Germinating tree seeds

 

Success with tree seed depends as much on the treatment before sowing as the method of sowing. Seed may need treating to break dormancy. Seed that has not germinated in the first season should be left for a further year as it may germinate in the second spring after sowing.

Scarification

Trees with hard seed coats, such as Robinia should be scarified to allow in moisture. Scarification can be carried out using sandpaper or a file to abrade the seed coat, or using a knife to nick the coat. Some seed can be softened in warm water by soaking for 24 hours; care should be taken when soaking seed, as rotting may be the end result.

Inhibitors

Inhibitors are found in some tree seeds once they have ripened, for example Acer campestre (field maple). Avoid this by harvesting mature seed, before it has fully ripened prior to dispersal. Sow immediately or sow stored seed in spring as normal.

Stratification

This is used for seeds which respond to either heat or cold. Stratifying will break dormancy by copying the conditions these seed are normally subjected to. Most commonly this is a spell of cold similar to that experience in the winter but with more reliable results. A few seeds have a multiple dormancy, germinating in the second spring after ripening with a spell of warmth in between, for example Fraxinus (ash). Subjecting seed to a warm spell followed by cold can increase germination in the first spring.

Cold moist stratification

• Place seed in a clear plastic bag filled with moist but not wet coir, composted bark, or a mix of equal parts of the above with coarse sand, perlite or vermiculite and seal the bag.
• Chill seed in a refrigerator, kept below 5°C (40^oF) for four to 20 weeks, depending on the species.
• Shake the bag periodically, and sow seed immediately if it germinates in the bag.

Warm moist stratification

• Place seed in a bag as above and keep in a warm place at 18-24°C (65-75^oF) for up to 12 weeks, before giving a period of cold stratification.
• Alternatively, sow in pots and place in a heated propagator for the required spell. Following this place in a cold frame for the winter.

Sowing seed in containers

This is the easiest way of sowing tree seed. Choose a free-draining soil-less compost for seed quick to germinate and a loam-based compost for seed slow to germinate.

Cover seed with fine grit or perlite to a depth of 6mm (0.25in). Place seed where it will receive the appropriate minimum temperature, e.g. a cold frame or greenhouse.

Transplant seedlings as soon as large enough to handle and harden off.

It is best to use Rootrainers or deep pots, and plant out seedlings as soon as possible. This will avoid too much root disturbance or letting roots becoming pot bound which will reduce establishment.

 

 

 

 

 

 

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