When Should You Stop Watering Your Plants in the Fall?
Roots keep growing long after you've hung up your trowel. See how far into fall you should water to keep your plants happy through winter.
When it comes to fall garden maintenance, shutting off your sprinklers shouldn’t be the first task on your list. Make it one of the last so your plants will be better equipped to make it through the winter. Let’s take a closer look at why.
Why Watering Plants in Fall is Important
Falling leaves may indicate the growing season is over, but there’s something going on underground — active root growth. Energy drains down from the tops of the plants and heads to their roots. Because the soil stays warmer than the air in the fall, roots continue to grow until the ground freezes.
Plant roots need moisture to grow. If your area receives abundant rain in the fall, you won’t need to providing supplemental water. But if you garden in a dry climate, or the usual fall rains just aren’t coming, it’s time to run the sprinklers or haul out the hose.
When your plants aren’t well-hydrated going into winter, they’ll lose foliage and branches, or the entire plant may perish. Sometimes a water-starved tree or shrub will appear to make it through the winter and leaf back out in the spring, only to die when the summer heat returns. In such a case, the death can be traced back to lack of water the fall prior.
Which Plants to Water in Fall
Your entire yard doesn’t need to be watered in the fall if you’re getting decent amounts of rain. Focus first on any perennials, shrubs or trees you planted or transplanted this year. Their roots have not yet extended deep into the soil, so providing water around the base of the plant will help their rootball stay hydrated.
Second, focus on evergreen plants. That includes broadleaf evergreens like rhododendrons and camellias, as well as needle evergreens like pine and spruce. Evergreen plants never get a break from the sun and wind because they don’t lose their leaves, so they require extra care to stay hydrated through the winter. This is especially true for evergreens planted this year.
Colorado State University Extension horticulture specialist J.E. Klett recommends providing supplemental water to shallow-rooted trees and shrubs in the fall. These include European white and paper birches; Norway, silver, red, Rocky Mountain and hybrid maples; lindens, alders, hornbeams, dogwoods, willows, mountain ashes, spruces, firs, arborvitaes, yews, Oregon grape hollies and boxwoods.
Lastly, water your trees or shrubs planted in windy locations. This is especially important for evergreens and any plants just getting established.
A newly planted broadleaf evergreen in a windy or sunny location will be especially susceptible to winter damage. Moisture transpires from its leaves during the winter, but because the ground is frozen the plant can’t get rehydrated. Burnt, browning foliage often indicates winter damage from dehydration.
How Much to Water Plants in Fall
In the spring and summer, 1- to 1-1/2-in. of water each week is sufficient to keep most plants hydrated. In cooler fall weather, the soil won’t dry out as quickly so you won’t need to water as often.
Water must saturate the soil down to the root zone, typically 12 inches deep, to be absorbed by the plant. Watering for a short amount of time more frequently does not help your plants. Watering less frequently but deeper will make them less vulnerable if drought occurs.
Here’s a good way of checking if you’ve watered deeply enough: Make a slit in the ground with a shovel. If the soil feels dry at the bottom of the slit, you need to water longer to allow the moisture to sink further.
When To Stop Watering Plants in Fall
When the air and soil temperatures consistently fall below 40 F, it’s time to stop watering. The ground can’t absorb water once the top few inches freeze. Continue to water your plants up until this point so they’re as well-hydrated as possible going into winter. That can make the difference between life and death for your plants.
If you live where the ground doesn’t freeze, continue to water all winter, just as you did in the fall.