When to Plant Rhododendron – Planting Guide 2022

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when to plant rhododendron

Did you know that the oldest rhododendron bush is over 100 years old? When you place this plant in your garden, you might just have a friend for life. Learn when to plant your rhododendron for the best chance of success.

When to plant rhododendrons: With year-long foliage and large, boastful blooms, rhododendrons are a great addition to many gardens. It is best to plant the shrubs when they are young, and you can find them at any local garden center. Plant in either spring or fall to allow the plant to establish itself. Rhododendrons need plenty of water as they have shallow roots that can’t access water deep down. You may also need to wrap your plant in the winter to protect it from cold temperatures. If you take good care of your rhododendron, you can have a healthy shrub for years, if not decades.

Planting Rhododendron in Different Climates

Tropical Climate

Similar to azaleas, which can be native tropical plants, rhododendrons can live in a tropical climate. While some varieties need a cold winter, others are fine with more mild winter temperatures.

Dry Climate

Rhododendrons can easily become dehydrated. They need soil that is moist and extra water when there is no rain, so a dry climate is not the best.

Temperate Climate

A temperate climate is great for rhododendrons. They will appreciate the rain in the spring and you won’t need to worry about wrapping them over winter.

Continental Climate

You may be able to grow rhododendrons in a continental climate. However, the winters can be very cold so you will definitely need to wrap them well to protect their shallow roots.

Polar Climate

Rhododendrons need more warmth than a polar climate can provide.

Choosing Rhododendron Seeds

choosing rhododendron

A perfect balance

Within the genus Rhododendron, you will find both rhododendron and azalea shrubs. While they have many similar growing expectations, there are a lot of varieties so you will want to pay careful attention to which one you bring home.

First and foremost when selecting a rhododendron plant is to make sure it will grow in your climate. They need the perfect blend of warmth and cold and if you tip the scales in either direction, you can lose your entire plant.

The best areas for rhododendrons are plant hardiness zones 5 to 8. This means the summers will be warm but the winter temperatures will not be too harsh.  

Bloom time

Another consideration with rhododendron varieties is when they bloom. The majority of plants will unleash their beauty in the spring but there are some types that don’t come into their full glory until the summer. There are also a few options for fall blooms.

Bloom time may not be an important factor when considering which variety to purchase but it is worth knowing when to expect the colors. This way you can pair appropriate flowers in your garden.

Varieties

There are over 2,000 varieties of azaleas and rhododendrons, so it can be hard to decide which one you want. While local gardening centers will always have a few basic varieties, you may want a more comprehensive list.

You can always join the American Rhododendron Society, which lists all the available varieties. The organization also selects the best varieties each year, which can give you some inspiration.

How to Plant Rhododendron Seeds

Selecting healthy plants

Most people start with young rhododendron bushes. They are readily available at local gardening centers or you can purchase them online for a wider selection.

If selecting your plants from a gardening center, make sure they are healthy. You want rhododendrons that have deep green leaves that have life to them.

Avoid plants with yellow leaves or stems that are wilting. This is often a sign that they weren’t watered enough in the store.

You can also check the soil of potted rhododendrons. Place your finger in the container and see if there is moisture in the soil. If the dirt is very dry, then select a different plant.

Shade conditions

The best place to plant rhododendrons is in dappled shade. This often looks as if a sparse tree is above the growing area and the sun is able to filter down through the leaves.

Full sun can wilt your rhododendron, especially in the first year after planting. Likewise, full shade won’t produce blooms and your plant won’t have enough energy to grow.

If you have an area that has full sun except for a few hours in the middle of the afternoon, this will be the best place.

Soil conditions

Overall, rhododendrons are not overly picky about their soil conditions. However, take the time to reflect on your soil before planting.

If the soil is compacted or hasn’t been used in a while, you can add compost or manure and turn the whole area over.

Timing

It is best to plant your rhododendrons in either spring or early fall. For spring planting, wait until the threat of frost has passed.

For fall planting, start early, at least six weeks before the first frost date. In most areas, this translates to planting in either May or late September.

Dig a hole

Remember that rhododendron bushes can grow quite wide. You don’t want to constantly have to dig them up and transplant them, so plan accordingly.

Aim to plant your rhododendrons 3 to 6 feet from other shrubs. You will want to check the maturity size and amend this distance if needed.

Dig your hole so that it is twice the size of the root ball. Then, place the plant into the hole so that the tops of the roots are at soil level or just below the surface.

Rhododendrons have shallow roots. If they are planted too deep, the roots will become too moist and can actually rot.

Once your plant is in the hole, you can then fill it halfway up. Pause for a moment and then water well. Finally, add the rest of the soil and tamp it down

How to Water Rhododendrons

Rhododendrons run the risk of dehydration so you will want to monitor their water levels on a regular basis. There is a good chance you will need to water your shrubs, especially if you live in a drier climate.

Be sure to water your rhododendrons in the summer as these months are usually fairly dry. If your plant doesn’t have enough water, it can greatly affect the formation of flower buds, which will leave you with a green but uninspiring bush.

How to Grow Rhododendrons

how to grow rhododendrons

Add mulch

Rhododendrons have very shallow roots that stay near the surface of the ground. As such, they can become overheated during the hot summer months.

Be sure to regularly add a thick layer of mulch over the ground every year. This will keep moisture in the soil and shade the plant’s roots.

When adding mulch, don’t place any next to the trunk of the bush. If you do, it will keep the trunk too wet and rot can set in.

Fertilize

You don’t need to fertilize your rhododendron too much. In fact, if you over-fertilize, it can actually burn the buds.

If you would like to add fertilizer, do so once a year in the spring. The best time is when the bush is full of buds but before they pop out into flowers.

Deadheading and Pruning

While deadheading won’t always bring about new blooms, you can keep your plant tidy. Deadheading is more about keeping foliage vibrant and lessening the production of seeds.

For those that decide to deadhead, be quite careful. Underneath expired blooms are tiny buds that will turn into blooms the following year, so you don’t want to hurt them.

As for pruning, you can remove any broken or dead branches throughout the year. Those that want a more intense pruning should wait until after your shrub has flowered, which is usually late spring or early summer.

Protect in the winter

While rhododendrons need a bit of cool weather in the winter, they don’t like extreme temperatures. This is mainly because the roots are shallow and thus prone to exposure.

In places where winter weather can get extreme, you will want to wrap your shrub with burlap. Complete this process in the fall and then unwrap your shrub in late winter or early spring.

Remember that wind is a real culprit when it comes to cold. Snow can actually insulate shrubs but cold wind can evaporate moisture in the plant and actually cause it to die.

How long do rhododendrons take to grow?

It can take up to 10 years for a rhododendron to fully mature. Height-wise, this can be up to 10 feet tall.

Most gardeners will purchase young rhododendrons. This means that they will already be at a place where they bloom so the first year you plant your shrub, you will have flowers.

Conclusion

Rhododendrons are a true sight to behold. With their large flowers and evergreen foliage, they are perfect year-round. Plant your rhododendrons in either spring or fall for the best results.

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