SEED SAVING AND STORAGE

The following extracts are from Garden Organic, RHS, and Kew Gardens websites, further info can be found there.

SEED STORAGE FROM ORGANIC GARDENING
1. Think dry and cool no matter where you store seed. Humidity and warmth shorten a seed’s shelf life.
2. Keep seed packets in plastic food storage bags, plastic film canisters, Mason jars with tight-fitting lids, or glass canisters with gasketed lids.
3. The refrigerator is generally the best place to store seeds.

4. Keep your seed-storage containers well away from the freezer section of your refrigerator.
5. To keep seeds dry, wrap 2 heaping tablespoons of powdered milk in 4 layers of facial tissue, then put the milk packet inside the storage container with the seed packets. Or add a packet of silica gel. Replace every 6 months.
6. Store each year’s seeds together and date them. Because most seeds last about 3 years, you’ll know at a glance which container of seeds might be past its prime when planting season comes.

7. When you’re ready to plant, remove seed containers from the refrigerator and keep them closed until the seeds warm to room temperature. Otherwise, moisture in the air will condense on the seeds, causing them to clump together.

8. If you’re gathering and saving seeds from your own plants, spread the seeds on newspaper and let them air dry for about a week. Write seed names on the newspaper so there’s no mix-up. Pack the air-dried seeds in small paper packets or envelopes, and label with plant name, date, and other pertinent information. Remember, if you want to save your own seeds, you’ll need to plant open-pollinated varieties. They’ll come back true; hybrids won’t
9. Or dry saved seeds on paper towels. They’ll stick to the towels when dry, so roll them up right in the towel to store them. When you’re ready to plant, just tear off bits of the towel, one seed at a time, and plant seed and towel right in the soil.

10. Even if you’re organized, methodical, and careful aboutstoring seeds, accept the fact that some seeds just won’t germinate the following year. Home gardeners will find that stored sweet corn and parsnip seeds, in particular, have low germination rates, and other seeds will only remain viable for a year or two.

RHS Info On How To Collect SeedBack to top

Types of seedheads:
Seed comes in many different natural packaging. The most common forms include;
Berries (e.g. holly)
Capsules (e.g. poppy)
Catkins (e.g. birch)
Exploding seedheads (e.g. Euphorbia lathyrus)
Nuts (e.g. hazel)
Pods (e.g. sweet peas)
Winged seed (e.g. Acer, sycamore)
Collecting seed

  1. Collect ripe seed on a dry day, as soon as the seedheads (e.g. capsules or pods) ripen. This is often indicated by a colour change from green to brown, black or red but before they open and shed their contents
  2. Pick the seedheads, either singly or on stalks, and lay them out to dry on a greenhouse bench, warm windowsill or in an airing cupboard. This enables seed to be more easily extracted from pods, cones or capsules
  3. If they don’t open when dry, gently crush pods and capsules to release the seed
  4. Collect seed from fleshy fruits and berries by mashing them in a fine sieve and then rinsing away the pulp in cold water. Leave the seed to dry for a few days on paper towels
  5. Exploding seedheads need checking every few days. Place a bag over them and shake – this will usually cause the ripe seedheads to explode into the bag. Alternatively, remove the seedheads on their stems as they turn brown and place in a labelled paper bag
  6. Nuts should be collected around the time they would naturally fall either by hand-picking or by placing a sheet at the base of the tree and shaking the branches until they fall
  7. After extracting the seed, clean off any surrounding material (chaff) attached to them, as this material could rot and lead to the seed damping off. Chaff can harbour moulds, pests and diseases

Storing seedsBack to top

Some seeds (e.g. hellebore) is best sown immediately as its viability reduces with storage. However, for many species, sowing is best delayed until a more suitable time of the year such as autumn or spring so the harvested seed will need to be safely stored until sowing. Storing is also required if surplus seed as been collected. Here's how;

