Monthly Archives: February 2019

  • Tips and Tricks: Seed Germination

    Germination

    Germination is the process by which an organism grows from a seed or similar structure and develops into a new plant. Three key environmental factors are important to trigger the seed to grow. We are going to call these the Germination Triangle and these factors are :

    • how how much water is available
    • the temperature
    • the planting depth of the seed

    A careful balance is needed between these three factors.  How dependent the seed is on them varies depending on the plant.  Some seeds will grow anywhere (and we wish they wouldn't!) whilst some need infuriatingly perfect conditions to germinate.

    Stagesseeds_in_bowls_pre_germination

    Water is key as the first stage is for the seed to fill with water in a process called imbibition. The water activates special proteins, called enzymes which that begin the process of seed growth.

    First the seed uses the carbohydrates and proteins stored inside to grows a root (radicle).  The root accesses water before the next stage begins: sending up a shoot above ground. As the shoot develops there will be secondary root formation and branching of the roots.

    By now the seed's reserves are running out so the next stage is to grow leaves to harvest energy from the sun. The leaves continue to grow towards the light source in a process called photomorphogenesis.

    etiolated_seedling_post_germination

     

    Light is very important at this stage.  If there isn't enough light this causes the plants to become etiolated. This is a natural adaptation to help the shoots elongate quickly to break through the soil and reach the light.  However, if it takes too long to reach light the resulting plants will not be strong.  The seedlings will become elongated, spindly, leafless and pale with a poor root system.

     

     

     

     

     


    The Germination Triangle

    Water

    The amount of water has to be just right for optimum growth.  Too little and the seed won't grow.  Too much and the seed will be unable to access the oxygen in the soil and won't develop.  It will basically drown.
    With careful watering, this balance is simple to achieve when you germinate your seeds in seed trays or pots.  If you are sowing direct outside preparing the soil ahead of planting will help you get the water balance right.  Ways you could do this include:-

    • Keep off the soil to prevent compacting - if you have to walk across it then lay long planks to use
    • Aerate the soil - if there are no air gaps then you can create them by aerating the soil with a garden fork or machines that do the job can be hired easily
    • Dig through a balanced fertiliser to break up and improve the soil
    • Use a Raised Bed - the easy way to do it but remember not to walk on it and compact the soil
    •  If your plot is very waterlogged adding a ditch or seasonal pond at the lowest part of the garden for excess water to soak away will be helpful.  This has the advantage of creating a habitat for slug eating frogs and toads which you can read more about in our Pests & Diseases - Slugs & snails blog.

    Temperature

    Temperature is also an important factor. The temperature a seed needs to germinate will often be determined by where the plant originates.  Those that come from Northern climates will often germinate at cooler temperatures than those native to the tropics.  Of course there are exceptions to any rule but many seeds will only germinate when the weather reaches spring temperatures. This can lead to confusion in plants when a freak warm spell causes them to germinate too early leaving them vulnerable to frosts which should be over.

    Some seeds only germinate after extreme temperatures, such as after a forest fire or an extended cold period but there aren't many of these plants in your average veg garden.

    The best way to judge soil temperature is to test with a metal thermometer.  Insert it 3 or 4 inches into the soil 3 or 4 days in a row.  The soil can be warmed by the sun later in the day so morning is the best time to test.  If the soil isn't warm enough then warming it with a Seedling Tunnel is a good option to allow you to start planting earlier than your neighbours.

    Charts are available online to tell you what temperature a particular plant may prefer.  From an optimum 40 degrees for a pea plant to 70 degrees for a tomato.  Once you feel the soil is warm enough, check the long range weather forecast for expected cold snaps and you should be safe to plant.  If the forecast fails you then methods such as or using Bell Cloches or Poly tunnels to shield young seedlings are foremost in the gardener's armoury to start successful germination.

