Black leaves on aucuba caused by root rot

Q: My aucuba shrub has many blackened leaves. About half are either totally black or have black spots. What is going on? Cindy MacNabb, Decatur

A: I’ll bet dollars to doughnuts that your aucuba has phytophthora root rot. This soil-borne disease affects several shrubs: Azalea, rhododendron, daphne and aucuba are common victims. I say “victims” because phytophthora dieback is fatal in most cases. The fungus itself is present in most soils. There is no way to eliminate it. The disease attacks susceptible plants when they become vulnerable due to compacted clay soil, drought stress, or winter injury. The disease works its way up from ground level; little can be done once a plant is affected except removing wilted branches. Nonetheless, a healthy plant in the correct environment can keep the disease at bay. If you decide to replace it, remove all the soil from a hole 1 foot deep and 3 feet wide and refill it with a 1:1 mix of native soil and mini pine bark nuggets.

Q: I have a Patio Peach tree that I planted in the ground. It’s a beautiful tree with full and wide limbs. A branch has sprouted from near the base of the tree and it has now grown 12 feet tall but has produced no flowers or fruit. Will this branch ever produce or should I cut it back? Pete Dawkins, Dunwoody

A: There are two kinds of ‘patio peach’. Some are genetic dwarves that are natural mutations of seedling trees. They have short internodes between adjacent leaves, which yields dense foliage. Subsequent breeding has produced trees with attractive foliage and a rounded shape. The tree is capable of producing medium-sized fruit if it is properly pruned. Examples of genetically dwarf peaches include ‘Bonfire’, ‘Bonanza’ and ‘Southern Sweet’. The other kind of small peach is one that has been grafted to a dwarfing rootstock. These are categorized as ‘patio peaches’ because of their small size, but sometimes the peach variety that’s been grafted to the dwarfing rootstock is not noted, leading to peach trees that are simply labeled ‘Patio Peach’. Even though the rootstock dwarfs peaches grafted to it, some rootstocks will grow large. That, I think, is your situation: The rootstock has sent up a vigorous branch. It should be removed immediately, before it affects the growth of your desirable dwarf peach.

Email Walter at georgiagardener@yahoo.com. Listen to his occasional garden comments on “Green and Growing with Ashley Frasca” Saturday mornings on 95.5 WSB. Visit his website, www.walterreeves.com, or join his Facebook Page at bit.ly/georgiagardener, for his latest tips.