How to Transplant Milkweed


One of the quickest methods to establish Common Milkweed is to transplant small plants from an established patch. Common Milkweed (Asclepias syrica) spreads by rhizome roots. Rhizome roots are horizontal shallow roots that new plants shoot up from, and we can easily transplant individual plants by digging and cutting the rhizome roots.

As a general rule, small Milkweed plants can be transplanted by digging up the rhizome root and plant. This works best when plants are small, either from just emerging in Spring or new plants growing from the rhizome root system. They can be transplanted anytime of year, but is best when temperatures are cool.

How do Milkweed Rhizome roots work?

Rhizome roots are long lateral roots that bore horizontally through the ground. They will go above or below obstacles as they encounter them, and send new shoots up to the surface to make new plants.

New Milkweed plants that grow from Rhizomes will not have developed taproots! So, it makes transplanting much more likely to result in success.

No taproot present!

Rhizomes serve two purposes. 1 – they allow the plant another way to spread and reproduce in addition to seeds. And 2, they serve as a store of energy for new and established plants to draw upon. [1] [2]

In this article I’m going to discuss:

How to transplant Common Milkweed ethically

First, we need to discuss the ethics of transplanting Common Milkweed. It is illegal to take plants from the wild, or property that you do not own pretty much anywhere in the world But – Common Milkweed is very prolific in various locations and permission can easily be obtained from the landowner.

If you find a large patch of Common Milkweed in a ditch or abandoned field and there is a house nearby, then knocking on that door is the easiest way to ask permission. However, if the identity of the land owner is not obvious, then there are many online resources available.

My favorite way to figure out who owns land is to know what county I am in, and search for “County Mapping” for that specific county. You can generally navigate to an online-map or parcel viewer and identify the land parcel in question, which will give the name of the owner.

Convincing the owner to let you have plants

It is a good idea to have a bucket of topsoil with you, as you can promise to fill in and level out any holes you make. This can reassure the land owner that you will not cause problems in your transplanting. Most people want to help the Monarch Butterflies, so this gesture will likely ensure permission will be granted.

Don’t be authoritative or self-righteous in your appeal. Be humble, and just calmly explain your desire to help the Monarch Butterfly.

How many plants should you take?

And once you do receive permission, the general guideline as to how much to take is to never take more than 10% of the plants [3]. That way you ensure that a healthy population stays healthy! Because the first rule in any nature setting is to do no harm.

So, if you found a patch of milkweed with 10 stalks, you should only take a single plant. And, you should do so before the plant is budding or blooming. Taking smaller plants will increase the chances of a successful transplant.

Ok, that being said, let’s get down to business.

Identifying Common Milkweed

To identify Common Milkweed plants look for a colony that is in bloom, or identify them by the stalk and leaves.

Stalk

The stalk of Common Milkweed is generally erect, stout, round, and light green in color. It may be smooth or have small hairs along it. In general there is no branching on a Common Milkweed stalk, with the exception of near the flowers. Sometimes multiple flower heads will be on a single plant and have limited branching to support.

If the stalk or leaf is broken, a white substance will ooze out (hence the common name). This white milky substance is toxic and should not be touched. People have gone blind form rubbing their eye after touching the sap.

Leaves

Leaves of Common Milkweed are opposite (paired) along the stalk and 8″ long by 3″ wide and oblong in shape. The edges have smooth margins and medium to dark green with a prominent central vein on the upper surface. The lower surface will have short hairs along it.

Flowers

A bloom of Common Milkweed consists of clusters of tiny flowers. The overall cluster is usually 2-4″ wide. Individual flowers are about 1/4″ diameter (6 mm) with 5 petals. The color ranges from white with purple mixed in on the stems.

Root System

Common Milkweed has an extensive root system of rhizome roots. This allows the plant to spread far and wide in an area. You’ll see in my example that I am transplanting small Milkweed starts that are 10-20′ away from the mother plant colony, but are connected by these long rhizome roots.

Milkweed Root System

In my experience Milkweed rhizome roots will be about 3″ deep in unobstructed soil. But the rhizomes will go deeper to get around any barriers.

Overall root depth of Common Milkweed has been found to go as deep as 14′. [4]

How to Transplant Milkweed Plants

Materials

To transplant common milkweed, you will need gloves (sap is toxic), a shovel or spade, and possibly a trowel. Also, a moist paper towel to wrap the milkweed roots, and some pots with moist potting soil.

Steps to transplanting established milkweed plants

Locate a common milkweed plant, at least 12″ away from the next plant. Make sure it is smaller than other nearby milkweed plants, as it will be more likely to be a plant started from a rhizome root.

1 – Dig around the plant, giving at least 6″ from the stalk, with your shovel angled 45 degrees down. This way you can be fairly certain you will get a lot of the rhizome.

2 – After creating your perimeter, lever out the clump containing the plant.

3- Identify the rhizome root and the direction it is running. Try to break/separate the clump parallel to the rhizome root so that it is not damaged.

4- Carefully remove / chip away any dirt attached to the rhizome/plant. Then, wrap the root in a moist paper towel. This step helps ensure the root won’t dry out and will survive. You want to have at least 3″ of rhizome root to increase chances of success.

5- Return home and plant in a container filled with moist potting soil immediately. Plant it about 2″ deep.

6- Clip the top portion of the plant (if there is one) so that only one set of leaves is showing. This step will reduce any heat stress/loading to the plant.

