More Trees Please
Tree planting success.
I approached two experts in the tree planting business to find out their secrets of success. Rob Bodenstaff is proprietor of the Arbor Centre and is best know for his work in transplanting and the ongoing management of large and mature trees. This involves tree surgery, transplantation, consultancy and tree surveys.
Bill Davey is the Director of Plantation and Landcare Services and deals principally in broad acre planting of tube size trees in farming areas as well as rehabilitation of mining sites and setting up tree plantations such as Indian sandalwood. A major recent planting was the Gateway WA project
Here are the questions I put to each of these experts and their answers.
Establishing new trees is not straightforward, what are the factors that affect the success rate?
Rob Bodenstaff: Quality of stock is the most significant factor for tree survival and success.
Adequate rootable soil volume (below ground space) is critical for city trees.
Success rates are improved dramatically by good site preparation including weed control and ripping the ground. The trees are planted into the rip lines, which act as a basin to collect water. This enables roots to grow deeply to access subsoil moisture. Deep ripping, mechanically breaks up compacted soil layers. Soil preparation is always critical and is more important than fertilizing.
A first year loss figure of 50% has been mentioned what do you think about the accuracy of this number?
Anecdotally this is common in the first year (Perth); and often followed by a further 20% - 30% loss in the next five to seven years. Less than 25% of trees planted in urban settings (private and council), ever reach the first stages of maturity (i.e. 15 – 20 years of age) – source 202020 Vision Conference, Perth, Dec 2015.
Professional tree planting companies achieve a much better rate than this and something has gone wrong if the strike rates for tree planting are just 50%. The reasons are usually poor stock, poor site preparation or late planting.
What is the best soil preparation for planting success?
For trees in Perth’s coastal sands it’s best to de-compact or aerate the sub soil to at least 800mm depth across the planting hole area; where the width of the planting hole area is at least 2 times the diameter of the plant container, or 1m width - whichever is largest.
Only apply organic soil blends, or blend in soil conditioners, to the top 200mm – 400mm. Organic matter buried beyond 500mm depth has a strong tendency to decompose anaerobically and cause other tree establishment problems.
Make provision for roots to be able to grow 10m or more beyond the planting hole in at least 2 directions.
Cover exposed soil areas with high-grade mulch
Ripping creates an environment where the root system can be well established prior to summer. Reducing the competition of invasive weeds in and around the planting zone is essential. If planting out large potted trees the root zone should be improved with the soil conditioner as this helps the soil hold onto moisture and provides nutrients. A conditioner with clay content is best for sandy soils.
Is autumn, winter or spring the best season for planting here or does the availability of irrigation mean that we can plant in any season including summer?
For most species, planting in autumn and early winter is optimal. It best facilitates root development that can sustain the tree through the heat of its first summer period. Planting in spring and summer means a greater level of irrigation support is needed after planting and subsequent growing seasons, before it becomes established.
If you have irrigation that’s a bonus as it means you can plant in winter, spring and autumn. Without irrigation, winter is the best time to plant out seedlings and smaller potted plants, which are watered in by the winter rains and establish well with little extra care. We plant 100,000 trees each year in low rainfall zones with no watering. Our high success rates are due to good site preparation, correct plant choice and excellent seedlings.
How important is mulch in the process and what do you recommend?
Organic mulch (to 75mm depth) is much better than no mulch; and is usually better than inorganic mulch. The main benefits of mulch are that it insulates the topsoil and reduces soil evaporation. Large particle organic mulch (75mm depth), over a thin layer of fully composted material that has high humus (Humic Acid) content.
High grade mulch has gone through the initial stages of decomposition and can commence sustaining soil microbial activities. The initial phase of decomposition can extract nutrients from the soil; and is why raw green mulch can be harmful to tree roots and slow down the tree establishment.
Bill Davey: Mulch helps retain moisture but the mulch must be weed free. Organic mulch which is free draining, consisting of large particles of chipped wood is the best. Composted mulch means that there is no chance of the mulch spreading dieback or other diseases.
Mushroom soil improver/fine mulch http://www.cwise.com.au/images/pdf/C-Wise_Mushroom_PDS_lr.pdf
Do you have some additional planting tips for landscapers?
You always get what you pay for. It is worth paying a fair price for good healthy stock.
Spend money preparing the soil. Don’t put a $10 tree in a $1 hole!
Choose the correct species for the correct soil type, rainfall and the final objective.
Plant selection must achieve the final aim whether it be for broad acre salinity control or providing shade in parkland.
Keep artificial grass at least 100km away from trees!