Natural diffusive deposition of radon daughter products from the atmosphere onto an aerodynamically rough, vegetated surface may cause an important enhancement of the ionization rate within the plant canopy. For example, the blades of grass in a lawn may become slightly radioactive, leading to higher ionization in the air between them than above their tops. The impact of this increased ionization rate is estimated from a simple model of the conductivity profile in the turbulent ''electrode layer''. It is found that an order-of-magnitude augmentation can have substantial effects on the electrical structure. With this motivation a one-dimensional, steady state model of radon daughter, dry deposition is developed for estimating the magnitude of the deposited activity. The effects of aerosol attachment and of the entire decay chain are included. This model predicts significant enhancements of the ''surface radioactivity'' under typical continental conditions.