This is a must-cover topic for this week. So many people cut too timidly when they make their spring cuts to roses, butterfly bush, hydrangea, rose of Sharon, evergreen herbs like the lavender and sage we use as illustrations, and most any woody plant.
Even a single healthy bud can grow lustily if it's driven by a strong root system. On the other hand, nothing good comes from cuts that left weak wood in place. Often the results are disappointing and also lead to further decline in the plant's health.
There's lots of cutting to do in early spring so take this crash course to recognize sound wood. Then go cut harder. Remove everything that's not sound wood so healthy buds are in charge and disease pathogens removed.
What you see below is what was left after our first cut to two 24" round lavenders. We made even more cuts afterward to remove bad stubs.
Why do we cut it this hard? For the plant's own good and so it will bloom more fully and be more dense of leaf.
Look at the difference between stems. The two stems at the left are healthy, fuller of leaf, and have a smaller proportion of shriveled leaves from the winter. The stem on the far right is in poor shape. Middle stems are intermediate.
Start with the old stem on the right in that photo. (Above).
See any discoloration and splits? In lavender bark, that's not normal, not healthy. Those spots develop where the cambium has been killed and so bark stopped forming. Each patch of dead cambium is a break in the connection between leaves and roots. It means a little less starch flowing to the roots, which cannot produce their own food and depend on the leaves.
Starved roots die. Then the foliage receives less water when times get tough. Such plants often wilt and die back in chunks during summer's worst heat.
Below: This wood is decrepit (two arrowspoint to splits) but has not quit. It has not stopped producing new shoots.
Several buds are swelling (one indicated by arrow). These buds will not produce such vigorous shoots as buds from wood that's intact. What a shame to have these grow and then die by midsummer.
So cut this stem right off!
Right: The lower portion of a stem from the middle bunch in our group shot.
Wood that has unhealthy breaks in the bark was usually infected when young, soft, barkless shoot. The fungi became a chronic infection, remaining as the bark and wood form. What is called a "spot" when it's on leaf or green stem becomes a "canker" on wood. As long as the branch lives and environmental conditions allow the fungus to live, the canker grows and makes the stem ever weaker. The fungi involved in this case are probably unable to attack the plant in its Mediterranean homeland, where dry conditions prevail throughout the growing season.
Above: Comparing that stem from the middle group to a youngster from the left group. Younger stem on left in this photo.
This is why we cut many shrubs and vines every year to remove old wood and have as much brand new wood as possible. We cut them very hard if they bloom on new wood, grow quickly and have any tendency to fungal diseases.
How gardeners treat hybrid tea roses is a bugaboo of ours. The canes harbor black spot spores and a can may itself be weakened by cankers and also borers, yet a gardener will let that weak branch remain because it has a bud.
Be ruthless, for the plant's own good. Cut it so its new shoots come from only the best wood. Don't worry that you're pruning after buds on the branches have already begun to grow. If the root system is healthy new buds will come from below your cut. (Take a look at it happening, in Mentors advice for cutting Weak wood hard.)
This is what we expect from cooking sage (Salvia officinalis) after winter. It should look like this or better -- even fuller.
Below: Sometimes, however, a sage looks like this. Look hard, sage is there. Much of it died out last summer but its outer branches had layered and rooted. What was left was a ring of stems with an empty center.
Below: Can you see what's left of the remnant center, right after we cut it and the living stems? (Look at it larger, and look for the remnant, decrepit trunk bases.)
(Janet, we need to modify these with arrows or circles or something! Re: odd notes)
Below: Here's what we have seen people leave uncut on such a plant, because "I can't cut the poor thing completely down!"
Yet that's a dying trunk, full of a stem rot. Any growth that comes from that point is weak and only going to get weaker as the temperature increases. It'll wilt and collapse in midsummer, if it makes it that far.
Below: All this trouble starts with infections on new, soft shoots. See the canker that develops from that that fungal spot?
The more years the canker's there, the weaker the stem. The more cankered stems there are, the more spores to infect new growth.
If a plant is going to come back from a cut back, let it come with healthy shoots, or not at all.
Try it. Let the plants surprise you. Cut that rose back hard and be rid of most of the black spot spores that overwintered on its canes. Cut the butterfly bush or blue mist spirea hard. Let the plants amaze you. Or, if the plants don't bounce back, admit that they were not well to begin with. Then, when you buy a replacement of that same kind, improve the drainage or the sun or both in that spot, so the new one has a fighting chance.
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