Learn When to Fertilize Hostas

When to fertilize hostas? Generally, this would be a “how long is a piece of string” question, but we’ve made an effort to answer it conclusively and specifically.

We need to consider several variables to optimize fertilizer applications to perennials like hostas. Application timing must coincide with growth phases, soil temperatures, plant hardening needs, nutrient requirements, and local climates.

Timing is essential in love, life, and fertilizer applications. Wherever you live, we’ve got you covered on the fertilizer application front; you’ll have to work the love and life parts out yourself.

Let’s start at the beginning and work our way through this essential element of growing hostas.

Fertilizer Timing for Planting Hostas

The age of your perennials is a vital consideration when fertilizing hostas.

Fertilizer for Planting Hostas (Year 1)

New hosta plants should be grown in beds or pots rich in organic matter with nutrients added according to the soil test recommendations (see above).

Growing hosta from scratch allows you to develop an ideal environment where the soil conditions meet the exact needs of the hosta plant, i.e. well-drained, moist soil, rich in organic matter and optimally fertilized.

Don’t add additional fertilizer in the first year in the fall, but rather allow the plants to harden off and get established.

Maintain a moist environment for the plant and its roots. Dig a hole that is slightly deeper than the root ball and at least one and a half times as wide as the root ball.

Place the hosta in the hole with the crown just above soil level, then fill in the rest of the hole with dirt as needed. The crown should not be buried, and the filler soil should not be tamped. Allow the soil to settle by thoroughly watering it to remove air pockets.

If you transplant in late summer, you will need to wait a season for your hostas to become prolific hosta foliage producers of your hosta variety. To encourage root growth, apply a starter fertilizer with a high phosphorus content to transplanted hostas.

Avoid fertilization too late in the season (see the table below). Boosting growth too close to the first frost doesn’t allow the time needed for the plant to harden off, causing harm to shoots and roots.

Although many hosta plants are drought resilient once established, most are native to areas with 50 inches or more (see the guide in the table below) of annual rainfall. You may need to supplement irrigation if your area is below this level for optimal development.

Drip tubing, soaker hoses, or similar watering techniques are preferred over overhead irrigation to minimize wetting the plants. Dry foliage decreases disease concerns and intensifies the color of blue foliage cultivars.

Fertilizing Hosta Plants in Their Second and Third Year

The year following their planting, your perennial hosta plants will reemerge after their first season of dormancy.

This generally happens four to six weeks after the last frost, with the first shoots reaching for light, stimulating root growth, and then the second crowning of hosta leaves.

The table below is a generalization for each state based on the averages of the first and last frost dates. The date given for your early spring hosta fertilizer application is to six weeks after the average last frost date.

Watch your plants for the second crowning of leaves (after the first set has hardened off) before you make the application.

We’ll discuss what that application should be later in the article. It’s essential that a soil test informs your application as too much nitrogen can cause your hosta plants harm.

While we believe the table will help as a general guide, other factors may influence the hostas’ emergence from dormancy, such as the severity of the winter and the time it takes for soil temperatures to warm.

Applying too much nitrogen fertilizer can be harmful. A 125-square-foot bed of hostas requires only 2-ounces of actual nitrogen per application. High nitrogen applications cause soft, wilting hosta foliage susceptible to foliar diseases.

High nitrogen levels also reduce the vibrancy of the variegated patterns. If fertilizer is required, add a slow-release fertilizer as soon as spring growth begins.

Feeding Established Hostas

Hostas can grow well for a couple of decades if they get regular water, are kept healthy, and get an annual compost top-up.

Watering via drip-feed lessens the risk of pathogens spreading on wet hosta foliage, and growing a hosta variety resistant to leaf spot and crown rot will help.

Hostas generally don’t need highly fertile soil, but adding triple-ten NKP slow-release fertilizer (10-10-10) will help to keep colours vibrant. Remember to limit the nitrogen to 2-ounces per 125-square feet, i.e. one pound of 10-10-10 per 100-square-foot bed.

When to Stop Feeding Your Hostas

With a short growing season, gardeners in the north should stop fertilizing in mid-summer. Gardeners in the south with a longer growing season should stop fertilizing at the end of summer. The table below is a more detailed indicator per state.

A helpful guide (used in the table) is to stop any growth-boosting activities, specifically fertilizers additions, at least a 30-days before the general first frost dates in your region.

Perennials become dormant when the environment no longer supports their growth, and some gardeners even trim their hosta leaves back for winter.

What can go wrong when you feed your plants too late in the growing season?

Perennials need resilience to endure the winter freeze. Part of that resilience comes from having a healthy, established plant at the end of the hosta growing season.

Hosta plants, whether in beds or as potted plants, can better survive the frigid winter cold if they’re stable in their growing phase.

Fresh growth taxes the plant’s energy, even if supported by fertilizer. The stress of the growing phase makes the plant more susceptible to diseases and attractive to pests.

Maturity has its advantages, and boosting growth too close to the winter months could cause damage that the plant cannot recover from.

To avoid this happening, don’t add nutrients to your hosta flower beds after the date given in the table below for your region (as a guide to 30-days before the first frost).

Annual Fertilizer Schedule for Hostas

Your hosta plants don’t need a lot of nutrients. Fertilizing every second year is enough, especially if the hosta plants are well established. The best fertilizer is organic, and the nutrients in compost are enough for an annual feed.

If you wish to boost your hosta leaves for a brighter display, do this on the date advised below, about 42 days after the last frost when the plants have had an opportunity to acclimatize to the warmer weather and the second set of leaves have emerged.

If you’re transplanting or creating a potted hosta display, do it at least a month before the first frost date (see above table).

Consider using a raised bed if you want a more extended season, enabling the soil to heat up faster. If you use a bigger pot, the soil remains warmer over winter.

Closing Thoughts

We learned that hosta plants don’t have a high demand for nutrients, the effects of the different nutrients in NKP fertilizer, the importance of timing, and the need to have a stable plant to cope with the winter stressors.