Collect acorns from parent trees which have the best possible form - tall with a straight trunk, without low or heavy branches and with a balanced symmetrical crown. There should be no burrs or epicormics.
Collect acorns in October and early November. Discard deformed acorns and those with holes. Put them into a bucket of water and throw away the 'floaters'. Plant the 'sinkers' as soon as possible. If you have to store them for a few days use a paper bag or hessian sack, not a plastic bag.
Plant the acorns in rows in boxes made from breeze blocks or sawn timber (fig.1) or in raised beds. The box or bed should be at least 30cm deep to allow room for the tap roots.
Our boxes are 1 meter wide but any desired length. If they are made form timber the sides should be held parallel with cross timbers at intervals as the outward pressure is considerable.
If only a few acorns are planted they can be put into deep plastic planters with drainage holes cut in the bottom.
The bottom of the box is filled to depth of 5cm with coarse gravel for drainage. A mixture of leaf mould and clay or compost made up for trees is added to form a layer 20cm deep and this is pressed down very firmly by walking all over it. If it is dry it is thoroughly watered.
The acorns are gently pressed into the compost 5cm apart in rows which are also 5cm apart. They are then covered with another 5cm of the leaf mould mixture which is again trodden down. Finally a 1cm layer of gravel is added to reduce evaporation and reduce predation (never use sand as this exclude the air and kills the acorns).
The rows should be labelled very carefully with the name and source of the seed. Small plastic labels can slip down between the compost and the wooden side of the box in dry weather and writing can fade.
The acorns start to grow in the autumn but the leaves which are dull red don't appear until April. Germination continues for several weeks.
The seedlings will almost certainly be attacked by mildew caused by Microsphaera alphitoides usually from May onwards. The leaves look spotty at first, then appear as if they have been dusted with icing sugar. The mildew must be treated as soon as the spots appear.
Spraying with colloidal sulphur obtainable from agricultural merchants is effective. Apply it every 2-3 weeks at the rate of 5cubic cm in 1 litre of water using a hand sprayer.
Lifting and Planting out
The trees are big enough to plant out into a woodland clearing or field when the root collar (the point where the root and stem meet) is at least 4mm in diameter. This will probably be in their second spring, ie 18 months after planting the acorns.
Trees should be planted before the buds break. Dig the trees out of the box with a fork not a spade as this causes less root damage. Sort them immediately into trees large enough to plant out and those that are not. As soon as the trees have been lifted place them inside thick polythene sacks to prevent the roots drying out. Tie the tops of the sacks tightly with string and store them upright in the shade until they can be planted.
Replant the undersized trees in the boxes and allow them to grow on for another year.
Wild Service (Sorbus torminalis)
In September the fruits are hard and olive green but they gradually turn brown and finally become soft and sticky by the end of October. This is the best time to pick them up from the ground.
The seeds must be separated from the fruits. This can be done by soaking the fruits in water for few hours and then either squashing them manually or in a food processor using a plastic blade. We pour some of the pulpy mixture on to a plate and collect up the plump chestnut brown fertile seeds with a teaspoon. These sink. Infertile seeds are darker and flat and usually float. Repeat the process until the whole mixture has been sorted.
The seeds need to be chilled for several months in the fridge. Mix them with sufficient sand/peat mixture (one part sand to two parts peat) in a small polythene bag to keep them well separated. Fasten the bag fairly loosely with a wire closure. Label the bag with the tree number and date and put it in the fridge until March. Examine it every fortnight to make sure it is not drying out. Add a little water if it is.
This will occur some time in March or early April. Tiny creamy radicals appear. The seeds should now be planted in a large plastic pot containing woodland soil or compost at least 30cm deep which has been well firmed down. Sprinkle the seeds over the surface and cover them with soil. Water well and leave the pot out of doors. The seedlings will grow about 10cm high in their first season. They do not seem to suffer from fungal or other diseases but must be kept well watered.
The young trees can be transplanted about 15 cm apart into nursery beds or Dunemann boxes in their second spring or left for a second season in their original pots. Those that are transplanted grow much faster. The young trees can be planted into their final positions in the autumn or the following spring. They need to be spot weeded but apart from this they do not seem to require much aftercare.
We treat spindle, dogwood. crab apple, guelder rose, purging buckthorn and various Prunus species in the same way as wild service. Guelder rose germinate in late summer. Hawthorn are quite different. They have a 16 month dormancy period and need to be kept in the fridge in a sand/peat mixture for this period. A few seeds may not need to be chilled for so long so it is worth looking at them from time to time to make sure they have not started to germinate.
A useful book on growing trees from seed was published by the Conservation Volunteers Northern Ireland, 159 Ravenhill Rd, Belfast several years ago and the BTCV handbook called 'Trees and Aftercare' is an excellent source of information.