    • Place dry seed in labelled paper packets in an airtight container with some desiccant to remove excess moisture. Suitable materials include calcium chloride (sold in DIY stores for use in dehumidifiers) or silica gel
    • Excess humidity or warmth can cause seed to deteriorate or die from fungal disease or rotting
    • Certain seed must not be allowed to dry out as they cannot then take up water necessary for germination. Examples are walnuts, oaks and magnolias. These seed can be stored in a plastic bag of damp vermiculite, sand, or a mix of moist coir and sand for several months
    • Store in a refrigerator at 5°C (41°F) until required. Most seed will remain viable in this way for many years

    Drying and storing seeds at a local level
    Local habitat restoration and species re-introduction projects, community seed banks and community-based initiatives to conserve medicinal plants may all involve short to medium term seed storage. Understanding how seeds age and how correct drying and packaging can slow down the ageing process can help such projects to store seeds for longer. This can help to improve seed security and/or reduce the need to re-collect seeds.

     

    KEW GARDENS INFO


    alternative methods of drying
    Low-cost options for detecting seed moisture. RBG Kew
    Seed moisture detection equipment
    Dial hygrometers consist of a chemically coated metal coil attached to a needle which contracts or expands as RH changes. They measure on a graduated scale from 0 - 100% RH. They reach equilibrium within a few hours and are accurate to within about +/- 10%RH.
    Self-indicating silica gel contains a methyl violet indicator which changes colour from green to orange below about 20-25% RH. It thus gives a very good indication that seed moisture is at a level that will permit safe storage for many years. The disadvantage of these indicators is that they are slower to equilibrate (several days) than the dial hygrometer or indicating strips.
    Moisture indicating strips are chemically impregnated cards which change colour as RH changes.
    A very cheap and simple salt test can be used by farmers to show if seeds are dry enough to store. Mix common salt with seeds in a glass jar and shake for a couple of minutes. Leave for 10-20 minutes and examine the walls of the jar. If the seeds are still wet the salt will have absorbed moisture and will be sticking to the sides of the jar.
    Seed drying
    Drying seeds to about 70% eRH (12-15% mc, depending on seed composition) minimises the risk of fungal damage and is generally regarded as a 'safe' moisture level for short term storage. This is also the maximum moisture content for sealed storage (which can help to prevent insect damage).
    However, drying seeds even further will slow down physiological aging processes and prolong their useful storage life. Down to about 15% eRH (4-7% mc depending on seed oil content) a simple rule of thumb applies: for every 10% reduction in eRH or 1% reduction in seed moisture content, seed life span doubles (Harrington, 1970).  


