Hostas grow best in nutrient rich, moisture-retaining, porous soils with a pH of 6-7 such as loam soil or soil that has been amended with plenty of organic matter.
Heavy clay soils or sandy soil require amending with materials such as compost, leaf mold, or manure to a depth of 16 inches before planting hostas.
Optimal soil for hostas quick guide:
| Soil Characteristics: | Hosta Soil Requirements: |
|---|---|
| Soil pH | pH 6.5 to 7.5 (this is the pH of most garden soils) |
| Soil Structure | Light, porous, friable structure. |
| Drainage | Soil that is well draining, yet retains moisture. |
| Fertility | Hostas require nutrient rich soil. Larger varieties in particular appreciate an application of fertilizer in the Spring to reach their full potential. |
| Composition | Loam soil is ideal, otherwise prepare the soil with organic matter such as leaf mold, manure, and compost. |
Keep reading to learn how to amend garden soil for growing hostas and why you should apply mulch around hostas every year at the start of Spring for healthy hostas…
Hosta Soil Requirements:
Well-draining soil is a crucial soil characteristic for hostas as they will not tolerate soil that is saturated for long periods of time. Boggy soil will cause the disease root rot which can kill the hosta.
The hostas roots grow relatively deep for a plant of its size so the soil should be well draining to a depth of 16 inches as this will accommodate the size of the root ball once the larger hosta varieties are established.
It is equally important that the soil retains moisture as hostas are very thirsty plants because of their large leaves transpire lots of water vapor so a constant source of moisture is required.
The soil should be porous enough for excess water to drain away from the hostas roots whilst still retaining moisture, so the roots can draw upon the moist soil when they need to.
Soil Fertility. Hostas require nutrient rich soil to grow to their best. Hostas are foliage plants with lots of luxurious plump leaves that require a lot of Nitrogen to grow every year.
For this reason, hostas will not grow well in sandy or stony soils as these soil types not only drain too quickly but also do not retain nutrients.
Loam soils are considered ideal as the clay content is very effective at retaining water-soluble nutrients such as Nitrogen and Potassium.
Soils with high organic content are excellent for growing hostas, particularly with the addition of mulch in the spring to add more nutrients.
The largest hostas such as ‘Patriot‘ and ‘Sum and Substance‘ which grow to a truly monstrous width of 36 inches (90 cm) require additional fertilizer in the Spring to grow to their full size and produce the prized foliage as they make considerably larger demands for nutrients than the more modestly sized hostas.
Soil Structure. The optimal soil structure for hostas is a light friable material with an areated structure. The roots of the hostas are white and fleshy and they grow very deep into the soil relative to the size of the plant.
The deep roots are a result of the plant’s reliance on a good supply of moisture and nutrients. Compacted soil restricts the growth of roots which will cause an inadequate established root system and increase the likelihood of stunted growth of the leaves and vulnerability to drought.
Therefore planting directly into heavy clay soils should be avoided and the soil will require significant amending, or you can plant hostas in pots instead.
Sandy soils provide the aerated structure that hostas prefer however they are often too low in nutrients drain too quickly and also require significant amounts of organic material added to the soil before planting.
(Read more about amending sandy soil for planting hostas)
Soil pH. Hostas prefer a soil pH of 6.5 to 7.5 which is slightly acidic, neutral, or slightly alkaline. This is the soil pH of most garden soils because the vast majority of organic material is either slightly acidic or pH neutral once it is fully decomposed so most gardeners have nothing to worry about.
However, chalky soils are often too alkaline and quickly draining for growing hostas. In alkaline soils, the hosta cannot properly uptake all the nutrients that they require and the hosta will either grow poorly or die.
In gardens with chalky or limey soils, it is far easier to grow hostas in pots.
Composition. Loam is the ideal soil type for many garden plants as it can retain nutrients, retain moisture and allow for good drainage.
If you are lucky enough to have loam soil in your garden then you can plant hostas without having to amend or adjust the soil in any way.
Hostas will grow very well in almost any garden if there is a high organic content in the soil. Soils can be greatly improved for growing hostas and other popular plants such as roses and azaleas by amending the soil with organic matter.
