How to Plant in Heavy Clay Soil

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Lantanas, like most plants, want sufficient water but will not tolerate sitting in it.  I planted these using my hilling method to avoid root rot and they are happy.

When I first moved into my new garden, it was my first experience with heavy, sticky clay – like the kind of clay you encounter in pottery class.  I’d had clay soil before, but not like this.

After a few of my new plantings (a couple shrubs and one tree) died or nearly died, I discovered upon digging them up that their roots were sitting in a clay bowl of watery soup.  Their roots were rotting.  Even though the top of the garden looked and felt dry, the clay soil I had dug into was acting like a bowl and holding all the water without allowing it to drain away.

From then on, I started planting almost everything using the hilling method described below.  And ever since then all of my plants have been healthy (at least in terms of soil water levels).

Photos soon to come…

Here’s my best method for planting your plants and shrubs on (not in) heavy clay~

1)  Buy or create a good quality soil blend.  I like to mix 2 parts top soil with 1 part compost.  Put this mixture into a wagon or on a piece of heavy duty tarp.

2)  Next, dig out the existing vegetation or top soil until you reach the clay soil underneath.  If digging out grass or weeds, make sure you get ALL the roots (you don’t want them to pop up through your new planting later).

3)  Now dig a shallow dip into the clay, just 1 or 2 inches down into the clay, no deeper.  Dig this shallow bowl twice as wide as the base of the pot your plant came in.

4)  Add a shovel-ful of your good soil mix on top of this shallow bowl.

5)  Sprinkle a generous handful of organic fertilizer (I like Microlife or Jobe’s Organic) into the bottom of the hole.

6)  Remove the plant from the pot and gently loosen the root ball so the roots aren’t all bound up in a clump. You want to encourage the root tips to aim out and down, not continue growing in a circle like they have while living in the pot.

7)  Pile your good soil up around the sides of the plant, like a volcano.  Pack it with your hands and continue to add soil until you have a good sized mound and the soil is piled up in a hill all the way up to where the plant originally emerged from the soil while it was in the pot.  You want the roots completely covered with plenty of room to grow outward into the good soil.

8)  Water thoroughly. This not only gives the plants the water they need to reduce transplant stress, but also settles in the soil around the root balls and removes air pockets.

9)  If needed, add more soil to your little hill.  You want every piece of root to have contact with soil.  Repeat this as often as necessary until the soil is at the correct level for all plants. See my photo for reference.

10)  If planting something that needs support, add those supports now (stakes, cages, etc.).

9)  Finally, cover all the newly planted soil with mulch. Natural wood mulch (not dyed!) or pine needles are best because over time they will decompose and add more nutrients to the soil.   *Please avoid mulch embedded with pesticides, as these harm all insects, not just the pesky ones, and our native pollinators are being killed left and right by excessive and unnecessary poison use. Cedar mulch is an effective deterrent to problem insects without harming beneficials.

10)  After mulching, water again.  New plants take a little time to recover from the stress of being transplanted; make sure you keep them adequately watered for the first few weeks.  After that you may be able to reduce water use depending on the needs of your particular plants.

 

Dwarf pittosporum looking happy in the garden.

This method of planting on top of the clay rather than in the clay allows the roots of plants to still burrow down into the clay for moisture and minerals, but not be surrounded by it on all sides and drowning in the excess moisture that clay holds once it’s been dug and amended.

These “Luna Pink Swirl” hardy hibiscus plants are planted directly into the clay because they like wet roots.  As you can see, this one is quite happy.

NOTE – This technique is for planting most plants.  However, if you are planting something that really likes to stay wet, like cannas, elephant ears, certain irises, hibiscuses, or anything that likes to grow at pond margins, then use the original, in-ground planting method instead of this hilling method.  Water lovers will appreciate the sogginess of heavy clay and even thrive when planted into it.

That’s it!  You can now enjoy your new plants and watch them grow and bloom.

Visit my “Tend Your Garden” page for the basics on keeping your garden healthy and happy.

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