The Traveling Gardener: Washington

Bigleaf Hydrangea I discovered in Seattle, Washington. Also known as French or Lacecap Hydrangea.

In the summer of 2021, I had the pleasure of visiting Seattle, Washington, on a business trip for a client needing garden design help. My second time in the area, besides working in my client’s garden I got the chance to explore various local plant tourist spots and was filled with glee and inspiration. Some highlights included Beacon Food Forest, a community garden where anyone can come to work, plant, and harvest, as well as Kubota Gardens, a beautiful Japanese-style park open to the public. I couldn’t help but notice three plants in particular that grow all over the Seattle area: Rhododendrons, Azaleas, and Hydrangeas.

These majestic plants come in varietal abundance and never cease to amaze. Rhododendrons and Azaleas can grow into large trees, shrubby bushes, or creeping ground covers. They bloom in springtime with clusters of delicate flowers ranging in color. Rhododendrons are typically the larger of the two. Hydrangeas, while common in many states, flourish here in the rainy PNW. From Mophead to Lacecap to Panicle, every single type of hydrangea is a sight for sore eyes. Tending to these beauties with care will help them thrive long-term and be an excellent addition to your garden.

Catawba Rhododendrons and Alpenrose Azaleas in my client’s garden in Seattle, Washington.

Close up of the Alpenrose, a common Azalea species.

Rhododendrons and Azaleas typically bloom in late spring (with some summer-bloom varieties) but usually retain their lush green color throughout the growing season. While Azaleas grow in various weather conditions and can be found everywhere in North America, Rhododendrons are more particular and only thrive in zones 5-8 (in a more temperate climate.) Their blooms are often fragrant and are deemed “showy” in the gardening community. When buying these from your local nursery, check their bloom time and variety, and only purchase plants with healthy green leaves. If you live in a hot area with temperatures 90ºF or above, avoid white-flowering varieties and buy larger, more established plants (smaller azalea starts often struggle in high temperatures.)

Choose a full sun spot with at least a few hours of shade per day; if you lack a location that meets those requirements, you can supplement by draping shade cloth over the plants. If you live in a hotter area, you will need to ensure they will receive daily shade. They prefer well-draining, acidic, humus-rich soil and will benefit from a ground cover or mulch to retain moisture in the soil. Plant in spring or early fall with at least 2 to 6 feet of space between plants. Dig a hole as deep as the root ball and two times as wide, making sure that their highest roots are just below the soil surface. Halfway through filling the hole with soil, water it a bit to help the soil settle around the root ball.

As for caring for them, reapply mulch yearly in the early spring along with some light fertilization (heavy fertilization will burn the foliage.) Water only in the summer when rainfall is sparse. Only prune off dead, decaying, or diseased branches and flowers. Be careful when deadheading, as next year’s buds are just underneath the dying flowers. Wrapping them during the dormant winter is only necessary for severe cold conditions. Rhododendrons and azaleas are not immune from common pests and diseases, so check your plants regularly and use pest control measures as needed.

More Bigleaf Hydrangeas from my Seattle trip this summer.

The intricate flower clusters shown in more detail.

Hydrangeas bloom in the spring and summer and will quickly fill up space in your garden with their beautiful flowers. Hydrangeas typically range in color from pink to blue, as well as come in white and green. Hydrangeas are ornamentals found in various climates, but they perform best in zones 3-7 and grow everywhere in Washington. Their blooms consist of rounded clusters of tiny, delicate flowers; however, they have slightly different formations depending on the type. Types include Oakleaf (best for the warmest climates), Bigleaf (the most common type for gardeners), Panicle (can grow up to 15 feet tall), and Smooth (excellent for cold climates).

Oakleaf hydrangea flower clusters are often conical and long..

Panicle hydrangea flowers are more bushy and conical in shape.

Smooth hydrangeas have smaller flowers in their clusters and create a “smooth” look.

When purchasing hydrangeas, look for bushier starts, so they don’t grow tall and gangly. The best time to plant these beauties is in the fall, and the second-best time is early spring. Fall planting will give you a better chance at bloom success for the following year. When planting, transplant them in the early morning or evening, and place them in a spot in your garden that gets plenty of gentle morning sun and afternoon shade to protect them from the intense heat. In hotter areas, using shade cloth to protect plants might be necessary.

As for soil requirements, hydrangeas love moist, well-draining, rich soil. Adding compost or organic matter once a year will assist your plants in thriving throughout the bloom and growing season. To plant, dig a hole 2 feet wider than the root ball and dig only deep enough to have the top of the root ball at the same level or just above the soil surface. Fill the hole in once the hydrangea is in place and water it in. During the growing season, water about 1 inch per week along with deeper watering up to 3 times a week (if you are expecting rainfall, hold off on watering.) Use an organic mulch for your hydrangeas to ensure moisture retention; an organic mulch will also break down over time and add nutrition to the soil, so reapply mulch yearly or as needed. The type of hydrangea you have will determine how to fertilize. Bigleaf hydrangea will need light fertilization in March, May, and June; Oakleaf and Panicle will need fertilization in April and June; Smooth will only need one fertilization in late winter. Pruning is not necessary; remove only dead wood or diseased sections when required.

While you will come across many other gorgeous plants native to Washington, these three stand out as some of the most iconic plants of the Pacific Northwest.

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