Plant breeding is a wonderful hobby that attracts an array of hobbyists, as well a plant professionals. Many plants, such as hemerocallis, hosta, hibiscus, and iris, are so easy that they attract the majority of hobbyist breeders. Professionals and the craziest of the breeders occasionally focus on more difficult plants that few others are willing to try. This includes plants where the pollen exchange is complicated either by timing, incompatibility, or other constraints. Such is the case with century plants (agave).
Peak flowering season for 2023 is drawing to a close at JLBG, while one new agave is just in mid-spike. We only had 13 different agaves flower this year, compared to 18 last year. Fortunately, we are able to save and store pollen in the refrigerator, where it will remain viable for at least 5 years.
Below are a few images of Steve Guptill of our garden staff, as he made crosses last week. At the bottom of the first image is our volunteer agave specialist, Vince Schneider, who is training Steve to make the crosses.
With agaves, the process involves waiting for the stigma to become sticky–a sign that it’s receptive to the pollen. Pollen is then gathered from our prospective father and then hauled up the 21′ ladder to the waiting stigmas. Not only are you high in the air, but you’re working around hundreds of bees that are busy gathering copious amounts of nectar.
Assuming we get seed set, they should be ripe by late September/early October.
Both spiking agaves in the photo below are our selected hybrids from previous years breeding.
Looking great in the garden this week is Agave x pseudoferox ‘Green Goblet’. This 1996 introduction from the former Yucca Do Nursery is one they found in Mexico and brought back as a single pup. Our original plant flowered in 2011 after 11 years in the ground, so this specimen has re-grown from one of the remaining small pups. Since we’re now at 11 years since last flowering, we’re preparing for a new blessed event. Since we can usually tell by now if it’s expecting, which it is not, the odds are pretty good for a 2024 flowering. Plant Delights Nursery will be offering A. ‘Green Goblet’ for sale in 2023.
In 2014, we decided our goal for the years’ century plant breeding project was to see how large a Zone 7b winter hardy agave we could create. We had seven agaves flower that year, but only two had the epic proportions we required.
One of those was a selection of Agave x protamericana from a Yucca Do collection in Northern Mexico. By the time of flowering at 15 years of age, it had reached 5′ tall x 9′ wide.
Agave x protamericana and Agave americana are the two largest blue-foliaged agaves, but only Agave x protamericana is winter hardy for us, here in Zone 7b, since it also has some ancient genes from the hardier Agave asperrima, which adds slightly to its winter hardiness. You can distinguish the two plants by feeling the back of the leaves. Agave americana has smooth leaf backs, while Agave x protamericana has sandpapery leaf backs. The largest size listed for Agave americana in Howard Gentry’s Agaves of Continental North America, is 6′ tall x 12′ wide.
At the same time we had a blind flower shoot on our giant Agave x pseudoferox ‘Bellville’. Agave x pseudoferox is another ancient Mexican hybrid in need of a DNA workup. We think it’s probably a hybrid of Agave x protamericana with Agave salmiana var. ferox and possibly Agave gentryi). Commercially, it’s usually called Agave salmiana var. ferox, which is similar in appearance, but with absolutely no winter hardiness.
Prior to full flowering at 15 years of age, our giant specimen of Agave x pseudoferox ‘Bellville’ had reached a mature size of 4′ tall x 8′ wide. We were able to make the cross prior to it fully flowering, by using something we mentioned above that we call “blind shoots” or boners.
Being monocarpic plants, the rosettes of most agave species die after flowering, but side shoots are an interesting phenomenon we see on all of our Agave x pseudoferox cultivars and hybrids. These “blind shoots” emerge from underground stolons instead of from a rosette. They are much shorter than normal flowering shoots which emerge from the rosettes (2′ tall vs. 20′ tall), and they have no impact on the life expectancy of any of the rosettes.
In the case of Agave ‘Bellville’, our plant began producing blind shoots five years prior to the clump producing a full size, rosette-based flower stalk. The beauty of blind shoots is that they breed and pass along characteristics of the parent without the need for a tall ladder.
