12 Flowers You Should Never Plant In Clay Soil

Of the six main types of soil, clay soil is often considered one of the toughest to manage. While sandy, silt, loamy, peaty, and chalky soils have their own setbacks, clay is notorious for stunting plant growth if not addressed. Due to its high clay content, this soil tends to cling to moisture and has difficulty draining. While some plants may benefit from this type of material, such as black-eyed Susans and New England asters, others, like poppies and tulips, require thorough drainage, making clay soil detrimental to their growth. If you think you may have heavy clay soil, the easiest way to confirm this is by performing a soil test. If the results show that your soil is more than 30% clay, you should not use it as topsoil. Instead, it's recommended to incorporate another type into the mix, like loamy, or instead grow your plants in raised garden beds with a completely different material, like compost.

While many types of flowers can easily thrive in clay-dominant soil, others will suffer as the clay will make it difficult for their roots to receive water. Flowers like lavender, peonies, and azaleas will not thrive in these types of environments, as they require loose soil that can easily drain. If your soil is primarily clay, you'll want to avoid adding these flowers to your garden, unless you plan on starting raised beds or you're able to improve the heavy clay soil in your garden. If you want to make the best of what you have, choose plants that thrive in clay soils, like hydrangeas or hardy geraniums. 

There are over 300 species of clematis, from leatherflower (Clematis viorna) to blue jasmine (Clematis crispa). These buttercup (Ranunculaceae) family perennials are typically vining flowers that require well-draining growing mediums, which makes them poor candidates for clay soil. These plants can also fall victim to root rot, which can happen when clay soils become waterlogged. If you have soil with a high percentage of clay, add manure or compost to the mix before planting clematis.

If you have a garden full of clay soil, you might want to refrain from planting tulips (Tulipa spp.). These popular flowers require well-draining soil, ideally sandy or dry, as they are especially susceptible to root rot and should not be overwatered. If you want to plant tulips but have a high clay concentration in your soil, try planting them in a separate raised bed or adding organic material like compost. Note, however, that too much compost can also add unwanted moisture to the roots.

The beloved herb lavender (Lavandula spp.) will, unfortunately, not survive long if planted in clay-heavy soil. This plant prefers a looser type of soil, like sand or gravel, and will not thrive with such a temperamental material as clay. When deciding whether it's better to plant lavender in the ground or in containers, consider your soil type. Make sure it is well-draining, as lavender roots can easily become waterlogged and rotted. If your ground soil isn't loose enough, grow your lavender in a container.

If you plan to add some peonies (Paeonia spp.) to your garden, you'll want to ensure that your chosen soil is not only well-draining but ideally sandy. While peonies can thrive in just about any type of soil, they are much more likely to rot in clay soil. If you are primarily working with clay material, you'll want to be vigilant about adding organic material to balance it out. Peonies will not survive in waterlogged or soggy areas, which clay soil tends to facilitate. 

Before you add this fragrant herb to your garden beds, make sure you check the contents of your soil first. While Russian sage (Salvia yangii) can be tolerant of various soil types, it cannot thrive in overly moist environments like clay soil, so much so, in fact, that it can even tolerate droughts. Like most plants, Russian sage requires a significant amount of water when first planted, so a well-draining garden bed is a must. If you can adjust your soil pH level, ensure it is at a level of 7 or higher, or on the alkaline side. 

Out of all of the clay-disliking plants on this list, hostas (Hosta plantaginea) are probably the most tolerant of clay soils. These luscious plants are often grown for their striking foliage, but they also produce pretty flowers. Hostas enjoy a moist environment; however, too much moisture can lead to poor drainage and root rot. If you plan on planting hostas in your clay soil garden, make sure to add a layer of compost or mulch to the soil to improve the drainage. This will help the hostas to grow healthy roots and avoid becoming waterlogged. 

Before you decide to add azaleas (Rhododendron indicum) to your garden, you might want to perform a quick test to see the contents of your soil. These flowers require a moist but well-drained environment, as their thin roots cannot withstand waterlogged soil. If you're working with a clay-heavy material for your azaleas, you should supplement about half of your soil with organic materials such as leaves or peat moss. This will not only improve the soil but also raise the bed, helping to drain water even more. 

If you want a self-seeding flower that will re-bloom every year without much assistance, you might want to try adding poppies (Papaver rhoeas) to your garden. However, these brightly colored blooms have specific requirements when it comes to soil. While they can tolerate pretty much any type of soil, they need it to be well-draining, which leaves heavy clay out of the running. To make your clay soil appealing to poppies, try adding compost or planting them in a raised bed. 

Wallflowers (Erysimum cheiri) can be a bright, fragrant, and easy addition to your garden as long as you facilitate the right soil conditions for them to grow. These biennials require well-draining soil and find it difficult to withstand soggy environments, like a clay-heavy soil. If you've performed a soil test and found that your garden leans on the wetter and heavier side, you can dry out your soil by adding a material like grit.

While more adaptable than many flowers, foxglove beardtongue (Penstemon digitalis) still requires a soil ranging from moist to dry, meaning that a clay-heavy soil is not the best option. If the clay soil is well-draining, these plants are more likely to tolerate it, but it may take some adjustment with organic materials to get the right balance. Ideally, these flowers live in slightly acidic soil with a pH level of 6.0 to 7.0. To make your soil more acidic, you can add elemental sulfur or aluminum sulfate.

This funky-looking perennial, which stems from the carrot family, can be a great addition to any garden as long as it lives in an appropriate soil type. Sea holly (Eryngium planum) does not require a ton of water and can tolerate drought, so a moist-heavy clay soil is not going to be the healthiest environment. To grow this blue thistle flower in clay soil, you will need to add some sort of additional material to your garden, like loam or sand, to give it a better chance of survival.

As you might be able to gather from its name, rockrose (Cistus spp.) thrives best in dry, rocky environments, making it a poor candidate for clay soil. These beautiful blooms do not require much water and can even withstand droughts, so a moist garden bed that receives a lot of rainfall is not the best option. While you can always add organic matter to the soil, you can also opt for mounding, which means piling soil around the plant base to assist with drainage.