It is difficult to be self-sufficient because it isn't possible to constantly have a harvest.
「家で畑を始めてみても、１年のそれぞれの時期にコンスタントに収穫できるわけではなく、収穫できる時期は限られているので、自給自足は難しいな」は英語で「Even if you start a kitchen garden, it isn't possible to constantly harvest throughout the year, and harvesting time is limited, so it is difficult to be self-sufficient.」という意味がります。
家で畑ーKitchen garden・Vegetable garden
収穫ーHarvest
自給自足ーSelf-sufficiency
アメリカ合衆国 
