Hydrangeas can grow in full sun as long as their in soil that holds onto moisture and they receive regular mulching to help retain water. Varieties from the species Hydrangea paniculata have been cultivated to grow very well in full sun and produce and beautiful display of flowers.
Hydrangeas in full sun will need up to 2 gallons of water every day during the hottest days of summer.
There are a few specific best practices for growing hydrangeas well in full sun that you will need to follow in order to get the best out of your hydrangea.
Keep reading to find out if you need to make any adjustments to your garden to grow hydrangeas that produce spectacular blooms in full sun.
1. Moisture Retaining Soil for Hydrangeas in Full Sun
If you’re lucky enough to have loam soil or garden soil that contains plenty of organic matter this is the ideal soil medium for most plants including hydrangeas that are in full sun.
However if you have sandy soil or soil that never receives any mulch then the soil will not be able to hold enough moisture, contain enough nutrients and will drain too quickly to successfully grow hydrangeas.
Most sunny gardens will need to have their soil amended before planting hydrangeas in order to retain the right moisture balance and so that the soil structure is loose enough so that the roots of your hydrangeas can establish nice and deep, which will make them more resistant to drought.
The best organic materials to amend your soil with to retain enough moisture to grow hydrangeas are:
- Leaf mould
- Compost (garden compost is usually better although commercial compost will work)
- Well rotted manure
All three of these organic materials have an exceptional capacity for absorbing water yet their structure is sufficiently friable (loose) so that excessive water will not pool around the roots of your hydrangea and cause them to rot.
Moist soil doesn’t mean wet soil so if you have heavy clay in your garden you need to ensure that the soil doesn’t become waterlogged for periods after rainfall. Moist soil with good drainage is essential.
Amending Soil for Sunny Hydrangeas
Hydrangeas roots are relatively shallow and tend to grow to only a depth of 6 inches or so when mature, however they do like to spread their roots out wide.
This means you will need to add organic matter such as compost or leaf mould in to a depth of just over 6 inches when planting.
In terms of width you will need too amend an area that is about three times the width of the pot in which you bought your hydrangea so that the roots can expand out and take advantage of the amended moist soil.
The dryer your soil is naturally, the more compost or leaf mould you will need to add. In sandy soils this may mean replacing all the soil in the planting area with compost.
I personally recommend heaping your chosen compost onto the planting site and digging in all the material to the required depth with a fork and spade. Or if you have one, you can use a tiller which does a good job of mixing the compost amendment into the soil evenly and saves on labour!
After planting and watering in your hydrangea in the new soil it is important to add a layer of mulch to the surrounding soil to slow down evaporation and help retain water. You need to apply mulch to hydrangeas in sunny spots regularly.
Scroll down to tip number 4 for advice on the best mulch for hydrangeas…
2. Watering Hydrangeas in Full Sun (use a Beaded Hose)
Hydrangeas are naturally very thirsty plants that like moist (but not wet) soil, so a good watering routine is very important.
Hydrangeas that are in full sun on the hottest days will need watering every day, but if there is some cloud cover and cooler temperatures you may only need to water once every two or three days.
It is more important that you personally monitor the moisture of the soil when decided when to water. If the soil is only slightly moist or perhaps dry to a fingers depth then your hydrangea will need a good generous soak.
If the soil still feels cool and moist to a fingers depth then you can skip watering for a day.
Water your hydrangea in the morning so that it is charged with water throughout the hot sunny day and so that the soil will be moist during the hottest part of the day.
How much water you hydrangea needs will depend on the size of the plant. The bigger the hydrangea the more water it will require. I would recommend you water the hydrangea with at least 2 gallons (7 litres) of water on sunny days.
Water slowly so that the water has a chance to sink into the soil and not run off the surface.
Watering in this way will keep the soil moist to a good depth which will encourage the roots to grow deeper, and thus they will be less susceptible to the drying effects of the sun.
If you have a particularly sunny garden I would recommend that you invest in a soaker (drip line) irrigation hose.
This will slowly release water onto the soil at a rate where it will soak in and keep the soil moist over the course of a hot day (without saturating the soil). These hoses can be kept on for several days during the very hottest of weather to ensure you meet the water requirements of the hydrangea.
An irrigation system will save you a lot of labour when it comes to watering and will provide the optimal conditions for all kinds of plants in full sun.
3. Choose a Hydrangea that is Suited to Full Sun
Hydrangeas from the species Hydrangea paniculata are best suited to full sun or morning sun followed by shade in the afternoon.
This is a species that grow in naturally in South China, Japan Korea and has been cultivated into a variety of colours with glorious flowers in various shades of white, pink and green that grows in a variety of sizes.
‘Silver dollar’ ‘pink diamond’ and ‘limelight’ are all popular varites with good specimens available online.
However I do recommend heading to your nearest garden store and checking out their range in the summer to really get a sense of the size, colour and smell of the flowers from the hydrangea to see whether it is right for your garden.
4. Mulch Hydrangeas Regularly (Helps Retain Moisture)
It is imperative that you apply mulch on the soil surrounding your soil on a regular basis to help your hydrangea stay hydrated!
I recommend two applications of mulch during the growing season. The first should be as the ground is beginning to warm up in the spring (usually around March/April) and another application at the end of July during the highest temperatures of summer.
Mulch can save hydrageas that are suffering from heat stress as it will cool the roots and slow water evapourating from the soil keep it at the optimal moisture balance. Roots like to be kept nice and cool so a layer of mulch will stop the sun directly beating down onto the soil.
When the sun is at its most intense and beating down on your garden, it can cause the soil to bake hard and even crack. This will cause water to run off the surface, into the cracks and not necessarily reach the roots. Mulch will help change the texture of the top soil and improve the structure to increase the rate of infiltration from rainfall or your watering.
Mulch can also stop wind from wicking away moisture from the surface of the soil if you have a more open garden.
5. The Best Mulch for Hydrangeas in Full Sun
The best mulch is organic matter that can hold onto moisture. Again, garden compost, leaf mould and well rotted manure are all great options as the will continue to add fertility to the ground and maintain a nice friable loose soil texture that hydrangeas love.
Wood chip (or bark), straw or pine needles are to be avoided as they do not retain water particularly well and take much longer to break down into the soil and therefore have less of an impact on improving soil structure.
How to Apply Mulch to Hydrangeas
Your chosen form of mulch should be applied in a 2 inch layer on the soil surrounding your hydreagea.
Make sure that you leave a 6 inch gap of bare ground between your layer of mulch and the woody growth of the hydrangea that is above ground. Growth that is above ground does not tolerate constant exposure to moist material too well and could possible lead to rot.
Apply the mulch over the surface and do not be tempted to dig or till it in. Digging will only disrupt the beneficial soil ecology and potentially severe precious roots.
Save yourself the labour and let the earthworms, watering and rainfall work the mulch into the soil naturally.
Hydrangeas from the species Hydrangea paniculata will grow very well in full sun. It is essential that the soil is kept moist on the hottest day and that you diligently apply mulch to the soil twice per year to help maintain the ideal moisture balance and soil structure.
Hydrangeas that are in full sun should be planted in plenty of organic matter such as (garden compost or leaf mould) as this will hold moisture and still provide good drainage.
Watering your hydrangea can be a daily task when the sun is beating down and drying out the soil. It is best to purchase a soaker hose irrigation system to help keep up with the demand for water.