How do tree nurseries grow and propagate rootstocks?
In this article you will read how rootstocks are grown and propagated. Rootstocks are commonly propagated by mound layering on stoolbeds. In this scenario we use our apple rootstocks as example. The mother plants, which in our case are all virus free certified base material, are planted in a 45 degree angle in spring time. The rootstocks are not too thick, because we need to ‘layer’ them later on.
In the first year, the obliquely planted rootstocks (picture above, left side) are bend down and braided together (picture above, right side) as a bed (= stoolbed). This is done in September/October. The picture shows newly planted M9 T337 rootstocks.
The new shoots growing out of the layered mother plants, are partially covered by a mix of sawdust and compost (click here to see a short movie on YouTube). Only the bottom part where the roots will grow is covered. After the sawdust/compost is added, the beds are mounded with special machinery (here is another short YouTube movie to see this in action). This mechanical process, the sawdust/compost is tightened around the section of the plant where the roots are needed. This will stimulate the growing of roots on the shoots above the layered mother plants. This process is repeated every year. The stoolbed or mothergarden remain productive for more than 25 years.
At the end of the growing season, the shoots are full grown, matured and ready to harvest. The new grown roots need time to harden. If the shoots, of we call it rootstocks now, are harvested too early, the softer not matured roots will break. This will result in less roots on the harvested rootstocks.
Harvesting is done by cutting of the shoots just above the layered mother plants. The mother plants are left in the soil, and will be used for a new round next year. The harvested rootstocks (or shoots) are brought in and firstly graded on quality. We check the number of the roots, the straightness of the plant, the length of the plant (we need at least 40 cm/15.8 inches length for grafting) and remove the dead plants. This is done with no automatization or machinery, just the human eye.
After the ‘pre’ grading on quality, the rootstocks are mechanically graded on size. With size we refer to the thickness of the rootstocks in mm. Commonly the rootstocks are graded in 4-6, 6-8, 8-10, 10-12, 12-14, 14+. Based on clients request, we can adjust this for example to odd sizes as 3-5, 5-7, etc. The smaller rootstocks, 4-6mm, are replanted to grow another year in thickness. This will give the two year old rootstocks.
The 6-8mm sized rootstocks are mainly used for summer propagation. Rootstocks from 8mm and bigger, are used for table grafting (or bench grafting).
The rootstocks we produce, are used for our own fruit tree production and are provided to customers worldwide. All our production fields are in line with the regulations of and checked by the Dutch plant health authorities.
Are you interested in high quality rootstocks? Please do not hesitate to contact us.