Watering the vegetable garden
Water your garden so that your plants always have enough moisture.
- On sandy, well-drained soil, you may need to water twice a week.
- For soils that hold moisture, such as heavier clay soils, or loamy soils rich in organic matter, watering once a week is fine.
- Soil covered by mulch will retain water better, and you may need to water less often.
Watering the garden is a must
It is nearly impossible to have a successful vegetable garden without watering. There may be weeks or even months when the perfect amount of rain falls. But nearly every summer brings a stretch of hot, dry days when garden irrigation is essential.
A lack of water can have major impacts on plants, even if it is just for a few days.
Plants draw nutrients in through their roots and move the nutrients through the plant in a water solution. A lack of water also means a lack of nutrients.
Photosynthesis transforms water into sugar and oxygen when light hits plant leaves.
How drought can affect your harvest
Under drought stress, garden plants may produce small fruit, such as undersized tomatoes or melons, or they may produce no fruit at all. They may become tough, fibrous or bitter, as with cabbage and turnips. They may bolt, sending up a flower stalk and stopping growth, as with lettuce and spinach. Or they may wilt and die.
Check the soil conditions to determine if it is time to water.
Remove the mulch from the soil surface, and then use a spade or a trowel to dig into the soil. The top inch of soil may be dry, but the soil below should be somewhat moist. If the soil is dry two inches below the surface, it is time to water.
If you want to take a more scientific approach, you can monitor the actual moisture in the soil, as described in these two articles from Yard & Garden News: Tools to Determine Soil Moisture Part I and Part II.
Do not wait for rain or for the perfect time to water
- Do not wait for rain to water your garden. If your plants need water today, a rain shower forecast for the day after tomorrow does not help.
- If plants are wilting or showing other signs of heat stress, water as soon as possible. This may be in the heat of the afternoon or evening.
- Although watering early in the day is a better practice, do not wait to water when plants are wilting and under drought stress.
The vegetable garden needs one inch of rain per week.
By using a simple rain gauge or following weather reports, you can determine if your garden received one inch of rain over the past week.
One inch of rain is a lot of water. For a 100 square-foot area, one inch of rain is 62 gallons. Figure out the actual size of your garden by measuring length and width in feet. Multiply those numbers to get total square footage. If a garden is 20 feet by 30 feet (600 square feet), after a week without rain, it would need 372 gallons of water.
You might receive rain, but not a full inch, over the course of the week. If it rained twice, but the total amount of rain was only three-eighths of an inch, you would need to supply the other five-eighths of an inch of rain. Five-eighths of 372 gallons is 232 gallons.
Water gardens on sandy soils twice a week, supplying one-half inch of water (31 gallons per 100 square feet) each time.
A water meter on your hose lets you know just how much water you are using on your garden.
Or you could use a clock and a bucket to figure it out.
Start with a bucket of known volume, like a five-gallon pail. Measure water into the pail and mark the level that is the actual five-gallon line.
Turn on your hose and set it as you would to water your plants. If you use a pistol grip or a sprinkler, put the attachment on the hose. Use the volume of water you normally do.
Begin timing and find out how long it takes to fill the pail to the 5-gallon mark. It may be a matter of a few seconds. Do the test again to confirm your first result. Whatever you come up with, it would take you 12 times as long to apply 62 gallons of water to a 100 square-foot garden area.
No one method of watering or of measuring water use will work for all gardens.
- Drip, trickle or soaker systems: Colorado State University has put together a good explanation of drip systems
- Slow flow from a hose near the base of the plants
- Water from a rain barrel
Plastic mulch or plastic film used as a cover for low tunnels will change the way water reaches the soil and the amount of evaporation from the soil. They also make it more difficult to irrigate unless you have set up a drip system before placing the plastic.
Non-plastic row covers are permeable to rain or water from a hose or sprinkler.
If you are using a hand-held hose, you may underestimate how much water you have applied, so measuring the rate is important.
- Reduce the water outflow and place the hose at the base of plants to allow water to soak into the soil.
- Lower volume will take longer to water and should not be strong enough to wash away the soil from plant roots.
Plant roots need the water, not the leaves. Wet leaves, especially in the evening, can cause leaf diseases. Low and slow watering will allow the water to soak into the soil and be available to plant roots.
However you irrigate, be sure that you are applying the water slowly enough that it does not puddle and run off the soil.
Sandy soil will accept water faster than heavier soils.
Too much water in the garden is also a problem.
Plants may decline and die because their roots are too wet.
- Roots take in oxygen from the soil to survive. If water saturates the ground, there is little or no oxygen available.
- Some plants may collapse and die after a few days if flooded.
- Other plants may survive too much watering, but their fruit may be bland.
- Crops raised for storage, such as winter squash, rutabaga, potatoes or onions, will not keep well after an overly wet season.
- Most leaf diseases do more damage during wet seasons.
- A gardener can do little if too much rain falls. One solution is to build raised beds.
Reviewed in 2018