The Key to Watering

After all the trips to the garden center have been made, and all of the flowers and vegetables have shifted from pot and pack into garden bed, many gardeners feel that their work is done. Now is the time to sit back and enjoy the fruits of your labor. This statement may be true for the first week, but then reality hits, it’s time to water! A few different factors can affect waterings. Let's dive in.

Impacts of Soil Type and Light Intensity on Watering

First, it is necessary to understand that the environment has a lot to do with how successful you will be in gardening. You’re planting, for the most part, in native mineral soil (i.e. top soil.) Where you live is largely responsible for determining what kind of soil you have. In fact, your soil may be different from the guy down the street even though you both have the same classification of soil. Different types of soil allow for different rates of water percolation (how quickly water is absorbed into and moves through soil) and different levels of water retention (how much water remains in the soil over time).

Soil type (sandy soil, sandy soil with organic material added, clay soil, amended clay soil, or any number of other iterations combination) will have a lot to do with the frequency of your irrigations. In sandy soil, water percolates quickly but isn’t retained well. In clay soil, water percolates slowly and is retained in greater amounts. Don’t despair if your soil is less than desirable, all soils can be modified with organic materials, peat moss or other additives. Clay soils can be made more porous and sandy soils can be modified to hold more moisture.

Another environmental factor that impacts watering is where you locate your garden in terms of light intensity and light duration. A full sun garden will need more frequent irrigation than a filtered shade garden. Note it is the frequency of the irrigation that is variable not the duration of the irrigation.

When you Water, Water Well

The single most important rule of irrigation is when you water, water well! Irrigation water needs to saturate the soil and come in contact with the roots in order for it to be taken into the plant and used for plant growth. Most root systems of flowers, vegetables, trees and shrubs should be thought of as a slightly reduced mirror image of the plant’s upward stems and branches. This root system is as wide as the plant is, and as deep as the plant is tall. You need to apply enough water to saturate the soil that holds this root system. This is why a quick 5 minute watering won’t work.

Those gardeners that have problems with watering, more often than not cause root damage by frequently watering but not watering well enough to have water filter all the way through the root zone. It is far better to water well but infrequently than to water too little but often. Plants that are watered often with just a bit of water will develop a shallow root system. The plant has no need to develop a deep root system. Then if water becomes less plentiful the plant doesn’t have a deep enough root system to sustain life. Plants that are watered slow and deep will sink roots deep into the soil. This large root system allows the plant to pull water from a larger area and will be less likely to suffer if water becomes less plentiful. A good rule of thumb is to slowly water your garden (not your lawn) one inch of water a week.

When to Water

Except when you are planting your garden, you should try to water in the early morning or at the latest by noon. There is a lot to be said about watering so that all free standing moisture has been absorbed either by plant or by soil at least 4 hours before darkness. Now this may be an old wives tale but it is the gospel to us. Wet plants at night are much more susceptible to fungal diseases than those plants that have no free standing moisture in the evening hours. There are exceptions to every rule. If you have to water to save a plant from death by drying go ahead and water. The immediate concern is more important than the possibility of disease. If you must water because evening is the only time you have in the garden, try to water so that the soil is moist but not the plant.

Early in spring when your plants are smaller and the temperatures are lower you may only have to water every 3 or 4 days. As the plants get larger and the mercury creeps higher be prepared to water every day, with small pots or water “pigs” you might even have to water twice a day. You will also need to water more quickly if it is a windy day. Wind will cause pots to dry out more quickly, especially hanging baskets. If you want to water less often use larger pots. Larger pots hold more soil volume. More soil volume means more water held in the pot. More water in the pot means watering less often. 

Sometimes during the summer, if you have been on vacation or perhaps missed a few irrigations your garden soil may end up being the consistency of cement. Water simply will not infiltrate the hard top layer of soil. Rather than renting a jack hammer to loosen the soil, try pre-wetting the soil with a mixture of a gallon of water and a tsp of dish soap (Ivory Liquid or something similar.) Use your watering can to apply this mixture to the soil and plants. Follow the pre-treatment with a normal watering. This pre-treatment actually makes the garden soil more likely to accept an irrigation (it makes water more slippery) and able to find a path between the soil particles and into the root zone.

