Soil Conditions

Dahlias need warm, well-drained soil. Your dahlias will do best when planted in your existing soil, if it has not been treated with Preen, Casoron, or other herbicides. If you have heavier soil, we recommend amending it with peat moss to help lighten it up. Do not amend dahlia beds with purchased topsoil or potting mix unless you are sure that it has not been treated for weeds or enhanced with fertilizer. Too rich of soil can burn your dahlia sprouts and cause them not to grow at all. Even if you think you do not have the best soil, this soil may be better than bringing in new soil.

To increase the nutrients in your soil, the best all-around soil additive is cow/steer manure. If you choose to add compost to your dahlia beds, please do so sparingly, as we do not recommend it. Most types of compost are high in Nitrogen, which promotes tall spindly plants, small blooms, less blooms, and tubers that are weak in storage.

If you are planting a new dahlia bed, make sure to check all soil, potting soil, and materials being used carefully. The soil must not be sterilized or contain any type of weed killers (herbicides), compost, or fertilizers. If weeds won’t grow in the soil, neither will your dahlias. Although many herbicides (Preen), on the market state they are safe for dahlias, we disagree as we have seen negative results. Hand weeding is the only option when growing dahlias. The pH level of the soil should be 6.5-7.0, slightly acidic. To adjust the pH level in your soil you may add Lime to increase your pH level, or Sulfur to decrease your pH level. Please check with your local garden center or extension office for recommendations for dosage and application.

Here is a local supplier, that has a soil mixture for dahlias that we recommend. Check out their dahlia blend. ( Custom Blends | Highway Fuel in Salem, Or. )