Taking care of the Angel Oak, a grand old lady Johns Island tree estimated to be 400-500 years old

The Angel Oak on Johns Island.

My grandmother is 100 years old.

When she was born, telephones required an operator. A new car cost $360. Indoor plumbing was fancy living. There was no such thing as air conditioning. There was ice. One hundred years is a lot of living, but it’s still not close to the Angel Oak.

Located on Johns Island, the Angel Oak is one of the most celebrated trees in the Lowcountry. Foresters estimate its age to be about 400 to 500 years old. That means it germinated before the United States was united.

Owned by the city of Charleston, the Angel Oak has received due attention in the past couple of decades. The trunk is almost 9 feet in diameter and about 28 feet in circumference. It would take five grown men to wrap their arms around it. Wider than it is tall, the Angel Oak casts just under half an acre of shade. Visitors, local and afar, make the free visit to see it during the season. Arborists have been said to weep upon seeing it.

Every tree species has a life expectancy. In fact, the Angel Oak isn’t the oldest living tree. It’s not even close. That honor goes to a bristlecone pine thought to be 5,000 years old. It germinated in the Bronze Age. But for a live oak, 400 years is quite a feat. And with age comes aches and pains and complications. Special precautions must be taken.

One of the greatest threats to its longevity is natural disaster. Trees are great conductors of lightning. A well-placed strike can rapidly end its life, bringing the sap to a boil as it travels to the root system. To prevent this, lightning terminals are posted at the top of the canopy to grab a nearby lightning strike and direct the voltage down a cable attached to the outside of the tree. This safely disperses the energy into the soil.

The branches are as large as the trunks of normal trees. They are so heavy that they lay on the ground. Cabling is used to network the branches together so the tree is more tolerant of high winds.

In the past, posts have been used to prop them up. While the support can prevent damage, it sometimes isn’t enough. A recent ice storm stressed many of the branches and bent metal posts.

Micropile footings are being explored as additional reinforcement. These are concrete footers only 6 inches in diameter and 60 feet deep. The reduced diameter will significantly minimize damage to roots.

Given enough time, all trees will develop decay. Long ago, cavities were filled to lend support but that practice is no longer considered necessary and can in fact cause more harm.

A healthy tree can compartmentalize the damage and prevent it from spreading. The best management of decay is proper pruning to minimize wounding and encourage health. Pruning is done primarily on an as-need basis.

With almost 300 daily tourists, a lot of attention is given to root care. The majority of feeder roots are in the upper couple of feet of soil. Compaction from foot traffic will reduce oxygen content in soil as well as alter drainage. Over time, this can degrade soil vitality and reduce root growth.

Despite some popular thought, fertilizer is not recommended to offset stress. In fact, fertilizer should be avoided at times of stress. Instead, attention should be given to cultural tree care, such as adequate water and mulch.

In the case of the Angel Oak, the root system is invigorated with an air spade. Much like a pressure washer uses water to clean a driveway, an air spade uses high-pressure air to loosen the soil around roots. This aerates, reduces compaction and invigorates microbial activity. It also can be used to increase organic matter in the soil.

Mulch is an essential element to protect the soil surface, moderating temperatures and moisture while offsetting compaction. In this case, the Angel Oak takes care of itself by shedding enough leaves to keep the soil adequately covered. Occasionally, additional mulch is added.

If you spend any time in the Lowcountry, witness one of the oldest live oaks in the South.

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, e-mail him at tony. bertauski@tridenttech.edu.