A Funny Thing Happened in the Gravel Garden

Newly completed gravel garden.
Only the row of small rosemary plants
(left side opposite the bench) were added.
Photo: April 28, 2011

What do I know about gravel gardens? Not mulch!

I don't live in desert areas where gravel gardens are used due to low rainfall. Desert areas in the United States grow the grasses and succulents—cacti, yucca and agave— that come to mind when I think of plants surrounded by gravel.

I don't live in the northern latitudes where gravel keeps plants from rotting in rain while warming up the area from the winter sun. Gardens in Europe use gravel around trees and shrubs and that was primarily where I drew my design inspiration, realizing that it is hot here in the summer with little rain.

My garden is in North Carolina, zone 7b and the idea of a gravel garden was a gamble that I was ready to take in April 2011. The project started as a problem solver as shown in the Before and After: From Driveway to Gravel Garden story. We were really looking more for a beautification solution to reduce maintenance, but have been surprised by the other advantages.

Here is a list of the plants that were left in place BEFORE we switched to gravel, removing all of the organic hardwood mulch:

Burford Nana (dwarf) Holly
Oakleaf Holly
Yucca
Buddleia (multiple varieties)
Crepe myrtle 'Tuscarora'
Osmanthus 'Goshiki'
Iris ensata (multiple varieties)
Monarda 'Blue Stocking'
Chamaecyparis pisifera 'Cream Ball'
Perennial heliotrope

We added a row of new rosemary and decided to take a "wait and see" attitude toward the existing plants. I watered the rosemary a few times to establish a root system.

The crepe myrtles bloomed and bloomed.
The container plantings of lavender,
juniper and succulents are thriving.
Photo: July 12, 2011.

So far, we've experienced a June and July of triple digit heat with very little rainfall. The gravel garden is on the southwest side of the house. The crepe myrtle trees provide a bit of shade until 11:00 am, then it is baking heat.  I have not given the plants in the gravel garden ANY supplemental watering. Seriously.

Meanwhile, in the cottage garden and the rest of the outer, deer resistant gardens, I've been dragging water hoses and watering cans in an attempt to keep—even my drought-tolerant plants such as agastache, salvia and coneflowers—alive.

Back in the gravel garden, the foliage of the Japanese iris looks splendid and green. The monarda 'Blue Stocking' bloomed gorgeously. Those moisture-lovers didn't get any supplemental water from me. Tucked against buddleia, neither did those plants receive the full onslaught of the sun, but enough sun that made those same plants wither and wilt in the hardwood mulched areas of my garden.

Interesting. I was curious. No watering and virtually no weeds in the gravel garden for three months. No adding of more hardwood mulch to keep the soil moist.

Perennial heliotrope was literally covered
in the gravel and emerged to make a happy
ground cover around the Oak Leaf Holly.
Photo: July 29, 2011.

The rosemary has grown a foot higher. The Burford hollies have increased in size. The buddleia are in bloom and the crepe myrtles put on a splendid show of blooms.The chamaecyparis has never looked so good. The yucca is happy. The osmanthus 'Goshiki' has a bit of scorch on the top leaves (not unusual), but is growing just fine. The perennial heliotrope emerged from BENEATH the gravel to make a soft skirt around the oak leaf holly.

After a recent rainfall of one inch of rain, I dug a hole in the gravel garden; a hole in the deer resistant garden; and, a hole in the cottage garden.

Eleven inches down, the gravel garden soil was moist all the way—even though I had never watered it!

The other gardens had barely an inch of moist soil and ten inches of bone dry powder and I had been struggling to keep those areas watered. If anything, the cottage garden and other outer gardens have better soil than that beneath the gravel plantings.

Can it be that gravel, a permeable surface that allows rain to penetrate also prevents evaporation of moisture, even in day-after-day of 100°F temperatures?

My test is not scientific, but it is definitely making me think carefully about other areas that can handle gravel. Many of my drought-tolerant plants will be happy surrounded by gravel.

Gravel is not temporary! Once in place, especially two inches deep, it is difficult to remove. Therefore, I shall proceed with caution as I convert more areas to gravel to reduce the need for supplemental watering.

It's far too hot to take on a project like this during the summer. I want to also see the performance of the gravel garden plants over the winter as well as whether the weeds will pop up in the gravel. More waiting, but in the meantime, I can honestly say that the gravel garden is making us very happy.

The rosemary is flourishing.
The foliage of the Japanese iris is green (without watering)
and the butterfly bushes are happy and healthy.
Photo: early morning, July 29, 2011.

Guests do park here and the weeds
have been so few.
Photo: early morning, July 29, 2011.

Merge of driveway with garden.
Perennial heliotrope skirts the large holly.
Photo: early morning, July 29, 2011.

Words and photos by Freda Cameron, Defining Your Home, Garden and Travel. Deer and rabbit resistance varies based upon the animal population and availability of food. All company or product or patented names mentioned are registered trademarks, copyrights, or patents owned by those respective companies or persons.