When to plant out cabbage seedlings (Z7)?

[Cranraspberry]

What temperature do you usually plant out your cabbage/broccoli/kale/etc seedlings? Our long term forecast in the DC area is showing early March with pretty steady highs in the 50s and lows in the high 30s, would this be a good time to get them out, or should I wait for the nights to get a little warmer? I do have some frost cloth and hoops I could set up if needed, however the logistics of that are a little tricky (community garden is a few blocks away and my 4 year old can have some very strong opinions on when she does and does not want to go there ha!).

[Uncle_Feist]

Properly hardened cabbage transplants will survive down to at least 20°.

[Cranraspberry]

@Uncle_Feist I was reading that cold-warm fluctuations can lead to premature bolting, so I think that’s my biggest concern! Has anyone ever had issues with that?

[rossomendblot]

I planted out my overwintered calabrese and cauliflower today. We don't often get hard frosts past February here though. They are covered with fleece and if a frost is forecast I will add another layer of fleece.

Last year I lost all of my overwintered calabrese to 'buttoning' (premature head formation) probably because the autumn and winter were quite warm and the greenhouse got too hot several times. Cauliflower is supposed to be more prone to it than calabrese, but last year the cauliflower were fine.

This year we had a spell of unusually cold weather in December and every pot in the greenhouse was frozen solid for 4 or 5 days. The calabrese coped just fine but the cauliflowers were very unhappy and I lost about half of them, so I wouldn't be surprised if they were to 'button' this year instead.

[Uncle_Feist]

@Cranraspberry
I've planted Cole crops at different times over the years in zone 6, and I have never had a problem. When I grew for market I tried to get cole crops out the first week of March. I have transplanted as early as mid February a few times with no issues.

[Cranraspberry]

That sounds very encouraging, thank you! I was planning on getting them out potentially as early as next week, but then read something about premature bolting and started second guessing. We've had some really lovely days already, and I kind of feel like if I were a cabbage I'd much prefer being outside too.

[Seven Bends]

I aim for 3/15-3/25 to plant out my cabbage and broccoli transplants. I'm outside the Beltway but just a few miles out. If you're closer in, or you're on the east side of DC, you probably could shave a week off those dates. If you're itching to get an early start, I'd say just put one or two in early and hold off until at least 3/7 for most of your transplants. Cabbage and broccoli transplants might survive a cold snap, but they'll be set back some and might do better if you just wait a little longer to plant them. Kale is a little hardier and probably could go in a little earlier.

The Virginia Tech planting guide for zone 7a says to put out cabbage and broccoli transplants from 3/15 to 5/5. I can definitely say that 5/5 would be much too late around here most years. I planted on 4/4 last year, and even that was too late because we got some very hot weather in May. So you have to fit the transplanting into a pretty narrow window for success.

[Tormahto]

Hardiness zone, has nothing to do with when to plant out. It doesn't matter if your average low temp in any year is 10 above or 30 below. Either will kill your plants.

There is good information here, about trying to find out what your daily low average, and perhaps daily historical record low, temps will likely be in the near future. The earlier one plants the more potential risk. I always like the idea of partial planting, and them more planting later on.

[Cranraspberry]

@Seven Bends thank you! I was initially planning to do mid-March, but it has been so nice out that I started wondering if I could get them out a bit sooner.

[Cranraspberry]

@Tormato planting things out a few at a time would probably be the smartest approach! I’ll probably start hardening off next week and see what the long term forecast looks like from there.

[Seven Bends]

Hardiness zone, has nothing to do with when to plant out. It doesn't matter if your average low temp in any year is 10 above or 30 below. Either will kill your plants.

I don't agree that hardiness zones have nothing to do with when to plant out. You're certainly correct that most vegetable plants will be killed just as dead by +10F as they will be by -30F, but most places that see -30F also stay cold much later in the year than the places that only get down to +10.

A map of the USDA hardiness zones for Virginia and a map of average last frost dates show a strong correlation between the two. The Virginia Tech planting date tables I referred to are divided by hardiness zone and also have last frost date ranges on them. Most people use average last frost date as the starting point in determining when to plant their various crops, adjusting based on their personal risk tolerance.

[karstopography]

I transplanted 10 big flat head cabbages and 9 early white Vienna Kohlrabi plants. Our local planting calendar has 10/01-11/15 as the dates for transplanting cabbages and kohlrabi.