Don’t put the hose away just yet

Winter is coming, but it’s not here yet. So don’t put the hose away.

“Although plants in your garden may look brown and bare, they still need water,” said Spencer Campbell, Plant Clinic manager at The Morton Arboretum in Lisle. “Unless there’s enough rainfall to keep the soil moist, continue watering until the ground freezes.”

Watering in fall is important to many plants for different reasons.

Evergreens need to store water in their needles, stems and roots to resist drying out from the cold and wind. “Without enough water in their tissues in the winter, branches or whole plants can dry out and die,” Campbell said.

Because evergreens keep their green leaves in winter, they will keep working whenever it’s not too cold, using sunlight to manufacture food. “That process requires water,” he said.

Deciduous trees and shrubs — those that lose their leaves and enter a dormant sleeping state, such as maple trees and lilac bushes — may not manufacture food in winter, but they continue growing roots in fall even after their leaves have fallen.

Watering these plants now also sets them up for spring. “When plants come out of winter dormancy, they will need a supply of moisture in their roots and in the soil,” Campbell said. The sap that rises from trees’ roots in spring is mostly water. New sprouts rise with water pressure. It takes water for plants to unfurl new leaves and flowers from buds.

“Even if water in the soil freezes into ice at the end of autumn, that ice will melt and be available to the plants’ roots in spring,” he said.

The general rule is to water enough to keep the top 6 inches of soil moist until it freezes. The easy way to know whether you need to water is to use a trowel to dig down 6 inches and then feel the soil for moisture.

The changing climate means we may need to water longer in autumn than we used to. “Our weather is much more variable now,” Campbell said. “Winter is coming later on average, and we’re getting more warm spells and dry spells even after the first frost or snow.”

Old habits and old advice no longer apply. “We can’t just forget about the garden once the leaves drop,” he said. “In some years, especially nowadays, the ground may not freeze until late December.”

This fall, keep track of whether the soil has frozen in your yard or garden and, if it hasn’t, whether the soil is moist. “If it doesn’t feel moist, water,” Campbell said. “Water trees and shrubs as well as flower beds. It’s the most important thing you can do to help your plants survive our increasingly unpredictable winter weather.”

For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.