What you’re describing indicates a massive infestation of black aphids (usually poppies, cherry trees, or other plant species, depending on the type).

The new spring shoots are like a feast for them, as they are full of plant sap and the tissue is still soft. This “living surface” or “crust” is created by the aphids reproducing in huge, densely packed colonies. The shiny appearance is due to honeydew—a sweet and sticky liquid secreted by the aphids.

How to combat aphids (without chemicals):

If you prefer gentler methods, try the following:

Mechanical rinsing (first aid):

Gently rinse the stems and shoots with a strong jet of water. This will simply wash away most of the aphids, preventing them from climbing back onto the plant.

Soap/oil spray:
This spray coats the aphids, preventing them from breathing:
Recipe: Mix 1 liter of lukewarm water, 1–2 tablespoons of liquid potassium soap (or regular fat soap), and 1 tablespoon of rapeseed or sunflower oil.

Application: Mix thoroughly and spray the affected areas from all sides (including the undersides of the leaves). Apply in the morning or early evening, never in direct sunlight to avoid scorching.

Natural enemies:
If you have ladybugs (or their larvae), goldeneyes, or ladybirds in your garden, leave them alone—they can wipe out aphid colonies within a few days. What to look out for: Watch out for ants crawling up the stem. Ants “cultivate” aphids for their sweet honeydew and actively protect them from natural predators. If you see ants, it’s advisable to cover the trunk or stem with ant-proof tape.

What type of plant or tree is it exactly (e.g., cherry, rose, bean, or houseplant)?