Many thanks to Milner Gardens & Woodland’s Gardening Advice line (a partnership between Vancouver Island University’s Milner Gardens & Woodland and the Vancouver Island Master Gardeners Association) for the following response:
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Thank you for your recent question to the Garden Advice Line:
Putting a new foundation down could aggravate the roots if some are already down around or under it. However, since it was planted after the foundation was there, they’re probably trying to grow away from it to find water, nutrients and light elsewhere.
Additionally, the lime in concrete acts as a binder, and an excessive amount can alter the soil conditions that the plant is accustomed to. New concrete laid can definitely leach more lime into the surrounding soil in the perimeter. While some hydrangeas can tolerate alkaline conditions, they generally prefer acidic soil. Perhaps you could explore having your contractor put in some kind of barrier between the existing soil and plant roots and the new foundation in order to prevent this leaching.
To protect the branches from the construction of new walls and other structures, you might consider using scaffolding, similar to a large tomato cage. This approach is certainly worth trying. If the old foundation is removed, it will provide a clearer view of the root system, allowing you to decide whether to relocate the plant.
Regards,
Carrie Ceasor and CyAnne Bertoia
Vancouver Island Master Gardeners Association
Phone: 250-752-0312
Email: GardeningAdvice.MilnerGardens@shaw.ca
Web: www2.viu.ca/milnergardens/gardening-advice.asp
Milner Gardens & Woodland’s Gardening Advice is offered through a partnership between Vancouver Island University’s Milner Gardens & Woodland and the Vancouver Island Master Gardeners Association.
Advice is given without charge and although it is believed to be correct, it is given on the basis that there is no liability on the part of the Master Gardener, VIU, or the Vancouver Island Master Gardeners Association.
