How to Grow The Best Peonies in Northern California

Growing a gorgeous set of peonies for your garden is actually easier than you think, especially in Northern California. The trick is to find a variety that does well in your hardiness zone and climate. Everything else after that is smooth sailing until they bloom.

Here’s how you can get started:

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1. Choose Peony Varieties with Suitable Chilling Hours to Grow Best in your Northern California Area
2. Plant Peonies in Well-draining Soil Enriched with Compost
3. Provide Peonies with 6 Hours of Full Sun with Light Shade
4. Water Peonies Once Every Week to Encourage Deep Root Development
5. Only Fertilize Peonies Biyearly During Its Initial Growth and Flowering Period
6. Provide Developing Peonies with Flower Stakes or Cages to Support their Heavy Topside
7. Remove Dead & Damaged Leaves and Blooms by the End of the Flowering Period
8. Don’t Kill Off Ants Running Around on Unopened Peony Buds

1. Choose Peony Varieties with Suitable Chilling Hours to Grow Best in your Northern California Area

California’s hardiness zone is like a keyboard – same notes, different tone, i.e., same seasons, different climates. Northern California is known for its cooler temperatures, but it also has its fair share of hot days. The temperature changes between day and night are significant in this context, contributing to an area’s total chilling hours.

Chilling hours refer to a duration when the temperature is between 32-45 degrees F per hour. This is usually tracked from November to March but varies in different regions and years. Honestly, the calculations can be pretty complex and tedious to keep track of. So I got myself a hack and used these sites to find out my area’s average chill hours:

National Weather Service: Observed Weather Stations – this is to find out my area’s weather station ID.
MesoWest Surface Weather Maps – You can also use this map to find your area’s weather station ID.
Get Chill – this is where I input my weather station ID to automatically calculate my area’s chill hours.

But what do chill hours have to do with growing peonies? Lean in closer because I’m about to let you in on the secret to successfully blooming peonies: Without the cold temperatures, they won’t flower. This is why they are primarily known as plants of the north.

Each peony variety will have various chilling hours required for guaranteed blooming. A majority of them require 500-1000 chilling hours to bloom well. Knowing your area’s chill hours will save you so much hassle from waiting on peony cultivars that will never flower in your garden.

For example, my area has an average of 100 chill hours. This means I need to find peonies with low chilling hours requirements to bloom well in spring. So my best choice is to get the early blooming cultivars such as Festiva Maxima, Early Scout, and Monsieur Jules Elie.

Some peony catalogs come with information on their required chilling hours. Some may not – in this case, I use the following system to gauge the chill hours needed:

Less than 500 chill hours = low chilling period needed. Hence, early-blooming cultivars are the best bet.
500-700 chill hours = medium chilling period required. Therefore, early to mid-season blooming cultivars are the better choices.
More than 700 chill hours = high chilling period needed. Thus, late-season blooming cultivars will grow best in these conditions.

Note that this is a very simplified way of determining chill hours. If you have the option of finding out more detailed information on your peony variety, by all means, go for it! It’s also worth noting that weather can sometimes be unpredictable enough to throw your planting season plans off. So don’t worry if your particular peony variety doesn’t do that well in your area despite meeting all the right conditions.

Luckily, peonies thrive in Northern California. Here are a few examples you can try out:

Coral Charm – Early season bloomer.
Coral’ n Gold – Early season bloomer.
Bartzella – Late mid-season bloomer.
Blaze – Early mid-season bloomer.
Festiva Maxima – Early-midseason bloomer.
Sarah Bernhardt – Late-midseason bloomer.
Sea Shell – Mid-season bloomer.
Julia Rose – Mid-season bloomer.
Scarlett O’Hara – Early mid-season bloomer.
Barrington Belle – Early mid-season bloomer.
Buckeye Belle – Early season bloomer.

2. Plant Peonies in Well-draining Soil Enriched with Compost

If you’re planting your peonies in the ground, mixing in compost is more beneficial than you think. Regardless of your soil type and fertility, compost improves drainage, provides nutrients, and transforms poor-quality soil into a rich, crumbly mixture.

If you’re planting your peonies in a pot, opt for good quality potting soil/mix with sufficient drainage. Container-grown peonies require a bit more care than their in-ground counterparts. For example, you will need a large, wide pot to accommodate its clumping growth habit into a bush. Intersectional/Itoh peonies are the best choice for this.

In terms of soil pH, peonies like it neutral at pH 6.5-7:

If it’s too acidic, adding limestone typically raises the pH.
If it’s too alkaline, mixing in sulfur will lower the pH.

Important note: Before you amend the soil, make sure to do a soil test or send a sample to be analyzed at a lab. Most garden soils are within an acceptable pH range to grow peonies and other plants. Mixing soil amendments will only be counterproductive if you don’t even know what you’re starting with. I talk about this in other articles if you’re interested to learn more about soil tests and soil amendments.

Peonies last a long time once they’re established. So taking the effort to provide the best growing conditions during their initial planting will ensure their longevity in your garden. Make sure to dig a hole about 2 inches deep from the surface and plant them if your area has cooler temperatures; 1 inch deep only for warmer climates.

