May 2024 Plant Availability | |
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Happy May! With our hundreds of milkweed babies in production and the bounty of blooms throughout the nursery this spring we have turned into quite the Monarch metropolis over the last month. Caterpillars and chrysalises abound! The Monarch butterflies are in the midst of their spring migration currently, laying eggs as they encounter milkweed on their journey northward. We get a lot of questions about how to help the Monarchs and which milkweeds are best, so below is the rundown of what we know!
***We also have an exciting event announcement, so be sure to read to the bottom if you want to attend a fun new festival later this month focused on helping the Monarchs by raising awareness, educating folks about the pollinator crisis and what we can do to help, and connecting our Bay Area community with resources to create a beautiful mosaic of pollinator habitat to have a lasting impact on pollinator populations throughout the Bay and beyond!***
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Why do Monarchs need Milkweed?
Milkweeds are the one and only larval host plant of Monarch butterflies– it is the only thing that the Monarch caterpillars can eat, so they simply can’t make it to adulthood without it! Because of this, female Monarch butterflies only lay eggs where there is milkweed present. Both the caterpillars and adult butterflies receive important cues from milkweed that trigger them to migrate and breed at the correct times of year. Keep in mind, not all milkweeds are created equal…
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The Trouble with Tropical Milkweeds
Unfortunately, the increased demand for milkweeds over the past couple of years by well-meaning people attempting to help save the Monarchs has largely been filled by tropical milkweeds that are not native to California. We understand the appeal– tropical milkweeds are beautiful, oftentimes easier to grow from seed, grow well in many California habitats, and are nowadays widely available in big name garden centers. Sadly, tropical milkweed can have dire consequences for monarchs. For one, tropical milkweed species do not go dormant in the winter like our native milkweed species do, so unless they are manually cut back in the fall, they can disrupt Monarch migration (causing adult butterflies to breed at the wrong time and place) or cause them to abandon their migration altogether. Year-round growth of tropical milkweeds can also perpetuate OE, which is a common protozoan parasite that infects monarchs (check out this video to learn more: This Parasite is Cramping The Monarch Butterfly’s Style | Deep Look).
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California Native Milkweeds
There are 15 species of milkweed native to California, all of which are deciduous. They go dormant in late fall and sprout new growth in the early spring, coinciding with the natural timing of monarch migration. For the western Monarch population that we encounter here in California, the migration generation heads to the coast from mid- to late- August through November, where they overwinter until early spring. Around March, they begin spring migration away from the coast, laying eggs as they encounter milkweed and dying along the way while their offspring over 3 – 4 more generations complete the journey north. It takes 5 generations total of monarch butterflies to complete this migration cycle, so as you can imagine they need A LOT of milkweed on their journey to breed adequately for enough generations to complete the trek.
The two most widely available California native milkweeds include Narrowleaf milkweed (Asclepias fascicularis; pictured above) and Showy milkweed (Asclepias speciosa); both can be quite vigorous and even weedy once established, but they can be initially slow to establish and easily outcompeted when young. Because they break dormancy in late spring, these species can be vulnerable to encroachment from earlier germinating species when planted from seeds, and often require intensive site preparation and mowing to reduce weed competition. We recommend planting from transplants since (in general) habitat established in this way is more successful and requires less maintenance than seed sowing.
The preferred season to plant milkweed transplants/starts is the fall before it has gone dormant, with irrigation during the dry season until the plants are established after a few years. A. fascicularis and A. speciosa are fairly drought tolerant, so water requirements are minimal after they become established. Mulch around transplants helps to conserve moisture and reduce weed competition!
Our native milkweeds can tolerate full sun, but it is important to plant them in partial shade (we recommend morning sun and afternoon shade) so that any caterpillars that utilize the plants do not overheat!
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Should I plant Milkweed if I live near the coast?
