5b is the warmer of the two. Around here, where elevation changes and nearness to the river can cause drastic but predictible temperature changes, there is one tried and true method of finding out your zone. YOU take a min/max thermometer and put it in YOUR backyard. Once you have a few years of minimum temperature data, the calculation is pretty easy. However, you may not find it the most useful information. For the last ten years here, there is a cluster of lows around -15°F, and another cluster around zero. It averages out to a 6a. However, zone 6 plants can't handle the -15°F temperatures, so aren't appropriate.

by the way, zone-wise, i'm along the IL/WI border in Green Co, WI

Usually my mowing in April is to get the yard cleaned up and the grass is beginning to grow. This past weekend was the second week I've mowed, and the grass really grew in that one week despite not receiving a lot of rain. I also started seeing butterflies in mid April, again earlier than usual. So I figure nature is moving along a couple weeks earlier this year. I only put out a few feeders to see if I attract any hummers, and will put out more when I see more birds.

Paniculatas are very reliable bloomer and many get larger in time so it may get a good plant that -depending on how it likes the site- may grow too big for it. Can you elaborate on the plant not getting morning sun? Is it just because the fence shades over that section? Hydrangeas are deciduous so you will see the fence during the winter time. I assume this is ok? Limelight is a favorite of people trying to do hedges. You can ck out posts about it by doing a forum search for 'limelight hedge'