When and How To Use Silicon for Freeze Protection and Recovery

By Muhammad A. Shahid and Davie Kadyampakeni

Silicon (Si) is getting a lot of attention from citrus growers as a tool to help trees handle stress, especially during cold and freeze conditions. It toughens up plant tissues, strengthens cell walls and helps trees better handle stress when it is applied at the right time.

BEFORE FREEZE

The most important thing to remember is that Si works as a preventive tool, not a last-minute fix when a freeze is already in the forecast.

Si applications for freeze protection should start well before winter arrives. In North and Central Florida, the best time to begin is late summer to early fall, typically August through September. At this time, trees are still actively growing and can take up Si through both roots and leaves. Si builds up slowly in plant tissues, so giving it several weeks or months before cold weather is critical if you want to achieve real benefits.

For citrus, a combination of soil (drench or fertigation) and foliar applications at 200 parts per million (ppm) of Si has proven to be most effective (Figure 1). Soil applications help establish a baseline level of Si in the tree roots, while foliar sprays reinforce leaf and stem strength. Products containing monosilicic acid tend to be more readily absorbed by the plant.

Applying Si during an active freeze event provides little benefit and is not recommended. However, Si can make trees more tolerant to cold stress, resulting in less leaf burn, reduced dieback, firm fruits and faster recovery after a freeze.

AFTER FREEZE

After a freeze event, Si can be very helpful as part of a recovery program. Foliar plus soil applications at about 200 ppm, applied every 15 days for three to four times, followed by monthly treatments, can help reduce stress, support new growth and prepare trees for any additional cold events later in the season.

BOTTOM LINE

Start Si applications early, stay consistent and use it as part of an overall cold-management program. Trees that go into winter with Si already on board are simply better prepared to handle the stress when temperatures drop and will experience less freeze damage.

Read more about Si benefits here.

Muhammad A. Shahid is an assistant professor at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) North Florida Research and Education Center in Quincy. Davie Kadyampakeni is an associate professor at the UF/IFAS Citrus Research and Education Center in Lake Alfred.