Suckering – good or bad?

Just as there are those who recall with a shudder the cost and upheaval of removing dead elms from their land at the time of the main disease outbreak, so there are a few people who bear another somewhat lesser grudge against the elm. It tends to sucker.

In an amenity planting root suckers can admittedly be a disadvantage. They are not wanted in that environment, and it is hard, repetitive work removing them. If they are not removed, a thicket can result where the aim was to grow a specimen tree.

Not all elms sucker (Wych Elm does not) but most have at least some propensity to do so. This is gradually appearing to be true of the new hybrids as well. It is an established fact in the case of Morfeo and Patriot, and “Morfeo’s Brother”, FL506, can probably be added to the list. News recently received from the trial site at Great Fontley in Hampshire is that the popular Lutece can produce suckers. But are suckers necessarily a bad thing?

Perhaps the first point to make is that sucker growth is easily controlled by regular mowing in, for example, a parkland planting. Furthermore it may not occur at all if elms do not suffer root disturbance or substantial checks to their top growth. Many a line of English elms grew in parks and never produced a single sucker.

To the elm conservationist, however, suckering is a positive attribute. Of the rich array of elm strains which grew in this country before elm disease came, most would now be extinct were it not for the ability of sucker growth to survive the death of the main tree and preserve its genome. English elm itself would certainly be long extinct, since it reproduces exclusively by suckers. Other elms would have struggled to maintain a place in the hedgerows had they been solely reliant on successful seeding (moderately unusual in this climate). What is more, their suckering secured them not only an environmental but also a cultural advantage. Elm suckers are easy to transplant, and that is one of the reasons why the tree was so widely planted.

For the elm breeder, suckering is beneficial for a distinct but equally fundamental reason. If disease resistance, or other desirable attributes, can be achieved by breeding, the goal is that it should persist down a tree’s generations without dilution. Vegetative reproduction by suckering ensures genetic stability through time, whereas sexual and therefore recombinative reproduction by seed may entail the loss of the very characteristics for which a cultivar was first selected. In planting (for instance) a Morfeo elm in a hedgerow, one can feel some confidence that the one tree will be succeeded by others whose resistance to elm disease is undiminished.

Finally, for the planter working in the rural landscape, the suckering of elm holds out the future prospect of elm boles surrounded by their sheaves of brushwood, a delightful pairing of maturity and youth. And where the subsequent generation of stems will be set out by nature rather than human design, it will be the more effective.