Last updated on May 3rd, 2022
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Astilbes are generally not too difficult to grow in pots and containers, as long as you have a semi-shady area in your garden and a good quality soil-based compost to help retain moisture. They add a delightful splash of colour and you can find compact, dwarf varieties if you are simply filling a small space or using a smaller container. Alternatively, there are taller cultivars if you want something a little taller.
How to grow Astilbes in pots
Choosing the correct sized pot
The first thing you want to do is to make sure you have the right-sized pots or containers for your Astilbe. If you are growing a single plant, you don’t need a container that’s any larger than 30-40cm deep and around 45cm wide. If you are planning to grow more than one plant in the same pot, that’s perfectly fine and can work well, you’ll just need a slightly larger container to accommodate the root system.
Before you plant any Astilbes, you need to check the bottom of the container you are planning to use to make sure it has adequate drainage. It never hurts to add extra holes if you can (by drilling a few extra holes in the base) and don’t forget to cover these holes with some crockery (broken pots or stone) to prevent the holes from becoming blocked.
Other than size, you don’t really have to worry about the material the pot is made from because these plants are pretty flexible. Ceramic pots are always a viable option but they will suck the moisture from the compost so keep a close eye on watering. Plastic is obviously the easiest to move around if you need to move your containers from one part of the garden to the other, especially around winter because they are the lightest.
Bear in mind that if you are going to grow multiple plants in a single container that the larger sizes with the additional soil to accommodate will be heavier, so it’s best to put the containers in their final position before you add the compost and the plants.
Sowing seeds vs buying potted plants that are established
You have a few options here. You can start by germinating Astilbes from seed if that’s something you’re into, however, they can be very difficult to germinate which is why many people purchase potted plants already growing from garden centres and nurseries.
Despite the difficulty, if you want to germinate, you simply fill the pots with high-quality potting mixture and add the seeds directly into the pot then give them a light cover of potting mix. If you plan to do this it’s in your best interest to place multiple seeds directly in the pot and then once they reach about 10cm in height you can thin them out and leave only a few, spacing them approximately 10-14cm apart for smaller plants, or 14-18cm apart for larger plants.
You need to make sure that you thin them out and only leave the strongest of the young plants so that the container doesn’t become overcrowded. Overcrowding can lead to fungal diseases and root rot so don’t be tempted. Astilbes are fast spreaders anyway.
Planting established plants
If you are starting with established growing plants, you want to follow the same rules by filling your containers with a high-quality potting mixture, only after you have verified that the containers have adequate drainage holes. We recommend using a John Innes compost because this is soil-based and will retain moisture better, which creates the environment Astilbes like.
It is worth noting that you want to start with a plant (at least) that has been grown in a 9cm pot, but you will get near-instant results if you plant the larger plants that come in a 2 or 3 litre pot. Most garden centres will sell these, and sometimes the options of 9cm, 1 litre or 2-3 litres, whereas online garden centres tend to sell only the 9cm pot versions. These (smaller plants) are also established and work well when planted with 2 or 3 plants in the same container.
Maintaining your Astilbe plants in containers
Plant in moderate shade or minimal sunlight
Astilbes thrive when they are planted in moderate shade or minimal sunlight. You can grow them in total shade but they won’t flower nearly as well as if they get a little sun.
If you live in a warmer part of the UK (usually further south) in a position with a lot of direct afternoon sun, the Astilbes won’t do that well and the soil drying out too quickly can be a problem, so a partial shade position is better.
Once they are in place it’s best to check the container regularly and make sure that you give extra water once the top few centimetres feel dry. This will mainly be something to do in the summer months when it’s warmer and the plants are actively growing. You always want to make sure the containers drain well, which is why it’s advantageous to add extra drainage holes. This prevents the soil from becoming soggy, which leads to fungal diseases and root rot but you still want the soil to be moist most of the time.
Feeding once every two weeks once they are showing signs of growth
Once spring has sprung and you notice the new growth on the plants it’s always beneficial to give them a water-soluble fertiliser twice a month, something that you should stop once the plant goes into dormancy in the autumn.
Divide Astilbes every 3-4 years to keep them looking good
Every 3 or 4 years it’s important that you divide the container-grown plants and either do away with the divisions, repot the plants you have divided into new pots or spots in the garden, or repot the larger Astilbe in a new (bigger) container.
This is a very simple process where you simply remove the plant from the container, gently dig out the main network of roots, pull apart the rhizomes by looking for the “eyes”, and pinching off root sections that have 3-5 eyes each. You can then transplant these new sections if you so choose.