Question 8

Fire Impact on Raspberry Brambles

What experience have folks had with the effect of spring burn on raspberry brambles in an oak woodland? My DNR forester is concerned that fire would stimulate rather than help suppress brambles and is recommending mechanical control + herbicide instead. My preference is to run fire first, then use mechanical control approach. Any thoughts/experiences/anecdotes are greatly appreciated! Oh yes, we're in Iowa County in Wisconsin.

Answer 8

From ten years of burning and woodland restoration on Lake Kegonsa woodlands, burning definitely stimulates caneberry growth. If there is little herbaceous growth to fill in following a burn, Rubus will fill-in. Especially if some canopy removal has occurred, which often accompanies oak woodland restoration.

Woodlands differ from prairies in that they take longer to respond to management efforts. This is the case of most oak woodlands that have not been burned for many years. The herbaceous layer has been suppressed so long that it takes several years (if ever) for it to kick-in and produce enough vegetation to cover the ground. In the mean time Rubus can take off within 1-2 years.

Most woodlands in So. Wisconsin have taken more than 50 years to get where they are now. It will take at least five to ten years to get them back to some semblance of an herbaceous rich ground layer. When removing the dense understory, do it over a series of removals, beginning with exotics (Buckthorn, Lonicera, etc.) and work-up to overpopulated natives (elm, cherry, etc.)

Be sure and save those young oaks, hickories or walnuts, if any. This will give the herbaceous layer an opportunity to begin recovery before caneberry erupts following significant shrub layer removal and burning. Some woodlands have been suppressed beyond abilities to recover and seeding of some species will be needed. Watch out because some woodlands were nothing but weeds before they "closed over" and they will show themselves within 1-2 years after burning.

A suggestion is that you begin burning a portion of the woodland and follow-up with Rubus removal on that portion. This removal may involve mechanical or chemical treatments. Another reason to start on a portion is that you won't be overwhelmed if a tidal wave of Rubus/weeds pops-up after the burn. This control will give the herbaceous layer a start that may take up to 5 years to fully realize (be even more patient than on prairies!). Then continue to remove, or at least break-up the dense shrub layer. DO NOT REMOVE THOSE BIG OAK/HICKORY/WALNUTS! What you are trying to do is let in just enough light to the forest floor to permit the native layer to start but not so much as to stimulate Rubus or other weeds. This is a difficult balance and may take a little practice, hence, start in a portion of the woodland.

Rubus is part of the native landscape and some should be permitted to grow but if dense Rubus does take over an area that you really don't want, wait until September. At this time, dense Rubus may be the only thing green (everything else being shaded out). Spray the Rubus leaves in September with glyposate, wait until November then cut the stems to the ground. Spraying and cutting Blackberry canes is hellish work! Rent a heavy duty weed whip that you can put a saw blade on and wear a helmet and face mask, and heavy clothes/gloves. Seed what you would like after cane cutting. Follow-up with hand cutting next May during leaf-out for remaining Rubus stems. This will give the seeds an opportunity to germinate and get a little growth and compete successfully with Rubus.

I know you are hot to start ripping and burning, and you want results NOW but that won't happen. Gird yourself for the long term, and prepare for lots of hard work. I can assure you that it's worth it. Come to Kegonsa St. Park at the end of May for some spectacular results! Look me up, hope to see you.

From: Birch, Gary [gary.birch@dot.state.wi.us]

Great question you posed.
Gary: great answers. How about leading a field trip there? Sounds like many of us would like to see the site.

Fire brings too many other benefits to leave that off as a treatment. So go ahead and burn, but be prepared to treat afterwards. Although Gary gave a terrific summary, there are a couple of things to add.

First, Andrea mentioned these were raspberries which are a lot easier to deal with and don't make the terrible thickets that blackberries do. They also dry up and don't hold green leaves as long into the fall as blackberry and so are not as susceptible to fall herbicide treatment, unless you treat each cut stem, a real pain.

