Phacelia as a green manure

[ourarka]

So I have been experimenting with a few green manures, and am very impressed with the germination rate and coverage of Phacelia (never mind its gorgeous, insect friendly flowers). I intend to chop flowers down before they seed, but can I still leave the plant in if I'm not yet ready to incorporate it? (and will it flower again?)

Also, I have read that in the warmer areas you can use Phacelia through the winter months - again is this true?

To incorporate I am intending to trim down to the ground and then rotivate. Will this work?

[Thelma Sanders]

In my garden I just leave it! - the frosts kill it and by Spring all that's left are a few strawy stems to rake off - no digging needed.
Suits me just fine

[Two_Sheds]

For the maximum benefit from a green manure, you need to cut it down BEFORE it flowers. You can always leave a few of course, for the bees and the seed.

I don't dig in any of my GMs (or anything else). I just roughly chop them and leave them on the soil as a mulch. Make life a little easier for yourself: don't dig.

[ourarka]

No digging? I like the sound of that! But, if I want to plant quite soon after would I not need to dig it in as presumably them little earthworms wouldn't incorporate it quite that quickly?

Anyhow, interesting about the flowers .... I will bear that in mind from now on. If I cut flowers off can I still leave it? It seems that Phacelia flowers reasonably quickly after germination (within a few weeks) but a lot of places/people talk about leaving it in the ground for a long time, even over winter?

[Two_Sheds]

if I want to plant quite soon after would I not need to dig it in

No, you just push the mulch aside if you want to plant something. No digging required

It seems that Phacelia flowers reasonably quickly after germination (within a few weeks)

It shouldn't: it will go to flower quickly like that if the weather is hot & dry though. The plant is dying so goes to seed as quickly as possible.

Yes, it can stand over winter in very mild areas: usually though a frost will kill it, then new plants will come in the spring (if you've allowed it to self-seed)

[marchogaeth]

So if you plant Phacelia now how will its life cycle run? ie will it flower before it gets frosted and set seed.
Also TS (or anyone else), do you save seed from it for future plantings.
How deep are your chopped surface mulches? I am a bit concerned that surface mulches here (in wonderful wet Wales) will be too much of a haven for slugs.

[WPG]

I sowed phacelia at the start of last August and just left it till the spring. It flowered up until around early December and then the cold and frost gradually killed it. By the spring all that was left was a layer of straw-like stems which were very easy to dig in with a fork. Although I'd let it flower, I'm guessing the winter weather must've killed the seeds because I wasn't troubled by any seedlings.

I didn't try to collect any seeds Marchogaeth - there's so many in the packet that it didn't seem worth the effort. Still got at least half of last years packet left, which I'm going to sow in my empty beds this weekend.

[marchogaeth]

I didn't try to collect any seeds Marchogaeth - there's so many in the packet that it didn't seem worth the effort. Still got at least half of last years packet left, which I'm going to sow in my empty beds this weekend.

I looked at the sowing rate on what looks like quite a big packet from MrF and worked out that I'd get about seven of my typical sized beds out of it which is not quite a year's worth of if I only use phacelia. Not a lot compared with other fertilizers, I know. It's just that I'm keen on the idea of seed saving whenever possible.

[WPG]

Fair point Marchogaeth - think I'll try to collect the seeds from this years' sowing so I don't need to buy more next year.
I did collect the seeds from last year's red clover green manure, as it was just so pretty. I scattered them all around the edges of the plot and it seems to have germinated very well. Maybe too well in fact....hoping it doesn't get too invasive.

[Snadger]

Most green manures are supposed to be dug into the soil BEFORE they flower aren't they?
Flowering always depletes the soil of nutrients especially Potassium so could be counter productive!
It could become a trade off of doing good by adding organic matter but doing bad by depleting the soil nutrients already present. Nitrogen depletion will occur anyway as the organic material breaks down.

Just saying.

[marchogaeth]

Most green manures are supposed to be dug into the soil BEFORE they flower aren't they?
Flowering always depletes the soil of nutrients especially Potassium so could be counter productive!
It could become a trade off of doing good by adding organic matter but doing bad by depleting the soil nutrients already present. Nitrogen depletion will occur anyway as the organic material breaks down.

Just saying.

Good point and that is why I'm asking. I know TS leaves some to flower for the bees etc, I wondered if she also kept some (or even the bee stuff) for seed, too.

I wondered about the N depletion due to the C being used up but if it really is only a few stems you dig in the value of the manure will be in not letting the nutrients leach out and in soil structure, won't they?

If you dig in green stuff it will lock up N which is why I'm interested in the mulch which will be a slower less dramatic breakdown. When I put grass cuttings down, I try to water them with pee and water every so often. It's probably also the case that if you green mulch regularly you change the soil microbe population and the N:C balance is less affected but I haven't done the reading to confirm this.