Watering is a subject with a lot of variables and to cover it completely would take a book. However, we have covered the basic points of how much and when to water. The most important things to remember are:

  1. Proper soil preparation will help irrigation to be more efficient and effective.
  2. Water slow and deep less often rather than a little bit more often. An inch a week should be sufficient for most plants.
  3. Water in the morning if possible, wet plants at night increase susceptibility to disease.

Watering Containers

Proper watering of the plants in your containers is crucial to having them perform their best. Once you get a little bit of experience, understanding when and how much to water becomes almost second nature.  However, when you are first starting out, figuring out how to make those plants happy can be pure frustration. The most common cause of early plant death is generally considered to be over-watering. Luckily for us, ninety percent of the plants out there will be happy if you follow these simple guidelines.

-If you are planting in a pot, make sure there is at least one drainage hole in the bottom of the pot. Proper drainage is essential to happy roots, and happy roots are essential for happy plants. Pots that do not have proper drainage are very easy to over-water.

-Rather than watering on a set schedule, check first to see if your plants need water. If your plant is in a pot, check the surface of the soil in the pot either by looking at it or touching it with your finger. Wet soil will be dark in color while dry soil will be lighter in color.  If the surface of the soil is dry to the touch (or looks dry) water your plants. You may need to check your plants twice a day to see if they need water. Remember just because one pot needs water that doesn’t mean they all do. Differences in pot and plant sizes will impact how quickly a pot dries out.

-When you water be sure to moisten the entire root zone. In other words, water until water comes out of the drainage hole in the bottom of the pot.  It may take as much as ¾ or a gallon of water to thoroughly water a 10 to 12 inch container. More plants are killed with a ‘cup of kindness’ rather than a good long drink of water. Plants that frequently receive a cup of water, seldom develop roots in the bottom 2/3’s of the container. When that daily cup of water is not available, the plant wilts and could easily be lost due to dehydration. Making sure the whole root zone is watered is important for two reasons. First it will encourage roots to grow all the way to the bottom of the pot, which means happier plants. Second, you won’t have to water as often if you water thoroughly.

-Do not allow the pot to sit in water. Pots sitting in water will keep the soil in the pot too wet, allow excess water to drain away.

-It is best not to water at night. If you water your plants too late in the day the foliage will tend to stay wet all night. Wet foliage at night makes a great breeding ground for disease. If your plant isn’t wilting and it’s after 6:30 at night you should be able to wait until morning to water. If the plant has wilted, go ahead and water that evening, its need for water outweighs the chances of catching a disease.

Oh no! My plant is drowning! What do I do?

CPR for Drowning Plants

  1. Move the planter to a shady area, even if it is a full sun plant. The roots of your plant are unable to take up enough water to keep your plant hydrated. Plants in shaded locations will use less water. Once the roots are healthy move sun plants back to a sunny location.
  2. Be sure the pot is draining. If no drainage holes exists add some or repot the plant into a pot with drainage holes. Do not allow the pot to sit in water, this will keep the soil too wet.
  3. If possible, create additional air spaces around the root ball. One way of doing this is slowly tilt the pot to its side and then gently tap the container, the soil ball should now be loose within the container. Carefully re-stand the pot up when completed there should be small air pockets between the pot wall and around the soil ball. This will allow the soil to dry quicker and at the same time bring oxygen to the root zone.
  4. If the plant isn’t too large, repot into a different pot. Be sure to add new soil. This will give the roots nice, clean soil to grow into. If the plant is too large to be easily repotted go on to number 5.
  5. Begin watering only when the surface of the soil is dry to the touch. Do not allow the plant to get extremely dry, this additional shock could be enough to kill the plant. If the plant is wilting badly, you can mist or syringe the plant’s foliage with water which will prevent too much leaf scorch. Do not fertilize. With the roots in a delicate state it can be easy to burn the roots with fertilizer. Once the plant resumes active growth return to normal fertilization.
  6. Treating with a broad-spectrum fungicide can be helpful. Your local garden center should be able to help you choose one.
  7. If the plant is going to make it you should begin to see improvement in a week or so. Once the plant seems to be growing nicely move it into a sunnier location and begin fertilizing again.