March 2016 heralds a delayed spring 6


For March there is a big change to the weather pattern with more winds from north and east, cold showers and frequent frosts. There is no rush to sow, particularly outside, and see the tips below on using fleece, a great help to plants in cold springs.
February temperatures were a little above average but its ten frosts, mostly in the second half, made it the coolest month of winter here, also the sunniest.

Propagation, warmth

Artificial warmth is expensive and precious. The most effective time to provide it is when seeds are germinating, for two reasons:

  • Higher temperatures are often needed for germination than for subsequent growth. This prevents seeds springing to life before its likely to be warm enough for successful growth. 
  • You can fit a lot of germinating seedlings into a small area of propagating heat.

At Homeacres I use a hotbed of fresh horse manure, currently its 47C 117F, one foot below the surface and two weeks after being assembled. Already it has sunk a lot and soon I shall take plants and pallet off temporarily, in order to add more fresh manure and maintain the heat.
In smaller gardens, electric propagators or windowsills are good for getting seedlings underway.

If you have no way of warming seeds, seeds still germinate but more slowly and sometimes unevenly. Undercover without heat its fine to germinate lettuce, brassicas, peas, broad beans, onions, spinach.

Sowings in early March, undercover

My tomato seeds are hitting the compost some time in the next three weeks. Moon-wise there are fruit days on 3rd, 4th, 12th, 20th and 21st. The last two days are just before full moon, when strong waxing forces can encourage stronger growth in sowings made then.

Undercover in early March its good to sow Boltardy beetroot, peas for both shoots and (in milder areas) pods, onions of all kinds though not leeks yet (risk of bolting of sown too early), lettuce, spinach, summer brassicas (not Brussels etc), radish, dill, coriander – and not basil which craves more warmth and light, is best sown in April undercover.

In a polytunnel its good to sow carrots now, if you haven’t already.

See video https://www.youtube.com/watch?v=jSKHHPHlfzk about sowing and pricking into modules.

Sowings in early March, outside

In view of the cold weather its mostly better to wait until mid March. Broad beans are the main sowing now, you can dib individual holes about 2in (5cm) deep. If your plot has mice eating their seed, and possibly peas too, I would sow seeds undercover in modules to have plants in 3-4 weeks, preferably in cells of around 3in (7cm) depth.

You can sow parsnips outside any time from now. I find that mid March is good and draw drills in the surface compost, whether it is homemade, green waste, old animal manure or whatever. See video of outside sowing into surface compost https://www.youtube.com/watch?v=qZs17nwxgtg 

Growth differences undercover and in the open

In spring you obtain huge benefits by protecting plants from wind, because the sun is becoming so rapidly stronger, while temperatures are often low. Even if nights are frosty, daytime growth undercover can be strong, especially of cool-tolerant vegetables such as lettuce, brassicas, carrots etc. 

Covers range from fleece to cloches to polytunnels and greenhouses. 

Using fleece

Simply lay fleece over and on top of any plants you wish to bring on. For example I have covered existing beds of sorrel, spinach and spring cabbage, also a new planting of peas for shoots. Incidentally pea plants are hardy and survive frost, but the fleece encourages new growth.

Fleece is so light that plants can push it up. Having it close to their leaves means the warmth is kept where its useful. Fleece keeps out about 30% of light but at this time that does not matter because there is more light than warmth. Also it lets enough rain and air through that neither watering or ventilation are necessary, unlike with cloches.

Green manures

The tricky bit is how to remove them or stop green manures growing. The mustard I grow (Sinapsis alba) is “agricultural mustard” and is killed by frosts of around -5C (23F) or lower, so finally its dying off. All that is left is a straw-like residue of the stems, which you can rake off to compost and then spread compost if you wish, or sow/plant in the clean soil.

There are no weeds growing on there, I pulled a few little ones in the autumn, the surface is beautifully clean and in this case will be waiting for squash plants in late May, the fourth year in a row in those beds, one of my experiments.

