Tuesday, October 27, 2020

Oh Deer

Even though as winter sets in deer metabolism slows and feeding/browsing damage becomes less obvious, deer still manage to cause some major damage to the landscape

A willow, Salix discolor, that has suffered multiple deer attacks, yet has survived. 
The trunk guards were put on after the fact.

Last February I came to the realization that if I wanted to grow new trees, especially conifers, I would need to protect them from the deer, especially the males during mating season. Here in the Mid-Atlantic November brings on rutting season, the time when white tailed deer mate.  During rutting season male deer rub their antlers against trees and shrubs to remove the velvet from the newly grown horns.  They also will rub trees to mark their territory and to take out their heightened aggressions as mating season kicks in.  What deer prefer for this rubbing behavior are trees and shrubs 1-4” in diameter with smooth bark, like willows and magnolias.  Aromatic cedar and other conifers are also favorites.  Once a tree is marked they will often return to the same one.  At one time I had a nice little Canaan fir, Abies balsamea var phanerolepis,  that I surrounded with chicken wire after it had been rubbed a little.  Two days later all that was left was a bare splinter of a tree.  Now is the time to put up some protection to save some of our precious young plants before they are destroyed.  Following are some of the actions I've taken.

Trunk Protection
Last year I tried horizontal fencing for the first time and did not have great results.  It did not protect a young magnolia from rubbing, but a number of small evergreens did not take any damage.  Based on the photos I have, the deer appeared to skirt the areas with fencing lying on the ground. 

The pink flags indicate where I have put 2"x4"welded wire fencing on the ground around this little Canaan fir tree. 
The idea is that it creates unstable footing that the deer don't like.  The flags help me avoid the fence when mowing. 
I want to add some block underneath to lift the fencing further off the ground.

This year I have plastic mesh poultry fencing wrapped around the trucks of most of the stag-susceptible trees.  For others I have a heavier duty  4” drain pipe around the trunk.  (I’m a little concerned about heat build up under these black tubes.  For that reason I drilled ¾” holes every 6”to aid in ventilation.)  I also used some paper tree wrap on some smaller specimens.  One product that looks very good to me is a white spiral plastic.  It looks like it will protect the bark from rubbing and is open enough to prevent heat build up and not harbor insects.  I haven't bought any of that, yet.  A welded wire barrier surrounding the tree trunk has also proven very effective.  This is most efficient with single trunked trees with few lower branches.  Chicken wire may do a good job of limiting browsing but I've seen it ripped away from small trees that had been rubbed by a buck.

I wrapped the trunks of this fringe tree, Chionanthus virginicus, with plastic poultry fencing. 
It's easy to cut and can be tied together with zip ties or wire.  This material should protect the bark,
but will not support the trunk.

Here I am using a spiral cut 4" drain pipe to protect the trunk of this persimmon tree,
Diospyros virginiana.  I drilled holes in it every 6" to reduce heat build up.  This is
pretty tough material and should hold up to attack.

This Sassafras is being protected with a conventional welded wire cage. 
It's been here 4 years, but now it's of prime size for a deer attack. 
Hopefully the large size cage will be a good deterrent. 
I pulled the cage away during the summer to strengthen the trunk.  
Except for the open mesh materials it is a good idea to remove bark protection in the spring.  Heat and moisture build up can damage the bark and in some cases can harbor insects.  Also too much rigid support can keep a tree from developing a strong trunk.  I found this with my young sassafras.  It was getting floppy and the truck was not able to support the top growth on its own.  I pulled away the support this past spring and now the truck is much firmer.

Here  on this willow I'm comparing a variety of protection devices. 
On the right is a paper tree wrap.  Not sure how that would hold up versus a buck.

In winter deer’s metabolism slows down, but they are still out there browsing.  Evergreens, branch tips and leaf buds are at risk.  Fencing and cages are effective at keeping deer far enough away to prevent browsing.  Burlap warps that are used to prevent winter burn on arborvitae should also work.  Repellents are also helpful.  In colder weather taste-based repellents have an edge because they do not need to be volatile.  It is often recommended to alternate among different repellants through the season so that deer don't get used to any one of them.   So far I haven't done that.  

Reading about all the different recommendations for deer repellants, as well as deer resistant plants, it has become clear that not all deer are the same in regards to their likes and dislikes. Be flexible and try different recipes and products.  I've had good success using Bobbex which contains a variety of taste and odor deterrents. 

Planning Ahead
I’ve seen a number of people on Facebook ask about starting gardens in areas with lots of deer.  My deer seem to test every new plant that goes in the garden.  For new shrubs I usually put a chicken wire cage around them.  As far as planning an new large planting, I like the advice I’ve read in ‘Deerproofing Your Yard & Garden’ by Rhonda Hart.  She recommends fencing in the new garden space before doing any planting.  This is because deer are creatures of habit.  If they have never found anything of interest in an area, then they are not likely to return.  But, once they have found something tasty there, they will make every effort to return.