    eRH%

    Seed Survival

     70-85%

     Seeds at risk of rapid loss in viability

     50-70%

     Rate of deterioration slower; seeds may survive for 1-2 years

    30-50%

     Seeds could survive for several years

     10-30%

    Seeds can be kept alive for decades

    Remember also that temperature affects seed longevity. A similar rule of thumb applies: seed longevity doubles for every 5°C reduction in storage temperature. Thus, seeds dried to 70% eRH and stored at 20°C will survive twice as long as similar seeds stored at 25°C. If average local temperatures are relatively high, try to compensate for this by drying seeds to lower moisture levels. 
    Ambient drying
    In many countries, farmers traditionally use sun drying to reduce seed moisture before storage. This involves spreading seeds out in a thin layer, sometimes on a tarpaulin. It is important to turn seeds regularly, because high temperatures may cause damage. Drying tables, or other methods of raising seeds off the floor to increase air circulation, will speed up the drying process.
    The lowest seed moisture level that can be attained using sun drying depends on the local climatic conditions (temperature and relative humidity) and the species in question. In arid regions, where average relative humidity is low, safe moisture levels for short term storage are readily attained.
    In locations where average relative humidity is quite high but falls during the day, it is possible to dry seeds in the late morning and afternoon when the weather is favourable. Cover seeds up when temperatures begin to fall in late afternoon to prevent moisture uptake as relative humidity increases.
    In humid regions where relative humidity remains high throughout the day it is virtually impossible to dry seeds to safe moisture levels. It is very difficult for farmers to store seeds for longer than a few months without significant loss of viability and/or insect attack.
    Charcoal seed-drying
    Drying seeds using charcoal
    Using charcoal to dry seeds
    Drying seeds with desiccants
    Some traditional seed storage methods suggest placing a layer of charcoal on top of seeds before sealing them for storage. This technique may help to deter insects. However, dried charcoal and other desiccants such as dried rice can also be used to dry seeds before storage. Charcoal and seeds such as rice or maize are readily available, inexpensive potential desiccants that can be found in rural areas throughout the world.
    The desiccant must be dry to start with, otherwise it will not be able to absorb much moisture, and the seeds will not dry properly. Being black in colour, charcoal has the potential to absorb solar heat during the day thus causing it to dry below ambient humidity levels. Charcoal exposed to direct sun for about 5 hours will reach a very low moisture level and will have a lot of drying potential. Otherwise, dry the charcoal over a low heat (e.g. over a stove or fire).
    Place the dried charcoal in a sealable container and spread a thin layer of seeds above the charcoal. Separate seeds from charcoal with a thin sheet of newspaper, or similar porous material. Alternatively, place seeds in a porous bag or envelope above the charcoal.
    Seal the container and leave in a safe place, not in direct sun. Depending on the size of the seeds and how dry they were to start with, it will take about two weeks for the seeds to dry. After drying, seeds need to be sealed in a moisture-proof container to prevent them from gaining moisture again. 
    How much charcoal to use?
    Charcoal drying works because the charcoal absorbs moisture from the seeds. Therefore, the wetter the seeds, the more charcoal is needed. If the seeds are freshly harvested and are still very moist, you would need a lot of charcoal to absorb the moisture from the seeds. It is best to first dry the seeds as much as possible using sun drying. This will remove some moisture and means that you will need less charcoal. Once the seeds are air dry, a ratio of one part seeds to three parts desiccant (by volume) should work well. 
    Keeping seeds dry
    Remember that dried seeds will only remain dry if the air around them is dry. In very arid environments, it may be possible to store seeds in bags for one or two seasons without too much loss of viability. In most environments it is better to store seeds in sealed containers to prevent them re-absorbing moisture. Sealed storage also helps to prevent insect damage.
    Glass drinks bottles, plastic tubs and buckets and many other locally available containers can be used to store seeds. The most important thing is that they have a good lid. Test if containers are air-tight by holding them under water. Sealing can be improved by adding a rubber gasket cut from an old car inner tube. Fill the container as full as possible with seeds.

    Further information
    Harrington J.F. 1970. Seed and pollen storage for conservation of plant gene resources, pp 501-522.  In: Genetic Resources in Plants - Their Exploration and Conservation.  IBP Handbook No. 11.  Eds: Frankel O.H. & Bennett E. Blackwell Scientific Publications, Oxford, UK.
    Seed collection/harvest
    It is important to collect or harvest seeds at the right time. The majority of crop and wild plant species produce orthodox or desiccation tolerant seeds, which are able to withstand drying. By the time of natural dispersal or harvest, with very few exceptions, seeds are desiccation tolerant, and will have reached their optimum storage potential. If seed collections contain a significant proportion of seeds that are not fully mature, use post-harvest ripening methods to improve their storage potential. 
    Seed ageing
    Seeds begin to deteriorate as soon as they are harvested or collected. Depending on ambient temperature and humidity, there is a risk that they will be dead by the time they are needed for planting.
    For practical purposes, aged seed lots are not very useful. If more than 50% of the seeds have already died, potentially important characteristics will have been lost. These might include genes for disease or drought resistance, early ripening, or other characteristics contributing to diversity and adaptation. Even if they are still alive, aged seeds will:

    • Germinate more slowly.
    • Produce fewer seedlings overall and more abnormal seedlings.
    • Germinate poorly under extreme or stressful conditions, leading to poor field establishment.
    • Produce lower yields.

