
Certified GKH Gardening Expert
Both require fertile, well draining soil. You can add compost or well-rotted manure to the soil prior to or at the time of planting to help enrich the soil. If you had nice healthy tomato plants last year but no tomatoes, there may have been too much nitrogen in the soil, which will produce lush growth but little to no fruit. Here is more information that should help: https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-blossoms-no-tomatoes.htm
https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-fertilizer.htm
https://www.gardeningknowhow.com/edible/vegetables/onion/onion-info-tips-for-growing-big-onions.htm