Asparagus is one of the healthiest vegetables to grow. But I wanted to figure out whether it’s a good vegetable to grow in my container garden.
You can grow asparagus in a pot that is at least 12 inches deep and wide. You need to provide at least 8 hours of direct sunlight to the plant. Water it well so the soil remains moist but not soggy. Add compost and organic fertilizer that contains potassium to grow asparagus in the pot.
I’ve written all the details you’ll need to grow asparagus in a pot in your container garden. Do note that it will take 2-3 years for the asparagus to be ready for harvest.
1. Pick a suitable variety for the pot
You can pick any variety of asparagus as it will take the same effort to grow in a pot. But I would recommend using a male plant because they have better yield and the asparagus spears are larger as well.
Here is a list of male asparagus plants that you may find useful to choose from.
2. Choose the best time to grow asparagus
Asparagus is a perennial plant that takes several years to grow and become ready for harvest. The best time for starting an asparagus plant in spring.
The plant needs the temperature to be at least 75 degrees so it can germinate and grow well. It can grow at lower temperatures but the growth will be slower.
If you have a short growing season, it’s best to start seeds indoors and then transplant when the seedling has grown at least 3 inches tall.
You should wait till the last frost date of winter has passed before you think about transplanting the seedlings outdoors.
The asparagus plant will continue to grow in spring, summer, and fall. As the weather gets colder, the plant will start to dry out as it prepares to overwinter.
It will go dormant in winter but the roots will be alive. The plant will start growing back once spring arrives and the weather starts to get warm.
3. Understand how long it takes to grow
You really need to have the patience to grow an asparagus plant. It’s a perennial plant that can grow for several years but it takes the first 2-3 years to mature.
If you start the asparagus plant from seed, the first year it will develop roots. In the second year, it will continue to expand its roots and develop the crown. And it will be ready for harvest starting from the third year.
If you transplant the asparagus grown, you will be able to harvest the asparagus starting from the second year.
The first time you harvest asparagus, you will only be able to harvest them for 2-4 weeks. And from the next year onwards, you can harvest them for 8 weeks.
4. Choose the right pot to grow asparagus
Asparagus prefers to have deep roots and spreads wide. So choose a pot that is at least 12 inches deep and wide. This will help the plant grow at least for a few years till you can get the harvest from it.
You can choose a pot made from any material that pleases you such as plastic, terracotta, ceramic, metal, or concrete. I prefer plastic because it’s lightweight, durable, and inexpensive.
It also does not lose moisture as quickly as some of the other options which helps reduce the frequency of watering the plant.
Whatever container you choose, make sure it has drainage holes at the bottom. Asparagus can be a drought-tolerant plant when fully developed. But you will need to water the asparagus plant well when growing it in the first few years.
The drainage holes will help drain out the excess water and prevent the roots from getting infected with a fungal disease like root rot that will kill that plant.
5. Prepare the pot for planting asparagus
You may have bought a brand new pot or reusing an old one. In both situations, I would recommend sterilizing the pot. You can do this by soaking it in a mix of 1 part bleach and 9 parts water.
Keep the pot in this solution for at least 1 hour. You can then rinse it with clean water and dry it before use.
Now you want to add potting soil to this pot. Don’t use garden soil because it may contain harmful materials like chemicals, pests, and diseases.
The garden soil may contain too much clay or sand making it unsuitable to grow asparagus. The plant needs potting soil that has a good texture that retains enough moisture but drains out the excess.
You can purchase such potting soil from a local garden center, nursery, or an online store. Or you can make some yourself mixing 1 part perlite, 1 part vermiculite, and 1 part coco coir.
I would also suggest adding some compost and rock phosphate to the potting soil. This will give the asparagus plant nutrients and a dose of phosphorus that will be beneficial to its growth.
Make sure the pot has drainage holes at the bottom. Or you can drill some holes yourself. Keep a layer of newspaper at the bottom of the pot so the potting soil does not fall out of these holes.
Fill the container with potting soil but leave 2-3 inches from the top of the pot. This will help prevent the potting soil and water from spilling out of the pot when watering.
6. Plant the asparagus in the pot
You can grow the asparagus plant from seeds or propagating them from existing roots or crowns. If you start seeds, it will take about three years for the asparagus to be ready for harvest. If you start from crowns, you can start harvesting the asparagus after a couple of years.
You can get the asparagus seeds from a local garden center, nursery, or an online store. You want to make sure to get male seeds because they have a better harvest. And the asparagus grow longer with such seeds.
I would suggest directly sowing the seeds in the container if you have a long enough growing season. This helps you prevent moving the roots around and damaging them once the seedlings start growing.
Before you can plant the seeds, soak them in warm water for 24 hours. This will help the seeds germinate faster.
You can plant 2-3 seeds in the pot that we will thin later after the seedlings grow. Make sure to push the seeds 1/2 an inch inside the potting soil. Keep the potting soil moist by spraying water on it. The asparagus seedlings will germinate from the potting soil after about 2-3 weeks.
When you start seeds, the asparagus plant will spend one year growing strong roots and crown in the potting soil.
The other option you have is to buy asparagus crowns or get them from your friends and family if they are growing some. The benefit of using crowns to grow asparagus is you can start harvesting them after two years.
You will need to dig a trench in the potting soil so you can spread out the crown and roots in it. Then you need to cover the crown well with 2-3 inches of potting soil.
Water the crowns well till the water starts draining out from the holes at the bottom of the pot.
