, makes it a favorable location for fall planting.
- Columbia River Gorge (specific areas): The Gorge’s unique microclimates can offer excellent growing conditions. Areas with good air circulation and well-drained, often rocky, soil are ideal. For example, the area around The Dalles, Oregon is conducive to lavender production.
Most Risky Areas for Autumn Planting:
- Intermountain Valleys (Idaho and Western Montana): These regions experience much colder, harsher winters with early and prolonged freezes. The short fall season means there is a much narrower window for root establishment, making new plants highly susceptible to winter kill. Spring planting is generally a safer and more reliable option in these areas.
- High-Elevation Areas and Eastern Washington/Oregon: Locations with high elevations, as well as central and eastern Oregon and eastern Washington, face similar challenges to the Intermountain Valleys. The risk of early, deep frosts and heavy snow cover can be detrimental to young lavender plants. Attention should focus on the most hardy angustifolia cultivars for autumn planting.
- Areas with Heavy Clay Soil and Poor Drainage: Regardless of the climate zone, any location with heavy, poorly-draining soil is risky for autumn lavender planting. Excess moisture during the wet season can lead to root rot and plant death.
A Potentially Rewarding Investment
Autumn planting of lavenders in the Pacific Northwest, when done with careful consideration of timing, cultivar selection, and technical details, can be a rewarding investment. By allowing the plants to establish a strong root system during the cooler, moister fall months, you’ll set the stage for vigorous growth in the following spring and summer. Embrace the autumn planting season and enjoy the fragrant rewards of your lavender patch for years to come.
Contributed, edited & formatted by
Michael Lemmers & Christine Mulder
RavenCroft & Barn Owl Nursery
