I want to plant a 35'-50' tree with red fall foliage and non-invasive roots near a sidewalk on the fully exposed front north slope of our house in USDA zone 9, inland valley northern CA. I want a vertical columnar form so as to minimally block the light from the windows. I liked acer rubrum "Autumn Spire" or "New World" but the representative at our nursery said the roots become invasive. I've been unable to verify this. I've also considered nyssa sylvatica "Forum" or "PRP1". Liquidamber "Palo Alto" was another consideration but again I was told the roots would become invasive. What would you suggest and are you aware of any difficulties with invasive roots for Acer rubrum or Liquidamber? I should also mention we have a problem with fireblight in the area.