Planting hostas in containers can bring wonderful variety and flexibility to the garden. It also allows plants to be enjoyed on a patio or other shaded area where they can’t go directly into the ground.
The nutritional needs of hostas grown in a contained environment are different from those grown in beds. The effects of higher soil temperatures, increased drainage rates, root density, and the growing medium used all play a part in how to fertilize your hostas in containers.
Let’s review how these factors impact your hostas fertilizer needs as you create a spectacular display of colors, textures, hues, and three-dimensionality.
What to Fertilize Your Hostas
These fertilizers can be used separately or in tandem. Micronutrients such as copper, iron, zinc, boron, and manganese are also required by plants and can be provided by a micronutrient solution. Note the difference:
- Controlled release: These are synthetic fertilizers coated with materials to reduce their immediate solubility and availability to plants.
- Slow-release: Can be organic or synthetic. The release rate is a product of soil temperature, particle size, and the growing medium’s organic content and microbial life.
- Liquid fertilizer: This allows you to replace leached nutrients after extended rainfall quickly. Best suited for established plants.
- Foliar fertilizer: Dilute several times to avoid burning plant foliage and spray under the leaf for best absorption. It is not a substitute for either of the top three options – merely an addition if needed.
- Granular fertilizer: Not recommended for containerized plants as the risk of burning the plant’s roots is too high.
Fertilizer Applications for Containerized Hosta
Pre-plant fertilizer ensures that plants get off to a good start. If you used a controlled-release fertilizer before planting, you’d need to fertilize again in eight to ten weeks. Transplants can be fertilized three weeks after planting.
As nutrient levels decline through leaching, additional time-release fertilizer or liquid fertilizers can be applied once a week at a half intensity or once every two weeks at full power.
Salt buildup can be a concern when applying liquid fertilizers, as seen by a white crust on top of the potting mix. If the medium has accumulated salt, it should be leached to eliminate excess nutrients by gently running water through it for several minutes.
The rate of nutrient release is accelerated by higher summer temperatures and greater moisture in the growth medium.
Top-dressing rather than incorporated fertilizing reduces nutrient losses since nutrients must travel through the growth media, increasing their chances of being absorbed by the plant.
Allowing the top-dressed fertilizer to dry in between waterings may also help to reduce nutrient leakage through the fertilizer coating in controlled-release fertilizer.
Watch Your Watering
Drainage is the most crucial aspect of container gardening. Extra drainage holes can be inserted into the bottom of the pot to keep it open.
Adding a layer of gravel or stones to the bottom of the container does not help drainage; rather, it reduces the amount of soil and roots developing area available in the container. Drainage is ensured using a fast-draining soil mix.
Limiting the gap between the hosta root ball and the sides (about an inch) aids growth but requires you to water more frequently.
More frequent watering is also needed as temperatures increase, especially as the soil in pots warms quicker than that in beds. All these factors contribute to an increased need for fertilizer applications.
Adding Epsom Salt
Epsom salts (magnesium sulfate) lowers the pH and provides magnesium and sulfur, two nutrients often deficient in alkaline soils. Benefits of magnesium for hostas include:
- Aids photosynthesis by helping the hosta to create chlorophyll
- Promotes healthy cell division and protein formation
- Increases the hosta’s ability to retain water
- Allows the hosta to take in and use phosphorus
Magnesium has a poor cation exchange capacity (CEC), i.e. it binds poorly to soil particles. The only way your plant gets access to it is if it remains in situ near the roots.
With well-drained soil, it is most likely that much of the plant’s required magnesium gets flushed through, requiring additional applications. If additional applications cause no visible improvement in the condition of your hosta plants, discontinue adding Epsom Salts.
Growing hostas in containers afford gardeners flexibility in arranging different displays of color and texture in their gardens, including shaded paved areas, patios, and driveways.
It’s important to remember that your hosta plants require an annual cold spell of more than 30 days to go dormant, so reduce feeding and watering six weeks before, to aid dormancy.