On the Bright Side?
Deer browsing results in some unsightly damage to many landscape plants.  It is not uncommon to find hedges of arborvitae and junipers chewed back up to about four feet off the ground.  There are some aspects of deer browsing behavior that could be considered beneficial.  The following two photos show where deer have pruned away branches from the lower 4 feet of a yew and a rhododendron.  This sort of pruning opens up the ground plane for lower growing herbs to fill in. In the absence of deer these would be mounds of foliage.  I've also seen this with spicebush, Lindera benzoin, in the woods. This can happen when there is not excessive deer pressure.  Had there been more deer here say 10 years ago these shrubs may not have grown more than a foot tall before being destroyed, unless they were being protected with cages and repellants.

The lower branches of this yew have been munched away over the years.

This rhododendron has been 'limbed up' by deer.

What methods have worked for you during rutting season?  I'd love to hear about them.

Tuesday, October 13, 2020

2020 Stiltgrass Wrapup

As we are coming to the end of stiltgrass season for 2020 I wanted to review what I’ve learned about controlling this invasive species on my Mid-Atlantic property over this year. 

Pulling Japanese stiltgrass, Microstegium vimineum, is an effective means for controlling this annual grass, but it is extremely labor intensive.  While its primary germination period is mid-spring it does continue to germinate into summer, particularly if more openings appear in a previously shaded area.  So you may find that you need to redo areas in late summer that you thought had been taken care of earlier.  This was the case in a shaded woodland where I thought I did a pretty good job clearing the stiltgrass at the end of July.  When I returned to that place in mid-September it was in need of more pulling.  Apparently I left enough scraps around that they were able to regrow.  So if you only want to pull stiltgrass once in a season get every bit out the first time, or wait until just before it goes to seed, maybe early September (depending on local conditions) and then pull out all that you can. 

This was the initial condition, before any clearing in 2020.

This was after clearing in late July, by September this area was
overgrown again with stiltgrass.  This time it only took about 10 minutes
to clear the area.  The underlying Rosey sedge, Carex rosea, still looked good.

While searching for more information about the cleistogamous seeds in stiltgrass (those seeds hidden in the stem), I found a Master’s thesis by Samantha Nestory of the University of Delaware.  There it was noted that Japanese stiltgrass grown in sunnier locations had more cleistogamous seed than in shade, 47% vs 28%.  It also pointed out that, at maturity, there is a cleistogamous flower stalk at nearly every joint along the stem. After reading this I checked out some of the stiltgrass that was ripening.  Sure enough, nearly every joint had a flower stalk hidden or nearly hidden within.  In the woodlands I did not find as many of these hidden flower stalks.  Another observation about JSG is that it is able to put out roots wherever a leaf node, or joint, touches the ground.  By this means a single stiltgrass seedling can cover a large area.  Also residual fragments can quickly reestablish.  I’m not sure what this means for stiltgrass that is pulled then dropped back on the ground.  Will it reroot? 

Next to my finger you can see the flower stalk that was hidden under the leaf sheath. 
In sunny locations by early fall there can be one of these at each joint.

This brings up the topic of how to allocate our most precious resource, time.  While I often dive into some of the most thickly infested areas and rip out the biggest plants, it is actually more effective to begin in less densely infested areas and clear them completely.  After those areas are clear, move on to thicker areas.  The idea is that if an area is totally clear you won’t need to come back to redo it as much.  Whereas while you are battling a thick infestation, the lightly infested area is getting worse and then you end up with twice as much heavily infested space. 

Here's a small scale example of complete removal of Japanese stiltgrass. 
Ideally, I won't have to come back again this year and can spend my time elsewhere. 

This year I was late on reseeding the lawn.  I didn't get out there until early October.  I typically use a bow rake to tear our residual stiltgrass, then overseed with an appropriate cool season turf grass in mid-September.  (We are near the southern limits of where cool season grasses are preferred.)  Overseeding helps to fill in the gaps in the lawn that would otherwise be filled by more stiltgrass.  By seeding in fall these cool season grasses can get established and not be affected when I apply a pre-emergent herbicide in the spring to kill the stiltgrass.  I should have raked out the stiltgrass much earlier, before the seed was ripening.

I’ve had great success controlling stiltgrass in the lawn using pre-emergent herbicides in early spring.  Most products labelled for pre-emergent use to control crabgrass are effective.  I have noticed that the amount of hairy cress, Cardamine hirsuta, has also been reduced (this is due in part to mowing at least once in mid-spring to cut off the flowers before they can set seed.) While the pre-emergent works very well in the lawn, it is not as effective in the rougher meadow areas.

In this mini-meadow I have started to use the pre-emergent herbicide Dimension™
to augment pulling of Japanese stiltgrass.  Naturally occurring species that are flourishing
here include deer tongue and purpletop grasses, wingstem (Verbesina alternafolia)
and wild blackberry.  I have also planted in some panic grass, wild bergamot and brown-eyed Susan.