    Planting Depth

    Planting at the right depth improves the seeds chances dramatically and will increase your germination success rate.  The seed will only store enough energy to sprout and reach the light so planting too deep may mean it does not have the energy to make it out of the ground.  If you plant it too shallow then it may fall prey to birds or dehydrate preventing germination.

    Generally the seed packet will clearly show the planting depth so is simple enough to achieve.  But what if a friend gave you the seeds, you harvested them yourself or just lost the packet?   You can look it up on the seed company's website or check out similar packets at your garden centre.  Or you could try and work it out yourself.

    To calculate it yourself, the word on the allotment is that seeds should be planted no deeper than two (or three - opinions vary!)  times their diameter.   This may differ from what's on the seed packet which too often seems to be 1/4 of an inch.  So experimenting planting some at the packet depth and some at the calculated depth might improve germination rates.

    Shallow planting

    Some seeds actually need light to germinate e.g. lettuce and dill.  These tend to be very tiny and should be placed on the surface of the soil and not covered.  The challenge with these is to keep them moist as they quickly dehydrate without a covering. If growing in seed trays  - cover with plastic to prevent the water evaporating away. Or cover with a fine layer of vermiculite - a soilless, mineral growing medium - which is porous and lets light shine through, while keeping enough water around the seeds so that they remain moist.

    Deep plantingRootrainers_with_seed_gemination

    Those that need to be planted deeper can benefit from Rootrainers where deeper cells can be chosen for plants that need the extra depth and moisture can be retained by using the integral cover.

    Position

    The final piece in the puzzle is where you plant them.  Some seedlings such as carrots do not like to be transplanted so it is important to sow these in the position you want them to grow.  Others can handle being moved so give you an opportunity to make the most of the short growing season by starting them off inside and transplanting them into growing position the minute growing conditions are right.

    table_of_veg_

    I hope that this has given you some tips to increase the germination success rate in your garden.  Given the delicacy of the balance that needs to be struck for healthy robust seedlings to germinate and grow you can only marvel at how the self seeders in your garden manage so easily what gardeners work so hard to achieve.

  • Grow at Home: Leeks

    What are they?Leeks_in_soil

    Leeks, which are famous as the Welsh national emblem, are related to the onion but easier to grow.  They have flat overlapping leaves forming an elongated cylindrical bulb which together with the leaf base, is eaten as a vegetable. They generally mature in autumn/winter and hence are a tasty addition to any winter stew or soup such as your classic Leek and Potato.

    Types

    As with other plants there are three main varieties – early, mid season and late. So decide which ones you want to have or get all three. I would just go for one variety as I want as many different vegetables growing in my patch as possible. It depends how many leeks your household gets through...

    Planting

    SOW SEEDS IN GREENHOUSE/ON WINDOWSILL:       February to April

    SOW SEEDS DIRECTLY OUTDOORS:                            March to April

    TRANSPLANT OUTDOORS:                                             May to July

    DEPTH TO PLANT SEEDS:                                               ½” (2cm)

    DISTANCE BETWEEN ROWS:                                         12” (30cm)

    DISTANCE BETWEEN PLANTS:                                       6” (15cm)

    Soil Type

    Leeks are tolerant of a wide variety of soil types but prefer firm, well drained soil.  A safe bet is to dig well rotted garden compost into your soil.  Freshly manured soil is not suitable.  There will be too much leaf growth and the resulting leeks will be coarse, tough and no good for eating. 

    When to Plant

    There are 3 sowing dates for leeks – if planting from seed they should be sown in Rootrainers before planting out

    Variety Sow Plant Out
    Summer and Autumn (Hannibal)

     

    February Mid April
    Autumn & Winter(Blue-green winter, Northern lights)

     

    Mid March Mid May
    Late Winter (Blue Solaise)

     

    Early May Early June

    It is usual to start the seeds off in containers or a seedbed before moving them to their final position once they are established.  This is because sowing them directly into their final position takes up a lot of space which could be being used for fast growing crops such as lettuce. Leeks are perfectly happy to start off in the greenhouse or windowsill and move when your salads are done. 

