We have grown in late winter for the past several years in unheated greenhouses. So long as your aware of a few tips you can do so too.
#1 Choose only cold hardy plants from the list below
#2 You must place and remove the covers daily.
#3 Plants grow best after winter solstice and daylight has returned to greater than 10 hours.
#4 harvest when the greenhouse is warm.
#5 Plant into black plastic and warm soil.
#6 A source of water is helpful
For covers use 19 weight row cover every night. The cover needs to be held up for an large airspace. When it's colder than 25 use two layers. When it's in the teens use three. Even if it's cold in the AM remove the covers as soon as the sun is up.
Plants that will grow and thrive from mid January on in most areas. Temps are listed as outdoor temps. In the tunnel it will be warmer. Each layer gives about 5F protection. So if you planted a less hardy variety add an extra layer if unexpected cold is in the forecast. One thing to keep in mind is a strange extra cold day isn't a big deal because the greenhouse will stay warmer if it's colder.. For instance the temps have been 20's for the high and low teens for the low. Then you get a -15 day. The greenhouse won't get nearly as cold as if it had been -15 for a month.
Mache 0F
lettuce, onions and carrots 10F
swiss chard and spinach 15F
kale and collards 20F
Chinese greens and beets 25F
You can also do the hydroponic method I outlined in previous posts for greens.
#1 Choose only cold hardy plants from the list below
#2 You must place and remove the covers daily.
#3 Plants grow best after winter solstice and daylight has returned to greater than 10 hours.
#4 harvest when the greenhouse is warm.
#5 Plant into black plastic and warm soil.
#6 A source of water is helpful
For covers use 19 weight row cover every night. The cover needs to be held up for an large airspace. When it's colder than 25 use two layers. When it's in the teens use three. Even if it's cold in the AM remove the covers as soon as the sun is up.
Plants that will grow and thrive from mid January on in most areas. Temps are listed as outdoor temps. In the tunnel it will be warmer. Each layer gives about 5F protection. So if you planted a less hardy variety add an extra layer if unexpected cold is in the forecast. One thing to keep in mind is a strange extra cold day isn't a big deal because the greenhouse will stay warmer if it's colder.. For instance the temps have been 20's for the high and low teens for the low. Then you get a -15 day. The greenhouse won't get nearly as cold as if it had been -15 for a month.
Mache 0F
lettuce, onions and carrots 10F
swiss chard and spinach 15F
kale and collards 20F
Chinese greens and beets 25F
You can also do the hydroponic method I outlined in previous posts for greens.
