Cold nights bring danger to fruit, plants ... even in Palo Alto
Palo Alto gardeners should feel lucky that we can grow winter crops. In a typical winter there are usually only a handful of really cold days below 40 degrees Fahrenheit (friends anywhere else in the country other than Florida would scoff at that). In the past weeks we have seen below-average temperatures and the forecast is for more sunny but crispy-cold mornings on the way. These nights are more dangerous for your garden than a winter storm.
Protecting your garden is easy and you probably already have the materials at home. Any tarp or cloth covering will go a long way towards protecting vulnerable plants. Tuck them in with an old blanket. You can secure it with rocks so it doesn't fly off and prop it up with large sticks so it doesn't break the branches.
Don't forget to remove the cover in the morning to allow the plants to breathe and get some sun, then cover them up again at night. If this is too much work, a clear plastic tarp will work like a mini-greenhouse, but make sure you leave holes for ventilation.
Christmas lights emit a little bit of heat — just barely enough to protect young saplings from our mild winters. LED lights do not give off enough heat. A bush or a tree can provide significant protection. A layer of mulch (dirt, bark dust, dead leaves) will also provide insulation. The plants that are out in the open are most vulnerable.
Citrus trees will survive a freeze but their fruit might not. Some farmers spray oranges and tangerines with water in anticipation of a cold night. An ice coating forms around the fruit, insulating it like an igloo.
A greenhouse is a great way to grow veggies in the winter. They run from about $100 for a plastic tent-like canopy to several thousand dollars for larger structures with wooden frames and glass panels. Recycling enthusiasts and do-it-yourselfers can build their own greenhouses out of old windows and tarps. But even a greenhouse is not enough for tropical plants that would die at anything below 50 degrees. For that, a thermostat-controlled heating lamp is needed.
Frost-prone plants include hibiscus, bird of paradise, orchids and hoyas. Some succulent varieties may suffer also. Older plants that have developed a hard layer of bark usually do better while fresh green stalks, waxy-leaf and broad-leaf species are in danger. Water inside those leaves expands when it freezes, breaking cell walls and causing the plant structure to collapse.
For many gardeners all of the above information might be a little bit too late for this season. If you already woke up to find droopy, wrinkly, brown and black plants covered in frost don't despair. Prune off the afflicted branches or leaves, water lightly and the plant just might recover. Some plants might look dead but as long as the roots are intact, they can flourish again come spring.
Crops that do particularly well in cool weather include kale, broccoli, radishes, turnips, green onions and carrots. Brussels sprouts even benefit from a light frost. Snap peas enjoy the winter while fixing nitrogen in the soil for next season's round of veggies. Potatoes are tricky because they like cool weather (the will die if it gets too hot) but suffer when temperatures dip into the 30s. The tubers will survive a frost but the above-ground stalks will die. Removal of the troubled shoots should yield new leaves sprouting in a week or two.
Good luck weathering this cold spell! Some of us can't go an entire winter without therapeutic garden work. Fortunately, it doesn't get that cold around here. From here on out the days are getting longer. Spring will be here before you know it.
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POTENTIAL DROP QUOTE:
Some plants might look dead but as long as the roots are intact, they can flourish again come spring.
Freelance writer Be'eri Moalem can be emailed at email@example.com.