There’s been some mixed messaging over the last few years about planting milkweeds along the coast of California. The primary concers is that the western Monarch population overwinters there, and the presence of milkweed (even native milkweeds that naturally go dormant in the winter) may disrupt their overwintering. To the best of our ability we follow the recommendations of the Xerces Society, which are as follows:

To avoid disrupting the natural behavior of the western Monarch population, avoid planting milkweeds along the coast within 5 miles of monarch overwintering grounds and other areas where milkweed has not historically occurred (for example, high elevation forests). If you aren’t sure if there is an overwintering site near you, check out this interactive map: https://westernmonarchcount.org/map-of-overwintering-sites/
If you do live within 5 miles of an overwintering site along the coast the best thing you can do to support Monarchs is to plant nectar plants that bloom in early spring, late fall, and winter to provide fuel that the adult butterflies need for their migration and overwintering. For most other parts of California (like the Central Valley), planting milkweed may be especially beneficial to restore the historical abundance of native milkweeds in those areas!
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Interested in creating Monarch habitat in your community? Below are some of our native milkweeds and nectar plants in stock right now to get you started 🙂 | |
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Narrowleaf Milkweed
Asclepias fascicularis
Available in D16 pots for $7.30 each!
- Hardy, easy-to-grow perennial that reaches up to 3.5 ft. tall
- Individual plants grow only 1 ft. wide, although this species has the potential to become weedy as it spreads via rhizomes underground as well as by seeds.
- Blooms in clusters of light lavender-tinted pink flowers
- Tolerant of summer drought and grows well in clay as well as fast draining soils.
- The single most important larval host plant for Monarchs in California, with the widest range across the state of all of our native milkweeds
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Showy Milkweed
Asclepias speciosa
Available in D16 pots for $7.30 each!
- A fantastic plant with fragrant, alluring, furry, pale pink, star-shaped flowers
- Typically grows 4 ft. tall by 4 ft. wide
- Spreads readily with underground stems– so it can become weedy, but can be pruned back quite hard (after established) during the winter when it is dormant
- Napa and Fairfax skirt the southwestern extent of its natural range, so Narrowleaf Milkweed and/or nectar plants would be better suited if you live south/west of there
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California Aster
Symphyotrichum chilense
Available in D16 pots for $7.30 each and 1-Gal pots for $14.50 each!
- Grows 1 – 3 ft. tall and spreads by rhizomes to nicely fill out a flower bed!
- Likes moist soil, but can tolerant summer drought
- Blooms with vibrant purple daisy-like flowers from late summer through fall, and may reappear if pruned to the ground after finished flowering in fall
- Monarchs delight in its nectar, and it’s a favorite among a variety of other butterflies and moths, plus birds eat the seeds!
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Yarrow
Achillea millefolium
Available in D16 pots for $7.30 each and 1-Gal pots for $14.50 each!
- Semi-evergreen herbaceous perennial that grows 1 – 3 ft. tall
- Its fern-like foliage makes it a lovely choice for soft meadow gardens and will stay green all year with some summer water
- Spreads by rhizomes, which makes it a fantastic slope stabilizer!
- The white umbel flowers bloom throughout spring and summer, providing the perfect landing pad for butterflies to rest and sip nectar from the abundant compound flowers
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Mulefat
Baccharis salicifolia
Available in D40 pots for $8.18 each and TP4 pots for $14.30 each!
- Deciduous perennial shrub that grows rapidly to 8 – 10 ft. tall
- Grows in dry, rocky arroyos with an upright open form
- Sprouts suckers, forming a graceful thicket, which can provide excellent cover for birds…and people! Great screening replacement for Oleander
- A lovely, abundant food source for a variety of insects
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Coyote Mint
Monardella villosa
Available in D16 pots for $7.30 each and 1-Gal pots for $14.50 each!
