Sauk County: Gardener When frost arrives in the garden

“Life starts all over again when it gets crisp in the fall.” ~F. Scott Fitzgerald

With October just around the corner, frost is going to inevitably arrive. I’m hoping it holds out a bit longer because I still need to dig many of my geraniums to overwinter in the house and I have to find a winter home for my Caladium. I started the Caladiums from tubers this spring and they were very slow to emerge, so I’m considering simply moving them indoors and using them as a houseplant until next spring.

I recently read an article about how to predict frost that I’m going to test this year. In a nutshell, if it has been a beautiful, sunny day with moderate temps (less than 75 degrees F), clear skies, low humidity, and no wind in the evening, there is a chance that the evening temperatures will drop low enough to cause frost. There are other factors, such as microclimates, that come into play as well, but I should be able to at least get an idea if I need to protect my plants if I forget to check what the local weatherperson says.

Tender vegetables (tomatoes, beans, cucumbers, melons, etc.) in the garden can’t withstand a frost. However, there are several more hardy ones that can handle a light frost if you add a heavy layer of mulch to keep the ground from freezing around them. It also helps to water well before a frost as moist soil can hold more heat than dry soil, up to five degrees F warmer. Those that can handle a light frost include beets, broccoli, cabbage, celery, lettuce, parsnip, arugula and Swiss chard to name a few. Brussel sprouts, carrots, garlic, kale, peas, radishes, spinach and turnips can survive a hard frost, so if you’re short on time, wait to harvest these last. Many times, a first frost is followed by a period of frost-free weather so you can save or prolong your harvest and blooms if you cover them during the first frosty nights.

Within a week or two after the first killing frost is the time to plant garlic. This is typically mid- to late September through early to mid-October, so have your bulbs ready to go when the time is right. I enjoy garlic scapes, so I plant the hardneck variety. I bought my initial bulbs last year at the farmers’ market; this year I will be planting some of the bulbs I harvested out of my garden about a month ago.

If you plant tender bulbs in your flower gardens and containers, the first killing frost is a signal to dig them before the ground freezes. For convenience, I’m going to refer to bulbs, corms, rhizomes and tubers as “bulbs” from here.

Here’s a short list of ones that can be saved from year to year with proper care:

--Begonias (tuberous), callas, cannas, dahlias, gladiolus and elephant ears. Dig them once the foliage dries up or after a first hard frost. If the foliage is killed by frost, it needs to be dug within a few days to make sure rot-causing organisms do not enter the bulb. Take care to not cut, damage, or bruise the bulbs, as that is where pathogens will enter and cause them to rot during winter storage. Clean off all the loose and excess soil and cut off the stems. Gently wash them and leave them to dry. However, glad corms should not be washed; just remove the soil after they have dried. Wait until next spring to divide the bulbs and get rid of any damaged ones to avoid the chance of rot during storage. Before you store your tender bulbs, they need to be cured or dried. Most only need one to three days, glads and callas are exceptions – they need closer to three weeks. Keep them out of direct sunlight in temperatures 60-70 degrees F where it is well ventilated. At this time of year, I can cure mine in the garage. I have an old picture frame with a wire screen that I will place on top of an open tote to help increase air flow. Storethe dried bulbs in a non-airtight container in layers of peat moss, sand, vermiculite, coir or wood shavings about two- to three-inches deep, and ensure they don’t touch. If you like, you can also dust them with an insecticide-fungicide just for that particular use. Put the container in a location where the temps are between 35-45 degrees F with relative humidity around 50 percent; an unfinished basement or unheated garage where they cannot freeze will many times suffice. Periodically throughout the winter check the bulbs for rot and toss any that shows of spoilage. If they appear to be shriveled or really wrinkled, mist the packing material to prevent them from completely drying out. If they are too moist, let them air dry and then repack in dry material. Use these simple guidelines to make saving some of your favorite flowers easier.

Jeannie Manis is a Wisconsin-certified Sauk County Master Gardener volunteer. If you have any gardening questions, please contact the Extension Sauk County by emailing to trripp@wisc.edu or calling the University of Wisconsin Madison Division of Extension Sauk County office at 608-355-3250.