Falling in Love with Autumn

Below the Surface, Roots Never Rest

With the first leaf display, the tree works on repairing, upgrading, and expanding its root system. Roots thicken and accumulate starch and minerals from the soil to survive the cold and prepare for spring flushing. Assisting the tree at this stage by lightly incorporating quality compost into the soil helps prepare it for winter and the coming spring.

As autumn progresses and fallen leaves accumulate on the ground, roots undergo lignification beneath the surface, acquiring a dark, protective sealing layer. While this reduces water absorption capacity, it enhances the root’s ability to generate “positive pressure.” This enables the tree to continue pushing water up to its canopy even without leaves present to evaporate water and pull it through transport vessels.

Understanding the importance of positive root pressure underscores the need to maintain soil moisture. In containerized media, this need is heightened. Irrigation should maintain moisture without waterlogging the substrate. When Israeli winters yield sparse rainfall, supplemental watering prevents root zone desiccation.

As temperatures drop further into deep winter, stored root starch breaks down into sugars and moves upward throughout the tree, functioning as a natural antifreeze to protect delicate tissues from frost damage.

With preparation complete, the tree enters dormancy. Bud scales sealed with wax protect embryonic tissues, waiting for the first sign of spring to resume growth.

Do We Also Enter Dormancy in Winter and Stop Planting?

A common belief holds that gardens remain static in winter, requiring planting to wait until spring. However, dropping autumn temperatures, accompanying rains, and reduced solar radiation favor planting. This is an ideal period to plant trees.

A veteran agronomist once shared a key principle regarding autumn planting: “As long as you can sink a shovel into the ground, it is a good time to plant, provided you plant on a slight mound and maintain positive drainage”.

Agronomic Tip

When late-summer nutrient deficiency signs appear (such as interveinal chlorosis), growers sometimes forgo treatments like iron, assuming the tree will soon enter dormancy. However, knowing that nutrients accumulate in tissues for spring development highlights the importance of year-round supplementation. While foliage may not fully regain a vibrant green before winter, correcting nutrient deficiencies prior to autumn supports both fall color displays and healthy spring growth.

The Secret of “Chilling Units” and the Importance of Cultivar Selection

“Chilling units” influence color and serve as the tree’s internal alarm clock. Trees track cold exposure hours and must accumulate sufficient chilling units through autumn and winter. Without adequate chilling, trees struggle to break dormancy, leading to sparse or uneven spring bloom and growth.

The timing and intensity of leaf drop depend on temperature variations across species and cultivars. Trees of the same species may require different chilling totals depending on the specific cultivar.

Despite its compact geography, Israel encompasses distinct climate micro-regions. A tree cultivar planted along the coastal plain displays leaf fall differently than the same cultivar in mountain regions. For example, coastal and lowland areas suit trees such as Chinese tallow (Triadica sebifera), crape myrtle (Lagerstroemia), Chinese pistache (Pistacia chinensis), sweetgum (Liquidambar), callery pear (Pyrus calleryana), as well as cold-sensitive tropical trees like Spathodea, Bolusanthus, and Pongamia. Mountain regions require cultivars adapted to higher chilling requirements rather than heat-loving tropical species.

Are You in the Mountains or the Lowlands?

The right cultivar depends entirely on your geographical location and microclimate. Note that fall foliage timing in the Coastal Plain and Lowlands is delayed compared to the Mountain region, as trees at higher elevations accumulate their “chilling units” much earlier in the season.

This is precisely why we have spent years breeding and selecting specific cultivars capable of delivering a classic European autumn display tailored to each local microclimate.

How do you know which cultivar is right for you? That’s where our expertise comes in. Drawing on years of experience and our extensive selection of tree species and varieties, the fall foliage specialists at Ilan Nurseries will personally match the best trees to your site. Contact us today, and we will ensure you get the exact cultivar to deliver the most breathtaking display for your home or project location.