Moisture Meter- The Simple and Smart Watering Gadget You Need

August 3, 2015 | By Carrie Dubberley | Reply More

Summer watering can be quite a chore and confusing too, what with our cycles of droughts and floods. The endless spring rains may have temporarily relieved us of our watering duties, but just because our lakes our now full, we should still be smart about how and when we water.

Moisture Sensor Meter

A basic moisture meter with a probe and meter box. No batteries required!

For smart watering practice, the one watering tool I recommend to all my garden coaching clients is not a fancy irrigation system but a simple, inexpensive device called a moisture meter (also known as a moisture tester or moisture sensor meter).

As the name implies, use it to measure moisture levels in your garden soil or pots. You’ll be watering wisely and could save time, money, plants, and of course water if you get in the habit of checking your soil before turning on the sprinklers or hose.

You can pick one up for around $10 at North Haven Gardens in Dallas or at any reputable nursery.

Every plant’s needs are different, but the following guidelines should give you a better idea of how to use a moisture meter in your own landscape.

How To Use

Simply push the probe vertically into the soil towards the edge of the plant’s root ball. For a good reading, insert 5+ inches down for larger plants and 2-4 inches for smaller plants. The meter on the device will indicate a scale of 1 through 4, with 1 being dry and 4 being wet.

Moisture Meter

If the meter reads 4, you don’t need to water, especially native trees, shrubs, and perennials. These generally prefer well-draining soil and conditions on the drier side. Not all plants have the resilience of natives though, and the moisture meter watering guide can help determine what needs water.

The handy little chart that comes with the device shows which types of plants to water at each level. This chart is a good starting point, but it does not take into account our natives and how well-established a plant may be.

New vs Established Plants

As a general rule, if a plant was recently planted (within the last season), it will need extra attention to make sure the root ball doesn’t dry out. Take a few readings around the plant by inserting the probe within the root zone.

Planning Ahead

When starting a garden keep in mind that good soil prep and thick mulching will help reduce the amount of water needed.

If the meter is between 2 and 3, give it a good deep watering. Re-check about an hour after to make sure you’ve applied enough water and that it has seeped in. If not, then water some more! It may take several soakings.

During the summer, new plantings may require watering up to three times a week.

Established native plants may not need supplemental watering, except during periods of drought/in absence of rainfall. If it hasn’t rained in two to three weeks, check with your moisture meter to see what needs watering.

Native and well-adapted plants can generally take much dryer conditions, between 1 and 2, once fully established.

Always water deeply rather than frequently. This is especially important in our native clay soils that tend to retain moisture.

Vegetables and Annuals

Flowering annuals and vegetables need to be kept on the moist side, between 3 and 4. Maintaining consistently moist soil will give you better production. And since the roots of these smaller plants are closer to the surface, be sure to take your reading at only 2-4 inches down.

Container Plants

Potted plants will often need daily and even twice daily watering due to the soil drying out. Small, shallow, and crowded pots tend to dry out more quickly, so check these more regularly to develop your watering schedule for your container plants. Tropical plants like coleus, caladiums, canna lilies require a lot more water, a reading between 3 and 4. Most non-tropicals will be happier in the 2 to 3 range.

When Not to Water

Using your moisture meter will not only help keep your plants from getting too thirsty but will also save them from root rot caused by over-watering.

You may notice your plants are looking wilty and sad and assume they need water. But this is not always the case, and the moisture meter may even register a wet soil in these conditions.

It is not always lack of water that is the problem but could be a number of other variables: the summer heat, sun, and/or wind. All of these can make a plant wilt. Over-watering in these case may just kill the plant.

Just because you see cracks in your clay soil doesn’t mean you need to water either. It is ok for most established native and well-adapted plants if the top 1 inch or so dries out and cracks. Native plants particularly are adapted to our clay soils and can withstand some cracking (once established).

Hide the cracks with a 2-3 inch covering of mulch to protect the soil from some of the drying effects of the hot summer sun.

If you’ve developed a watering schedule, re-check with your moisture meter after a rain so you are not wasting water and effort.

Taking Care of Your Meter

Once you’re in the habit of using your moisture meter, you will find it an indispensable tool. So be sure to take good care of it! Maintenance is really easy. Do not leave the probe in soil or water, and wipe it dry between tests.

Every Year is Different

Every season brings new challenges and new water conditions. This summer seems to actually be harder than last year on many established plants that I’ve observed, even with the plentiful spring rains.

Perhaps our plants were pampered with all the rain and cooler weather in the spring and weren’t able to acclimate to the heat and dryness? Maybe the rain caused root rot and a loss of the fine feeder roots that take in water. Excessive rainfall could also have brought feeder root growth closer to the surface to access air, leaving them more susceptible to summer heat stress.

So, though last summer may have been longer and dryer, you may find this summer you need to turn on the water a little more often to keep your plants alive.

The takeaway is watering is not a static, unchanging task, but a moisture meter will help you adapt to the ebb and flow in your gardens.

Each season is a new adventure for us gardeners! With this simple device and the above guidelines, I hope to take some of the confusion out of your watering tasks so you can better keep your plants alive through the summer and beyond, no matter what the weather brings!

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Category: Gardening

Carrie Dubberley is a horticulturist, garden coach, teacher, writer and speaker. Carrie's passion is sustainable landscaping, specializing in North Texas native and well-adapted plants and water conserving rain gardens. Learn more about Carrie.

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