Picking
The scarlet hips should be picked from the beginning of October onwards. If you pick them too early, you risk the seeds being immature. Collect them directly from the plant by gripping the branch below the hip and pulling. In this way, no damage is caused to the parts of the tree that will continue to grow. Each hip contains many seeds, so a large number can be collected quickly.
Extraction and Storage
Use the usual extraction method to separate the flesh from the seeds.
Pre-treatment
The extracted seed should be mixed with equal parts horticultural sand or a sand/compost mixture (for these seeds the addition of compost to the mixture can help break dormancy). Use 50% leafmould or peat-free compost and 50% horticultural sand. For each handful of seeds add two or three handfuls of mixture. Select a pot that has enough room for this seed/sand mixture (and a bit more) and put a layer of stones in the bottom. Cover the stones with sand. Place the seed/sand mixture on top of this and cover this with 2-3cm sand. Label the pot and stand in a shady spot outdoors.
The pot needs to remain outside for eighteen months. This is where patience is required! Water the pots if they show signs of drying out and protect from birds and mice if they discover your seeds. We will be sowing the seeds the second spring following collection – dog rose seed is deeply dormant and needs this long before it will grow.
Sowing
In late February or early March of the second year after collection (February 2020 if you collect your seeds in October 2018) check for signs of germination. If about 10% are showing signs of germination, they are ready to sow.
Yound dog rose growing in the nurseryIn a 1-litre pot sow four or five seeds and cover with no more than 5mm of compost or grit. Firm gently and water. On a seedbed broadcast the seed quite densely – aim for about 2cm between seeds. Firm with a roller or board to press the seed well into the soil. Cover with 5mm of grit.
Watering
Ensure that the seeds and young plants are kept moist at all times.
Growing
Don’t forget to remove the weaker seedlings to leave the strongest when you are growing in a container.
Dog rose will grow quickly if kept well fed and watered. Use a liquid or granular fertilizer every 4-6 weeks until the middle of July. The plants should be ready after either the first or second year for planting out.
Watch out for mildew! Good hygiene can reduce the risk – don’t touch your plants when they are wet and don’t water the foliage too late in the day. Both these measures can help prevent infection. If mildew does appear, treat quickly with a fungicide, preferably organic.
Planting
Prepare the site well by clearing away any weeds or grass and make a hole big enough to accommodate the root ball. Plant carefully in the hole, to the same depth as it was growing previously, and firm back the soil.