Establishing Trees in a Xeriscape Garden

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Written By Lyrae Willis

Environmental Scientist & Plant Ecologist

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Xeriscape gardens are quickly gaining popularity worldwide, particularly in areas where water is scarce.

Water is so valuable and necessary for food production that it makes sense to plant as many trees as possible, particularly for aesthetic purposes, that require little to no water once established.

Xeriscaping saves you money on water bills, decreases time spent on maintenance, and, grown next to your home, reduces your cooling costs and increases property value.

Growing a xeriscape garden is incredibly easy, but let’s look at a few simple steps that will help immensely when establishing trees in a xeriscape garden.

The Basics: Establishing Trees in a Xeriscape Garden

How to Plant Trees in a Xeriscape Garden

Choose the Right Tree For Your Climate and Location

First, you must know your USDA Planting Zone. The trees you choose for xeriscaping will differ entirely if you live in a mild, cold, hot, moist, or dry climate.

Once you know your hardiness zone, look up what trees will work for you, such as these drought-tolerant trees for New Mexico or Southern California.

Next, research your tree’s light, moisture, and nutrient requirements, as well as its growth rate and mature size, to ensure it’s a good fit. Choosing the right tree for the right spot in your yard will save you time, money, and heartache trying to make the wrong tree work.

Planting Your Trees in Your New Xeriscape Garden

Now that you have chosen the perfect drought-tolerant tree(s) that will work for you, it’s time for the fun part!

First, dig a large hole for your tree, ideally three times the width of the root ball. It’s best to create a hole with sloping sides instead of straight to give the roots room to grow out horizontally.

Usually, trees should be planted at ground level, where the soil surface is just barely above their root collar (where the trunk begins to flare into roots). Planting too deep, by burying the lower trunk above the root collar, can damage or kill the tree.

In arid climates, trees can be planted in a pit below the natural ground surface. This can dramatically increase soil moisture and tree growth. Over time, however, you need to remove dirt or debris that falls in so the trunk doesn’t become buried. Also, this method should not be used with compacted or poorly drained soil since rain events could result in your xeriscape tree getting too much water for too long.

I use a modified pit method in New Mexico, where I plant my trees just a few inches below ground level so they can capture rain. I also add gravel to the bottom of the pit and in the backfill soil since my soil doesn’t drain very well. How you plant will depend on your climate and your soil.

Modified Pit Planting Method for Trees
Image by Lyrae Willis, Own Work – for Tree Vitalize

Now, place your tree carefully in the hole or pit. Be sure that the tree sits flat and its trunk is straight, or just sits naturally if the trunk itself is not straight.

Then, backfill the soil in the hole. People sometimes recommend pressing the soil to remove air pockets, but it’s best to only lightly tamp it down since pressing can cause compaction. It’s better to add more soil after you have watered it and it has settled than to have compacted soil where the delicate new roots have to struggle to grow and breathe.

If you planted your tree at ground level, you can also build a berm around your tree’s drip line, creating a ‘moat’ that will hold in water when it is received. Ideally, build the berm about 6” high to allow room for the mulch. A berm of rocks and soil will hold up the best over time.

Water-Holding Berm for Xeriscape Trees
Image by Lyrae Willis, Own Work – for Tree Vitalize

Should I Use Soil Amendments When Planting Xeriscape Trees?

When it comes to xeriscape trees, they tend to have low nutrient requirements, so soil amendments are often unnecessary and can harm newly planted trees by promoting growth too quickly. Of course, some trees prefer richer soil, so carefully research your tree’s requirements.

Another exception is very poor-quality soil with little to no organic matter. In this case, simply mix in some topsoil with your native soil and use that to backfill the hole.

Mulching Your Trees in Your Xeriscape Garden

Now that your tree is planted add 3 – 4” of organic mulch around the dripline of the tree’s canopy. This helps keep the root zone cooler and conserves moisture.

Bark mulch, wood chips, straw, grass clippings, and leaves are all great organic mulches. Compost is also great but should only be used for trees that prefer rich soil since their nutrients are more rapidly available than other organic mulches.

