Hostas are valued by gardeners all over the world for the luxuriant foliage and their ability to grow in the shadier parts of the garden where other plants would struggle.
Due to their large leaves hosta can make huge demands for water at the hotter times of the year and the soil must stay consistently moist (but not saturated) for hostas to be healthy.
Small and medium hostas require watering once per week with a generous soak, if planted in the shade. In hot weather, watering should increase to 3 times per week. Large hostas require watering twice per week and watering once per day in hot weather if planted in full sun.
How much water hostas require, very much depends on the specific growing conditions:
|How to Water|
|Large Hostas (90cm or 36 inches across)||Large hostas will require up to 1 gallon (3.7 litres) per plant once or twice per week when planted in shade in temperate climates. At the height of summer large hostas may require daily watering if in partial or full sun.|
|Small (20 inches 50 cm or more) and Medium Hostas||Smaller hostas require at least 0.5 gallons (1.8 litres) of water every three days during summer. Water generously once per week in cooler climates with overcast days ensuring that the soil stays moist.|
|Full Sun||Hostas that tolerate full sun (such as ‘Sum and Substance’) require significant watering. Mature larger plants in full sun require as much as 3 gallons (10 litres) per day in blazing sun to maintain leaf structure. Smaller hostas also require daily watering with a generous soak each time.|
|Pots and Containers||Pots drain quicker then garden boarders, therefore hostas will require more frequent watering. Water every three days in summer so that water trickles out the drainage holes at the base of the pot but check soil moisture regularly and water more frequently if necessary.|
|Arid Climates with low Rainfall||In dry climates, hostas prefer to be in the shade or at least partial shade. 1 gallon (3.7 litres) every three days with medium hostas and up to 3 gallons (10 litres) for larger plants. Water more frequently if the soil feels dry.|
|High Rainfall||1 inch of rain per week can sustain small to medium hostas but supplemental watering will ensure a healthy plant. Large hostas still require watering even with a inch of rain per week.|
|Sandy Soils||Amend the soil with organic matter for planting and use a mulch to help conserve water. Hostas require moist soil so water 0.5 gallons (1.8 litres) every three days in the summer or more frequently to maintain the moisture of the soil.|
|Slow Draining Soils||Amend slow draining soils with organic matter and grit to improve drainage (hostas require moist soil as opposed to saturated). Water as frequently as required to keep the soil moist but ensure the soil does not become boggy as this causes root rot.|
|In Fall and Winter||Soil evaporation is much lower in Winter but hostas require some soil moisture to maintain the structure of the leaves. In most climates hostas will only require occasional watering in the Fall and no additional in during their Winter dormancy if they are planted in moisture retaining soil with plenty of organic matter.|
The goal for watering hostas is to keep the soil consistently moist.
Hostas need the soil to be consistently moist to keep their leaves plump with a healthy sheen and upright as hostas are foliage plants and do not have a wood structure for self support.
The large leaves transpire water vapour throughout the day which creates a partial vacuum that stimulates the roots to draw up more water from the surrounding soil. (This process is know as turgor pressure).
If the soil dries and the roots cannot draw up more water the leaves will droop and loose their shape, stunting the plants growth.
For healthy hostas, it is important that the soil is rich in organic matter, and a mulch is applied regularly to conserve water so that hostas maintain their shape during the hotter and dryer months of the year.
How Frequently to Water Hostas?
How frequently hostas require water will depend on:
- How well the soil is prepared (high organic content is best)
- How quickly the soil drains
- The specific climate or weather
- How many hours of sun per day
- Whether the hosta has to compete with other nearby plants and trees for moisture.
Hostas require a soil that maintains a consistent level of moisture without becoming boggy or saturated.
Hosta will only have healthy, plump leaves if there is enough moisture in the soil around the root system which grows relatively deep compared to other plants.
For this reasons their watering requirements are much higher the most garden plants at the height of summer.
If the soil has been amended before planting with water retaining materials (such as leaf mould and compost) and the hosta is in the shade for most of the day then watering one or two times per week is sufficient for most circumstances.
However, in quick draining sandy soils, arid climates or at the height of summer and in blazing sunshine, hostas may require watering as often as every day with a generous soak each time in order to maintain the structure of the plant and the succulent, luxuriant nature of the leaves.
In temperate climates with higher rainfall large hostas may only require watering once per week if there has been 1 inch of more of rainfall, particularly in early Spring or Fall. It is possible to skip watering for smaller and medium hostas during weeks with significant rainfall as long as the soil retains moisture effectively.
If hostas experience drought or are not watered frequently enough then they will not grow as large as they should and the variegated species tend to have less pronounced contrast on their leaves.
In the Fall and Winter the level of soil evaporation is dramatically reduced compared to summer and in a lot of climates there is more rainfall at this time of year.
Hostas may only require water once a week or so on overcast days of the Fall and little to no water in Winter as the plant is in a state of dormancy and will likely attain all the moisture it require from the surrounding environment without the need for additional water.
Always Water in the Morning
Always water hostas in the morning rather then the eveing if possible.
A common irritation for gardeners are hosta leaves that have been eaten by slugs and snails as they leave their tell tale holes in the foliage. Watering in the evening will promote the moist conditions that the nocturnal slugs prefer as they emerge looking for food.
Watering at the start of the day charges the hosta with water before a hot day ahead and gives the surrounding soil a chance to dry out somewhat before the slugs emerge at night.
