The best row cover for tomatoes is a medium-weight fabric at 0.5 to 1.0 ounce per square yard. This weight gives you good tomato frost protection while still letting in plenty of sun for growth. Use the cover from transplant day through the first flower bloom. Switch to insect mesh after that point if pests start to show up on your plants in the warm months.
I have grown tomatoes both covered and uncovered for six years in my own backyard plot. The covered plants always start fruit set two weeks sooner than the open ones in spring. My yield jumped by 30% the first year I started using covers on new transplants. The plants grow more leaves and stronger stems under the cover and bounce back from any cold snap with no setback.
Tomatoes need wind and bug pollination to set fruit on the vines once they start to flower. Bees pick up pollen and move it from one bloom to the next as they feed through the day. A cover blocks this work from taking place. No bees in, no fruit out is the simple rule to follow when your tomato plants start to bloom in the bed.
Per Wisconsin Hort, tomato blooms drop off the plant once temps under cover hit 86°F. The plant pulls the flower off the stem when heat stress kicks in. You get no fruit from that bloom and the plant wastes weeks of growth on a dead-end branch. Heat under cover is a real risk on sunny spring days even when the air outside still feels cool.
A medium-weight row cover at 0.55 ounce per square yard is the sweet spot for tomato use in spring. It blocks frost down to 28°F but still lets 80% of sun through to the leaves. I use Agribon AG-19 on my own beds and it has held up for three full seasons so far. The fabric does tear at the edges but I patch it with clear tape and keep using it.
Drape the cover on the day you transplant your starts into the bed. Use hoops to hold the fabric 6 to 8 inches above the top of each plant. This space lets the plant grow tall without pushing on the cover from below. Anchor the edges with soil or rocks every three feet. Check the cover after each big wind to make sure no edges have pulled loose.
Pull the cover off for good once you see the first yellow flower on any plant in the bed. Switch to tomato pest exclusion mesh only if you spot pests like hornworms, stink bugs, or aphids on the leaves. Mesh lets bees in but blocks bigger bugs from laying eggs on your fruit. Most years I do not need to use mesh at all on my tomato bed.
If you do switch to mesh, pick a fine-grade net like ProtekNet that blocks flea beetles while letting bees through. Drape it the same way as your spring cover with hoops and tight edges. Take it off once your fruit starts to ripen so you can pick with ease. The right cover at the right time can double your tomato yield with very little extra work each season.
Read the full article: Row Cover Garden Guide: Weights and Timing
