The case of the haggard Hydrangea

This Hydrangea plant was given to an online client by a friend of hers as birthday gift a month ago. As shown here, it has been kept since that time in its nursery pot on the shaded side of a garage. The client was watering the plant once a week when it looked like it was needing water, but otherwise just let it sit. A few days ago, she came out to it looking like this. Fearing the worst, she reached out for help.

As plant situations go, this one is not great. Plants don't typically enjoy being in small pots, especially water-thirsty Hydrangeas. In an ideal situation, this plant should have been taken out of its pot and planted in the ground

as soon as it was brought home from the birthday party. An ideal planting site for these shrubs is in partial shade, though they can take full sun for most of the day as long as they get shade during the warmest hours (usually between 2 and 6 PM). Hydrangeas like slightly acidic soil with a pH of between 5.8 and 6.2 that is well-draining but kept moist. 

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Diagnosis

What's this plant? It is a Pinky Winky Hydrangea, or Hydrangea paniculata 'Dvppinky'. It is considered a hardy Hydrangea, meaning that it is more tolerant of cool temperatures than other plants in its genus. Pinky Winky is an absolutely beautiful cultivar with cone-shaped panicles of flowers that open from bottom to top. Base flower petals are pink to dark pink, and gradually lighten to white towards the tips. These plants are commonly grown as garden ornamentals in Sunset zones A2, A3, and 1-21, and are large shrubs that reach 6-8 feet tall and 4-6 feet wide.

Pinky Winky Hydrangeas are also sold by some nurseries as small trees, which can reach about 8 feet tall with a 6 foot wide crown. For more information on more species and varieties of Hydrangea, as well as care information, click the link below to be taken to their plant page:

Hydrangea

What's Going On?
It looks like this Hydrangea is in serious need of some water. With the somewhat cooler weather we've had in the past week here in the Bay Area, many gardeners took a short break from watering their plants so frequently (I know I did!). But it's important to remember that the plants we care for (especially those grown in pots) still do need to be at least checked for soil moisture daily; they have no way of sending their roots further down in search of water. Watering once a week is not sufficient for a Hydrangea plant in a nursery pot, a more ideal watering schedule would be at least 2-3 times per week.

Also, by this point the soil in the pot is most likely hydrophobic, meaning that it will not do a great job absorbing water for roots to use. Most of the water will run off the top of the soil, down the sides of the root ball inside the container, and right out the holes in the bottom without so much as touching a root. Further concerning the root system of the plant, it is possible that because the pot size is so small, the plant is root-bound. Luckily, all of these issues are fixable.

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Suggestions

To try to save this plant, we'll do some initial pruning and soil rehydration followed with a repotting and top dressing. 

A Little Haircut
Cut off the flowers on this Hydrangea plant. Flowers take a lot of water to form and bloom, and cutting them off will allow the plant to send more of its energy and resources to repairing itself and forming a strong root system. If there are any smaller flower buds on the plant, cut them off as well.

Rehydrate the Soil
Fill a 5-gallon bucket or similar container with water and lower the Hydrangea in its container into the water. It will try to stay afloat at first, but the longer it is held under, the more it will take on water and become less buoyant. Once the pot is staying under the water on its own, it can be pulled out and set aside to drain. Repeat this process every 2-3 days until water poured at the base of the main stem is readily absorbed by the soil.

Repot the Hydrangea
The plant may take some time to recover, depending on how much damage it underwent from drought stress. We still have a good amount of summer weather before temperatures drop in the fall and the plant goes dormant, so with any luck we can get the plant to recover and put on some foliage and new growth before that time. Once the plant is putting out new buds (pictured), it is time to repot.

Find a pot with nice drainage holes that is 4-5 inches wider in diameter than the nursery pot and fill the bottom of the pot with well-draining potting soil. A good mix for container-grown Hydrangeas is a standard potting mix with a scoop of perlite and a generous amount of compost thrown in. Don't worry about fertilizing at this point; it's possible that it will overwhelm the plant's recovering root system to have to deal with so many changes at once. Add enough soil to the bottom of the pot so that when the nursery pot is set inside, it sits about 2 inches below the container rim. Then, remove the Hydrangea from its nursery pot and check out the root system.

If the roots are looking dead​, they can be trimmed up at this point with a pair of sharp, cleaned shears. If the roots look a bit like those in the picture, you're pretty set to get that Hydrangea into its new home without much more work. Because the current pot is so small, it is a good possibility that the root ball is constricted, and in that case it would be helpful to untangle the roots before placing the root ball in the pot. Once the plant is sitting in its new pot, fill in soil around.

Make sure that the Hydrangea is surrounded with enough soil to keep it in place, but don't pack it down too much. The soil should have enough pore space to allow for healthy root growth. Give the new pot a soaking and ensure that good drainage is happening. 

Topdress the Pot
​The final step to bringing the Hydrangea back to full health is to add a 2 inch layer of organic mulch to the soil surface. Ensure that the mulch doesn't go right up to the main stem of the plant, keep it about 2-3 inches away. Adding mulch to your container will help to keep moisture in the soil, suppress weed growth, and maintain soil temperature.

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After taking these steps, it's time to sit back and watch your Hydrangea recover. The container should be placed in an area that is somewhat sheltered for a while, to avoid any other issues from taking hold while the plant is vulnerable. Make sure it is protected from direct afternoon sun, and water every 2-3 days after checking for soil moisture. If an eventual goal is to put the plant in the ground, wait until next springtime to give it time to recover and get used to the climate in your garden. With some luck, this plant will be saved!