epicormic growth

Do you have epicormic growth?

Epicormic (epi = upon, kormos =  tree trunk) growth is the technical term for shoots that develop from hidden buds on tree trunks and branches.  Suckers, which grow out of tree trunks, often at their base, and water sprouts, that grow up vertically from tree branches, or at any angle from stubs of broken branches, are the two types of epicormic growth that trees produce.

Suckers and water sprouts develop as a response to stress.  They grow from latent, invisible buds beneath the bark that may lie dormant, in certain oak trees, for as long as a hundred years.  These buds are a tree’s insurance policy in case of sudden environmental stress brought on by extreme cold, branch breakage, flooded soil, fire, insect pest devastation, or fungal or bacterial disease.

Epicormic growth at the base of the trunk is common on fruit trees, especially if the graft union is less than perfect.  Fruit trees purchased at nurseries consist of the cloned scion variety (‘Eureka’ lemon, for example) grafted onto a rootstock, which is typically grown from the seed of a different species such as — in the case of citrus trees — Volkamer lemon, sour orange, or citrange.

Rootstock species are chosen for the vigor they impart to the scion.  However, if the graft union is flawed, suckers will sprout from the rootstock.  If you allow rootstock suckers from citrus trees to grow and develop fruit, that fruit would be bitter.  Water sprouts proliferate on branches of trees whose growing conditions leave something to be desired.  For example, citrus trees that do not receive all day sun are prone to develop water sprouts on their branches.

Suckers are also frequently found on roses owing to the extreme vigor of the rootstock species and the fact that quality control, where grafting is concerned, is sometimes an issue when tens of thousands of plants are being grafted by a single grower over a short period of time.  Always purchase the highest quality roses you can find, even if it means you have to pay a little more.  Roses come in three grades: 1, 1.5, and 2.0, with 1 being the highest grade and the most expensive, but also the best value in the long run.

Suckers and water sprouts should be removed as soon as you notice them.  They compete with flowering shoots for the tree’s mineral resources.  It’s true that water sprouts, coming from the top portion of the tree, will eventually produce fruit of the scion variety but that will not happen for several years and, meanwhile, water sprouts take away valuable resources from already fruitful branches and shoots whose crop, if water sprout growth is left intact, will be diminished.

There is one occasion when water sprouts are a welcome sight and that is when a branch breaks, whether in a storm or under the weight of too much fruit.  After cutting away the stub of the broken branch, water sprouts are likely to grow up from that spot.  Prune off all but one of those water sprouts and then train the one that remains so that, in time, it will fill in the area left vacant by the broken branch.

A correspondent who gardens in Downey sent a picture of a peach tree with seemingly healthy branches that has neither leafed out nor flowered this year.  Suckers are growing from the trunk.  I believe this peach variety is ill-suited to its location, meaning it needs more winter chill hours (hours below 45 degrees Fahrenheit) to leaf out and flower than it got this past winter or that the soil is dangerously wet, another factor that can prevent spring growth in deciduous trees and result in sucker development.

Tip of the Week:  Five years ago, after tasting a ‘Reed’ avocado at the Pasadena Farmers’ Market, Linda Roselund, who gardens in Rosemead, purchased a ‘Reed’ avocado tree from San Gabriel Nursery.  It took a while for the tree to settle in, but now it has begun to produce a good sized crop and the fruit, she writes “are the size of softballs, with a tough outer skin and creamy inside.  My largest fruit weighed one pound, four ounces!  Even though surrounded by a large ‘Valencia’ orange to the north and two tall redwood trees to the south, the site gets good sun from late morning until the end of the day.”