We gave our hybrids the seed strain cultivar name, Agave ‘Bluebell Giants’. From these, we selected 23 clones, which were planted in the trial fields in 2016. Of those, only 4 survived our subsequent trials for winter hardiness.
Our best and most winter hardy seedling from the cross pictured below is now 6 years old in the garden. We’ve given this the name Agave ‘Supersize’. It has achieved a size of 6′ tall x 8′ wide in that time. To put this in perspective, it is larger at 6 years old than both parents were at 15 years old. If Agave ‘Supersize’ waits until age 15 to flower, it could easily reach more massive proportions that any Zone 7b winter hardy agave in existence.
Our 2016 century plant hybrid is looking quite lovely in the garden this month. This plant, which we named Agave x victorifolia ‘Prince of Whales’, is a hybrid of the Whale’s tongue century plant, Agave ovatifolia (male parent), and the Queen Victoria century plant, Agave victoriae-reginae (female parent).
Since both parents are non-offsetting, this means that the offspring will grow to maturity, flower, then die. Consequently, in order to be able to propagate and share, we will have to drill out the central core of the plant to trick in to offset. While this ruins the appearance of the original, it’s the only way for this to ever be shared and preserved. This plant has been in the ground since 2018, so we expect to have another eight years (guessing) prior to flowering. Consequently, so we’ll probably gamble on waiting a few more years before performing surgery. Winter hardiness is Zone 7b-10b.
A few weeks ago, we posted images of the flower spike of our Agave ovatifolia ‘Vanzie’ just beginning to spike. Now, the giant beast is in full flower. The first photo below is the plant with its full expanded stalk in full bud, just prior to opening. After that, each image shows the progression of the flower development.
Agaves are monocarpic, so those species like Agave ovatifolia that do not make offsets will die after flowering. Agave ovatifolia is, however, one of a handful of species that usually forms baby plantlets on the tip of flowers stalk after seed set.
First flowers just beginning to open
We set up our Little Giant ladder, which allows us to climb up, collect pollen and to make crosses with other agaves.
The lower flower clusters open first and flowering continues to progress each day moving higher up the stalk.
Climbing the ladder gives you a bird’s eye view of the amazing buds as they are ready to open…usually 200-300 per panicle.
Below is a half-open flower panicle. The pollen is ripe before the stigma is ready to receive pollen, so pollen can be easily gathered without worry of self pollination.
Below is a fully open flower panicle. Each panicle weighs 5-10 pounds. No wonder the stalk needs to be so sturdy. Once the temperature warms in the morning, the flowers are abuzz with pollinators…mostly bees.
Looking down from above the flower panicle makes a pretty crazy photo
Our intern Zoe is working with our volunteer agave curator, Vince Schneider to gather pollen and make crosses with other previously gathered agave pollen
I usually don’t climb this high…a fear of heights, but this photo opportunity was just too good to resist
In case you missed this section of the garden during spring open house, this is where we created a small vignette that comprises both bog and desert conditions in the same space. The low central area was created for pitcher plants and other bog lovers, while the higher areas to each side, are home to dryland loving plants like agaves and bearded iris. We hope to show how dramatically diverse habits can be created in a very small space. The wet space is created by installing a seep, which is nothing more than a continually dripping water line.
Just over a year ago, we built a new berm garden, adjacent to our Open House welcome tent. Here is that garden today. The soil is composed of 50% Permatill (slate gravel), 25% compost, and 25% native soil). This is in an unirrigated section of the garden. Like all garden spaces at JLBG, no commercial fertilizers are ever allowed. The exceptional drainage and high nutrient content from the compost and Permatill result in an amazing growth rate.
If you’re able to visit during this years spring open house, it will be hard to miss the look of love in the air. We have a record 20 century plants in spike in the garden…a number far surpassing any flowering record we’ve set previously.
