Anyway to dodge elm disease?

[woodyguy]

Don't forget that "English" Elm isn't a native tree!!

[agg221]

Don't forget that "English" Elm isn't a native tree!!

 

True enough - English Elm, or as it should probably now be known Ulmus minor var. Procera is definitely not, but U.glabra almost certainly is and U.minor may well be. Since they hybridise naturally, elms of the Dutch elm type would be likely to be too, although not the specific Dutch elm x.hollandica as that is a cross between English Elm and Wych Elm.

 

Anyway, tall, imposing elms have been around for a while...

 

Alec

[woodyguy]

Alec, have to agree with you about the difference between scientifically tested resistance and the "lucky" tree that survives a few years longer than its peers. I'm still reluctant to shell out a few hundred pounds for trees that may well not survive. But happy to grow Wych elm at low initial cost in the hope that some will survive. Also growing American, chinese and Siberian elm from seed at minimal cost.

[openspaceman]

Anything over 6 feet high gets it and dies, below 6 feet and its fine. So an Elm hedge is OK if kept trimmed but Elm trees are not unless resistant.

 

A

 

The beetle is the vector for the fungus and normal codit applies in resisting the attack I think. So if the beetle feeds on the bark then the infection rapidly runs up and down the current annual ring. The tree reacts by producing tyloses and you can see these in a cross section of the sapwood. These effectively block sap movement so the twigs fed by that sapwood wilt. The big problem arises when the phloem is thick enough to support a breeding gallery, this infects the next years new sapwood. The trees defence mechanism blocks its sap transport and kills the crown above.

 

The english elm which I am familar with is a clone, possibly introduced by the romans because it produced a straight pole and a lot of heartwood early on, this is possibly significant. As it has a high heartwood formation it is highly dependant on the current years sapwood in later life. Thus bigger trees killed themselves in reacting to the fungus, younger trees sent up suckers

 

Younger trees have no sapwood and can withstand the loss of the current years sapwood.

 

The elms I see felled nowadays, U glabra and variants of U minor are not like english elms , they have much less heartwood for the same size. When felled we often see the black stains of tyloses laid down from previous years infections that these trees have survived.

 

So you can keep english elm clones going vegetatively by coppice and layering/suckering.