I planted astilbe two years ago in partial shade, and it's grown really well, but there haven't been any flowers. My friend says the problem might be with light or nutrients. What do I need to do to get it to bloom?
Your friend is right, it's most likely a light issue. Astilbe loves partial shade, but it needs at least a few hours of direct sun a day to flower - try moving it to a brighter spot. Also check the soil: it should be moist, loose, and rich in organic matter. In spring, feed it with compost or a fertilizer for flowering plants. If you move it and fertilize it, you should get flowers next season.
It might not be about light at all. Astilbe does flower in partial shade, but it often refuses to do so because of depleted soil - over two years the plant has sucked up all the nutrients from the ground and simply doesn't have the energy to flower. Try adding good compost or well-rotted manure under the bush (a layer of about 5-7 cm), or better yet do it properly in spring - dig around the bush and add a balanced fertilizer for flowering plants.
The second common reason is soil acidity. Astilbe prefers slightly acidic soil, and if your garden has alkaline soil, flower buds simply won't form. Look at what weeds are growing nearby and what the soil looks like - that'll help you figure out the acidity.
And here's a lifehack I use: don't skimp on water during budding (from late spring through early summer). Astilbe loves moisture, and if there's not enough water during bud set it drops the buds, even if everything else is fine. Mulch the bush with pine needles or leaves - it'll keep the moisture in and slightly acidify the soil.
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