Plant profile: Psoralea pinnata, the Kool Aid bush

Today we have another wonderful article by P. Garden supporter and Potrero Hill resident Josh - click his name to see all his articles. Enjoy!
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Plant Profile: Psoralea pinnata, the Kool Aid bush
Fabaceae Family

A few years ago, I was on a garden tour in San Francisco. As a group of us plant geeks walked down a street, hunting for the address of the next garden, we passed a small tree, or large shrub, covered in a haze of blue flowers. From a distance, it appeared to be a Ceanothus, but as we got closer, we realized that it was a large Psoralea pinnata, the South African shrub pea, or fountain bush. It was definitely popular with the local bees and other pollinators, and was practically buzzing with their activity.


Psoralea pinnata has been grown in gardens since the late 1600’s, when it was introduced to English gardens from seeds brought back from South Africa. Like many South African plants, it thrives in the milder parts of California, where it is safe from frost. The name fountain bush refers to its habit of growing along streams and in wet places in the wild. In cultivation, it does best in well-drained soil, and needs little water once established. It can be pruned after blooming to limit its size, or it can be allowed to grow into a small, elegant tree up to 12 feet tall. The flowers are not very large, but they blanket the ends of the branches in a cloud of color ranging from blue to purple. They look almost like blue moths; in fact, the flower structure is described as ‘papillonaceous’, or butterfly-like, by our botanist friends. When in bloom, the amazing fragrance is similar to grape drink, leading to another common name: the Kool Aid bush.

The Latin name for this plant comes from the Greek word ‘psoraleos’, meaning warty. This refers to the dots that cover the leaves. The species name, ‘pinnata’, refers to the pinnate form of the leaves.

Psoralea pinnata is easy to grow from seed. While small, make sure it gets regular waterings. Once it is larger and planted in the ground, it can do with occasional watering during the dry season. Flowering is best in full sun, although the plant can tolerate some shade. Seedlings can often be found growing near an older plant, and are easily dug up and given to lucky friends.

There is a small kool aid bush in the Pennsylvania Garden, near the bench. It hasn’t bloomed yet, but hopefully this summer we will all be enjoying the scent of grape Kool Aid and watching the bees dancing around this plant.

Update: Photos above show our plant flowering away!

UPDATE December 2015:
After 7 years in the ground and 4 years of drought, this plant grew to 15' tall but very sadly succumbed to the drought in the end and died after years of beautiful flowers and an excellent, evergreen form. I would love to replace it, even though it could not handle extreme drought.

Mulch

Today we have another splendid article by P. Garden supporter and Potrero Hill resident Josh. Enjoy!
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Mulch is such an evocative word. It always makes me think of something vaguely mysterious, with an earthy smell and unclear origins. In reality, mulches are one of the gardener’s best friends. There are many different materials that can be used as mulch, but they all have many of the same benefits for the garden. Mulches shade the soil, keeping plant roots cool in the hot sun, and warmer at night when the air temperature drops. Mulches also help the soil retain water, so that the soil moisture is more even between waterings, and can reduce erosion from water runoff. Mulches can also reduce weed growth in the garden. Many types of mulch decompose over time, adding nutrients to the soil. Besides these practical reasons for using them, many mulches just make a garden look nicer.

There are organic and inorganic mulches. The inorganic mulches include plastic sheeting, gravel, tumbled glass, and in some gardens, bowling balls and broken dinner plates. Obviously, these mulches are not going to break down and add nutrients to the soil, but they will perform all the other roles of mulch that are listed above. Some plants, such as succulents and cacti, don’t like lots of organic stuff in their soil or at their feet. Inorganic mulches, such as pebbles, gravel and rocks, are ideal for these plants. I’ve seen tumbled glass  used as a striking mulch in several gardens. There are few limits in terms of materials that can be used as inorganic mulch, so let your imagination run wild!

