How to Make a Hypertufa Pot for Conifers
Discover how to make your own hypertufa (stone-like) containers for your conifers.
After attending my first National ACS conference in Oregon several years ago, my idea of using single season annuals in containers changed. Container gardens typically include tall spindly plants surrounded by colorful annuals, planted in faded plastic containers. As the season comes to an end, the plants get sadly redirected to the compost bin, one season and gone.
The conference tour visited several beautiful display gardens where I saw hypertufa (stone-like) containers planted with small conifers and alpine perennials arranged to form miniature landscapes. I realized then that there was a new group of plants that I could use in my container gardens. It did not take too long for my Pennsylvania garden to include many conifer containers of all shapes and sizes.
After the conference my goal was to create containers just like the ones I had seen in Oregon. I purchased and made many different containers. I experimented with different plants, different soil mixes and then I worked on making my own containers. This is what I found to work best for me.
What is a Hypertufa Pot?
Hypertufa allows you to be creative, childlike, and artistic, while making your own container. Even mistakes can look good. Instructions on how to make hypertufa containers can be found on the internet and in many garden magazines. However the most complete source of information was in the book, Creating and Planting Garden Troughs by Joyce Fingerrut and Rex Murfitt.
There are many ways to make hypertufa. My formula starts with equal parts of Portland cement, peat moss, and perlite. Thoroughly mix the cement with water to form a damp, but not wet mixture. Add liquid cement color to the wet mix to make the container more decorative.
Apply the mix, about 1½” thick, to the inside (or outside) of a mold, usually a large plastic container. After a day, gently remove the slightly hardened hypertufa from the mold. Wire brush the pot to create a textured, stone-like finish. Place the container in a plastic bag to keep it moist, slowly allowing it to cure for a few weeks. As it cures, the container will become stronger. Once properly cured, these containers can remain weather resistant for many years.
Making a Planting Mix for a Hypertufa Pot
Building a house requires a good foundation. Making a good container garden requires great soil. Whether you are growing conifers in hypertufa containers or annuals in plastic pots, success begins with creating a healthy environment for root growth. The growing medium has to provide roots with sufficient oxygen and also allow gas exchange in the root zone.
Bagged potting soil is mostly peat moss and within a short time the peat moss breaks down and compacts. My conifers need to stay in the containers for a few years and, therefore, the soil mix needs to remain functional. While searching the internet for just the right soil mix, I discovered the Garden Web forum and read about Al’s Gritty Mix, one of two mixes created by Al Fassezke – or “tapla” as he is known on the forum. His mix of ingredients not only creates a well drained, highly aerated soil for containers, but also allows for air to move through the root system and by-product gasses to escape. The ideal growing environment!
When you make your own containers you can control the size and number of drainage holes. My containers have at least one 2” drainage hole which is then covered with a piece of window screen. We have been taught to use a layer of gravel on the bottom of the container beneath the soil to improve container drainage – no longer true.
Instead of extra water draining immediately into the gravel, the water actually “perches” or gathers in the soil just above the gravel. This wet area has no air space, which is not an ideal environment for roots. Roots grow best in well aerated soil. So the addition of gravel only reduces the available space for roots to grow. More detailed information on “perched water table” can be found by doing a search on the internet.
Conifer Selection for a Hypertufa Pot
Unfortunately the conifers used in the container will eventually outgrow their space, and using slower growing plants will keep your planting undisturbed for a few years. Conifers are classified as mini (grows less than 1” per yr.), or dwarf (grows 1-6” per yr), which helps when selecting the right plant for your container.
The next concern will be to pick a plant that will survive the winter in a container. Start by using a plant that is at least one zone colder than your zone. However, additional winter protection may still be needed. Here are just a few examples of conifers and perennials that I have been able to grow successfully year round in containers in my USDA Zone 6 garden: Chamaecyparis obtusa ‘Nana’, Zone 5, Juniperus communis ‘Gold Cone’, Zone 4, Picea glauca ‘Jean’s Dilly’, Zone 4.
There are hundreds of alpine perennials, for example, selections of Sedum, Zones 2,3,4 and Thymus, Zone 3, Sempervivum - Zones 3, 4, and occasionally I use non-hardy succulents like Echeveria, Zones 8, 9 – around 150 species – which I bring inside as it begins to get cold.
Designing the Landscape of a Hypertufa Pot
A conifer container can have a design, one conifer in one container, or you can create a mini landscape. Many nurseries now carry mini and dwarf conifers in 4” containers, making it easy to plant multiple conifers and several alpine perennials in one container. Design is a matter of personal taste. I place a tall accent plant, possibly a small juniper, off center in the container.
To create a natural looking scene, place a grouping of rocks inter-planted with several alpine perennials around the conifer, add a creeping Sedum or thyme to hang over and soften the edge. Mixing leaf textures will create visual interest. Once everything is planted cover the soil with a mulch of fine gravel.
Hypertufa Pot Maintenance and Fertilization
Conifer containers require a sunny location and minimal care once established. Newly planted containers will need to be watered a little more frequently until the roots get established. Since the recommended soil mix has no nutrients, fertilizer is required. Care should be given not to overfertilize. More is not better no matter what you grow. Excess fertilizer in soil makes it more difficult for plants to absorb water and nutrients. Only give plants what they need.
I have found good success with a fertilizer that has low NPK (nitrogen, phosphorus and potassium). I use a very weak solution of liquid fertilizer on a frequent basis. In nature, plants do better with regular access to low levels of nutrients, as opposed to sudden large infusions. I use a fertilizer like Dyna-Gro’s Foliage-Pro 9-3-6, or similar NPK in a 3:1:2 ratio. It has all the primary macronutrients, secondary macronutrients (Ca, Mg, S) and all the micronutrients. Its NPK formula is very close to the ratio most plants actually use. I also supplement with a little time-release fertilizer in case I forget to apply the liquid fertilizer.
Conifer Winter Care for Hypertufa Pots
Many conifer containers can be kept outside all year. However, plant survival will increase if you provide some extra protection. Roots are exposed to colder temps in containers than they are if growing in the ground. As I mentioned above, select plants that are at least one zone lower than yours.
As winter approaches, one option is to relocate the container to a microclimate near the foundation of your house. Avoid the south side because it might cause the plantsto warm and freeze resulting in heaving. For colder climates dig a shallow hole and sink the container in the hole. Mulch the container. Another option would be to place the container in an unheated garage or shed. The plants donot need light during the dormant period. Bring the pot back out as the temperature outside begins to warm in the spring.
Container gardening with conifers is something that anyone can do, even if you only have a small patio or deck. You are limited only by your imagination and a sunny location.
This article was originally published in the Spring 2011 issue of Conifer Quarterly. Join the American Conifer Society to access our extensive library of conifer-related articles and connect to a nationwide group of plant lovers! Become a member for only $40 a year and get discounts with our growing list of participating nurseries in our Nursery Discount Program.