Gardening experience

I was privileged at the London Garden Press Event (Barbican Centre, February 18th) to share tea with Peter Seabrook and Chris Baines. Peter, in his 80th year, is organising a Chelsea garden with 80 suppliers of plants, and he was so animated when discussing all his plans for it. And he is still gardening editor for the Sun. And he still likes digging! we have had a few good discussions about that.

Chris is a wildlife veteran, he was advocating gardens for wildlife years, even decades before anyone else. He was telling us about working at the BBC where he was an early presenter of Countryfile in 1988 which evolved from his television programmes “Your country needs you”.

He recounted how he left that  job when the producer decided that better, more objective questions would be asked by younger, less experienced presenters. Its an interesting call and made me reflect on how valuable it is when gardening to have the experience of ages! There are so many variables that it helps to have a lot of reference points to make good decisions, for example not to sow seeds too early!

Peter Seabrook in centre and Chris Baines on left, in the Barbican Centre London, February 18th

Peter Seabrook in centre and Chris Baines on right, in the Barbican Centre London, February 18th


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6 thoughts on “March 2016 heralds a delayed spring

  • Rhys

    I’ve been germinating various onion seeds this February and I’ve noticed that some strains benefit hugely from 48hrs of ‘undersoil heating’ as it were in terms of transforming the germination frequency. Most have had it between 7 and 15 days after setting the modules up.

    Kelsaes had germinated 6 of around 80 seeds after 10 days, but after 48 hrs sitting on top of our outside boiler and germination went up to over 60 seeds.

    van Rynsburger modules barely germinated any seeds before some heating, but now have a respectable 50%+ seeds germinated (last year’s seeds).

    Lisbon Salad onions failed to germinate at all and are currently sat on the boiler with seeds now germinating and coming through.

    Sturons however have germinated far more without heat, with an 84-module tray already having >50% of seeds successfully germinated. The modules are about 100% germinated after 48hrs of heat.

    I’ve no idea if this is just the luck of the draw – would be interesting to know if anyone else sees any difference in germination frequencies with or without heat for onions.

  • Stringfellow

    Hi Rhys, glad you are getting improved germination rates. This matches my experience over the last few years where i noticed that heat certainly aided germination of onion seed. I start mine inside the house on heated trays and, once underway, take them out to the glasshouse.

    Great to be finally getting things underway 🙂

    • Rhys

      It’s my first year trying in February, so I’m winging it somewhat. Last year I didn’t sow onions until mid-to-late March and even grew some very successfully as clumps by direct sowing into the garden in mid-to-late April. Last year all seeds germinated very, very well without heat in a plastic staging contraption, with the exception of Kelsaes which did rather badly. Having seen how Kelsaes responded to heat this year, I now understand why!

      The real question is whether getting them into the ground earlier will actually be beneficial here in NW London. Like all things, you have to experiment a bit to hit on optimal approaches….

    • charles Post author

      Yes it does for sure! Then you need lesser warmth for heathy growth to continue.
      Do bear in mind Rhys with your experimenting, that what works one year may not work the next.
      When sowing earlier than the normal recommendations for your area, there is an element of gambling: some years results are good, other years less so.

      • Rhys

        Absolutely – I guess the oracle would tell you which years will have early warm springs and which won’t! But I’ve not been given a key to that just yet…..

        Same with seed saving – my 2014 tomato seeds were brilliant, my first germinations of 2015 went OK but not like the previous year. I resowed Maskotka and Black Cherry with 2014 and 2015 side-by-side and the 2014s roared through 100% within 5 days and the 2015s are struggling to emerge. Both were harvested on identical sun+moon in Leo days, but they were at opposite ends of the lunar apogee/perigee and full-moon/new moon configurations.

        Of course, the more likely explanation is that somehow I screwed up making the 2015 seeds! But the Maskotka plant was the highest yielding plant I’ve ever grown in my life, so there was nothing wrong there……

        Good to know how vigorous the 2014 versions still are though. Says that if you get a good batch, use them for a few years……