resorted to grow the lettuce up on the balcony in pots, with aluminum
foil around each plant to deter the squirrels from digging in them.
Though this mostly did the trick of keeping the squirrels from digging
up the plants, they did occasionally still dig in it and the aluminum
foil was a mess. Additionally, the aluminum foil also did little to keep
the plants moist.
The soil under the foil would become dry from the frequent winds we experienced. These winds were so constant, that they wicked a large portion of the moisture from the plants – which stressed the plants enough to cause them to become bitter.
So – putting foil over the soil of potted plants to keep squirrels away is a messy, inconvenient process that is only worthwhile if your plants don’t turn bitter. Perhaps sometime in the future I will grow out lettuce transplants in the greenhouse for putting out into the garden. But only if I can somehow protect them from the squirrels.