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Propagating Plants for your Garden

Buying new plants for your garden is one of life’s little pleasures and can be extremely satisfying but often expensive. Equally as satisfying and an awfully lot cheaper is propagating your own plants.

Softwood Cuttings

These cuttings are taken from this year’s young growth between April and June. Choose a young side shoot and cut below a node about 5-10cm from the tip. Remove the bottom leaves and immerse in a fungicide solution to avoid fungal infections and dip the base in rooting powder. Place a few cuttings in a pot of 50:50 sand and compost and place the pot in a heated greenhouse or propagator or on a windowsill enclosed in a polythene bag. Keep the compost moist. Once you begin to see new growth, pot individually into 10cm pots. Before planting out in the garden get them used to cooler temperatures by placing them outside during the day or move to a cool greenhouse.

Semi-ripe Cutting

These cuttings are taken from this year’s ripe growth between June and August. The base of the shoot should have started to turn brown. Cut just below a node about 10-15cm from the tip or pull the shoot off with some of the woody tissue (heel) attached. Remove the bottom leaves and immerse in a fungicide solution to avoid fungal infections and dip the base in rooting powder. Place a few cuttings in a pot of 50:50 sand and compost and place the pot in a heated greenhouse or propagator or on a windowsill enclosed in a polythene bag. Keep the compost moist. Once you begin to see new growth, pot individually into 10cm pots. Before planting out in the garden get them used to cooler temperatures by placing them outside during the day or move to a cool greenhouse.

Hardwood Cuttings

These cuttings are taken from this year’s woody growth between September and November. Cut a length just below and above a node about 15-30cm long. Remove the leaves and dip the base in rooting powder. Place a few in a pot of 50:50 sand and compost and place the pot in a cold frame or in the ground in an open, sheltered, sunny position. Ensure the soil is well drained. The cuttings should be rooted by the following Autumn.

Root Cuttings

These cutting should be taken between September and November. Expose the roots of shrubs or lift herbaceous plants and select a young root near the crown of the plant. Cut a length 5cm long with a straight cut at the top and a diagonal cut at the base. Immerse in fungicide and insert in a pot of compost so the top is level with the top of the compost. Cover with 0.5cm compost. Fine roots should be laid on the top of the compost and covered lightly. Place in a cold greenhouse or cold frame and keep the compost moist. The cuttings should have rooted by the following spring when they can be potted on.

Leaf Cuttings

There are three methods of taking leaf cuttings. The first involves taking a whole leaf including the stalk (petiole). Dip the stalk in tooting powder and insert in a pot of 50:50 sand and compost so the stalk is buried. Place in a propagator at 18-21 degrees C or enclose in a polythene bag and stand on a warm windowsill. When growth appears at the base of the leaf lift and pot on. The second method is to take a whole leaf and cut halfway through the main vein on the back of the leaf. Place the leaf, cut side down, on the top of the compost. Place grit on top of the leaf to keep it in contact with the compost. Place in a propagator at 18-21 degrees C or enclose in a polythene bag and stand on a warm windowsill. New growth will appear at the cuts. The third method is mainly used on long leaves. Cut the leaf into 5cm sections and dip the bottom edge in rooting powder. Insert the leaf vertically into the compost to about half it’s length. Place in a propagator at 18-21 degrees C or enclose in a polythene bag and stand on a warm windowsill. New growth will form at the base.

Division

Division involves dividing a plant into two or more plants and should be carried out on most perennials every 3-5 years to maintain their vigour. Divide in late autumn or early spring. Lift the plant taking care not to damage the roots and shake off the soil. Using a knife or spade cut the plant into three or four similar sized pieces and plant out each new section as soon as possible, adding compost and a general fertiliser.

Layering

Layering works well on woody plants and involves growing a new plant while it is still attached to the parent plant. It is best carried out between late spring and autumn. Find a stem which is flexible enough to bend to the ground. Make a cut about 5cm long through a node and apply rooting powder. Where the node touches the ground dig a small hole in the soil and add compost. Bury the stem 10cm deep at the node and peg down to secure. Tie the end of the stem to a support. Roots should develop within 18 months at which point it can be removed from the parent plant and planted in its own spot.

Seeds

There are several advantages and disadvantage to propagating by seed.

  • Advantages: Large volume of seeds readily available, Cheap, Simple, Vast choice of varieties, Can be stored for a length of time
  • Disadvantages: Not all seeds come true to type, Some plants have lost the ability to produce seed, Some plants take a long time to mature and flower

Most people will buy their seeds from a garden centre or specialist seeds man and just follow the directions on the packet. However it is very easy to collect seed from your own garden and also completely free. Some plants will seed themselves, usually where you don’t want them. Once they have seeded just thin them out and/or transplant to another part of your garden. You could also pot them on and give them to friends and family. If you do use your own seed you must remember that most do not come true to type so will not necessarily resemble the plant they came from. You must collect the seed when it is ripe; store pods in a warm, dry place until they split. Once you have the seed label them and keep in a dry, dark, well ventilated area at between 1 and 5 degrees C.

Seeds have six requirement in order to germinate:

  1. Seeds have little water which is why they stay dormant for so long
  2. The temperature required to germinate vary by seed but generally heat helps
  3. Oxygen is required for respiration Food Food is supplied within the seed. If planted too deeply the food with be exhausted before it is able to photosynthesise
  4. Some seeds require light to germinate
  5. Some seeds have chemical inhibitors which need to diminish before germination is possible
  6. Some seeds are difficult to germinate and a number of techniques have been developed to overcome these difficulties:
    1. Soaking seed in warm water for 12-24 hours will soften the coating and help it absorb water and remove chemical inhibitors
    2. Scarification: Nick large seeds with a knife or rub smaller seeds with sandpaper. This weakens the coating and allows water to enter
    3. Stratification: Some seeds require a period of cold before they can germinate. Place the seeds in a 50:50 mixture of moist sand and compost and place in the fridge for 4-12 weeks

Hardy Annuals can be sown outside in March or April when the soil has started to warm up. Biennials and Perennials can be sown later in May or June. Sow directly where you want them to flower/fruit or sow in seedbeds and transplant later. The soil should be raked to break up the soil and to remove any stones. Firm the soil with the back of the rake and apply a general fertiliser. If the area is dry, water well and allow to drain. This should be carried out 3-4 weeks in advance of sowing to allow weeds germinate. Weed the area well then sow the seed thinly in drills 5-15mm deep. Cover lightly with soil. Ensure the soil is kept moist and weed free. When the seedlings appear thin them out to around 10cm apart, carry out a final thinning to 15-20cm depending on the size of the final plant.

Other seeds can be sown in a greenhouse, a propagator or on a window sill. Ideally use a compost formulated specifically for growing seed. Fill a seed tray to the top with compost and gently firm, wet the compost and allow to dry. Scatter the seed thinly on the surface of the compost and cover lightly with compost. Cover with a sheet of glass or place in a propagator at a temperature of 18-21 degrees C. Do not allow the compost to dry out. Once the seedlings begin to show remove the cover/glass and move to where they can get maximum light but not in direct sunlight. When the seedlings develop their first proper leaves prick them out into individual pots being careful not to damage the roots. Never handle seedlings by their stems.

If the seeds are to go outside they need should be first moved to a closed cold frame to get them used to the change in temperature. After a few days they can be left in an open cold frame or stood outside during the day. They can be planted out into well prepared ground once all risk of frost has passed.