Table 3.

Differences in root incidence at sidewalk joints within 1.8 m of trees of four genera. The percentage of positive root probes, years since planting, number of joints observed and P-values for differences among genera.

	Positive root probes raw %	Years since planting	Number of observations	P-values for differences (binary regression)
	Positive root probes raw %	Years since planting	Number of observations	Gleditsia	Zelkova	Koelreuteria	Quercus
Gleditsia	83	5-12	212	—	0.092	0.065	<0.001
Zelkova	60	6-12^*	197	0.092	—	0.806	<0.001
Koelreuteria	55	5-12	162	0.065	0.806	—	<0.001
Quercus	27	5-13 ^{^*}	347	<0.001	<0.001	< 0.001	—

↵^*Observations not available for Zelkova at year 5 and Quercus at year 12.