Three months ago I planted an Afgan Pine (Pinus elderica), Juniper (Junipcrus chinensis), Navel Orange (Citrus sinensis), and a Thuja Green Giant Arborvitae, all between 3 and 4 feet tall. Using a moisture meter, wooden dowel or my finger, I recently noticed that starting about 12" away from the trunk, the closer you get to the trunk, the drier the soil becomes. Is that because the root ball dries out quicker then the surrounding soil and if so should I water when the soil about 6" away from the trunk is 'low moist'? I use a 1/2" soaker hose wrapped twice around the trunk at about 6" from the trunk. The soaker hose dripping for two hours dispenses between 18 and 24 gallons depending on which tree I am watering. Generally I water every 3 to 4 days now because in southeast Arizona the temperature reaches 100 t0 105 F during the afternoon. All trees are in well draining soil and have 3" of compost mulch.
Yes: It is because the rootball is a different texture than the surrounding soil. This is a common phenomenon. I have weeded a tree grown originally in soilless potting medium and found that medium to be dust dry - during the rainy season, years after planting. This tree had been established and making good top growth before I saw how dry the base was. With several other trees planted on the same site in recent years - all grown in claylike field soil which was left intact at planting - I have been having problems with poor establishment. One (a dogwood) even malingered for a few years and then died, another (a magnolia) died back. The dead one got copious watering each time it started to roll up in summer, yet probably was still sitting in a clot of dust. http://www.puyallup.wsu.edu/~Linda Chalker-Scott/Horticultural Myths_files/Myths/B&B root ball.pdf
Thank you for the information and the web address. The way she says it, it makes sense although most nurseries will say the opposite. So I should keep watering as before...when the surrounding soil is 'low moist' and the rootball area is almost dry.
