I have Somerset Grape Vine and Magenta Grape vine which I planted last year and they are coming out well.
1) I want guidance on fertilizing them. Want to avoid harmful fertilizers?
2) I have provided 20″ X 20″ box to grow them with a depth of 2 feet. (See Picture)Will this box be enough or should I enlarge it?
Firstly, let’s deal with your container size. When grapevines are planted out in the field, they generally have 6 feet spacing between plants. That being said, people have successfully grown vines in large containers giving the plants much care & attention. I would suggest that your 20″x 20″ x 2′ boxes are somewhat on the small size and should be enlarged. From the picture you attached, it looks as if you could do this by extending outwards into your lawn while leaving the patio undisturbed. This would have the added bonus of allowing the deep rooted vines to grow downward into the garden under the actual container box.
As for fertilization, a general 10-10-10 fertilizer can be used at bud emergence in the spring. Judging by the photo, your plant is already in leaf so you have missed this ideal window of opportunity. That being said, you could use a water soluble fertilizer to make up a 1/4 strength solution (10-10-10) and apply, using a watering can, to the soil at the outermost edges of your container. If you did this now, you would likely get the growth you want without the plant experiencing adverse root burning or excessive vegetative growth which may not have a chance to harden off going into the winter.
Below, I’m including some general tips on growing these grapes for your information.
Well drained, sandy with a course texture & good aeration. Adding organic matter such as sheep manure or good compost will improve soil structure and aid drainage. A home soil test will show you the soil pH which is important as ideally it should be in the range between 5.5-7.0. To raise the pH, add lime and to lower the pH, add sulfur. A 1-2″ layer of mulch on the top of the container will help retain soil moisture and keep weeds controlled.
- Plant in full sun.
- Pruning should be done while vines are dormant when temperatures reach below -5 degrees C. Prune out all but 3-6 healthy strong canes. Do not prune at any other time as plants will bleed.
- Hill the graft to protect it from cold winter temperatures.
Both Magenta & Somerset grape vines are hardy to Zone 4 so should be able to withstand most winter conditions in Toronto. They are both disease resistant varieties that produce sweet red table grapes. They are self fertile and should mature to fruiting in year 3.
Good luck with this project.