Plant care & info

Family: Ericaceae

Genus: Rhododendron – row-de-DEN-dron

Common: Rhododendron!

1000+ species, mostly from Asia but some from Europe, North America, and Australia.

A very diverse genus, with both evergreen and deciduous members. Trumpet-shaped flowers in a wide variety of colors are generally borne in clusters in spring.

Range from inches-high shrubs to small trees. “Dwarf” rhododendrons generally are less than 3’ tall in 10 years; many popular varieties will be 5-6′ tall in 10 years, and much larger in decades.

Rhododendron thrive in acidic soil with a pH of 4.5-5.5 which is commonly found in Portland and on the rainy side of the Cascade Mountains. Most would appreciate better soil drainage than is typical in Portland, so adding mulch to the garden bed yearly will help. Use a fertilizer appropriate for acid-loving plants.

Over-watered plants and waterlogged soil both cause roots to decay, foster fungal problems, and cause plant death.

Rhododendrons often prefer some shade, and almost all require protection from hot afternoon sun. Blooms will be sparse in deep shade, however. Some varieties are more tolerant of sun.

Healthy plants that receive the right light, water, and soil, are less likely to have pest and disease issues. We do see:

Sunburn
Phytophthora
Rhododendron lace bug
Root weevil

Rhododendron is a huge genus that includes not just the familiar tree-like large-leafed plants that flank old Portland houses, but also a variety of smaller and different-textured shrubs with interesting leaves and a wide range of flower colors.

Most cultivated “rhodies” are evergreen, grow best with some shade, and prefer acidic, well-drained soil. Many, many wonderful varieties have been bred by rhododendron fanciers through the years, but we also get to delight in the qualities of species of rhododendrons.

Because the roots of rhodies are relatively shallow, it can be challenging to underplant them when they get big – so if you want them to have company, use shallow-rooted groundcovers or plant perennials just outside the root zone while the shrub is still small.

The widely used flowering shrubs, azaleas, are technically a subgroup of rhododendrons! Learn more about Deciduous Azaleas here.

Explore More Rhododendron

Classic Large-Form Rhododendrons

Classic Large-Form Rhododendrons

The most familiar rhododendrons, with big leathery leaves. They grow into large bloom-encrusted shrubs, and with decades can become the twisting “trees” seen outside older houses. In shorter garden timeframes, they often get to 5 or 6 feet tall in 10 years.

Horizon Monarch
Taurus
Sappho
Purple Passion

Dwarf Rhododendrons

Dwarf Rhododendrons

A much easier fit in an urban garden! Slower growing than their large cousins, and with a finer texture, they often get to 3 feet tall in 10 years. Can be very effective massed!

Shamrock
Cherries and Merlot
Ramapo
Nancy Evans

Favorites For Foliage

Favorites For Foliage

The leaves are what you’ll see for most of the year, and rhododendrons can serve up a great variety of gorgeous leaves.

President Roosevelt
Wine and Roses
Yaku Hybrids
Ostbo Elizabeth

Favorites for Fragrance

Favorites for Fragrance

Yes! There are fragrant rhodies, too. Feast your nose on these.

Coastal Spice
Elsie Frye
Scented Sunrise
Rhododendron Edgeworthii

Species Rhododendrons

Species Rhododendrons

The origin of rhodies’ diversity is the wide array of natural species that have been brought into garden culture. Here are a few we sometimes see.

Rhododendron lutescens
Rhododendron spinuliferum
Rhododendron racemosa
Rhododendron stenopetalum ‘Linearifolium’

Sun Tolerant Rhododendens

Sun Tolerant Rhododendens

While rhodies generally need protection from sunburn, some are better at taking it – in fact, some of the low growing ones are great for rock gardens. Rhodies in the hot sun will need more watering to stay healthy and look good.