You may be giving your plants too much fertilizer which can make them bushy rather than fruiting. Heavy rainfall, lack of pollinators or extreme temperatures can also impact fruiting. Some of these factors are not in your control but there are a few key steps to doing the most you can to produce a good harvest of cucumbers and tomatoes.

Productive cucumbers begin with generous compost added to the soil before planting for a fast-draining and fertile planting area. These are hot season plants so wait for the plant's introduction into the garden until night temperatures are at least in the upper 60's. (In our area that's usually June.) Transplant very gently - they dislike the disruption and can take some time to recover. Keep the soil moist and thin the plants if necessary so that each plant has plenty of soil and nutrition to itself.

An organic fertilizer, like fish emulsion is great, applied every two weeks, but won't make up for a lack of good soil and moisture. They need excellent soil and full sun for most of the day. Once you have flowers, keep the soil very evenly moist to avoid misshapen and bitter fruit. Use net row covers if insects are a problem. Choose disease-resistant varieties and do not plant successive year's cucumber crop in the same planting area.

Plants may also lack fruit if a rapid change in temperature interrupts pollination while the plant is in flower or pollinators are not present. You can hand pollinate your plant to increase your chances of fruit if weather is uncooperative. Support pollinators by planting a varied garden.

Tomatoes also need richly organic soil and a full sun location (6 to 8 hours direct sun daily). Do not overfertilize or allow lawn fertilizer to get on the planting area or it will reduce fruit. Do not transplant them out until soil temperature is in the 60's and harden off plants to ease the transition. Fertilize with fish emulsion or an organic tomato fertilizer once planted and repeat with a dilute solution every two to three weeks.

Give the plants plenty of room so they are not competing for soil nutrients and water and leaves do not shade and cool the soil. Be careful not to disturb roots when you transplant as it can shock the plants and delay development. You can use mulch to keep the roots warm once the soil heats up. 

Opinions on the need to prune tomato plants vary. While it is important to keep a decent amount of foliage on the plants for energy and to prevent the tomatoes from getting scorched by the sun, many indeterminate tomatoes are so vigorous that if you don't do some pinching you will end up with a jumble of foliage.  Pinch out the suckers or side shoots (the small growth that appears in the V-shaped area where the stems attach). Pinching makes staking easier and will concentrate the plant's energy, making a more manageable plant.

Courtesy of NYBG Plant Information Service