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Growing astilbes in pots and containers – Planting and care guide
Last Updated on March 24, 2020 by John
Astilbe are generally not to 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 make for a delightful splash of colour and you can find compact, dwarf varieties if you are simply filling a small space with a small container or taller cultivars if you want something a little taller.
How to grow astilbes in pots
Choose the right-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 going to grow more than one plants in the same container, that’s perfectly fine and can work well, you’ll just need a slightly larger container to accommodate the root system. You’ll want to check the bottom of the container you choose to make sure it has adequate drainage. It never hurts to add extra holes if you can, by drilling a few extra holes around the base and don’t forget to cover the holes with some crockery (broken pots or stone) to stop the holes from becoming blocked.
Other than size you don’t really have to worry about materials for the pots because these plants are pretty flexible. Ceramic pots are always a viable option but they will suck the moisture from the compost so keep an 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 weight.
Keep in mind 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 resting place before you add the plants.
Sowing seed vs buying potted established plants
You have a few options with containers. You can start by germinating astilbes from seed if that’s something you’re into but they can be very difficult to germinate which is why many people purchase potted plants already growing from garden centres and nurseries.
However, 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 reached about 10cm in height, you can thin them out and leave only a few approximately 10 to 14 centimetres apart for smaller plants, or 14 to 18 cm 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 is 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 high-quality potting mixture only after you have verified that the containers have adequate drainage holes. We recommend using a John Innes compost which is soil-based and will retain moisture better which astilbes like. It’s worth noting that you want to start with at least a plant grown in a 9cm pot but you will get near-instant results if you plant a larger plant in a 2 or 3 litre pot which most garden centres sell, online garden centres tend to sell the 9cm pot version but these 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
These container plants thrive in moderate shade or minimal sunlight. You can grow them in total shade but they won’t flower nearly as well than if they have a little sun. If you live in a warmer part of the Uk, further south in a position with a lot of direct afternoon sun, the plants won’t do well and the soil drying out to 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 the extra drainage holes, as 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 fertilizer 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 or repot them in a new larger 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. Then transplant the new sections if you so choose.