Down the Garden Path: How and when to water your garden

Watering plants always brings along a lot of questions: When? How much? What is the best way? What kind of watering attachment? Can I use harvested water?

How to water

One thing to always remember if watering by hand is to water the soil, not the plant. Why? Foliar fungal diseases need wet plant leaves to develop and cause plant damage, so dry leaves are preferred.

If overhead watering is going to be done, such as with lawns or large plantings, then get out early in the day so the foliage dries quickly once you are done. Fungal diseases require the leaves to remain wet for several hours in order to infect leaf tissue. The adage “water on rising temperatures” is so true.

What device to use

Now that we know watering the soil is preferred, the question of how do we apply water comes up. The goal is to soak the soil rather than splash the soil around while we water. Those foliar diseases we just talked about overwinter in the ground, so splashing water droplets with soil particles on the foliage is not a good thing. Methods to reduce splash include:

  • Mulching bare areas.
  • Watering at a slow rate of flow.
  • Using a true water breaker on a watering wand to reduce the water pressure from the garden hose.

In my book, the best combination is to turn down the spigot and use a water breaker, and the water will just “bubble” or flow quietly. However, there are other methods, such as drip irrigation options, for the home garden.

When to water

This question will depend on what you are watering. All seeds need that moisture to start the germination process. Transplants (annuals, vegetables, perennials, etc.) need that water to get through transplant shock and quickly develop a strong root system for the rest of the summer.

Vegetables will need to be watered regularly if you want good-looking fruits, seed pods and root crops. Critical dry periods for vegetables are:

  • Crucifers: head development.
  • Sweet corn: silking and tasseling.
  • Cucurbits: fruit development.
  • Tomatoes and peppers: fruit development.
  • All beans: flowering through pod fill.

Annual flowers need water to establish quickly and begin their summer bloom show. Perennials will be working on establishing a permanent root system the first year and typically begin to bloom the second or third year, depending on the size of the transplant.

Those small fruits, such as strawberries, brambles, currants, and gooseberries, behave just like perennials. Once the root system is established, flowers and fruits follow. Be sure your watering matches production.

How much water

Between Mother Nature and us, our plants should get about 1 to 1 ½ inches of water every seven to 10 days, depending on the growth stage and fruit development. For overhead watering, an easy way to figure that out is to time how long it takes to fill a traditional tuna can with water using your sprinkler. (No tuna can? Try a 1-inch deep dish or container or place a 1-inch mark in an empty butter tub or another small container heading to the recycling bin.) That filling time will be equivalent to about one inch of water applied. For watering by hose or can, remember to water the soil, not the plant. Overall, use the best method of watering you can, or what conditions allow.

How to use rainwater

Harvested water, like from rain barrels, can be used in various areas in the yard, but should be avoided for the vegetable garden. The main reason being health concerns, such as potential transmittable disease and possible contamination from roofing materials. Save that collected water for your lawn, flowers, trees, and shrubs.

Want more gardening advice? Our Master Gardener Help Desks are now open for questions via email, phone, or visit. In Kendall County, volunteers are available 9 a.m. to 12:30 p.m. Monday, Wednesday and Friday, at 630-553-5823. For information, visit

• Richard Hentschel is a Horticulture Extension educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. This column originates on his blog at To get tips from Hentschel, listen to his “Green Side Up” podcast or watch his “This Week in the Garden” videos on Facebook and YouTube.