If you need to lower the soil pH slightly, using pine cones or pine needle mulches will help acidify the soil and retain moisture.

Organic mulches break down and should be topped up yearly until the tree is established. You can continue adding it after establishment in arid areas or for trees that prefer rich soil.

Inorganic mulches like pea gravel can also be used. They are more permanent, retain moisture, and are better for trees prone to fungal diseases. However, they reflect heat and light, which can be problematic. They also don’t help with soil development and can be difficult to keep weed-free because they are not topped up yearly.

Using gravel as mulch in a Xeriscape garden
Using gravel in a Xeriscape garden – Image by Fern Berg (Own Work) for Tree Vitalize

Watering Trees in a Xeriscape Garden During Establishment Phase

When it comes to establishing a xeriscape garden, regular watering is essential during the establishment phase.

When you purchase a tree, it has a small root system requiring frequent watering. Furthermore, transplanting always shocks the tree, regardless of how careful you are.

Your tree needs time to grow and establish roots in its new home before it will actually become drought-tolerant.

Drip Irrigation Systems Conserve Water

Drip irrigation systems are the most efficient method of establishing xeriscape trees. They conserve enormous amounts of water and help prepare your trees for their low-water future.

To use drip irrigation, emitters are placed near the tree’s base. They slowly drip into the soil, going down to the roots. Very little is lost during the process since they are not sprayed into the air or poured onto the soil, increasing evaporation.

Drip Irrigation of Grapes in California
Drip Irrigation of Grapes by Tim McCabe, Public Domain

There are lots of different drip irrigation systems available. Find one suited to your yard and follow the instructions carefully to ensure a successful installation.

How Often Do I Water My Newly Planted Trees?

Water your new tree daily for the first week, then every other day, reducing it to once weekly within 3 – 6 weeks, depending on your climate.

If it rains sufficiently, skip watering. Overwatering your trees weakens them and makes them prone to root rot. If your soil is still moist, do not water it!

Should I Water My New Trees in Winter?

People sometimes assume new trees require no water in the winter while dormant. However, as long as temperatures are above freezing, they still require some water. If you don’t receive winter precipitation, continue watering your tree once or twice monthly during establishment.

When and How to Phase Out Watering in a Xeriscape Garden

The duration of the establishment phase varies significantly with the tree and the environment. This can take anywhere from six months to five years, but one to two years is most common.

After the first year, if you irrigate your trees once weekly and they are very healthy, reduce that to once every two weeks and see how they respond. If they look stressed, then they are not ready to phase out watering.

However, if they look healthy after a couple of months of watering every two weeks, then reduce it to once monthly and again wait and see. If they still look healthy after a few months, they are probably ready to stop watering altogether.

One caveat is that even once established, sometimes xeriscape trees still need irrigation. This may happen during particularly long, hot, dry spells when your trees’ leaves may droop, scorch, or fall off the tree.

Some trees are adaptable to this, simply losing their leaves early but still flourishing the following year, while these spells can severely damage other trees. So, to be on the safe side, if your tree looks stressed during an extended drought, give them a one-off deep watering treatment to help them through the dry spell.

Successfully Establishing Trees in a Xeriscape Garden

Establishing Trees in a Xeriscape Garden

I hope this has helped you answer some questions you may have about how to establish your new trees in a xeriscape garden and how and when to water and phase out watering.

Once your trees are established, you will be rewarded with a beautiful, low-maintenance, money-saving xeriscape garden that you can enjoy for many years to come.

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Lyrae Willis

Environmental Scientist & Plant Ecologist

Lyrae grew up in the forests of BC, Canada, where she got a BSc. in Environmental Sciences. Her whole life, she has loved studying plants, from the tiniest flowers to the most massive trees. She is currently researching native plants of North America and spends her time traveling, hiking, documenting, and writing. When not researching, she is homeschooling her brilliant autistic son, who travels with her and benefits from a unique hands-on education about the environment around him.

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