North Knob and Oak Wilt
These photos are taken in North Field from the base of North Knob looking west. We first noticed oak wilt on North Knob in June 2002. By August it was clearly spreading as you can see that a tree on the right which was green in June is now showing dead leaves. By 2010 both North Knob and South Knob were clearly oak barrens. The oak barrens effect is so cool that it has made us happy to have the oak wilt. There are still some standing dead oaks as we are leaving them for woodpeckers. Initially we thought that the oak wilt would affect mainly the black oaks but Norris the large white oak at the very north end of North Knob was dead by 2007. And it appears that Dilbert the large bur oak on the northern boundary line may also succumb.
Interestingly once we identified the presence of oak wilt, we could see it in earlier photos. This photo is on top of North Knob just west of the dead trees in the above photos and looking south. Note standing dead oak at left (not girdled) and dead oak on the ground. There were also a lot of dead oaks on the east face of Middle Knob. Oak wilt has created a really great oak barrens with the only activity on our part being to clear away the fallen trees and seed in conservative hill prairie species. October 2001 photo is looking south towards Middle Knob. November 2002 photo is looking west from the same location. It was many days of work to stack and burn only the fallen down dead stuff.
A great deal of time and effort have gone into removing storm damaged tree chunks all over the unit. See Brush Removal Section. Norris, the large white oak on North Knob is only one example of the many trees affected by storms. Norris is one of the named trees which allows us to quickly identify the location which we are referencing in conversation. In the past ten years we have seen literally dozens of trees or large pieces of trees destroyed by high winds. It is really true that oaks don’t bend in high wind! At this point in time we had no idea that Norris would die from oak wilt and even more pieces would be falling down. Standing dead black oaks in these photos continue to eventually fall over due to oak wilt.
Norris before the large upper limb fell off. The south and west low limbs on Norris are clearly visible in this photo. Most of the small black oaks were gone by 2010. How many more trees will the oak wilt take; certainly all the small oaks still visible. Check out Big Woods in 2020. (The limb on the ground in the previous photo is the big limb growing out of the right side of the trunk in the photo above.)
This is the low north branch of Norris. It was already dead when we took the unit in 2001. It was the first branch we removed. It took several different workdays before we removed the entire branch. Before we removed it, we arrived one day to find a large pile of raccoon poop on the top of the branch near the tree trunk. Left of the north branch you can see small yellow leaf cherry “bushes” and green leaf honeysuckle. Right of the limb, they had already been removed before this photo was taken.
This is the low west branch. As you can see Norris was not on the top of the hill. So this branch was literally touching the ground in places. When that branch died we knew that the oak wilt was taking Norris. It was a really cool branch so we were sad. The knob will be spectacular without the tree.
Branch to the left is the west branch. Branch to the right is the south branch. You can see that the south branch had broken off either from its own weight or perhaps overloading with ice. It was also dead as of 2001. We did not finish removing it until 2004 when we were picking up the giant branch pictured above which fell off in a summer 2004 storm.
This photo is taken from the northern boundary / Lee County line looking south at the north face of North Knob. The north dead limb has been removed but there is still lots of cherry bushes to remove. Most of the small black oaks on top of North Knob in the right half of the photo died from oak wilt and are gone.
Oak wilt has killed Norris. More big pieces have fallen off and been removed, but there will still be a lot of wood to haul away and burn. Photo looks to the northeast.
We were surprised that Norris fell over as quickly as it did. We decided that we would do unacceptable damage to spring flowering plants if we put enough foot traffic on North Knob to be able to clear away the remains of the tree. We will leave it laying on the ground until November or December. This is the same view as June 2004 when the large branch fell off.
In nearly all the photos in this section you can see the dozens of oak grubs on North Knob and its flanks. We are not able to tell if they will be significantly impacted by oak wilt. So far they are resprouting when top killed by fire. North Knob has been a focus of heavy overseeding. See Seeds Section for planting plan details of this area. Part of the tops/sides mix goes here every year. For several years we have planted Asclepias tuberosa plugs on the east face of North Knob. For more oak wilt sequences see Middle Knob Saddle Section and North Knob West Section.