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Rhododendrons are the go-to plants for making shady spots more attractive. Whether bordering a garden or planted in pots, these shrubs boast lush foliage and clusters of brightly colored bell-shaped blooms that can delight for decades. A potential downside to this rewarding shrub is that it only grows well in the right medium. Will ericaceous compost make rhododendrons thrive?
Ericaceous compost is an ideal soil supplement or potting mix for rhododendrons because its acidic pH helps the shrub absorb all the nutrients it needs to flourish. Ericaceous compost’s pH is generally between 4.0 and 5.0, which falls within the range for rhododendron health.
Give your rhododendrons a happy home, and they will treat you to a magnificent flower display year after year. The trick to getting your rhododendrons to grow to their full potential is to ensure their soil is acidic, moist, and well-draining. Let’s see how ericaceous compost can help create the conditions to make your rhododendron the standout feature in your garden.
Do Rhododendrons Need Acidic Compost?
Suppose your soil is naturally neutral or alkaline. In that case, you’ll need to lower its pH before you experience success growing rhododendrons. A popular way to make the soil more acidic is by regularly working in ericaceous compost.
There’s another option for gardeners with soil on the wrong side of the pH scale who yearn for a rhododendron-filled yard: planting the shrubs in ericaceous compost in pots. This is the way to go if your soil is strongly alkaline.
Ericaceous compost can also be used to enrich the soil with organic matter, nutrients, and microorganisms and insects that help make nutrients available to plants and encourage airflow.
Yet another use for ericaceous compost is mulch to help keep the soil moist, control weeds, and protect rhododendrons against icy weather.
Why Is Ericaceous Compost Good For Growing Rhododendrons?
Ericaceous compost is the right choice for rhododendrons for these reasons:
- It has an acidic pH. Ericaceous compost’s pH (around 4.0 to 5.0) creates the acidic environment rhododendrons are so fond of.
- It holds moisture. Rhododendrons’ roots don’t grow deep, so they rely on water in the upper soil layers. Ericaceous compost is rich in organic matter, which helps keep the soil moist.
- It drains excess moisture. Not only does ericaceous compost’s organic matter retain adequate moisture, but it also releases anything extra to stop the soil from becoming waterlogged. This is important because soggy soil can make rhododendrons sick.
Like ericaceous compost, regular compost contains plenty of organic matter. So it also helps create a good moisture balance. But regular compost’s pH is close to neutral, making it unsuitable for acid-loving rhododendrons.
The secret ingredients that produce a compost mixture that satisfies rhododendrons’ acidic taste are high-acid organic wastes like oak leaves, pine needles, and coffee grounds.
What Is The Ideal pH For Growing Rhododendrons?
Rhododendrons are one of the top 3 acid-loving plants (along with camellias and pieris). They need a strong to medium soil acidity (between 4.5 and 6.0) to grow happily.
If you tried growing rhododendrons in neutral or alkaline soil, they’d likely develop a nutritional deficiency. This is because these shrubs can’t use iron and manganese in soils with pH levels of 7.0 and up.
The telltale sign that rhododendrons are lacking essential nutrients is yellowing leaves. Young leaves are most at risk of this effect. The leaf edges are the first to change from green to yellow (pale or bright). If the nutrient deficiency isn’t corrected, the yellowing can spread to the entire leaf, leaving only green veins.
So, no matter how green your fingers are, you’ll never grow your dream rhododendrons if you plant them in alkaline soil.
How To Use Ericaceous Compost To Grow Rhododendrons
If a test has revealed that your soil’s pH is neutral or alkaline, you can use ericaceous compost to create a more welcoming environment for rhododendrons.
Note: The right soil pH goes a long way toward creating favorable conditions for rhododendrons, but the soil type is also important. Loam soil is great at holding adequate moisture without becoming saturated and is the top pick for rhododendrons.
Here are 4 ways to use ericaceous compost to bring out the best in rhododendrons:
Work Ericaceous Compost Into The Soil Before Planting
Lower the pH of neutral to slightly alkaline soil before planting your rhododendrons by working ericaceous compost into the topsoil. Follow these 2 steps:
- Step 1: Place a 4-inch layer of compost on the planting area.
- Step 2: Work the compost into the upper 10 inches or so of soil using a garden fork or spade.
Tip: Prepare your soil in the fall for springtime planting.
Regularly Apply Ericaceous Compost To Existing Beds
Suppose you’re blessed to already have thriving ericaceous shrubs. Keep them that way by working about an inch of compost into the top soil layers yearly.
The compost will improve the soil’s condition, which means lovelier rhododendrons for you to admire!
Warning: Gently work the compost into the soil to avoid harming your rhododendron’s shallow root system.
Use Ericaceous Compost In Pots And Containers
Rather than fighting the soil in your garden to make it rhododendron-friendly, create ideal growing conditions for your shrubs in pots or containers.
Smaller rhododendron varieties easily make themselves at home in pots filled with peat-free ericaceous potting compost on shady patios.
Tip: Re-pot your rhododendrons in new ericaceous potting compost every 2 years to keep them in peak condition. Freshen up the pot in the years between by replacing the top 2 inches of potting compost.
Mulch With Ericaceous Compost
Apply a 2-to-5-inch layer of ericaceous compost on the soil’s surface to discourage weeds, protect your rhododendron’s roots, and keep the soil moist. Replace the mulch layer yearly.
Alert: Don’t let the mulch get too close to your rhododendron – keep it a few inches away from the shrub’s trunk.
Tips For Growing Rhododendrons
Planting rhododendrons in acidic, moisture-holding, well-draining soil rich in organic matter is essential to their health.
Here are more things you can do to help rhododendrons look their best:
- Plant the shrubs in partial shade (avoid deep shade and areas with full morning sun).
- Choose a spot that’s sheltered from the wind.
- Use rainwater for watering because tap water is alkaline.
- Snip off dead flowers and dead or diseased branches, but leave the shrub to sprawl freely.
Watch this video to see a rhododendron wonderland and get tips for growing these eye-catching shrubs in beds or pots:
Ericaceous compost is a must for rhododendron care because it creates the acidic, organic-matter-rich environment rhododendrons need to thrive.
Ericaceous compost can be worked into rhododendron beds before planting, added to the soil yearly, used as a growing medium in pots and containers, and placed on the soil surface as mulch.