    Growing from seed is easy and germination rates are high.  Sow your seeds into Rootrainers or small 3” (8cm) pots.Germination should take from 14-21 days.
    Start thinning the seedlings out straight away.  Thin to about 2" (5cm) the first time as some of the plants may die, and then thin again when everything seems to be going well, so that the plants are about 4" (10 cm) apart.

    If you don't want to plant seeds you could also let someone else do the work and buy established seedlings and plant out as the weather permits.

    Planting Out

    When the leeks are about 8" (20cm) tall, plant them into their final positions. If possible plant when the weather is showery, if not then water them well. Keep watering well until they are really established.

    To ensure you get lovely blanched stems make a deep hole around 6" (15cm) to plant the leek.  Fill in with an inch or two of soil and allow the remainder of the hole to fill up with soil as it is washed in with watering.  This will ensure some white stem on your leek which many think is enough (both white and green parts of the leek are edible).  If you want more white and less green though, see the section below on Blanching, for how to use collars.  

    Where to plantContainer_Leeks_in_snow

    When choosing the site to sow leeks make sure you consider that you might want to leave them in the ground to be dug as required during the winter months, and you could leave them in the ground for a year or more.

    It is not advisable to grow leeks in the same place year after year as there will be an increased risk of pests and diseases such as Leek Rust. 

    In crop rotation, leeks follow lettuce, cabbage or peas.  Many people leave planting their leeks until immediately after lifting early potatoes. However, do not plant them where the potatoes were as the soil will be too loose and disturbed and leeks do best on a firm soil.

    Feeding

    Leeks need food and will benefit from a sprinkle of something like a seaweed feed around the roots. This will increase the thickness of the leeks. Don’t feed overwintering leeks after August.

    Blanchingpulled_leeks

    The leeks you buy in the supermarket will have long white stems.  To increase the length of white stem in your home grown leek, blanch the stem by gently drawing up dry soil around the stem in stages.  Start this process in August. 

    If you have your leeks growing in a trench, gradually fill the trench in with soil to the bottom of the lowest leaves each time until the plants have finished growing, which will probably be around mid to late autumn. You are aiming for 4-6" (10-15 cm) of blanched stems. Use dry, fine soil to do this as wet soil will cause rot to set in and lumpy soil wont keep out the light properly.

    If your leeks are growing in a flat bed or container, push the soil up around the plants increasing the soil depth by about 2" (5 cm) each time. You can keep the stems free of soil by using collars.  Secure them around the leeks leaving around 5" (12.5cm) of leaf showing. 

    Collars

    Get your recycling hat on for this bit as many materials are suitable to make a collars. For instance, sawn lengths of plastic piping, the middle of toilet rolls and wrapping paper, or brown paper tied up with string or rubber bands. Whatever type of collar you decide on the minimum diameter should be 3" (7.5 cm) and 12-15" (30-37.5cm) long. Attach the collars before carrying out the earthing-up process.  The collar will keep the light out and the soil will stop it blowing away in the wind.  As the plants grow, draw up more and more soil adding another collar if needed.

    This will increase the amount of the plant that is edible and improve the flavour.  Keep the soil from falling between the leaves otherwise you will have a lot of cleaning to do or risk gritty stew!

    Harvesting

    HARVEST: September to Mayfrosty_baby_leeks

    Harvest your leeks by lifting gently with a fork, either as pencil thin baby leeks or as fully grown 3” (8cm) diameter ones.

    If you want to eat them then do not let your leeks flower as the leek turns into a woody stem once the plant flowers and is too tough to eat.  Leek flowers are a very decorative addition to the garden though so you might want to let some of them flower as they will produce seeds that you can happily collect to use the following year.

    Eating

    Leeks will stay fresh for 1 to 2 weeks if stored in a cool place. Once harvested they are delicious in soups or stews or try them in a white sauce covered in cheese and grilled.  A perfect side dish for your Sunday roast and a lovely vegetarian lunch in its own right..       

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