- Perennial wildflower that grows as a small, mat-forming shrub about 2 ft. tall and wide
- Lavender flowers provide valuable nectar for many butterflies throughout the summer
- Leaves have a lovely minty scent that can be seeped to make tea
- Perfect for planting under an oak or in dry locations with either shade or sun!
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Sale plants
Looking to create butterfly habitat on a budget? We’ve got you covered! Check out these wonderful nectar sources at a discount– they’ve gotten a bit rootbound (but still healthy!) while waiting for their perfect new home, so they are more than ready to get in the ground and get to work providing food for the Monarchs!

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Marsh Gumplant
Grindelia stricta var. angustifolia
Available in D16 pots (50% off) for $3.85 and D40 pots (25% off) for $7.43 each!
- Gumplants are a fun addition to any garden, and this marsh-loving variety will tolerate heavy clay soils and part shade, growing into an evergreen perennial sub-shrub between 3 – 5 ft. tall and wide.
- Produces many bright yellow flowers per bush from spring to fall, providing nectar to pollinators including Monarchs! It is also a very important plant in restoration work and for providing protection and habitat for the California Clapper Rail
- The button-shaped flowers produce a “gummy” resin that has been used to make chewing gum and adhesives.
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Western Goldenrod
Euthamia occidentalis
Available in D16 pots (50% off) for $3.30 each!
- This deciduous, spreading perennial grows to about 4 ft. tall, and loves water–plant along rivers, streams, tidal channels, or fresh to brackish marshes.
- A colorful, sunny addition to the garden, and an excellent wildflower for pollinators, blooming throughout the summer and fall.
- A patch of goldenrod in bloom is one of the best ways to view native pollinators–we see these covered in native bees, butterflies, wasps, and beetles galore!
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Buttonwillow
Cephalanthus occidentalis
Available in D16 pots (75% off) for $1.93, and D40 pots (50% off) for $4.95 each!
- Is there a more whimsical native shrub than the buttonwillow? We adore their new leaves as the emerge in spring, with twisty stems giving way to bright pink, to yellow, to eventually lime green leaves, and the pom pom shaped white blooms in fall!
- Fast growing, this winter deciduous shrub will get to be 6-12 feet tall
- Though it naturally occurs in damp areas, it is also well adapted to drier locations, just be sure to keep an eye on watering for its first season or two
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Mock Heather
Ericameria ericoides
Available in D40 pots (75% off)for $2.48 each!
- AKA California goldenbush
- This is a small mounding, evergreen shrub grows to about 3 ft. tall and 3 – 4 ft. wide
- The golden colored flowers cover the plant from late summer into fall, providing late season color, pollen and nectar
- Happiest in a sandy soil or coastal conditions
- Looks its best with a bit of winter pruning
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We hope you’ll join us at… | |
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We are a proud sponsor and vendor for the first ever Bay Area Butterfly Festival, hosted by our friends the Monarch Milkweed Project and the Vallejo People’s Garden in conjunction with the Solano and Contra Costa Resource Conservation Districts!
This will be the largest Butterfly Festival on the West Coast!
There will be a food court, a beer garden, a main stage with live music, a children’s stage with an area filled with activities and fun, and over 100 vendors including us (yay!), artists, conservation, pollinator, and other groups.
You and your family can learn all about our pollinators, how to plant milkweed and native plants for Monarchs and pollinators, and so much more!
Date: Sunday, May 19th 2024
Time: 10am to 5pm
Place: Mare Island Promenade at 860 Nimitz Ave. Vallejo
Cost: $5.00, 12 and under are FREE
If you would like to attend (which we really hope you do!)…
Get your tickets here:
www.bit.ly/BABF2024
If you’re interested in volunteering, please fill out this form:
https://forms.gle/o3Bx27kFusyriu2P6
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Monarch Migration and Overwintering
Tropical Milkweed risks
Aphids
Native Milkweed
Nectar plants
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Happy Spring, ‘Bee’ Well, and Go Natives! from all of us at the Watershed Nursery
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