Frost might have already visited your garden. Ahhh. For me the first frost is celebrated for the completion it brings, to the plants and to me. What remains after a first killing frost are the cold weather vegetables, ensuring fresh nutrition a little longer.That said, I love the end of the season,and each season as they roll along.
All frosts are not equal
As one gardens, one will observe that growing food and flower has dependent factors, like sunlight/shade, soil condition, and such. Frost is similar. Here are some factors:
- location, location
- high or low
- type of plant
- water-soil content
- temperature
One might be surprised to know that temperature is not the only, or sometimes the primary, determinate for frost effecting a plant than all the other factors!
Location
- where is the plant,
- as in orientation to the sun (N/S/E/W), thus how warm does the soil get during the day and is the warmth retained and radiate under the plant for the night of the frost.
- is the plant near a wall, fence, the house, large rocks, or such features that, themselves, store heat from the day and radiate it at night protecting the plants nearby. (In summertime this property of heat transfer can be quite detrimental, in that it increases the heat stress to the plant.)
- is the plant in the ground or in a raised bed; and how high is the raised bed. (more in high or low)
High or low
- Frost effects high before low, as a rule. That is typically due to warmth from the soil. The further from the soil, the air is colder.
- Therefore, raised beds will generally frost before ground planted vegetables or sensitive flowers.
- Similarly, edging flowers will often withstand the first frost or two but taller forms of the same species, like marigolds, will frost out with the first cold night.
- Raised beds: the taller the bed, the more likely it is to frost.
Type of plant
- Is it a vegetable, fruit -ex. raspberry or such, apple or another Autumn variety, or flower?
- Vegetable plants: squashes are the first to go. Squashes will die from cold at 34-35° F, unless right against an adobe house. (both winter and summer squashes)
- Beans will frost at 33-34° F, especially climbing varieties (high). The ground parts of the plant might not have died, but the tops will have.
- Tomatoes are next or will have gone with the beans; usually at 33-34° F. But, location plus high and low will be important factors. (more below)
- Corn will have already completed, except any being dried on the stalk for seed. No worries yet.
- Cold crops such as some varieties of peas, brassicas, chards, beets, carrots, lettuces, spinach, hon tsai tai, brussels sprouts, cabbage (the last two are brassicas) will be happy, some down to 26° F.
Fruit, berries, apples
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- Autumn strawberries here are far superior to July strawberries if your environment supports this renewal. This is the case here.
- Raspberries are in their full glory as temperatures drop. The warm days ripen the fruit; the cool nights sweeten the fruit.
- And, we all know that apples need the cold nights to sweeten their fruit.
- These types of fruit do not frost until 32°, as a rule.
Flowers
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- Cosmos are hardy ’til 32-33° F.
- Marigolds frost at 34-35° F unless location and height are factors.
- Mums can be hardy, down to 30-31° F, if supported by location. Not all varieties are hardy, however.
- Calendula will go down to 33° F with location support.
- Nasturtiums, surprisingly, will usually be vibrant until 33° F.
- Others, such as summer annuals, are gone with the first frost including morning glories, zinnias, dahlias (34° F), geraniums.
Gather up the good stuff
There are those who gather every green tomato on every vine as the first frost is likely. There are various ways to store them and ripen them indoors. Or one can focus on those that are close to ripe and kiss the others goodbye for the season. I, personally, like the paper bag method for finishing the ripening; though I have used trays with newspaper for many seasons. (too much for this body now) One’s storage space is a factor in what to gather or let go; plus one’s psychological attitude on letting go, in general.
My knowledge base is limited, but I think almost all baby squash bulbs are edible. Gather them up. They are great as a chopped vegetable in soups and stews. Small, but immature squashes, also.
Important: Winter squashes needed to be cured for storage and sweetening at least 10 days before the first frost. The plant will indicate its readiness for harvesting of the squash or pumpkin.
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- The stem on the squash will no longer be all green; but will be yellowing, often as lengthwise stripes. Once that sign is prominent, the squash can be cut. I use this method to test how fully sweetened one is as an indicator of how much longer to leave the rest of that same variety on the vine to sweeten.
- If one waits a bit longer than this indicator, as nights cool into the middle 40’s, the squash or pumpkin will easily snap off the vine. The plant has decided that it’s done and all is just right.
- Curing should be done outside, in a dry, non-sunny location thus cool. Curing takes 7-10 days, and hardens the outer skin/shell of the winter squash for storage. Squash like Kabocha or Jarradale will store in the house after cured for up to six months in a dry, cool (45-50° F) environment. I use my guest room, with no heat and the door closed. Butternut, acorn, or Hubbard can last 4-5 months. Pumpkins are much shorter. (Remember that not all pumpkins are edible varieties.)
- If the outer shell of squashes or pumpkins are kissed by a frost, they will begin to rot where the frost touched. Blotches will likely be seen. So, it would be wise to process those, if possible. They will not store for long at all.
Brussels Sprouts, kales, chards, broccoli, and such love the cooler weather. Enjoy the bounty if you seeded them in mid-August. (photo is of bush snap peas by the house)
Water-soil content
There’s a old wisdom on this: dry soil frosts first. I have found that high/low and sheltered are more influential. However, it is true that if a leaf is freshly wet, the water on the leaf will tend to freeze before the leaf does. We see this when a September snow comes. It protects the plant rather than killing it.
Temperature
We can see from all of the above that frost can effect a plant from 35° F.
So, here’s some photos:
- squash plants toast, but nasturtiums still vibrant
- new peas very happy. Old pea plants were already molding with the rain.
- a cosmos that got laid down by the rains, but flowers on nonetheless!
