How to Fertilize Hostas (A Simple Method)

Hostas are beautiful shade plants that need fertilizer to grow and keep their deep green coloring. Find out how to fertilize your hostas all year round.

Hostas do best with applications of slow-release, 10-10-10 fertilizer with a release period of about 3 months. Don’t apply more than one pound of fertilizer per 100 square feet. Apply the first round of fertilizer once in late March to early April and again in mid-June. For liquid fertilizers, apply weekly when your hosta’s leaves unfurl.

Are you ready to learn how to fertilize your hostas all season long to bring out that lush green coloring and help them thrive? If so, read on. Our step-by-step guide outlines everything you need to know to grow these shade-loving plants. 

How to Fertilize Hostas—New and Established Plants

Depending on the soil, hostas need more nutrients to help them grow to the larger sizes you see in many people’s yards. They’re very low-maintenance, but not getting enough of the nutrients they need can cause stunted growth and underdeveloped plants.

However, over fertilizing your hostas is just as bad as under-fertilizing them. When you over-fertilize, your hosta can start growing new plants at the wrong time of the year, and the frost can kill these fresh shoots. It also makes your plants weak and easier targets for diseases and pests.

Adding a thick layer of mulch around your hostas is important because you can’t allow the soil around your hostas to dry out. Mulch helps to trap moisture and hold it close to the ground’s surface. As long as the mulch stays moist, it’ll encourage the fertilizer to release into the ground. Mulch can also reduce your need to water every day.

The last thing you want to think about is the type of hosta you have. Luckily, they all have close to the same fertilizer requirements and growing conditions.

What If I Can’t Find 10-10-10 Slow Release Fertilizer?

Fertilizer math is pretty simple. If you want to apply 1 pound of triple ten (10-10-10) fertilizer per 100 square feet and can only find 19-6-12, a common Osmocote formulation?

Use the first number of the formulation, which is the nitrogen content of the fertilizer. Our 19-6-12 has almost twice the nitrogen as the 10-10-10, therefore, use the 19-6-12 at half the rate of the 10-10-10.

It is rare that you will notice a difference in plant growth because the phosphorous and potassium. Changing the rate of application does not change the ratio of the fertilizer. In this example, both of the fertilizers are excellent for most plants.

Fertilizer Requirements for Planting Young Hostas

New roots and young plants need fertilizers that have a high phosphorus content to boost the root growth and help the plant establish itself in the soil. You’ll want to get a starter fertilizer when you plant your hostas because this will give your hostas the best chances of rooting and being robust enough to withstand pests and diseases.

You want to plant your hostas early in the spring with a good mix of starter fertilizer. The exact application requirements will depend on the brand. Mix your starter fertilizer according to the manufacturer’s directions into the soil before you plant the young hosta plants. Once it’s well incorporated, put your plants in their pre-dug holes and lightly water them.

How to Fertilize Established Hostas

Established hostas do best when you apply a slow-release, 10-10-10 fertilizer. You should plan to apply your first round of fertilizer at the beginning of spring, so in late March to early April, depending on your location. You’ll apply another round of fertilizer at the start of summer in the middle of June. This will last your hosta until next spring.

Never apply fertilizer after the middle of July or the start of August. If you do, you could accidentally encourage your hosta to grow tender new shoots. They won’t have time to mature before the frost comes along and damages them. Spread your fertilizer in an even layer underneath your hosta onto the soil. Don’t get any fertilizer trapped at the base of the hosta’s stems because it can burn it. When you get an even layer, water the area deeply to encourage the fertilizer to sink into the ground.

Starter vs. Slow-Release Fertilizer

Starter Fertilizer

Slow-Release Fertilizer

Application Amount

Once

Once or twice a year

Best Application Time(s)

Early spring/new plants

Summer/established plants

Form

Granular or liquid

Granular

Most Important Nutrients

Nitrogen and Phosphorus

Nitrogen and Potassium

Purpose

Boost root growth

Encourage uniform growth

How to Fertilize Hostas by Season

Along with fertilizing your new and established hostas, it’s important that you set up a routine and fertilize all of your hostas through the different seasons. Doing so will ensure that you get large plants with deep coloring that thrive in the shaded areas of your yard and make gorgeous statement pieces. They can get big enough to divide and replant in different areas of your yard if you stick to a fertilization schedule.

Early Spring

Springtime brings warmer weather, and the ground thaws. The hostas come out of their dormant phase, and you’ll notice that the buds poke up out of the ground. These bud scales work to protect the true leaves from frost, and they’ll slowly open. The bud scales will recurve and allow three or four cigar-shaped leaves to come through and open up. They end up hanging a decent distance above the ground.

If you have established hostas, you won’t have to apply any fertilizer until a little later in the spring. New hostas need starter fertilizer when you plant them. However, water your plants thoroughly because water is an important component that will help them grow as large as possible all season long.

