10 Perennials For Clay Soil (+ Soil Preparation)

Every plant has its own requirements. Some require specific types of soil and a controlled environment to thrive.

perennials

While many perennials thrive in normal garden soil, the range of plants for heavy clay soil is much more limited.

It’s rare to find perfect soil in gardens.

Preparing clay soil, in particular, is a challenge for the gardener, as it is laborious to work and difficult to plant.

The 10 perennials we’ll cover in this article are particularly suitable for clay soil.

What exactly is it that characterizes a clay floor?

First of all: a certain amount of clay is present in every normal garden soil. It ensures that water and thus also nutrients stay in the soil longer, so it makes the soil less permeable.

In particularly loamy or clayey soils, this can become a problem, because if the proportion of loam is too high, the water cannot run off and the location is too humid for most of the perennials in no time at all. 

In addition, the high proportion of clay ensures that only a little oxygen can reach the roots.

Here, the incorporation of sand can increase permeability and improve the soil.

If that is too troublesome for you, you should make sure when choosing plants that you only plant perennials that — even if they don’t necessarily love clay soils — at least tolerate them. We present a small selection of these perennials.

Which perennials tolerate clay soil? Here’s a list of 10 perennials you can grow in clay soil:

  • High flame flower (Phlox paniculata)
  • Sun bride (Helenium)
  • Sonnenauge (Heliopsis helianthoides)
  • Rotblatt-Aster (Aster New-England)
  • Bergenien (Bergenia)
  • Chinese meadow rue (Thalictrum delavayi)
  • Candle Knöterich (Polygonum amplexicaule)
  • Herbst-Eisenhut (Aconitum carmichaelii)
  • Stork’s beak (Geranium)
  • Splendid muscles (Astilbe)

Perennials for clay soil in a sunny bed

There are some perennials that tolerate clay soil, especially for sunny beds. The reason: The high level of solar radiation ensures that the soil does not become too damp.

These perennials include, for example, the high flame flower (Phlox paniculata), which, depending on the variety, blooms in all imaginable shades of white, pink, purple and red between July and September.

It prefers a loamy, nutrient-rich soil, but is somewhat sensitive to waterlogging.

The popular summer bloomers sun bride (Helenium) and sun eye (Heliopsis helianthoides) also get along well with loamy soil.

How to improve your garden soil

Very few gardens are endowed with good soil. With sand, compost, and other additives, a successful soil improvement is possible even in seemingly hopeless cases.

These two herbaceous genera have some things in common. 

Not only do they belong to the same family (composites), they both bloom exclusively in warm colors. While the flowers of the sun eye are exclusively yellow and, depending on the variety, sometimes unfilled, sometimes filled, the color spectrum for the sun bride ranges from yellow to orange to red. 

Some varieties, for example, the hybrids ‘Biedermeier’ and ‘Flammenrad’, also have flowers with color gradients from yellow to orange or red. Both genera bloom between July and September.

With the sun bride variety ‘Flammender’ you can light up every bed

From August onwards, the pink or purple flowers of the Reinblatt aster (Aster novae angliae) contrast nicely with the bright colors of the sun bride and sun eye.

It also prefers a loamy, humus-rich, nutrient-rich soil. Because of their height of up to 160 centimeters, Rotblatt asters are particularly suitable for back bed areas. Varieties that remain small, such as ‘Purple Dome’, come into their own further up in the bed.

Bergenia(Bergenia) also thrive best in a sunny location and bloom here much more profusely than in the shade, even if they tolerate a partially shaded planting place. Although they prefer fresh soil, they can also cope with drought quite well. 

We particularly recommend the hybrid ‘Eroica’, which, in addition to its purple-red bloom in April and May, is an absolute eye-catcher in the bed in autumn and winter with its bright red undersides of leaves.

How to loosen up clay soils

»Tip 1 – work organic material into the soil:

Compacted clay soil can be optimized by mixing plenty of organic material into the top layer of soil. Ripe compost and shredded material are ideal for this. You can also work coarse sand into the clay soil. This creates cavities that improve water drainage.

»Tip 2 – lay drainage:

If the compaction of the clay soil reaches very deep, superficial improvements may not be sufficient. In this case, you can put drainage or have it laid.

Suitable drainage pipes are available from gardeners and hardware stores.

However, the cost of a large-area drainage system is very high. You should only make the effort after consulting a professional.

Creating drainage in the garden clay soil 

If the soil is very firm, it makes sense to use drainage in the garden

Lawn will not grow on clay soil if the rainwater stops. Annual scarifying and aeration only solve the problem temporarily.

If flowers, shrubs, and vegetables stand with wet feet after every heavy downpour, growth depression and bad harvests are inevitable. 

Affected gardeners tackle the problem at the root with permanently improved rainwater infiltration.

The following tips outline a simple variant of how you can use drainage to make clay soil with waterlogging more permeable over the long term:

Preparatory work

Measure the course of the pipe system for the drainage to the infiltration system exactly. You then create a detailed plan sketch so that you can precisely determine the material requirements.

