5 Tips to Grow Hostas under Pine Trees Successfully

Hostas are shade-loving plants that can grow well under pine trees if organic matter is added to the soil before planting. Hostas under pine trees will need regular applications of mulch and fertilizer during the growing season to reach their full potential.

Here are the 5 things you will need to do to grow hostas under pine trees

  1. Add plenty of compost and leaf mold to the soil before planting to help retain moisture.
  2. Mulch around the hosta every spring to improve soil structure and prevent the soil from drying out.
  3. Water the hosta, ideally will a slow soak, drip line to counter the dry conditions under a pine tree canopy.
  4. Add fertilizer as the soil under pine trees may be lacking in nutrients.
  5. Monitor the moisture levels of the soil regularly in the growing season.

Hostas will be competing with the pine tree’s roots for resources such as water and nutrients so keep reading for the best practices and easy solutions for growing hostas under pine trees successfully…

Amend the Soil with Organic Matter

The soil directly underneath established pine trees will be composed of dry soil that has years of pine needles at various stages of decomposition.

There is a misconception that the soil will then be too acidic to grow plants such as hostas, however, once pine needles are fully decomposed into compost the material will be pH 6 which, fortunately, is the right level of acidity for growing hostas.

The unamended soil underneath pine trees will be:

  • Too dry for hostas, partly because of the canopy intercepting rainfall.
  • Low in fertility or perhaps lacking a more complete nutrient profile.
  • Not of the be able to retain enough moisture for growing hostas which need consistent moisture.

Therefore when planting the hosta you must add a significant quantity of organic matter. A combination of compost/leaf mold and well-rotted manure yields great results when growing hostas.

The leaf mould in particular can hold up 500 times its own volume of moisture which is perfect as hostas need a constant source of moisture to retain their shape and structure.

The manure is rich in nutrients which, combined with the compost will be better able to retain fertility in the long term.

  • Organic material will also stimulate microbes and beneficial worm activity so that the soil becomes more ecologically active which in turn benefits the hostas as worm casts concentrate important nutrients into a chelated form that is more available for the hostas nutrient uptake.
  • When digging your hole for planting the hosta, dig out a much larger area of soil than the root ball of your plant as the larger the area you amend the better for the long term prospects of the health of the hosta.
  • How large your hole has to be will be determined by the size of the specific variety of hostas with larger varieties ‘Jade Cascade’ can grow 3 feet wide at full maturity compared with ‘Amber Tiara’ Hosta which only grows around 14 inches wide.
  • Make sure when you are planting the crown of the hosta (the point at which the stems meet with the roots) is at ground level.
  • Backfill your hole with a combination of compost and ideally some manure (hostas are heavy feeders) and firm the soil for some stability without compacting the soil as the roots like a porous structure so that they can establish effectively.
  • For best results, after planting you should water thoroughly with as much as 3 gallons for larger varieties and around 1-2 gallons for medium or smaller varieties and distribute mulch around the surrounding soil…

Why you Need to Add Mulch to Hostas under Pines

Adding mulch in areas underneath pine trees is very important to continue improving the following:

  • Soil structure
  • Water retaining capabilities
  • Adding nutrients to improve the soil every year to replenish the nutrients absorbed by the heavy-feeding hostas

Pine trees can stay particularly dry due to the lack of soil quality and the fact the canopy intercepts a significant amount of rainfall so that less water reaches the hostas planted beneath.

Distribute a 1-2 inch layer of mulch on top of the soil surrounding the hosta. However, it is very important to leave a 6-inch gap between the mulch and the crown of the hosta.

Mulch can be applied at any time of year but it is often best to distribute the mulch at the start of spring, to provide nutrients for the upcoming growing season and to retain moisture for the warmer months of the Spring and Summer.

The best materials for mulching around hostas to combat the dryness (the biggest problem) under pine trees are the same sort of materials that you would use to amend the soil initially.

Well-rotted general compost, manure, leaf mold, and grass clippings are all good options. Avoid mulches such as wood chips, or bark as they are less effective for retaining moisture and contribute very little in the way of soil fertility.

The mulch also has the added benefit of suppressing weed growth, saving you time and effort.

A nice 2-inch layer of mulch will act as a big sponge absorbing the water and slowing down the rate at which soil evaporates, yet it still retains a porous, friable structure that allows excess water to drain away. Crucially, the roots need a constant supply of moisture but they do not like to be sat in saturated ground with pools of water.

Water with a Drip Line for Hostas under Pines

The best course of action to water hostas under the canopy of pine trees is to lay down a dip line or soaker hose and leave it on for a few hours during the summer.

