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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Jul 06

July in the Garden

Posted on July 6, 2018 at 8:08 AM by Ann Vallee

by Charlene Burgi

July can be a stressful time in the garden—for our plants, that is. The cause? Our plants are putting on more growth as well as more fruit and flowers, the sunlight hours are longer, and the evapotranspiration (ET) rate has reached its peak. This is the time when our plants typically require more water than any other time of the year. 

 plant wilted in summer sun
 Plant wilted in summer heat

 succulent leaf types
Succulent leaf types
Evapotranspiration is the water lost from exposed soil through evaporation and from plants through transpiration (people perspire, plants transpire). Plants may wilt or experience burned leaf tips if they cannot get enough moisture to compensate for the lost water. 

Water loss from soil is a relatively easy fix. When covered with a thick layer of organic mulch, the soil will retain moisture far longer than soil exposed to the sun. Mulch will also keep the roots of your plants cooler, allowing them to access more available water to keep them viable during the heat of the day. Additionally, mulch helps limit unwanted competition, as weed seeds have difficulty germinating under mulch. Weeds can and do rob your plants of needed water!

Plant transpiration is a bit more difficult to control. Choosing low-water-use plants for the hot sun exposures of the garden or native plants that go dormant during the summer are a few options to offset the amount of moisture required during July. Plants with thick succulent- or leather-type leaves retain their own reservoirs of water, and are another great choice for the sun. 

But what of existing plants that tend to wilt despite the moisture content in the soil? First of all, when planting moderate- to high-water-using plants with a lot of foliage surface (like hydrangeas), consider the exposure where they are placed in the garden. The recipe for success for these types of plants is to choose a location receiving morning sun and afternoon shade to save them from heat-wilt. Consider, too, that their large, thin and abundant leaves require a lot more water to keep them turgid. Thus their wilting doesn’t necessarily mean these types of plants are lacking water. It is only their inability to draw the water up fast enough to offset the plant from wilting. Typically, as evening approaches, the wilting plant will recover without damage or, at worst, might experience some burned leave edges. 

Another idea to help sun-exposed plants through heat spells is to provide shade cloth cover during the dog days of summer heat. Constructing a tent or lean-to to protect the thin leaves will ward off the scorching heat from the direct sunlight. You might think of that shade cloth cover as the equivalent of our sunblock lotions. Shade cloth even comes in different percentages providing different levels of protection from the sun.

Most important, while our plants are experiencing stressful days ahead, remember that we, too, must remain hydrated and plan our time in the sun accordingly.

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