Broccoli and cabbage leaves turning purple

[SirPenguin]

I planted in some broccoli and cabbage about three weeks ago and I've seen very little growth, and purple leaves. I planted a bunch of other stuff as well and it's all doing well. Also new growth seems to be good looking. I was worried that it was a watering issue so I turned the watering down to twice a week. What is wrong with my broccoli and cabbage?

 

[Chuck]

It is probably a nutrient deficiency, either calcium or phosphorus. Most soils naturally have plenty of calcium but it is tied up and the plant cannot uptake. I would try epsom salts as it somehow enables a plant to uptake tied up calcium. If that doesn't work fertilize with a good organic fertilizer. Change will not be fast.

 

[Tetters]

Here I would think that purple leaves were a sign of cold weather - lots of plants in my garden have purple leaves in the winter. As well as that, I would never expect to see a spurt in growth on anything at all in the middle of winter - that usually happens when the sun comes out in the springtime.

By the way Sir.... welcome to the forum

 

[headfullofbees]

pH could be the problem, as brassicas like neutral to slightly alkaline soil.
If your soil pH is too acidic for them, it would explain why other plants are thriving.
Give them a small handful of lime around the stem.
This will not only see to any calcium deficiency, but will keep slugs/snails off as they hate lime.

 

[Don Perry]

Purple leaves is definitely a nutrient problem.

 

[headfullofbees]

Purple leaves is definitely a nutrient problem.

Wrong pH prevents nutrient uptake.

 

[goatherd]

Fertilise them.
Purple tones usually mean phosphorous deficiency ... but the slow growth/purple leaves often involves nitrogen deficiency too, if your oldest leaves are turning yellow/pink and falling off?

For quick access, get some general garden granular fertiliser, grind/soak to dissolve it in their next watering.
About a tablespoon per 10 litre bucket water. I have 6 young caulis in 5" pots that looked TERRIBLE purple and sad just 2 days ago and I watered them like this and pulled off a couple of the oldest sadder leaves too.
Now they're almost twice the size.

Be careful though, sometimes plants showing these symptoms are suffering root damage due to overwatering, so if that could be a possibility ??? You say you worried about a watering problem and reduced to twice weekly watering.

Depending on the soil, plants that have been overwatered may take weeks to need watering again. Because the roots are damaged they will drink very little water and nutrient.

Are your plants outdoors in the garden or in a poly tunnel? I'm not sure what your climate is like, but in mine there is no need to water outdoors except in the summer.

Your profile shows USA, I'm in the southern hemisphere but I'm pretty sure you're in late winter/early spring?
Even indoors plants use less water in cold temps, you might need to water less ...