After two years of treatment in small meadow I have opened up enough space to get some more desirable plants established like wild beebalm, Monarda fistulosa, black-eyed and brown-eyed Susans, Rudbeckia sp.,and grasses like Virginia wild rye, Elymus virginicus, and panic grass, Panicum virgatum.  I noted this year that, in addition to a decrease in stiltgrass, the nonnative invasive bull thistle, Cirsium vulgare, was largely absent this year.  This thistle is a short lived annual or biennial species so is susceptible to control by pre-emergent herbicides.  I have been watching for other changes in the species mix because of the pre-emergent treatments.  Since I have put in some black-eyed Susans, which depend on reseeding to survive, I will not use pre-emergent in that area next spring to see if I can get them to come back on their own.  Ideally I would like to build up a strong network of native species that can exclude the stiltgrass on their own. 

I have not been using post-emergent herbicides on Japanese stiltgrass, but they do have their place in the arsenal. I found research that indicated that the use of grass selective herbicide can be effective, without causing damage to non-grass species.  Fluazifop-p-butyl is a selective post-emergent herbicide that can adequately control M. vimineum with minimal effect on the non-graminoid native plant community (Judge et al. 2005b). Fenoxaprop-p-ethyl, is a selective post-emergent herbicide that provides excellent control of M. vimineum and can maintain or even increase cover and richness of native species post-treatment (Judge et al. 2005a, b, Judge et al. 2008, Pomp et al. 2010, Ward and Mervosh 2012).  Fenoxaprop is not effective on sedges or cool season perennial grasses, like red fescue, so that would be a good thing, since there are many sedge species occupying my woods.  However there are also many shade tolerant grasses like bottlebrush grass, deer tongue grass and mannagrasses that could be affected.  So I would be hesitant to use these useless it was in a very targeted fashion.

These past few years I’ve been using fire, primarily from a garden torch, to control Japanese stiltgrass.  I’ve found that fire is good for clearing a space prior to planting, but not for clearing without a plan for back fill with desirable species.  In some areas I’ve burned the stiltgrass seedlings in early summer only to have the area recovered with more stiltgrass; mostly from rooted stems coming in from nearby plants. Fire alone is more effective in late in season (August) when there is not enough time for new JSG to germinate and reach maturity.  It can work particularly well if there are well rooted perennials in the area.  These perennials are able to resprout after their tops have been singed off.  Cool season perennial grasses are a good example of these.

Here I used my garden torch to burn away the stiltgrass. 
Then I planted some plugs of switch grass, Panicum virgatum

This year I also used fire to dispose of late season stiltgrass that was full of seed.  After realizing just how much seed is contained in a stiltgrass stem, I decided that rather than moving piles of stiltgrass around I would burn what I had in a central location.  Fortunately, I live in an area with plenty of space and that allows burning.  The key to getting stiltgrass to burn well is to allow it to dry out.  I allowed my big piles [photo] of stiltgrass to dry about 2 weeks to get it dry enough to burn rapidly,  In all I estimate I had nearly 2 cubic yards of stiltgrass stems plus thatch from where I reseeded.  This was reduced to less than 2 cubic feet of smoldering ash. [photo].  When burning remember to follow all local regulations.  Don’t burn on windy days, keep the flames under control, and have water on hand to put out any unintended fires and dowse the ashes when done.

These piles of ripe stiltgrass, plus some additional thatch raked out of the lawn,
were reduced to a couple of cubic feet of ash.

Native Competitors
A more exciting aspect of stiltgrass control is finding native plants to fill in or even resist Japanese switchgrass.  Many people, myself included, have noted that golden ragwort, Packera aurea, is very effective at excluding JSG.  

In the woods nearby is a large dense patch of mayapples, Podophylum peltatum, a spring ephemeral.  I have noticed that during garlic mustard season (April to June) there is no garlic mustard growing there.  This year I also realized that there was not any stiltgrass there either, even though the ground is essentially bare save a few sedges and Virginia creeper, once the mayapple has retired for the summer.  I recently saw a post on Facebook where there was a patch of wild ginger, Asarum canadense, that was relatively free of JSG.  These two species spread extensively by rhizomes.  May there’s something to that?  

In early through spring the area circled is covered with mayapples. 
This dense cover seems to have excluded both garlic mustard and Japanese stiltgrass.

There are also grasses that maybe useful.  River oats, Chasmantheum latifolium, grows in dense stands and I have found stiltgrass only on the outer edges.  In the woods the rosy sedge, Carex rosea, has done very well with just a little help from me. In a moist wooded area I noticed that I had an early season grass that excluded the stiltgrass until it went to seed in June.  I’m pretty sure it was a species of mannagrass, Glyceria sp.  (I keyed it out as American mannagrass, G. grandis, but that is a rare species in Maryland, so I will double check when it blooms again next spring.)  In late summer while pulling stiltgrass I came across another patch of grass that had just a very few stiltgrass stems.  Currently unidentified, it seems to block the stiltgrass with a dense layer of thatch from a previous season’s growth.  This is another one to try to identify come spring.

This small, yet unidentified grass seems to have repelled an invasion of stiltgrass.

Next Year:
  • Continue with the pre-emergent treatments on the lawn and in limited areas in the meadows.
  • Focus my efforts in areas to achieve 'complete' removal before moving on to new areas.
  • When burning to clear an area have something ready to fill in.
  • Identify those grasses and see what else is holding its ground.
If you have any additional ideas or know of other competitive native species I'd love it if you could share that here!