I use el-cheapo bamboo ka-bob skewers to test my containers to see if they need watering. Stick skewer into container and if see if it comes out damp or dry. Usually about $1 for a package of skewers.

Good idea! Thank you for the suggestion! I appreciate it.

My hanging baskets with those plants are 14-16 inches in diameter and maybe 8-10 inches deep, lined with coir. They need watering every other day when the plants are full grown in mid summer. If when you say they are four feet high you mean they are four feet above the ground, then I would guess they are similar to mine. I just stick my finger in an inch or so and water if the soil feels dry. You can use a skewer, but the coir lined planters drain so well that you are at little risk of overwatering. When in doubt, I water. They will wilt fast if they're thirsty.

I feel like, as you say, it would be difficult to over-water and yes, this wire planter basket is four feet off the ground so will not only 'air' out but will suffer from heat in the hot summer. I plan to take a pic today when I head back down to mulch and weed again. We have a wedding reception here on our farm in three weeks so I have to do what I can to get everything looking as pretty as possible!