Agaves are a genus of mostly monocarpic plants…they live their entire lives to flower once, then after experiencing a giant-sized orgasm, they fall over dead. In the wild, many species take up to 100 years to flower, which is why the name century plant stuck as a common name. In our more rainy climate, our century plants typically flower in 12-15 years. Several of our current crop are actually less than a decade old, but their enormous size has already been achieved, so they’re ready to reproduce.
Some species of agaves offset, and in this case, only then central rosette dies, and the offsets continue as is the case with bromeliads. Those agave species which never offset are one-and-dones, but hopefully will leave behind a plethora of seed for the next generation. From the start of the spikes to full flower is usually about 8 weeks. Below are a few of our babies in spike.
It’s always interesting when we introduce a plant we think is an incredible addition to the garden, but virtually no one purchases it. Thank goodness, it doesn’t happen too often, but I’m reminded of one such case every day when I get home and admire our row of Agave x striateosa ‘Straight and Narrow’. This 2015 introduction was the first ever hybrid introduction of Agave bracteosa and Agave striata…both non-spiny century plants.
We couldn’t stand to throw out all the plants that didn’t sell, so we planted a row under a wide overhang along our home, where they never see any water, and are in shade for more than half the day. Here is one of those plants five years later, providing a texture and form that you simply can’t find with any other plants that tolerates those conditions.
We have a second seedling from the same cross, which we’ve never been able to share, but which flowered in 2015. Despite our best attempts, we were not able to get any seed set. Now, we await the first flowering of this clone in the hopes it is more fertile, so we can create some more unusual hybrids. Unlike most century plants, Agave striata is not monocarpic (doesn’t die after flowering), so we expect this hybrid to also live on in perpetuity after flowering. Winter hardiness is Zone 7b-10, at least.
One of many great attributes of mangaves, compared to one of their parents, agaves, is that they don’t die after flowering. Agaves are mostly monocarpic, which mean that they behave like bromeliads, where each rosette grows to maturity, then dies after flowering. Those species of agave which offset, live on after flowering, by means of un-flowered offsets. Those agave species which don’t offset are a one and done after they flower and reproduce by reseeding.
By incorporating manfreda genes to create xMangaves, the monocarpic trait disappears. After a mangave flowers, it dies to the ground, but like a good zombie, it soon pops back from the dead. Here is a current photo from the garden of two clumps of xMangave ‘Blue Mammoth’. The first, larger clump has not flowered, but should do so next year. The second clump with all the offsets, flowered in 2020, and re-grew to this point in 2021. Next year, the rosettes will continue to re-grow in size.
This summer, two of our spiking clumps of Agave ovatifolia became dislodged from the ground during a violent thunderstorm. We wondered if they would still set viable seed despite being without roots, since the energy built up from 15 years of growth was still in the foliage. We made several crosses without having to set up a ladder and it appears that we’ve got good seed set. Nature is amazingly in its desire to survive.
The bees are buzzing with excitement over the impending flowering of five clones of Agave ovatifolia here at JLBG. We’ve never had a year with quite this many whale’s tongue agaves spiking at once, so it should be quite a show. Here’s our Agave ovatifolia ‘Frosty Blue’, which was the first to spike, but the other four aren’t far behind. Full opening probably won’t occur until our summer open house, but in the meantime, they are still something to marvel over.
We posted this a few weeks ago as our Agave ‘Mountain Man’ (A. gentryi x montana) prepared to open. We’ll, the big moment is here…below are a few shot from today.
The seed were wild-collected in Mexico in the late 1990s by our friends at Yucca Do, and our seedling was planted in May 2000, so it took 17 years to flower. Fingers crossed for good seed set, and fortunately we have many more agaves in flower (and a tall ladder) to help the process.
Look what showed up in the garden. Our specimen of Agave ‘Mountain Man’…a hybrid of Agave montana and Agave gentryi decidied to flower for our spring open nursery and garden. This unusual hybrid starts its flower spike in the fall, which stops for the coldest part of winter, then starts growing again in spring. The spike showed no damage despite a winter low of 13 degrees F. Be sure to check this out when you visit…located just behind the welcome tent.