Make a note of slotted drainage pipes that are coated with coconut fiber on the shopping list.

The special drainage pipes lead into a collecting line that allows the water to flow into a drainage basin.

In addition, you need sand, gravel, grit, seepage fleece, wooden slats as formwork, spade, shovel, ideally a mini excavator or powerful helpers for the sweaty excavation work.

Lay the drainage pipes and collecting line

A slight gradient of 2 to 3 percent is of decisive importance for the functioning of a drainage in the garden clay soil.

Regular checks with the spirit level guarantee that this important premise is adhered to when the clay soil is excavated and the ducts are then filled. 

In addition, the following guidelines are relevant so that rainwater infiltration in the garden becomes a successful project:

  • Dig channels for the drainage pipes (15-30 cm under lawn / turf, 80-150 cm under vegetable patch and orchard)
  • Use wooden boards as formwork in the pits
  • Line pipe ducts with seepage fleece
  • Fill in a layer of sand as protection for the fleece and pour in the gravel pack over it
  • Lay the drainage pipes and collecting line

It is important to note that there is sufficient distance between the drainage pipes and the basement of your house so that you do not have to struggle with wet basement walls. It must be ensured that rainwater from the drainage line does not get into the house’s drainage shaft and flow into the sewer. 

Under these circumstances, trouble with the authorities is inevitable and sewage charges skyrocket.

Drainage basin

A drainage basin solves two problems in one operation. If the size of the garden area allows it, the hollow functions as a collecting basin for the collecting line of the drainage pipes and blends harmoniously into the creative garden design as a natural wet biotope. 

The following overview summarizes the key points:

  • Excavate the drainage trough below the collecting line of the drainage pipes
  • ideally dig into a permeable soil layer at the site (no gravel packing or filter fleece necessary)
  • Alternatively, line the dense clay soil as the bottom sole with fleece and fill it with sand and seepage gravel

In contrast to the drainage shaft on the house, simple drainage in the garden clay soil does not require a building permit. This requirement applies as long as the construction is limited to optimizing the natural rainwater infiltration in the lawn or garden soil.

 Any additional measures for the drainage of clay soil are subject to legal regulations, such as the Water Management Act or the building regulations.

In many municipalities, it’s also forbidden to drain rainwater into the public sewer system using a garden drainage system. 

Therefore, please contact the responsible authority if your plans go beyond the simple drainage variant explained here.

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»Tip 3 – vigorously dig up clay soil in autumn:

Another way to improve your clay soil is to dig vigorously at the end of the growing season. Water can easily penetrate the dug-up soil.

As soon as it freezes in winter, the water molecules expand and separate coherent chunks of clay.

In spring, it is then advisable to add a layer of humus. On the one hand, this provides important nutrients and, thanks to its dark color, helps to conduct heat into the earth.

Clay soil with a largely closed surface remains cold for a very long time in spring and delays plant growth.

Perennials for partial shade

For partially shaded and shady garden areas, the selection of perennials is a bit smaller. But the right plant can also be found for this.

Most of these perennials thrive in partial shade as well as in the sun.

 These include Chinese meadow rue (Thalictrum delavayi), candle knotweed (Polygonum amplexicaule), autumn monkshood (Aconitum carmichaelii), and types of cranesbill (geranium).

In the genus of the cranesbills there are numerous species that also feel comfortable in loamy, humus-rich soil. In addition to the brown cranesbill (Geranium phaeum), the hybrid ‘Rozanne’ should of course not be missing.

The extremely robust perennial inspires with its violet-blue bloom from June to the first frost. 

The Chinese meadow rue forms filigree, violet-pink flower panicles in July/August and brings wonderful lightness to plantings on the edge of the wood.

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With a height of up to 180 centimeters, she is happy about the support. It thrives in any humus-rich, fresh garden soil, but it is only really stable in moist, light locations.

Candle knotweed (Bistorta amplexicaulis) does not bloom until late, but until frost

The candle knotweed also prefers moist, loamy soils and should therefore not be omitted from this list. Not only does it grow quickly, but it also blooms tirelessly from late June until the first frost. 

The color spectrum of the flowers ranges from white through various shades of pink to dark red. For partially shaded to shady places on the edge of the wood, we recommend planting splendid sparrows (astilbe).

They prefer humus-rich, fresh soil in such locations. 

If you plant splendid sparrows in a sunny spot in the garden, on the other hand, the soil should be very loamy so that the perennial gets enough water.

The autumn monkshood also thrives in partially shaded to shady locations and is enchanting in September/October with its dark, blue-violet flowers.

Similar to the Astilbe, the following applies to this perennial: the sunnier it is, the more humid the soil should be. This is why the monkshood is also very suitable for loamy soils, as they store water well.

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Summary

Explore a comprehensive guide to selecting and caring for perennials in clay soil. Uncover expert tips and tricks for enhancing soil quality and promoting healthy plant growth.

Conclusion

Perennials are great for your environment and gardens.

Having clay soil in your garden should no longer be a problem after going through this guide on what to do, and the perennials to use.

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