3. Provide Peonies with 6 Hours of Full Sun with Light Shade

In colder climates where the sun isn’t too harsh, it’s ok to let your peonies get the full blast of the sun. Give them a minimum of 6 hours to get the best bloom in spring. However, in warmer climates with scorching sun, it’s better to plant your peonies where they can be shaded from the heat of the day but still receive enough sun. Too much exposure to the hot sun will cause them to fade and get damaged.

For shade, avoid planting peonies underneath trees or other shrubs. They will be competing for nutrients fiercely, and these contenders are not the best companions to have around. Use a row cover or black mesh netting instead to protect the peonies from most of the sun’s harsh rays.

4. Water Peonies Once Every Week to Encourage Deep Root Development

By planting the bulbs deeper in the soil for colder climates, you encourage peonies to extend their roots further below in search of moisture. If you water them too often, you encourage shallow roots to develop instead. Also, you risk overwatering the plant, causing a festive pool of perfect fungal breeding ground. The same goes for peonies planted 1 inch deep in the soil in warmer climates.

The only exception to this rule is during the peonies’ initial growth stage. They need more water to develop their leaves and flower buds. But once the roots are established, peonies often become drought-resistant.

5. Only Fertilize Peonies Biyearly During Its Initial Growth and Flowering Period

Fertilizing peonies are usually optional, especially when organic fertilizers such as compost or aged manure have already been added in the beginning. It is even encouraged to fertilize these flowers a couple of years apart. As mentioned in the title, fertilizing is ideal for supporting root establishment and robust foliage growth during their initial development. And during the flowering period, the flowers will bloom better from an extra boost of nutrients.

But it’s alright to leave the flowers to grow without fertilizers. It’s an extra precaution as well to prevent over fertilizing. So don’t start dumping spoonfuls of fertilizers in your peonies when nothing is growing. Peonies naturally grow slower at the start and can take up to 3 years before being fully developed. Afterward, they can pretty much grow on their own with little maintenance over the years.

6. Provide Developing Peonies with Flower Stakes or Cages to Support their Heavy Topside

Peonies are notorious for having weak stems to support their big blooms. Let’s be honest, they are stunning, but they also skipped leg day at the gym. This is where adding a stake or cage will aid in holding them up as they grow taller.

Usually, this is what’s needed for herbaceous peonies. But Itoh peonies and tree peonies can stand independently with no problem. If your peonies still struggle to stay up despite their type, get the stakes or cage out and help their big head from toppling to the ground.

7. Remove Dead & Damaged Leaves and Blooms by the End of the Flowering Period

Getting rid of the dead leaves and spent blooms stimulates new growth. Keeping them on will only waste the flowering plant’s energy to maintain the dead foliage and flowers. Pluck or trim them off in a collection and discard them in your compost pile. Do not simply let them fall to the ground. This will encourage pathogens to accumulate and feed on the dead growth at the base of your peonies.

If you’re thinking of adding mulch, only apply a skinny layer if you live in a warmer climate. It helps retain moisture in the soil and suppress weeds. But generally, peonies don’t need that mulch anyway.

If you need to do heavy pruning to your peonies to get rid of dead and damaged stems, only do this to herbaceous and Itoh peonies. Tree peonies won’t grow back after intense pruning sessions regardless of whether they need it or not. Fun fact: tree peonies result from grafting two different pieces of a plant together.

8. Don’t Kill Off Ants Running Around on Unopened Peony Buds

When ants are found hanging around your peonies, this means they are feasting on the sweet nectar produced by unopened peony buds that have nectar on their exterior. Their presence does not cause any damage to the budding blooms, so it’s fine to leave them as is.

But this opens up another realm of possibility. Because ants are attracted to sweet substances, their presence could also indicate sap-sucking insects such as aphids. These pests excrete sweet, honeydew secretions from digesting a plant’s sap. Luckily for you, ants will chow down on both their sweet excretions and pests themselves.

So either way, refrain from getting rid of the ants and touching your peonies for a while. They’ll get rid of the aphids for you in no time and generally have themselves a good snack for their sweet tooth.

And that’s all there is to it! Here’s to you growing fabulous peonies for your garden. Happy planting 😀

References:

https://hoke.ces.ncsu.edu/2017/06/peony/

https://hoke.ces.ncsu.edu/2017/10/peony-part-2/

https://hgic.clemson.edu/factsheet/peonies/

http://www.ladybug.uconn.edu/FactSheets/peonies.php

https://content.ces.ncsu.edu/peonies-for-the-home-landscape

https://extension.psu.edu/peony-diseases

https://www.uaex.uada.edu/yard-garden/resource-library/plant-week/peony.aspx

https://ceventura.ucanr.edu/Gardening/Coastal/Veg-Fruit/Chilling/

https://plants.ces.ncsu.edu/plants/paeonia-hybrids/

https://www.gardenia.net/plant/paeonia-lactiflora-monsieur-jules-elie-peony