Secondly, Rubus spp.,although perennials, have a biennial lifestyle, one year sending up a non-flowering cane and the next year a flowering cane. Like other biennials, then, it seems that they are best treated two years in a row, not every other year, which just stimulates them more and allows them to set seed. Of course, treating them every year for many years is even better.

I would not treat in September without having a botanist look it over. You may have good species that have come in that will still be green. Some of the woodland grasses are likely to be green through September,and certainly things like Short's aster will be green. You don't want to kill these off.

As I recall, you have a good brush mower and can perhaps cut the whole stand of berries every year. This, with burning, will control them without herbicides. Cut them in the early summer when they are fully grown, then again later if possible.

Some might be curious as to the mechanism of Rubus flourishing. In part it is do to higher photosynthetic efficiency. There was a great study on this published in Ecology.

Reich, Peter B., M. Abrams, D. Ellsworth, E. Kruger, & T. Tabone. 1990. Fire Affects Ecophysiology And Community Dynamics Of Central Wisconsin Oak Forest Regeneration. Ecology 71(6):2179-2190.

Bob Wernerehl
Ecologist, the Blue Mounds Area Project
Blue Mounds, WI

Regarding bramble control:

We have been watching the effect of fire on brambles for the past six years.We have had some good burns through large bramble patches.

A good burn will top kill all the brambles. However, it doesn't kill the rootstock. By May the plants have all budded out and have formed rosettes of leaves.These grow into regular bramble canes by mid summer. Thus, a burn does not eliminate brambles, although we have not seen any sign of stimulation.

For at least two years, we sprayed top-killed resprouting bramble patches with aqueous Garlon (2-3%), usually in mid May when the leaves were still in the rosette stage. This certainly killed some, but not all, and we were never successful in eradicating a patch that way.

This past year, I did an experiment where I sprayed rosettes (after a burn) with either Garlon or Krenite (the latter is good on woody species and definitely kills brambles). This killed the plants, but I am not sure about the root stocks. I have all these plants marked and will be waiting to see if any of them come up this year.

Another method I have tried which seems to work, is to basal bark bramble canes with Garlon 4 in oil. I have only used this in areas where the brambles are scattered. I have done this only during the winter/early spring, because Garlon 4 is volatile and does kill nontarget species.

To reduce the amount of Garlon 4 used, I used a device called a "paint stick" (sometimes called a "stain stick") that you can buy at a lumber yard (Menards). This has a spongy or porous end (wick) and a hollow handle. You fill the handle with Garlon 4 and it oozes out the wick. The idea is to keep the herbicide from dripping on the ground. I walked through the prairie (in late winter after snow was gone but before the prairie was burned) and rubbed each cane with the wick, near the base. This worked, and there did not seem to be any kill of nontarget species if done in the cold part of the year. However, this method would be difficult to do in big bramble patches, because it would be hard to get every cane.

We were hoping for a method that would not involve herbicide (because of the potential for hitting nontarget species). For the past three years we have been mowing brambles with a brush cutter, usually in mid summer. The theory is that at that time, when they are starting to flower, the roots are the weakest and will be set back. Most of these mowed patches do not grow back
the same year, but we don't know about whether the rootstock is still viable. In 2003 I marked some large patches handled that way and I will be looking to see what happens this year.

There is one sure way to eliminate brambles, but it is horribly labor-intensive. Cut each cane with a hand clippers and treat the cut stem with 20% (active ingredient) glyphosate. We use a small spray bottle and touch the tip of the bottle directly to the cut stem, allowing a small drop of herbicide to cover the cut surface. If you do all canes in a patch, you can get rid of the patch. Once they have been removed, then you can keep them out by burning. We have only done this in areas of high visibility (near trails and roads).

Just yesterday I timed myself on a patch handled in this way. It took me an hour to do a patch 20 X 50 ft, which is not a very large patch! Kathie has used this method a lot, but it is slow and backbreaking.

As others have mentioned, raspberries are biennials, forming a vegetative shoot the first year and a flowering shoot the second. However, the root system is perennial, so the important thing is to kill the roots. This is what herbicides do! (To make things even more complicated, some species of brambles also tip-root!)

Good luck and keep us informed of your progress!

Tom Brock