Some varieties such as ‘Sum and Substance‘ and ‘Aspen Gold’ are more resistant to slugs then other thanks to their robust thicker leaves that the slugs have difficulty consuming.
Note that if you have a slug problem it is far easier to protect hostas in pots rather then planted in the garden boarder. For more information read my article which details all the best practices for preventing slugs and snails from eating hostas.
How Much Water?
Hostas are thirsty plants that can make serious demands of water during the hottest driest times of the year.
The largest mature plants such as hosta ‘Patriot’ will require a generous 1 gallon (4.5 litres) of water during the hottest days of summer to provide enough moisture for the hostas roots.
Smaller and medium hosta will require a more modest half a gallon (1.8) litres of water per day in the hottest days of the year if in more then 4 hours of sun.
If the weather has been overcast or there has been more then an inch of rainfall per week then you can skip watering for a few days as long as the soil is moist and the hosta is not deprived of rain water because of a tree canopy or the roots have to compete with other plant roots for moisture.
It is important to always water with a generous amount of water as this encourages the roots of the hosta to grow deep into the soil which further increases the hostas resistance to drought and allows the roots to access nutrients.
Watering hostas ‘little and often’ will only encourage the roots to grow nearer the surface of the soil as grow towards the water they require to keep the leaves in good health.
In cooler climates, with higher rainfall you can water with a watering can without any problems, however in dryer climates or at the height of summer a hose pipe is often the best way as hostas require significant amounts of water, to stay healthy and grow to their full potential.
How to Tell if your Hosta Requires Watering
The most obvious sign of stress in drooping leaves which is followed by a scorched appearance at the tips and margins of the leaves. A generous soak will usually alleviate drooping leaves within 24 hours however scorched leaves may take some time to recover.
Hostas are highly reliant on a moisture in the soil and they will be one of the first plants to show signs of stress if there is a drought.
If you are unsure test the soil to a fingers depth. If you can detect moisture then the hosta should be okay for a few days, however if the soil feels only somewhat moist or the soil is dry near the surface then give the hosta a good long soak to restore moisture levels and keep the leaves in good health.
Watering Hostas in Pots
Watering hostas in pots is much the same as watering hostas that are planted in a garden boarders, although pots do tend to dry out quicker.
Water hostas in pots with the same quantity of water you would use on hostas planted in the soil (large hostas require more then a gallon of water on hot days whereas smaller hostas require approximately half a gallon) but increase the frequency of watering to account for the increased rate of soil evaporation.
In most cases watering once every three days will suffice hostas in the ground during hot weather (as long as the potting mix retains moisture) however hostas in pots may require watering once every one or two days.
Look for the early signs of drought (drooping leaves) monitor the soil moisture and try to be proactive with your watering frequency in hot weather to ensure the hosta remains hydrated and stays nice and healthy.
The Importance of Soil and Mulch When Watering
Well prepared soil and an application of mulch in the Spring are essential for conserving moisture and work in conjunction with the watering best practices to ensure the hosta is healthy.
Soil amendments such as…
- Leaf mould
- Well rotted garden compost
- Well rotted manure
…are all excellent materials for holding moisture, adding nutrients and providing the soil conditions that hostas require.
Incorporate the compost and leaf mould when digging a hole for your hostas or planting the hostas in pots. This will also help to improve the soils structure so that its remains porous enough for water to drain away so that the soil remains moist but not saturated and boggy, which would lead to root rot.
The same organic materials also act as a very effective mulch to conserve moisture, improve the texture of the soil and keep the roots cool.
In the summer, the ground can quickly bake hard which increases the amount that water runs off the surface of the soil and does not infiltrate the soil to reach the roots.
Mulch not only absorbs moisture but also improves the soils structure so that it’s more porous to encourage water to soak into the soil to the roots where it is required.
Apply a one inch layer of mulch around each hosta on the surface of the soil at the start of Spring.
Ensure that there is a gap between the edge of the mulch and the crown of the hosta as the stems that are above ground do not like to be in constant contact with moist material as it will cause rot.
Too Much Water
It is very unlikely that a gardener will over water a hosta, however if the soil has a high clay contain and drains very slowly then the hosta can develop the fugal disease root rot.
Hostas require the soil to be moist and yet allow for excess water to drain away so that the soil is not boggy for long periods of time.
The optimal soil for hostas is porous to allow water to drain away but to also hold into moisture so that the roots can draw water when its required.
In gardens with clay soil it is much easier to plant hostas in pots rather then try to amend the soil to allow for hostas to grow.
- Water hostas as frequently as required to keep the soil consistently moist. Hostas rely on a constant supply of moisture for the foliage to maintain its structure and appearance.
- Larger hostas may require daily watering in hot weather if they are exposed to direct sun (with more then a gallon of water). Small and medium sized hostas require water every 3 days with a generous amount of water each time (half a gallon).
- Prepare the soil with moisture retaining organic material before plating hostas and apply mulch at the start of Spring to help conserve water.
- Water hostas in the morning to charge the plant with water for the day ahead. Avoid watering in the evening as this will promote the conditions that slugs and snails prefer.
- Hostas in Pots require more frequent watering as pots dry out much quicker. Water twice per week and increase watering to perhaps every day at the hottest times of year.
- Hostas do not require watering during their Winter domancy.
- Amend slow draining clay soils before planting to ensure excess water can drain away from the roots and ensure the correct balance of moisture for the roots.