My elaegnus and deutzia bushes are 3 or 4 meters tall. They are bare for the first 2.5 meters, and above that is the foliage & some shoots that appeared this year.
If I cut all the stems back to about 0.5 meters (18″) from the ground now, in mid July on the south coast near Brighton (UK),
Will I get new growth this year?
What do you think the result will be next year?
Should I expect any flowers?
Decided to answer anyway, despite my comment. Yes, you will get new growth this year, no you won't get flowers next year on your Deutzia, possibly not the year after either. Elaeagnus is not grown for its flowers, but that is also unlikely to flower next year if you proceed with your plan.
Both these shrubs sound ripe for renovation treatment, because it sounds as if they've been allowed to grow untrammelled, and have now become unproductive in parts, congested and overgrown.
For the Elaeagnus, you should really wait till winter, when the plant is more or less dormant, then saw down the branches at an angle to allow rain to run off, taking it down to around 2 feet to create a basic framework for the shrub, and at the same time removing any dead parts. In Spring, feed with a fertiliser such as Growmore, and then remove any thin and weak shoots, or shoots that you don't need or want, as the plant grows again next year. Doing this type of pruning now may force new, sappy growth which won't have time to harden off before winter sets in, and there may be excessive bleeding of sap from the cut areas, which will make the plant vulnerable to infection.
For the Deutzia, which flowers on the previous season's growth, you've got two choices - leave it as it is now, but in winter, (though you could do this now if you don't mind risking damage to new growth if winter sets in early) remove any dead parts and cut down a third of the healthy shoots to ground level, leaving the rest in place. This will mean you do get some flowers next year, and you should then prune immediately after flowering, removing any excess growth at the same time that you didn't take in winter. The other option is complete renovation - cut the whole thing down in winter, taking out all dead parts, and shape as growth appears next year, removing any unwanted growths, done around the time the plant would have finished flowering most years. You may need to repeat this the second year, for there may be no flowers then either. Thereafter, prune immediately after flowering each year.
If you have to prune now (it would be better to wait until winter), be careful, and hold on to the branches as you cut, so you don't strip the bark.
To answer your question:
Will I get new growth this year?
Elaegnus:
Yes, the plant will flush out quickly, and need to be watered heavily during this period.
If any branch does not flush out when the others do, cut it back to the ground, or the last growing point.
Deutzia:
Same as for elaegnus. The plant will flush out quickly, and need to be watered heavily during this period. Tip: pinch out the growing tips of the shoots after 1 foot, for better form.
Same as for elaegnus. If any branch does not flush out when the others do, cut it back to the ground, or the last growing point.
What do you think the result will be next year?
Elaegnus:
This depends on several factors. If the new growth hardens off before winter, you should expect heavy growth from this years shoots.
If the new shoots don't harden off, expect spotty regrowth from these, and a heavier growth from the old branches. You will want to prune out all dead growth.
Deutzia:
Should I expect any flowers?
Elaegnus:
Deutzia:
This answer is just to add information to what my cohorts have said. Pruning any shrub one needs to keep the bottom branch tips wider than the top. This has to do with how much food the leaves of the plant produce for the plant. Leaves that get less light produce less food, those that get the most light produce the most food for the plant and are supported by the plant in return. Those that produce less food are eventually 'turned off' by the plant causing bare and dead branches.
For formal hedges this is easy. Always make sure the bottom is slightly wider than the top. For informal shrubs it is still necessary to head and shape. Think of a big salad bowl. Turned upside down. I flatten the top of a shrub (most shrubs not all) to get the height and then take my shears to form a rounded slope to the bottom most branches. In this way you allow the lower branches to get as much sunlight as the top. It is the relative amount of light the branches/leaves of an individual plant are receiving. If lower leaves are shaded by upper leaves the plant will eventually get rid of leaves and branches not producing as much food as other leaves that get more light.
If you have a grouping of shrubs it is fine to them to merge yet each one has its own 'dome'...I have no idea how you have been pruning these shrubs. Both Eleagnus and Deutzia can be done this way but after shearing to the proper upside down salad bowl, one needs to take pruners and individually cut each branch back to a bud to look the best.
The flowers will come back. You probably have just created shrubs that are bigger than what the now productive upper growth can support. Rule of thumb is to keep the height to width ratio a minimum of 1 to 1 1/2. Ideal is 1 to 2. So if your shrub is 4 X 2 chop it in half and work at keeping it 2' in height as you coax the bottom to be 3-4' in width. A plant that is 4' high should be 6 - 8' in width. This means the leaves of the lower branches will be getting enough light to be productive enough that the plant will continue to support these lower branches. This allows the plant to use its full potential and live longer.
I hope this makes sense. Let me know and I'll try to add pictures if not.
Add compost to the top of your soil. Decomposed organic matter. If you are using bark or other mulch that is not decomposed this causes even more stress on your plants.
