Answer: Based on your description I am not certain what happened to your plants. Wisteria needs a location with full sun all day long and a well drained soil. In a low spot or if overwatered it might be damaged by excess moisture. If you planted your wisteria tree this spring, it is possible it was hit by a cold snap or freeze that might have killed the foliage but the plant is still alive. I would suggest you consult with your retailer and see.
As far as tomatoes, you have time to replant for this summer. Tomatoes need to be planted into a warm soil, a week or two after the last frost. Tomatoes will be killed by frost and can be badly damaged by cold temperatures below 45 degrees, especially if they are not hardened off prior to planting. To harden off your plants, place them in a protected spot in the shade for about a week, gradually moving them into longer periods of morning sun. Keep the soil evenly moist but not sopping wet, and protect them from excessive cold. When the weather seems settled, plant them in the garden.
Tomatoes need a rich soil that is evenly moist and yet well drained, they also need full sun all day long. The soil for tomatoes should be loosened down about ten inches and amended with organic matter such as compost. You could also add a general purpose granular fertilizer or slow release granular fertilizer per the label directions. After planting, water as needed to keep the soil damp like a wrung out sponge, not sopping wet and never dried out.
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