Since this word has okurigana (hiragana attached to the kanji) you know that it's probably going to be the kun'yomi reading, which you didn't learn with the kanji. Here's a mnemonic to help you:
You want to lower something. In this case, it's a tree, so you need a saw (さ). Lower the tree to the ground gently while you slowly saw it down!
Please tell me how to lower my blood pressure.
That shop has one wind chime hanging in its entrance.
I tried performing a rain dance to lower the temperature.