Is there any benefit to planting native plants at various times during the late summer and early fall? The answer is yes, and for a myriad of reasons. Late summer and early fall plantings allow the plants to push roots before the winter begins. This will provide many benefits in plant establishment.
To begin with, planting in early fall enables the plant to establish more root development before winter. The increased root development allows for better water and nutrient uptake the following spring and summer. Second, broadening the planting season resolves project delay due to rains in early winter. Another benefit is that the plants would need less or no watering the following year, saving time and labor cost.
In a recent study sponsored by DriWater Inc., Santa Rosa, California, a new theory was presented for a study. In the past, early spring and fall plantings have been the preferential method, but in this new study, the time of year for planting can be adjusted for optimal results. The theory was to begin planting in late summer to allow the plants to push roots before the winter began. Not only will it benefit native restoration projects, but also has practical applications for the landscape contractor.
While plants placed in the ground during the months of November, December and January may be protected from harsh summer temperatures, they do not necessarily receive the root growth momentum to survive through the following growing season.
These plants typically require some type of water regimen during the following spring and summer, which adds cost but may not improve survival rates.
The study results show that while late fall/early winter planting can provide the plants with the water necessary to survive the winter, it does not enable substantial root growth needed for long-term sustainability. Planting trees or shrubs that are dormant or near-dormant late in the season does not create optimum rooting conditions.
On the other hand, planting in late summer/early fall adds flexibility to planting projects by providing the necessary moisture and nutrients to increase rooting and decrease transplant shock. The already established root mass is likely to continue development during the dormant season, increasing plant success the following season.
The study delivered a time-released water gel with enriched nutrients to the plants over a 90 day period (August to November, 2009). This new technology gave the plants 90 days of consistent moisture to establish greater root volume. Controls with the same species were hand-watered, given 2.5 gallons on a weekly regimen.
The test concluded that the time-released water gel delivered better results than hand-watering. The data indicates a 69 percent average increase in root growth for the material planted with the time-released water gel, compared to the material hand-watered only. As of August 12, 2010, plants that were planted August 10, 2009, have shown superior growth and are thriving. No plants received additional water after the first 90 days.