Thursday, 21 November 2013

Reasons not to dig 9. Your garden plants will more successfully self seed

Poor weed control is the major reason why one might fail to establish desirable self seeded plants and inadvertently kill them. Minimum cultivation allied to enlightened weed control makes it easy to encourage self seeded plants. Many other benefits of minimum cultivation such as a fertile soil surface also satisfies self seeding success!

I have written before about how deeply buried weed seeds lie dormant in the ground for as many as a hundred years. This enforced dormancy is due to diverse factors such as lack of the stimulus of light, lower levels of oxygen, low soil temperatures and much more. It is essential for its own survival that seed does not germinate buried deep in the ground. The effect of digging and other deep cultivations is to bring weed seeds to the surface where when released from natural inhibitions they germinate as soon as weather conditions suit. It is fundamental to good weed control that such weeds are killed before they self seed. It is not for nothing the old adage, ‘one year’s seeding, seven years weeding’. If you stop bringing dormant weeds to the surface, then over a few years you build up a cycle of virtue so that every time the soil is gently disturbed you do not get a mountain of weeds. In a previous post I suggested how under such a regime in the vegetable garden you can broadcast seed such as carrots and leeks. You do not need rows to actually find them and hoe between them!

Under minimum cultivation regimes the surface soil is very fertile. It is near the surface that seeds germinate best. Nature has very efficiently adapted self sown seed to insinuate itself into the soil. Natural cracks, decaying surface litter and a receptive seedbed due to casting worms are some of the natural factors that make the undisturbed soil ready to receive and germinate seed. Zero cultivation is even better than methods where even shallow cultivation might scrape away unnoticed seedlings. After many years of minimal cultivations I can now readily spot any exciting new seedlings and not kill them when I weed.
There are other techniques used by minimal cultivators that encourage self seeding success. Organic mulches, for example are very receptive to seed. Gravel mulches with their superb water conservation properties are particularly ideal - providing they do not overlay plastic!

Plants that self seed in my own gardens

I have written before of self seeding hardy annuals, biennials and short lived perennials. Today I will say no more about them other than they serve a significant role. Here are some less well known examples of self seeding plants. Needless to say, there will be no seeding after thoughtless dead heading!
  • Bulbs. My dwarf tulips really love their gravel mulch and clumps of many varieties grow bigger each year. Naturalised lenten lilies, winter aconites, scillas, chionodoxas, crocus and anemones readily self sow in my borders. I am particularly fond of a patch of an accidental but fortunate mis-planting, where triteleia has prolifically self seeded amongst my agapanthus. Misrepresented by suppliers who wrongly mislabel triteleia as ‘minature agapanthus’, it looks really good flowering between the real agapanthus foliage before its own flowers appear. Fritillaria meleagris now grows everywhere in the moister parts of my garden. There is galtonia and so much more.
Even agapanthus self sows itself
  • Hellebors. Most species freely self seed and germinate as if they were mustard and cress every Spring. Helleborus orientalis is a particular favourite.
  • Dicentra. As holder of the National Collection the prolific germination in February of Dicentra  formosa can make it a weed. I have in the past grown-on such seedlings to select some fine plants. Seed raised Dicentra formosa are different from their parents!
  • Cyclamen. C. neapolitanum, and C.coum with the help of the ants are all over the place.

These cyclamen had a little help from me when I scattered the seed
  • Tender annuals and perennials. Some such as Ipomoea, Nicotiana sylvestris and Dahlia merckii are opportunistic and if there is a warm wet spell for example in April, they germinate freely. Most are destined to be killed by frost! I regularly furcul out and pot up seedlings of Dahlia merckii that go into my unheated greenhouse to sell on my open day a month or so later.

This self sown copper foliage dahlia has been undisturbed for three years
  • Shrubs and trees. Cotoneaster horizontalis, Daphne mezeurium  and Piptanthus laburnifolius supply me with stock of new plants.

This pittosporium has sown itself into a lovely long suffering prostanthera

  • Climbers. Some clematis such as Yellow Clematis tangutica and wonderful long flowering Eccremocarpus scaber are very welcome but can be a bit of a nuisance.

This Summer-long flowering climber gets everywhere

  • Vegetables. Today on 1st November, Brenda has just produced a beautiful starter of juicy conference pears, laced with a blue cheese sauce and laid on a copious bed of rocket served with balsamic vinegar. I am too lazy to sow rocket, coreander and spinach beet in my vegetable garden but they give me a degree of continuity when they self sow themselves and are there when the cook requests them! You will have gathered from my vegetable posts that I am not very tidy and I reclassify otherwise unwanted self seeded plants as a green manure! My self sown parsley and some of my seed raised asparagus reside in my flower garden!

