Kiddie Pool Plant

This plant is rather useful. It keeps plants cool during the heat of Noon. Most plants are tall enough that its low water level doesn't drown them, letting them be planted on it. You can plant Lily Pads on it, but the plants on the Lily Pad aren't cooled down. It can't be planted on the Roof directly, but it can be planted on a Flower Pot (but not a Lily Pad).

Plants that are too short to be planted in it
Potato Mine

Puff-shroom, but not the Sea-shroom

Sun-shroom

Scaredy-shroom

Spikeweed and Spikerock

Starfruit

Flower Pot

Garlic

Noob-shroom, Spammer-shroom, and Vandal-shroom.

Sniper Pea, Dual Sniper Pea, and Gatling Sniper Pea.

Compass Fruit

Butterfly Net-Shroom

Red Dwarf Star and Black Dwarf Star.

Jupiter Fly Trap

Hyper Spikeweed

Honey Pot

Hyperspace Pot

Plank Plant

Devil-Rock and Reaper-Rock.

Three-Pointed Starfruit

Light Pot

Four-Pointed Starfruit

Shroom-Weed

Mini-nut