Yes, it's true, shade is usually unwelcome in the vegetable garden.  Most vegetables need at least 8 hours of sun every day in order to produce a good crop. but there are certain times and circumstances when some relief of shade can make a big difference between success and failure of certain vegetable crops, especially in hot high-summer weather. 

Newly transplanted seedlings need some protection from full sun rays for the first few days after they've been planted, even if they have been hardened-off they will do better if protected a day or two from the hot, dry weather.  This can simply be done by driving a few stakes in the ground and laying light row cover over the top.

Fruiting vegetables require more light than leafy vegetables do, so shading them may depend on your climate, temperatures and zone. Here are some ideas on when to offer your summer garden relief from the hot sun rays.

Leafy cool season crops like chard, sorrel, spinach and lettuce can tolerate and even benefit from light shade in midsummer. Lettuce will be sweeter and crisper, while being less likely to bolt to seed if given some light shade in late spring and summer.   Inter-planting lettuce and spinach under and around tomatoes will lengthen the harvest into the summer while acting as a natural mulch which helps hold moisture in and keeps the tomatoes roots cooler during the hotter days.  When the days become longer, cool season crops will naturally want to go to seed.  Covering them for a few hours in the evening will give the plants a longer period of complete darkness which will slow this process. Row cover, old sheets or other light, loose fabric will work.

Strawberries love the sun when fruiting, but when summers are hot, they can burn. They will benefit from some shade as well.  planting taller crops on the south side can help with the hot scalding sun rays. 

Tomatoes, peppers and eggplant will often get scalded during long, hot summer days. By covering the south side and top with row cover will prevent this, while keeping them a little cooler and still letting 85% sun light through. Cooler temperatures will help with fruit set as well.

Constructing a box of lath and putting it over plants that need shade is another idea.  Lumberyards have inexpensive thin, narrow strips of wood that work well and this can add a bit of interest and whimsy to the garden.

Planting short plants in the shade of nearby tall plants such as pole beans, corn and sunflowers can offer easy shade.  As the sun moves through the day the shorter plants will receive light off and on, giving them relief throughout the day.

Protecting your garden from hot summer sun means better yields of lettuce, spinach, chard and tomatoes.  They will appreciate the cool shelter from the heat too.  Be creative and keep cool!