Dear Miss Floribunda,
When I was a child in a Gulf Coast state in the 1960s and ’70s, my granny grew super-fragrant sweet peas in every color of the rainbow along the chain-link fence between her little house and the elementary school. She encouraged all the kids to pick as many as they liked for their mothers and teachers. For her own grandkids, she also planted radishes for us to pull up, brush off on our jackets, and snack on anytime we wanted, and for herself she planted what she called Chinese cabbage because she liked it a lot better than kale.
Now that Hyattsville winters up here have gotten milder, do you think I could plant seeds for these things in the fall and have a winter garden like my Granny’s? Every March, I plant sweet peas, because they remind me so much of my sweet Granny, but by the time they produce a few token flowers, it gets so hot they just shrivel up. What month could I plant them to bloom in February through March like they did in Granny’s garden?
Nostalgic on Nicholson Street
Dear Nostalgic,
I think you are onto something, and there is scientific data to prove it. The first Department of Agriculture (USDA) hardiness zone map came out in 1960, and was first revised in 1965. In the 1970s, the area you describe was in Zone 8, and Hyattsville was in Zone 6, with a low winter temperature of minus 5 F. As of 2023, we have been rezoned to Zone 7b of the USDA map and the area of your childhood — Gulf Coast above the Florida peninsula — is now Zone 9a. It seems to me that it could well be feasible to grow cool-weather vegetables and flowers in a winter garden in Hyattsville, with some modifications.
I turned to my winter-garden expert, George Vandenberghe, and I received good news and bad news. The good news is he confirms that there are many vegetables that can be planted in fall for spring enjoyment, and he has agreed to give a talk and PowerPoint presentation at our next Hyattsville Horticulture Society meeting on Saturday, July 20 at 10 a.m. at the Hyattsville Municipal Center, 4310 Gallatin Street, in the downstairs meeting room. He will bring along seedlings of such brassicas as Brussels sprouts.
Mr. Vandenberghe will let us know which vegetables and flowers can be started as early as August and September, as well as what subset of winter vegetables can actually be planted after Thanksgiving into the first days of December. We will learn which plants are best started from seed planted directly in the ground and which are best planted from seedlings.
Now for the bad news. Along with the fact that in the long term these warmer winters mean hotter summers and dangerously rising sea levels — a disaster for our planet — in the short term, our Hyattsville January is still too cold for fall-planted sweet peas to survive till spring. These tender plants hate severe cold just as much as they hate heat. They require a soil temperature of from 55 to 65 F to germinate, and once they’ve sprouted, they flower well when air temperatures stay between 45 to 68 F.
The earth should remain consistently moist. In Hyattsville, even after the ground begins to thaw after January, we have to contend with wild fluctuations of temperature and precipitation during late winter and spring. And then, depending on variety and soil temperature, edible peas require only six to 17 days to germinate, but it can take an entire month for sweet peas to sprout.
Sweet peas are not easy to start indoors because of their need for such relatively low soil temperature, so you would have to keep the seedlings in a cool yet not very dark area of the house. In addition, they develop long delicate root systems and very much object to being transplanted.
I do think it’s worthwhile to try to start them under grow lights in peat pots in an unfinished and cool basement. Once the soil temperature outside reaches 60 F, you could plug them into the garden, peat pots and all, in the ground on a rainy day, and keep them watered during dry spells. If you are an optimist, place them near a fence or trellis to anticipate their need to climb. I actually plan to try this myself because your enthusiasm has inspired me. I will report the results in a future column.
I have mixed feelings about your grandmother’s encouraging children to pick sweet pea blooms. It certainly must have kept the plants blooming for a long time, since they thrive on being culled, and many mothers and teachers were no doubt delighted with their bouquets. However, the actual peas that develop from these flowers contain poisonous amines, phenols and glycosides. A curious child who sampled many would suffer serious, and even fatal, consequences. Your grandmother was probably well aware of this and removed any pods.
Though they might be less nostalgia-inducing than sweet peas for you, I’m happy to report that radishes and “Chinese cabbage” (napa), bok choy and all brassicas will overwinter nicely here if planted in fall. So will spinach, arugula and certain lettuces. Also, some native perennial wildflowers can be planted in fall. Mr. Vandenberghe tells me that he is experimenting with different types of edible peas to see which fall-planted varieties can survive freezing soil temperatures if well enough mulched and/or covered with blankets on very cold nights. He has had outstanding success growing citrus trees in his garage — his lemons can grow as large as oranges.
To learn more, please mark your calendar for July 20 and come to the municipal center at 10 a.m. There will be coffee and light refreshments, and a very brief meeting of the Hyattsville Horticultural Society.
