Even seeds that do not need winter chilling may germinate more quickly and uniformly after a short period of cold stratification. Most seeds of climbing plants and shrubs are best sown in containers.
There are many climbers and shrubs that can be grown from seeds. Remember that only species “come true” from seeds. A plant grown from seeds gathered from your favorite cultivar is unlikely to have exactly the same characteristics as its parent. There’s always a sense of excitement when germination takes place be it a Daphne requiring a winter’s chill or an Abutilon that only needs a warm, moist soil mix in spring. Some subshrubs that produce flower spikes may be treated as herbaceous perennials.
SCARIFYING SEEDS OF VINES & SHRUBS ( 3 METHODS)
- Nick the hard coat of very large seeds such as Paeonia with a sharp knife. Take care not to damage the “eye” of the seed or to cut too deeply.
- Place smaller, hard-coated seeds between two sheets of sandpaper in a seed tray and rub them to scratch and weaken the surfaces.
- Use hot water to soften the seed coats of smaller seeds, place in a bowl and pour boiling water over them. Allow to soak for 24 hours, then sow right away.
Many shrubs and climbers, especially members of the pea and bean family, have hard seed coats that prevent germination until the coat is broken down to admit moisture to the seed within. Nature softens hard seed coats by subjecting the seeds to warm, moist conditions in spring, when bacterial activity is at its height. This can be mimicked by storing the seeds in moist soil mix and hanging them up in a shed during the summer. For roses, compost activators may be added to speed up the process.
Some impermeable seeds have chemical germination inhibitors on the seed coats: remove these just before sowing by soaking the seeds in hot water, mild detergent or alcohol. Wash the seeds thoroughly afterwards.
Some seeds need several treatments for multiple dormancies; scarify them first to allow other treatments to take effect. A safer option is to sow the seeds outdoors and let nature take its course.
WARM STRATIFICATION BEFORE SOWING:
Some hard-coated seeds require a period of warm stratification. Place the seeds in a plastic bag in equal parts of sand and leaf mold, or equal parts of peat and sand. Store for 4-12 weeks at 68-77°F (20-25°C). This is usually followed by cold stratification.
COLD STRATIFICATION OF SEEDS BEFORE SOWING:
Some seeds are prompted to germinate by temperature changes. Many woody plants native to temperate climates exhibit cold-temperature dormancy, where seeds require a winter’s chill before germinating in spring. This can be done by placing the seeds in moist vermiculite or peat in a clear plastic bag in the refrigerator at 41°F (5°C). Label and store for 1-3 months. Alternatively, you can also sow the seeds in autumn and overwinter in a sandbed or cold frame. Sow seeds thickly in pans/pots of gritty seed soil mix, then cover with a fine layer of mix and one of grit.
SMOKE TREATMENT OF SEEDS:
In nature, some seeds only germinate after a bush fire. The flames scarify the seed coat, and chemicals in the smoke stimulate germination. To simulate this, sow a tray of seeds, cover with 2 ½-4 in. (6-10cm) of dry leaves, burn them, and water in the ash. Kits, smoke paper, and smoke water containing chemicals found in smoke may also be available.
SOWING SEEDS IN CONTAINERS:
- Fill a tray with seed soil mix. Firm gently, water and allow to drain. Sow the seeds evenly over the surface by tapping them from a folded piece of paper. For small or medium sized seeds, firm the soil mix to leave a ⅛ in. (3mm) gap between the mix and the rim. For large seeds, the gap may be ½-⅝ in. (10-15mm)
- AUTUMN SOWN SEEDS: Cover the seeds with a fine layer of soil mix, then add a ¼ in. (5mm) layer of grit or coarse sand. Label the containers and cover with wire netting to protect from birds or animals. Place in a sheltered place to overwinter at 14-28°F (-10 to -2°C) and subsequently germinate. Check them regularly and water if necessary. When the seeds are large enough to handle, transplant individually into cells, trays or small pots. Take care not to disturb the roots. This may be in the first spring after sowing, or up to a year after germination.
- SPRING SOWN SEEDS: instead of grit use ½ in. (1cm) layer of vermiculite. Fine grade for small or medium sized seeds. Medium grade for large seeds. Temperature of 59-68°F (15-20°C) is required for germination, unless otherwise stated. The surface of the soil must remain moist at all times. You can either place it in a closed case, under a plastic tent, on a mist bench, or cover it with a sheet of glass. Some seeds require bottom heat for successful germination. FINE SEEDS that lose viability at temperatures above 68°F (20°C) respond well to being placed on a mist bench but seeds requiring temperatures higher than this often struggle to germinate, owing to the cooling effect of the mist. Inspect the soil regularly and water as necessary. Never water the container from above once fine seed is surface sown. Place it in a shallow dish of water for a short time. Spray the seedlings occasionally with fungicide.
- Once the germinated seedlings are large enough to handle, lift them carefully using a knife or tweezers. Always hold the seedlings gently by their leaves.
- Insert the seedlings singly into 2 ½-3 ½ in. (6-9cm) pots, or in rows in trays, in soilless potting mix. Gently firm around the base of each seedling then label and water.
- Place out of direct sunlight until established. Harden off young plants by gradually exposing them to outdoor conditions.
For VERY FINE SEEDS such as rhododendrons or buddleja (buddleia), the seeds are so fine they don’t have sufficient food reserves to push through the soil mix, or they require light in order to germinate. Sow like seeds on the surface of the soil mix that has been sieved: tiny seeds can easily fall between cracks of a coarse surface. To give the seedlings as much light as possible, leave only a fraction of an inch between the soil mix and the rim. Mix the seeds with a small amount of fine sand, then gently tap the mixture onto the soil mix to sow evenly.
SOWING IN RAISED SEEDBEDS:
Some shrubs and climbers, especially those native to your area can be sown outside in raised seedbeds. Select a sheltered site and raise the soil level by 8 in. (20cm) to improve the drainage. Remove perennial weeds and dig the soil thoroughly. Large seeds can be sown in rows in autumn; smaller ones can be left until late winter. Cover with ¾-1 ¼ in. (2-3cm) of pea gravel. Do not allow germinating seeds to dry out; cover with fleece or loose leaves to reduce frost heaving.
Please be advised that this is a GENERAL guide to germinating Vine and Shrub Seeds. There are multiple resources on the web that are available and specifically tailored to the genus of the plant.
From personal experience, we had the best success by using a plastic seed tray, dome lid, heating mat and plant lights to get the seeds started. This way we were able to control the temperature and light requirements of the plants.