Answer: Most viburnums grow best in full sun but are just as content in light to partial shade. Give them moderately fertile, moist but well-drained soil with a pH from 5.6 to 6.6. When viburnums enjoy good air circulation, they rarely suffer from fungal diseases. If they're content in their site, they're usually not bothered by pests.
As for pruning, a light shearing each spring, when new growth begins, will promote a full, dense shrub. Without pruning, your viburnums can become leggy (bare at the bottom). You can prune the older canes out and leave the newer growth to fill in if you need to rehabilitate your plants. I would recommend that you do this pruning in the early spring (March-April) to ensure flower production and healthier new growth. Hit them with some fertilizer in the spring and they will flourish.
Viburnums should be feed in early spring with a slow-release formula high in phosphorous (10-18-12) to promote blossoms. If your soil is highly alkaline, you can use an acidified fertilizer and you can mulch over the root systems with peat moss (which will help acidify the soil).
I think with a little pruning and a regular watering schedule (one-inch per week), plus a spring application of slow release fertilizer, your viburnums will perform well for you.
Enjoy your garden!
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