7. Give the asparagus the required sunlight
Asparagus grows best when it gets full sun. So you need to provide it at least 6-8 hours of sunlight every day. It can grow in partial shade but the germination and growth will be slow.
The temperature should be around 75-85 degrees for the plant. If the temperature is too low or too high, the plant will not grow well. And if the temperature is too high, it can also cause the asparagus to lose shape.
The good thing about growing asparagus in a pot is you can move the pot around if you need to. You can use this to protect the plant from too much heat or cold. If it’s too hot, you can move the pot in shade. If it’s too cold, you can move the pot indoors or cover it up with a row cover.
8. Water the asparagus plants well
Asparagus is a drought-tolerant plant once it has matured which means it can survive even in low water conditions. But when it’s young and growing in the first few years, it needs a lot of water.
I would recommend always keeping the potting soil moist enough so the asparagus plant gets the water it needs. The best way to do this is to check up on the potting soil every morning.
Stick your finger 1-2 inches in the potting soil and if the tip of your finger does not feel moist, it’s time to water the plant. You should perform deep watering where you add water till it flows out of the drainage holes at the bottom of the pot.
This ensures that the water has reached all areas of the potting soil and helps the plant develop a deep and strong root system.
You can use a watering can to water the potting soil. If you have a lot of plants in your container garden, you could set up a drip irrigation system with a timer. This will help reduce your work when watering the plants.
You can also add mulch to the potting soil that will help retain moisture for a longer time. The mulch insulates the potting soil and does not allow the potting soil to dry out fast.
You can use materials like grass clippings, dried leaves, wood chips, hay, or moss as mulch on top of the potting soil. Make sure to add the mulch only after the seedlings have grown a few inches. Otherwise, the mulch will smother the seeds and prevent germination.
I think the best time to water the asparagus plant is in the morning. This helps the potting soil absorb the required moisture before the sun comes out. Then it will drain off the excess water on top of the soil and the foliage.
This prevents creating humid conditions on the plant that increase the chances of fungal diseases attacking the asparagus plant.
9. Thin the unwanted asparagus seedlings
We plant 2-3 seeds in the container when starting the seeds. This is done so that we increase the chances of at least one seed germinating.
After 2-3 weeks, you may find that all the seeds you planted have germinated. You can’t allow all of them to grow in the same pot because they will overcrowd each other and compete for nutrients.
You can either transplant each one to an individual pot or you can thin them out and keep just one in the existing pot. Thinning means you pull out the unwanted seedlings and keep just one.
It’s best to keep the seedling that looks the most healthy and pull out the remaining. You can add the pulled seedlings to your compost pile.
The best time to start thinning the seedlings is after they have grown 2-3 inches in height with a couple of leaves.
You won’t have to do the thinning if you’re growing the asparagus from the crown as the plant has already germinated and has a high chance of growing well.
10. Provide good fertilizer to the asparagus plants
Asparagus can be a resource-hungry plant when it’s growing and it’s best to provide good nutrients. I recommend adding compost to the potting soil when preparing the pot.
The compost will provide good nutrients, texture, and beneficial microorganisms to the potting soil. You can also continue adding compost every month to the potting soil when the asparagus is growing.
The other nutrient you should add to the potting soil is rock phosphate. This gives a good source of potassium that is beneficial to the asparagus plant.
Once the plant has started growing, you can add a slow-release fertilizer to the potting soil every month. It’s best to use an organic fertilizer that is low in nitrogen and rich in potassium. So one with an N-P-K value of 5-10-10 would do well for the asparagus plant.
Make sure to follow the instructions provided by the manufacturer to understand how much quantity to use and how often to add the fertilizer.
11. Prune the asparagus plant in the pot
There are two times you will have to prune the asparagus plants. One is when winter arrives and the plant starts to dry out and turn brown. The other is when you’re harvesting the asparagus spears.
We know asparagus is a perennial plant that will grow for several years. But the plant will become dormant in winter and grow back in the spring. When winter arrives, you will need to prune the dried out asparagus plant that may appear yellow or brown in color.
The pruning will help the asparagus roots to conserve their energy and avoid spending it on the dead parts. They will need to use that energy when growing back in the spring.
You can prune the dead parts near the base of the plant by using a knife or bypass pruner. Just cut the part and add it to your compost pile if you have one.
You should not try to dig up the potting soil and prune the plant underneath it because you will risk damaging the roots.
12. Harvest the asparagus from the pot
If you started from seeds, you will be able to harvest the asparagus spears only in the 3rd year of growing. And if you started from crowns, you can start harvesting them in the 2nd year of growing.
That’s because the asparagus plant takes a couple of years to develop the roots and crown of the plant before developing the asparagus spears.
In the 1st year of harvesting, you’ll be able to harvest them for about 2-4 weeks. After that, you may be able to harvest the asparagus spears for 8 weeks during the growing season.
The best time to harvest the asparagus spears is when they have grown about 6-9 inches tall.
You can use a scissor or a bypass pruner to cut the asparagus spear from the plant. I suggest cutting at the base of the spear rather than underneath the soil. Because you may end up damaging the roots or the young asparagus spears that are just starting to develop.
You can tie the asparagus spears together and place them with the cut end in a container filled with an inch of water. This will keep them fresh for a week.
If you want to store them longer, you can freeze them up. You will need to blanch them before doing this. You can cut the asparagus spears and throw them in boiling water for a minute. Take them out and immediately put them in ice water for a minute.
Take them out and dry them. You can then place them on a tray, cover it with plastic, and freeze them in the refrigerator for an hour. After that, you can transfer them to a container and store it in the freezer for about a year.