You do want to keep the soil moist around your hostas, especially the young ones. Spring brings winds, low humidity levels, and bright light that can quickly cause your new hosta’s leaves to get dehydrated. Watering generously in the early morning or late afternoon hours will keep them healthy.

Late Spring

The late spring is when you start to apply your first round of fertilizer to your established plants. You’ll get a slow-release 10-10-10 formula and apply it to your plants. If you live in an area with heavy rainfall, you’ll want to apply the 10-10-10 slow-release formula to your young hostas four to six weeks after you apply the starter fertilizer in the early summer.

To make your hostas grow the biggest, they can supplement your slow-release granular fertilizer with a liquid fertilizer every two weeks. This formula should have a higher nitrogen content with magnesium added in. A 20-20-20 or an 18-18-21 liquid fertilizer is a good choice. Just don’t splash it on the leaves because liquid fertilizer can burn them just like a granular can.

If it’s a dry spring, water your hostas every day. They need a lot of water to grow, and the water will cause your slow-release fertilizer to get into the soil and to your plant’s roots. If you don’t have enough water, you won’t see a lot of growth. A lack of water can cause your plants to wilt and be more vulnerable to pests.

Early Summer

The early summer months are when your hostas start to bloom in earnest. They need a host of nutrients to produce seeds and keep their lush green coloring with the large leaves. However, they shouldn’t have a high nitrogen diet at this stage. If you are using a liquid feed and your area gets a lot of rain, apply it weekly. When dry conditions hit, reduce your feeding to once every two weeks.

When your hosta leaves get as big as they can, you can stop feeding them the liquid fertilizer supplement. If it doesn’t rain in your area, your granular fertilizer is sitting on the ground and not releasing into the soil. You may have to water every morning or evening in hotter, drier weather.

The amount of water your hosta needs to grow goes down when their active growing phase ends. However, hotter temperatures increase the rate that the water gets pulled out of the leaves. This means that you may find yourself watering for longer periods in the morning or evening hours to help beat the scorching summer temperatures. If the soil gets dry, your hosta can go heat dormant or dry rot can appear on their crown. If your hosta is in a heavily shaded area, water them throughout the day.

Late Summer

Late summer is when the growing season winds down and your hostas prepare to go dormant for the fall and winter months. Around the middle of July, prepare to add the last round of fertilizer to your new hostas. Established ones won’t need it at this point. Use the 10-10-10 slow-release fertilizer on your young hostas. If you notice a few new leaves, give them one round of liquid fertilizer in the first week of August.

For established hostas, it’s time to put the hose away and stop watering them. A lack of water will encourage your plants to enter their dormant phase before the frost hits them. If you have new hostas, use a watering can and continue giving them normal amounts of water.

Fall and Winter

Don’t fertilize your hostas in the fall or winter months. These are plants that go dormant once the frost hits, and any new shoots will die off. This can have a negative impact on your plant as the spring comes around and they start growing again.

Monitor the weather and water your plants heavily so they get full of water the night before the first hard freeze comes through. Rain will typically come in the fall, but you may need to soak your garden one more time if you’ve had a dry fall. The water will help protect your hostas from the frost and push them into a dormant state until the ground unthaws in the spring.

If you live in an area that has dry winters with no snow, you may have to water once or twice during the dormant period. If you don’t, you could end up with smaller hostas or they could come up later in the spring.

How do I make my hostas bigger?

To grow big, beautiful hostas, you’ll want to fertilize every four to six weeks and water them thoroughly every day from spring until late summer or early fall. Adding compost to the soil and mulch will help inject more nutrients while holding more moisture in to prevent the soil from drying out. Make sure they’re in shaded areas of your yard and don’t splash any fertilizer on the plant itself. For more tips on growing bigger hostas.

How deep do your hosta’s roots go in the soil?

Unlike some plants, hosta roots grow and spread out horizontally along the soil instead of growing down deep in the soil. So it’s so important that you focus more on your planting hole’s width than the depth. If you don’t and the area is too narrow, your hosta can get root-bound and slow the growth.

Do hostas come back and grow bigger each year?

Hostas are perennial plants, and this means that they’ll come back year after year and get bigger as long as they have enough water, shade, and nutrients. Most hosta species grow well in Planting Zones 3 to 9, and it’s a versatile plant that is very low-maintenance.

Closing Thoughts

So, how do you fertilize hostas? Now you know they need a starter fertilizer when the plants are young and a slow-release 10-10-10 fertilizer applied every eight to 12 weeks, starting in spring and going through late summer. Water is a very important component of healthy growth. Hostas are a vibrant and beautiful perennial that will fill in the shaded areas of your yard and provide a low-maintenance plant that is a joy to have all season long. A lot of the advice here can also apply to any hostas growing indoors. Check out our article slow release fertilizer for hostas for more information

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