Question
QUESTION: I am looking at a house to purchase.  I noticed a very small cypress knee coming up between the foundation of the house and the patio cement slab next to the back of the house.  The very small knee is coming up in the area where the two slabs set - in the gap.  I know the cypress knees can grow and usually there are more growing.  There is a cypress tree in the backyard - no major water or wet lands in the area.  Any advice on killing the knee or should I be concerned about the effect the knee will have on the foundation.  thanks

ANSWER: You can cut the knee off and paint a herbicide called Roundup on the cut surface. This will kill the roots in that area and stop it from producing knees. If left alone the knee will damage the patio slab. Paint the knee as soon as you cut the knee off and the Roundup will be absorbed into the roots. It should not harm the parent tree.

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QUESTION: Should I be concerned about other knees popping up under the slab?

Answer
I would not be too concerned but I would watch for these. The Roundup should kill most of the root systems under the patio but some may not be connected to the present knee may survive to sprout new knees. Just treat these with the Roundup. May take through the spring to get them all.