Different crops have different water needs. Some vegetables, such as celery, are real water lovers and prefer to have moist soil around their roots at all times. Shallow-rooted crops (such as onions and cabbage) need more careful watering during dry spells than deeper-rooted crops (such as tomatoes) that can pull water from greater depths. You also need to keep in mind a plant’s growth stage when watering. Here are some general watering guidelines for different growth stages:

• Watering seedlings and germinating seeds: Water gently once a day to a few inches deep if it doesn’t rain.
• Watering transplants: To help roots recover from transplant shock, water frequently for two weeks after putting transplants in the soil. After that, water every few days to 6 inches (15 cm) or so.
• Watering established plants: Water established plants deeply, to at least 6 inches (15 cm) deep. Give the soil a chance to dry out slightly before watering thoroughly again.

In general, most vegetables use about 1 inch (2 cm) of water per week (1 to 2 inches (2 to 5 cm) in hot, dry climates). If you don’t get water from rainfall, you have to supply it. Each vegetable has a critical period when you need to be especially careful about watering, or your crop may be ruined. Table 2-1 shows the important watering periods for different types of vegetables.