 Self sown weed in my veg garden
  • Wild flowers - often bird borne You might imagine that because I spray glyphosate in my cemetery gardens there would be few wild flowers. You would be completely wrong. They are all over the place and I am sure I will be posting about them one day. Just a few of dozens of examples include honeysuckle, alpine strawberries and violets. When I look around these gardens I find that I have planted very few of the plants!
Unwanted self sown plants

  • Wind blown weeds. Epilobiums are the bane of my life and dandelions are generally unwelcome.
  • Over prolific garden plants. It there are too many of an otherwise desirable self sown plant they become weeds. Treat them as such. It is ironic that in one place you treat them with tender love and care and a few yards away you kill them. Dead head if you do not want any at all!  There are many examples of such unwanted plants. Here are a few. Bluebells, chives, lychnis, campion, poppies, Corydalis luteum, nigella, antirrhinum and limnanthes. Don’t get me wrong, I love them all but  I don’t want too many!
  • Trees. The wonderful soil surface created by long term minimum cultivation provides superb conditions for seedling trees. Willow, hawthorn, birch, sycamore and buddleia need to be ruthlessly removed before they take over. I know many gardens overgrown years later by an unwelcome originally unnoticed self sown forest tree.

I amazed myself when I took this picture of a section of my gravel garden that nine different  plants had put themselves there

I met a reader the other day who did not realise that the highlights in the text are links

11 comments:

  1. We have a daphne that appeared from nowhere as we didn't have one to self seed. It isn't growing on the best of places tucked up against an arch. Presumably deposited by a bird sitting on the arch. WE also have a hawthorn tree on the plot which I trained from a self sown seedling. As for cyclamen hederifolia 0 they come up everywhere even between crack in paving as does verbena bonariensis.

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    1. It sometimes seems easier to get daphne self seeding than doing it yourself!

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  2. I agree about the lychnis, I have it all over the place all self seeded. I've found a couple of antirrhinums too this year, the parent isn't in my garden so the wind must have blown the seed here.

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    1. Yes Jo my Lychnis coronararious really goes mad in my Worsbrough garden - it loves the stoney well drained soil. I have some antirrhinums that have well established themselves there too and now I am doing Cathi's garden she has a developing pink colony of it!

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  3. Half way through this blog I thought I would post a reply, I too have many self seeding plants - one I love is limnanthes which provides almost weedproof cover under the blackcurrants - also attracting hoverflies and bees - I notice this is one of your bad boys. I find seeds that delivery locally are easier to manage than long distance carriers like arum italicum which comes up everywhere thanks to the birds. I think control is mainly down to awareness - a few small meconopsis cambrian - welsh poppy - are easy to hoe or kick away but need a hefty fork a year later.

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    1. I am really glad to have your comments Pauline. I think you will find in my previous blogs that I love limnanthes - just pop it into my search box
      Interesting about arum italicum, I have raised this from seed (collected and sown direct in the ground) but mine does not appear to have sown itself but of course self sowing would be great.
      I also like Meconopsis cambrica - now that is a thug!

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  4. My favorite self-sowers include Wild Columbine, Anise Hyssop, and Swamp Milkweed. Excessive seeders include several asters, including Calico Aster, and Early Sunflower. And of course the damn maples!

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    1. Interesting examples Jason reflecting perhaps your warmer climate in the States.
      It's lovely to see the name columbine that does not get used much over here.
      One of my own 'mediterranean' plants the french marigold is not very hardy with me but hangs in there in my garden because it self seeds, Your mention of hyssop reminded me!
      Asters do not generally seed here - I wish the lovely fluffy seed heads on my Aster amellus would. I do have the occasional self sown Aster novae anglae

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  5. Preaching to the converted Roger. I had some really nice bright red acer seedlings this year, but on the down side my candelabra primula seedlings are more of a nuisance than bitter-cress. Incidently we never saw bitter-cress before the introduction of container grown plants.

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    1. I envy you having a primula problem! I have plenty of P.bulleyana seedings but I would like more of the other candelabras.
      Agree about bitter cress, despite me going on about my excellent weed control I can find four different clones of it in my gardens. Have you ever tried eating it? It's delicious!
      I wonder if you have come across another new scourge - Thale cress.

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    2. Never noticed Thale cress, perhaps it is too wet here. I Googled it and found that it is genetically very interesting. It reminds me of another brassica Shepherd's purse which we do see occasionally. I have tasted bitter-cress and you are quite right it is good to eat.

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