Dry soil is the biggest problem when it comes to growing hostas under pine trees. By day the hostas leaves transpire water through their large leaves which creates a partial vacuum that triggers more water to be then drawn up through the roots. It is this internal pressure and consistent moisture supply that gives the large hosta leaves their shape, sheen, and luxuriant feel. (This is achieved with a process known as Turgor Pressure).

Therefore I cannot emphasize enough the importance of a good watering schedule when caring for hostas in dryer conditions particularly when hosts have to compete with the pine tree for water.

If you cannot lay a soaker hose down near the hostas planting area then watering with a hose is advised for larger hostas due to the required quantity of water.

The larger varieties such as ‘Sum and Substance’ may need up to 3 gallons of water on hot summer days with medium to small varieties needing 1-2 gallons. On more overcast days or if there has been some rainfall you will need to water hostas once every 2-3 days.

Hostas are characterized by a need for moisture so it is important to water them thoroughly as this will encourage the roots to grow deep into the soil to tap into moisture reserves that are otherwise in short supply underneath pine trees.

Always water hostas in the morning to charge them with moisture for the day ahead. Watering at night will encourage slugs and snails which are frequent pests when caring for hostas.

Monitor Soil Moisture Levels

When growing hostas under pine trees it will pay to give special attention to the moisture levels.

Check frequently with your finger if the soil is moist. If the soil feels somewhat dry or only slightly moist, you must give your hosta a generous drink. This is a good preventative measure to stop hostas from drying up or dying in dry conditions.

As long as you have prepared the soil by amending it with organic matter before planting, adding mulch regularly and water frequently, hostas should thrive in the shady environment under a pine tree.

Fertilizer is Essential for Hostas under Trees

It is absolutely essential to use fertilizer when growing hostas under pine trees as the hosta will be competing directly with the much bigger pine tree for nutrients.

Adding mulch will help to improve the fertility of the soil but it will not necessarily contain all the nutrients the hosta needs in the correct concentration for it to grow to its full potential in terms of size, shape, and glossy leaves particularly when the pine roots are trying to draw up the same nutrients.

So to get the best out of the hosta in terms of size, shape and the glossy sheen to the luxuriant leaves a fertilizer is necessary, particularly with the larger cultivars.

Whilst hostas are relatively heavy feeders demanding Nitrogen (N) Phosphorous (P) and Potassium (K), they are not fussy. A generally balanced plant fertilizer is perfect for replenishing these nutrients along with the trace elements that contribute to the health of hostas.

A reputable brand of fertilizer (such as Miracle-Gro) will provide the right balance. Apply once every two weeks starting in early spring when the weather has warmed and there is no chance of frost. Carry on applying fortnightly until the middle of August.

Do not apply any fertilizer after August as it will stimulate new growth at a time when the hostas is preparing for winter dormancy.

Removing Pine Roots when Planting Hostas

A limiting factor when it comes to planting hostas under pines is finding space in the network of shallow pine tree roots.

If there is a dense network of roots from several pines or other surrounding trees then it may be very difficult to grow the larger varieties of hosta such as Hosta ‘Sagae’ which can grow to 70 inches across and you will have to plant smaller varieties instead such as ‘Gold Edger’.

It may be possible to use an axe to tactically chop some pine tree roots to accommodate the planting area of a hosta which can be a fairly modest area for the smaller cultivars.

The more roots there are in the planting area the more the hostas have to compete with the pine trees for moisture and nutrients therefore the need for fertilising, watering, and mulching will increase proportionately.

Key Takeaways

  • Hostas can grow well under the shade of pine trees if the soil is amended with plenty of organic matter before planting.
  • Compost, leaf mold, and well-rotted manure are great amendments that will provide nutrients and retain a consistent moisture supply that hostas need to maintain their structure and stay healthy.
  • Mulching in the spring is necessary to help the dry soil under pine trees retain more water and gradually improve the soil structure.
  • Hostas under pine trees will need fertilizer to help them compete with the roots of the pine and allow the hosta to grow to its full potential.
  • When growing hostas under pines you have to be particularly diligent about watering. Ideally, install a drip pipe or soaker hose or water large hostas with 3 gallons in hot weather and smaller varieties with 1-2 gallons every few days. Check soil moisture regularly and add mulch to help retain the water.
  • Plant smaller hosta varieties if there are a lot of shallow pine roots in the surrounding soil. You can chop away some pine roots with an axe to make room for hostas without long-term harm to the pine tree.

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