Hot Water Treatment
Recommended for the following species:
Pink Albizia (albizia julibrissin)
Siberian Pea Tree (caragana arborescens)
Katsura Tree (cercidiphyllum japonicum)
Eastern Redbud (cercis canadensis)
Chinese Redbud (cercis chinensis)
Judas Tree (cercis siliquastrum)
Bladder-Senna (colutea arborescens)
Scotch Broom (cytisus scoparius)
White Spanish Broom (cytisus multiflorus)
Honey Locust (gleditsia triacanthos)
Thornless Honey Locust (gleditsia triacanthos inermis)
Scotch Laburnum (laburnum alpinum)
Common Laburnum (laburnum anagyroides)
Narrow Leaf Lupin (lupinus angustifolius)
Wild Perennial Lupine (lupinus perennis)
Black Locust (robinia pseudoacacia)
Japanese Pagoda Tree (sophora japonica)
Common Gorse (ulex europaeus)
Chinese Wisteria (wisteria chinensis)
Hot Water Treatment is about the quickest form of seed pre-treatment and once performed the seeds will begin to sprout from around 3-5 days.
These seeds have no real dormancy to break down they have a very hard, water-impermeable seed coat and require pretreatment for successful germination to occur. Without pretreatment it is likely that 10% or less of the seeds will germinate.
Place the seeds in a heat proof container and pour hot (not boiling!) water 70-80 degrees Celsius over them and leave them to soak for between 12-24 hours. Seeds that have been successfully pretreated will have swollen to around 3 times their previous size.
Remove all swollen seeds as these will be damaged by further pretreatments. These can be sown immediately. This hot water treatment can be repeated up to 3 times, making the water a little hotter each time.
An alternative method of breaking through the seed coat method is by cutting or knicking the edge of the seed with a knife or using a file or even rubbing them between layers of fine sandpaper. All of these methods can be used to break through the seed coat.
Once you have done this soak the seeds in cold water for 12-24 hours and successfully treated seeds will have imbibed water and swollen greatly. Any that have not could be scarified again followed by another water soak. Sow all the seeds, even those that remain small as they may germinate later
Once the seeds have become swollen with water germination is very rapid if the seeds are kept at room temperature and a root will emerge with a couple of days.
Sow the swelled up seeds individually in pots filled with good quality compost at a depth of about 1 cm (just less than ½ an inch) and the plants will appear very quickly if they are kept in warm temperatures.
Keep plants weed free and well watered in a warm, sunny position.