Thursday, February 7, 2008

Handling Root Rot on Tristaniopsis laurina

Tristaniopsis laurina is also known as the Kanooka or Water Gum, and is of the Myrtaceae Family which consists of over 3000 species in 100 genera and are found in warm regions including Australia and North America. This plant, which can be grown as a tree form or large screen-shrub, tolerates full sun, and light shade and is said to be drought resistant once established.

One of our customers who recently had some tree work performed on her beautiful Tristaniopsis laurina remarked that
her arborist noticed signs of stress and possible root-rot. While the dense ground cover of Sweet Alyssum ( Lobularia maritima ) - which was literally covering the base of the tree, is beautiful and extremely fast spreading (to the point of invasiveness) it needed to be culled in efforts to increase air circulation to the base-crown of the tree. After clearing away a substantial flush of Sweet Alyssum it became very clear that the tree was in fact developing base or crown rot problems. The surrounding ground cover was undoubtedly the culprit.

Many value Sweet Alyssum for its fast growing, fragrant bouquet and bright white to violet flowers but the question remains, is this an invasive plant and should it be removed from local gardens to prevent its spread? We prefer to treat this issue on a case by case basis and see no need to exclude this ready ground cover - when managed - from a diverse plant list. A main point is in limiting the spread of the plant and removing it frequently, with no fear that the plant itself may die back as they are incredibly vigorous growers.

Mixed in with the low growing ground cover we also found a few small flushes of Woodland or California Strawberry (Fragaria Vesca), which we believe is a simply wonderful plant which serves the dual purposes of adding attractive cover while providing a ready food source for our local birds & insects, so we opted to leave some 2-3 feet out from the base.

We also raked the remaining leaf litter and excess plant/leaf material from the base to ensure quick drying and adequate drainage. To achieve this, we will be keeping the base & crown of the Water Gum clean and clear of any excess plant material. We will also discontinue the use of any ground covers or mulch around the crown-base and monitor the plant for future developments. We trust with regular monitoring and a clean base that the plant will enjoy a full recovery and live a long, happy life in its comfortable rural setting.

1 comment:

Organic Gardener said...

Water gum (Tristaniopsis laurina)is generally listed as 'disease and pest resistant' and this includes Oak-root fungus.

If you can, make sure that there are no Bay trees (California Bay Laurel (Umbellularia californica)) as the leaves can carry fungus and the fungal pathogen has been found in association or carried with the Laurel's leaves in many cases.

As always, keep any irrigation spray away from the base and you should be fine.

For a list of trees thought to be susceptible hosts of Phytophthora copy paste this link from the California Oak-Mortality Task Force:

Thx for the question :-)