7- Place the pot in a location that gets about 2 hours of sun in the morning, and keep it moist (not wet) watering if necessary. This will reduce the heat stress and loading on the plant, raising the chances of success.

8- After 1-2 weeks, you can plant the milkweed plant where you like. Or, move the pot so that it gets more sun. This helps the plant reestablish itself and will greatly increase your chance of success if you transplanted when temperatures are hot.

Also, for reference, I have overwintered Common Milkweed in containers in zone 6. So, they are fairly tough as long as you have a large pot.

This plant survived the winter in this very pot. (Forgot to plant it out)

Note – This method is what I’ve found to be the most successful for me. But, no transplanting is 100% guaranteed. So, follow the above steps and you should maximize your your chances of success.

Can I just take the whole clump of dirt with the plant?

When you dig up the dirt clump containing the milkweed plant, you don’t have to separate the root like I outlined in the above steps. Taking just the root/plant reduces the amount of weight you need to carry back to your car. But, taking the whole clump of dirt and just planting it will also work. Just make sure you fill in any holes with topsoil.

But most importantly, make sure it is heavily watered, and you remove any unnecessary leaves. Milkweed likes to grow in full sun, and this is quite stressful for a fresh transplant in hotter temperatures.

Where should I transplant my milkweed plants?

Common Milkweed likes to grow in full sun with well-drained soil. It can take a variety of moisture conditions, but seems to do particularly well in medium moist soil. It will not grow well in shadier areas.

Tips, lookalikes, and FAQ

Avoid lookalikes! Make sure you have the real thing.

Some plants that look similar to Common Milkweed include Dogbane and Pokweed. If you are not careful you may accidentily transplant one of these plants by mistake. The table below mainly relies on features to help you identify the plant before they bloom.

Common Milkweed vs Dogbane vs Pokeweed

AttributeMilkweedDogbanePokeweed
Does the stalk branchOnly near flowersFrequent BranchingFrequent Branching
Leaf Size8″ long x 3″ wide1-3″ long by 0.33″-1″ wide8-10″ long by 4″ wide
Leaf ShapeOblongElliptical to OblongLanceolate
Opposite (paired) or alternating leaves along stalk?OppositeOppositeAlternate

Both Dogbane and Milkweed leaves/stalk will produce a milky white sap when torn. Pokeweed also produces a sap. All saps from all three plants are toxic and should be handled with gloves. Do not get the sap in your eyes. [5]

When can I transplant Milkweed Plants?

As a general rule the best time to transplant Milkweed plants when temperatures are cooler in Spring. But, Milkweed plants can generally be transplanted as long as they are not blooming or producing seed. Just try to make sure they are smaller offshoots from the mother colony.

During blooming and seed production, all the plants energy is going into the flowers and seed. Transplanting at this time often has a lower success rate in my experience. But, the pictures you see above were done during peak summer in July and August.

But, if you follow the guidelines I’ve laid out and only take small rhizome offshoots, then you can generally transplant milkweed anytime. Just let the plants live in pots in a somewhat shady location for a couple weeks to reestablish themselves.

How much Milkweed rhizome root is needed for reproduction?

Research at the University of Nebraska has found that rhizome sections 15 cm (6″) in length could produce new plants in a greenhouse setting. [4] I’ve personally done it using as little as 7.5 cm (3″). So, the more rhizome length you have, the more likely you are to be successful.

What milkweeds can be transplanted?

Common Milkweed and Swamp Milkweed are the best candidates for transplanting. As they have shallower roots and rhizomes.

Other Milkweed types such as Butterfly Weed have taproots. Taproots are much more difficult to transplant, as any damage to the taproot can be fatal to the plant. It is best to propagate Butterfly Weed by seed.

Click here to read more about Milkweed Plants

References:

[1] – Tao, L., Hunter, M.D. Allocation of resources away from sites of herbivory under simultaneous attack by aboveground and belowground herbivores in the common milkweed, Asclepias syriaca . Arthropod-Plant Interactions 7, 217–224 (2013). https://doi.org/10.1007/s11829-012-9235-y

[2] – Hochwender, C., Marquis, R. & Stowe, K. The potential for and constraints on the evolution of compensatory ability in Asclepias syriaca . Oecologia 122, 361–370 (2000). https://doi.org/10.1007/s004420050042

[3] – How to ethically collect native seed. North American Native Plant Society. https://nanps.org/seed-collecting/ Retrieved 06JUN2021

[4] – L. L. EVETTS, O. C. BURNSIDE. Root distribution and vegetative propagation of Asclepias syriaca L. Paper No. 3557. Journal Series. Nebraska Agr. Exp. Sta. The research reported was conducted under Project No. 12-7., University of Nebraska. First published: October 1974 https://doi.org/10.1111/j.1365-3180.1974.tb01062.x. Retrieved 09JUN2021

[5] – Milkweed causing corneal toxicity. https://atlanticeyeinstitute.com/milkweed-poisoning-corneal-endothelial-toxicity/ Retrieved 09JUN2021

Joe Foster

Hi - I grew up outdoors in nature - hiking, fishing, hunting. In high school I got my first job at a garden center where I learned to garden and landscape. I've been growing plants from seed and designing native plant gardens for over six years. I hope to share some of my knowledge with you! Additionally I am a wood worker / DIY enthusiast. I enjoy designing/building projects (with hand tools when I can!). I hope to give you some tips and useful information!

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