Hi, I've got a gorgeous arbutus in my backyard. It's very big and I'm guessing it's quite old. I've got two questions: 1. The best way I can describe the bottom of the tree is to say that the large branches of the tree all converge at the base, with a 'pit' or 'hollow' in the middle. I can stand in this pit/hollow with all the branches (or maybe they are better described as trunks?) stretching upwards all around me. Does this pit or hollow indicate there is anything wrong with this tree? 2. Recently I started clearing out some vegetation around the base of this tree. Most of the vegetation is blackberry bush, and other weeds that had been left and had grown into a big mess. To get the roots of these weeds out I'm digging down 3-4 inches and sometimes up to six inches. Once the weeds are out I'd like to plant a few small shrubs around the tree (anywhere from 4 feet to 10 feet away from the base of the tree). To plant these shrubs I'd have to do more digging and probably bring in a bit of topsoil. Is it ok to do this? I don't want to damage the arbutus tree roots and if I think I'm getting close to one I will stop digging but I'm still concerned that this disruption might harm the big tree. What do you think? Thanks for your advice! Jill
1. Have an International Society of Arboriculture Certified Arborist look at the hollow. 2. Avoid barking (skinning) the tree's roots while working under it. Try to put back the same soil after weeding, rather than importing soil which may contain pathogens (root and stem rots) that could attack the tree afterward, or may have a finer texture than the existing soil, causing moisture to linger around the crown of the arbutus. If hollows are left even after shaking the soil off of the weeds, bring up the grade with a clean, coarse material, like washed sand or washed gravel, that is unlikely to contain water molds or cause moisture to remain around the crown of the tree. Choose drought-resistant, gray-leaved companions, such as manzanitas, hebes, rosemary, culinary sage, rock roses and other Mediterranean climate plants from the Pacific Coast and, of course, the Mediterranean region. These will be both culturally and visually compatible.
generally speaking hollows are to be left alone. the old days of filling with cement etc are behind us. If the hollow is filled with water, leave it filled with water. If it is dry, leave it dry. If it is filled with detritus and water, remove the detritus periodically (breeding grounds for nasty things).
Mature arbutus - advice Jill, If your multi-stemmed arbutus tree seems healthy then I would not be concerned about the 'hollow'. Could you post a picture of it for us? I would be careful to minimize disturbance around this tree. Arbutus are sensistive to root disturbance. Grubbing out blackberries with limited digging is probably okay. But in general avoid digging big holes around the tree. This will wound the arbutus' roots which can provide entryways for root rot disease (phytophthora). If you must plant under your arbutus then do it in the fall so that natural rains will help the new plants to become established. Use the smallest sized plants that you can (e.g. 6" or 1 gallon maximum) - this minimizes the size of the holes you'll need to dig. Don't add any amendments to the soil - a mulch of leaves (you'll have plenty of these from the tree itself!) is all that is needed. The plants you choose must be those that are drought resistant: Arctostaphylos uva-ursi (Kinikinick) is a good native ground cover. The shrubby Arctostaphylos like A. columbiana (also native) or A. hispida, are also good choices. Others include Choysia ternata (Mexican 'orange'), Spartium junceum (Spanish broom), Rosmarinus officinalis (Rosemary), Santolina chamaecyparissus (Shrubby germander), or Euphorbia characias, because these will thrive without any extra care (read: watering/fertilizing) and are compatible with the conditions that favour good health of the arbutus tree. Other compatible choices are plants native to the mediterranean or Californian climates that experience extended dry periods during the growing season, like Victoria does. Adding a loose layer of organic mulch will not harm the tree. But is it necessary? Your arbutus tree already produces copious litter; bark, leaves, fruit. Just leave this in place to rot down and suppress weed growth. Arbutus trees are native to Victoria, and don't need any help to thrive there. In fact, mature arbutus trees don't adapt well to supplemental watering, or to being incorporated into a traditional irrigated landscape. Do not raise the level of the soil !!! This will damage the root system by making oxygen less available than before. Note that roots need oxygen too. Arbutus trees need excellent drainage, and thrive in a coarse mineral soil. They don't need extra fertilizing. Be careful in your wishes to change things around the habitat of your mature arbutus. This is a tree you can kill with kindness. The effects of changes won't be apparent right away, but you'll find that over a number of years your tree will decline in health, becoming more susceptible to fungal diseases and branch dieback. Hope this helps!
Thank you for all of your responses. Here are some pictures of the tree, including the hollow. I apologize for the quality of the pictures, it was hard to photograph when part of the tree was in bright sun and part was in the shade. Thanks again! Jill