    How long can seeds live?
    How long a particular seed lot/seed collection will remain alive, and therefore usable, depends upon:

    • Seed moisture content - seeds stored in open storage in humid conditions will have high moisture levels and will not live as long as collections that have been properly dried and stored in sealed containers or those stored under dry conditions.
    • Storage temperature - seeds stored at higher temperatures will not live as long as seeds stored under cooler conditions.
    • Initial seed quality - seeds collected too early or too late will not live as long as seeds collected at the optimum stage.
    • Species - some species are inherently short-lived.

    The most important factor, and probably the easiest to control, is seed moisture content. Correct drying and packaging can make the difference between seeds surviving for a few months at best to being a high quality resource available for use for many years, possibly decades, into the future.   
    Measuring seed moisture
    Because seed moisture is so important to maintaining seed longevity we need to be able to measure it, or at the very least be able to determine when seeds are dry enough to store.
    Scientists often express seed moisture status as moisture content (mc). This is determined by an accurate, but destructive, oven method. There are also various types of portable moisture meters, less accurate, but still destructive. An alternative, non-destructive, method uses digital hygrometers to measure the equilibrium relative humidity (eRH) of the air surrounding the seed in a sealed chamber.
    This method relies on the fact that seeds rapidly gain or lose moisture depending on the relative humidity of the surrounding air. Moist seeds in dry air lose moisture; dry seeds in moist air gain moisture. After about 30 minutes there is no further movement of moisture between seeds and air, and seeds are said to be at equilibrium. This methodology is now used routinely in modern seed banks for monitoring seed moisture status.
    For those involved in short to medium term seed storage, who need to know whether seeds are dry enough to store, but not necessarily what the exact eRH is, there are acceptable, less costly alternatives. They are all based on the same principle as the digital hygrometers and need to be sealed in a container with the seeds until the moisture in the air reaches equilibrium with the moisture in the seeds.  

     


    eRH%

    Seed Survival

     70-85%

     Seeds at risk of rapid loss in viability

     50-70%

     Rate of deterioration slower; seeds may survive for 1-2 years

    30-50%

     Seeds could survive for several years

     10-30%

    Seeds can be kept alive for decades

     

     

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    How to transplant tree seedlings

    If you are not the land owner, you will need their permission before digging up any seedlings.

    Tree seedlings should be transplanted whilst dormant; between the end of November and the middle of March (depending on the weather and seasonal variation), when the ground is neither frozen nor waterlogged.

    When digging up seedlings to transplant, make sure that there are plenty of small root hairs on your tree. The tap root can be cut if necessary as it’s there to anchor the tree in the ground whilst the root hairs feed the tree.

    Seedling roots should be kept damp whilst being transplanted as young roots hairs dry out and die very quickly when exposed to air.

    Choose your containers carefully. Make sure they are large enough for the current root system (with extra growing room), that they are sturdy and have drainage holes.

    Plant your tree seedlings at the same depth as they were growing.

    Avoid peat based compost, not only for environmental reasons, trees don’t like it and won’t grow well in it.

    Go for a planting mix which is three parts top soil, one part sand and one part compost/leaf mould.

    It may be more convenient to plant tree seedlings in a bed where they can grow large enough to plant out (60-100 cm). Spacing should be 4 inches apart (12 cm )in rows in rows 15 inches apart .

     

     

    SEASONAL JOBS

    SEPTEMBER

    Those of you collecting seed may want to know that FreeTree has a licence to collect . So if your trees need to be local provenance certified please get in touch before you collect.

     

    .contact@freetree.info

    All collectors should read the info on the trees wanted page.

    OCTOBER

    Mark deciduous seedlings that will be lifted this autumn. Once the leaves fall off they can be hard to spot.

    NOVEMBER
    Small seedlings (1-2 years) can be lifted from this month and placed in the nursery. As tap roots need to be cut to encourage fibrous growth, don`t worry if a bit gets left in the ground –as long as there are sufficient root hairs ,the trees should thrive.
    Wait until dormancy at the end of the month before lifting larger trees.
    Collect leaves to make leafmould or if it`s more appropriate to your area try bracken. I add a little old plaster to mine so it`s not too acid . When decomposed  It`s a great addition to compost and encourages the growth of tree roots.

     

           

     

           

     

           

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