Amending Soil for Growing Hostas
Properly preparing your soil before planting hostas will ensure the plant stays healthy, grows to its full potential, and is resistant to slugs and diseases.
Three soil amendments that will ensure the soil has all the right characteristics for growing hostas are:
- Leaf mold
- Garden compost
- Well rotted manure
All three materials have an excellent capacity for holding moisture so that the roots of the hosta can draw upon this moisture when its required. This increases the plant’s resistance to drought.
The well-rotted manure in particular adds a good hit of Nitrogen which is the nutrient that is required by hostas in the greatest quantity in the Spring for foliage growth.
It is important to ensure the manure and garden compost is well rotted as recent manure can burn the roots of the hosta.
All three ingredients provide the optimal porous structure that allows water to drain and air to the roots for respiration and the establishment of the roots.
Ideally, if you have all three of these materials available, mix 1/3 of each ingredient in preparation for planting the hostas in the soil to gain the characteristics and broad nutrient spectrum of all three materials.
Other materials that work well include, pine needles and decomposed wood bark, as they help improve structure although they do not contribute the same level of nutrients as leaf mold, compost, and manure so should be added in smaller quantities.
Ideally, you should amend the soil to a depth of 16 inches for the larger hosta varieties to accommodate their root system and roughly 12 inches for smaller varieties.
If you amend too small an area of garden soil the roots may not fully establish into the surrounding soil due to the contrast of nutrient rich, moisture-retaining, amended soil and the less suitable surrounding soil.
If your soil is too sandy, too compacted, or has a high clay content, the solution is the same. Add lots of organic matter to the garden boarder before planting.
Compost improves sandy soils by retaining moisture, increasing nutrients, and reducing compaction and improving soil drainage for clay soils.
Avoid this Mistake!
Do not use wood bark or materials that are not entirely decomposed as a mulch or as a soil amendment. The decomposition of these materials can cause a temporary nitrogen deficit in the soil.
The process of decomposition of organic matter requires Nitrogen which is drawn from the soil around it. This means there is less Nitrogen available in the soil for you Hosta which can stunt the growth of the plant and you may have to add some fertilizer in the Spring to account for the deficit.
Nitrogen and other nutrients will be added to the soil if the organic matter has fully decomposed so always wait for around a year for materials to compost before amending the soil for planting or applying as a mulch.
Add Mulch Every Spring
Adding mulch to the soil around your hostas will ensure that the soil continues to improve in structure and maintains the ideal conditions for growing hostas. You should add mulch around hostas every Spring because:
- Mulch conserves water by reducing soil evaporation to keep the soil around the roots of the hosta moist despite higher summer temperatures.
- Adding organic matter will add nutrients to the soil and feed the soil’s ecosystem to ensure the hosta can access the nutrients it requires.
- Mulch improves the surface texture of the soil to allow water to infiltrate the soil and reach the roots. Soils without mulch can bake hard in summer which causes surface runoff and diverts water away from your hostas roots.
- The roots stay cooler in the summer and more insulated in the Winter which increases hostas resilience to freezing Winter temperatures.
- The addition of mulch can be the difference between having to water your hosta every day during high temperatures or every few days which saves a lot of effort.
Apply a one-inch layer of mulch around each hosta at the start of Spring as the weather is warming up. Ensure that there is a gap between the mulch and the crown as the hosta foliage above ground does not like to be in contact with consistently moist material.
The appropriate materials for mulch are the same as the soil amendments for planting the hosta, with leaf mold, manure, and compost all great options as they are excellent and conserve water compared to other types of mulch.
Key Takeaways:
- Hostas require soils that retain moisture yet have a porous structure so that excess water can drain away from the roots, so the soil does not become boggy.
- Hostas require soil rich in nutrients. Larger hosta varieties require a fertilizer in the Spring to reach their full size.
- Amend garden soil with compost, leaf mold, or well-rotted manure before planting to a depth of around 16 inches to accommodate the root system of a mature hosta.
- Sandy soils drain too quickly for hostas and heavy clay soils drain too slowly. Amend both with plenty of organic matter before planting to improve the structure of the soil or plant hostas in pots instead.
- Add a layer of mulch in the Spring to help conserve water and add nutrients to the soil.