The organic mulches include straw, garden compost, leaves, pine needles, cardboard, newspaper, wood chips, bark chips, cocoa hulls, sawdust and lots of other materials. All of these are derived from plants, and will break down over time and add nutrients to the soil. Generally speaking, no matter what kind of organic mulch you use, plan on using at least a 3-inch thick layer of mulch between plants. Keep the mulch away from the bases of plants in order to allow water to enter the soil and to keep the bases of the plants from rotting.

Depending on the material you want to use, there are many sources for mulch. The deep, luxurious mulch in the Pennsylvania Garden was donated by the Bay View Green Waste Management Company. You can contact them if you are interested in getting some mulch for your garden - they make their mulch from the contents of the city’s green bins.

If you are curious about this mulch, check it out the next time you are in the garden. Carefully stick your fingers in one of the planting beds and lift up a bit of the mulch. You will probably find that it is dry on top and moist further down. Most of the beds in the garden are thickly mulched (4 to 6 inches) to help compensate for the lousy soil, so you probably won’t hit dirt if you stick your finger in it. An added benefit of this thick mulch is that the weeds that do manage to grow are usually really easy to pull out! The succulent beds have much less mulch, and we are hoping to get some gravel to use in these beds. If you have any unwanted gravel, let Annie know!

Agaves in the Pennsylvania Garden

This is the first in (hopefully) a series of guest blog posts, written by people who have helped build the garden. Enjoy!
- Annie

Josh is a resident of Potrero Hill, dog lover, artist and gardener. He has spent countless hours weeding and planting in the garden, and can always be relied upon to be the voice of reason in matters concerning correct and aesthetic plant placement. His articles regularly appear in Pacific Horticulture magazine which is published by the non-profit Pacific Horticultural Foundation, and we're delighted to have his article grace this blog!

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A. filifera

As you walk through the Pennsylvania Garden, you can’t help but notice agaves and aloes, since there are some in several of the planting beds. Although they resemble each other, these succulent plants are not even closely related. There are over 700 species of agaves and aloes, which is good news for people who are into succulents. They tend to be very hardy and thrive with little care once established. If you look at the labels for this blog, you’ll see that agaves and aloes have more labels than pretty much everything else- there is a reason for this!

Annie wrote about Aloes in the April 22, 2009 blog entry, so I will focus on the Agaves in the garden.

A. parryi

The Agave family (Agavaceae) includes the agaves, beschornerias, furcreas, yuccas and hesperaloes, among others. The family name comes from the Greek agauos, meaning ‘related to kings and heroes, or noble’. Wow, who knew we had so much royal blood in the garden? The agaves are distinguished by the large spine on the tip of each leaf that most of them possess. Be careful near these plants, or you will add your own blood to the garden… Most of the agaves are monocarpic, which means that they flower once, then die. Luckily for us, most of them send out pups, or baby plants, from their base before they die. Others can only be grown from seeds. The agave’s biggest claim to fame is probably the fact that one species is fermented to make tequila.

A. shawii

Near the entry gate to the garden, you can see Agave filamentosa, also known as Agave filifera, with white filaments curling off of the leaves. This plant hails from Mexico, and sends out lots of pups. (photo top)

Nearby is Agave parryi, (second from top) a pale blue, almost round blob of beauty from Mexico, Arizona and New Mexico. These reappear throughout the dry succulent bed behind the storm drain, and up the hill in other beds. Although it is tempting to touch their wonderfully smooth leaves, the dark spines at the leaf tips are amazingly sharp, so best not to pet them.

A. americana variegata

Agave shawii, (third from top) no relation to Annie, is found along the Pacific side of the Baja peninsula into southernmost California. It is a smaller agave, very slow growing, and happiest near the coast far from frosts.

One of the more obvious plants in the garden is the ginormous Agave americana marginata in the center bed (second from bottom). These plants get huge, so if you plant a cute little baby, make sure you give it plenty of room. There are other variegated Agave americana types, such as A. medio picta and A. variegata. They differ mainly in the length of their leaves and the yellow or white stripes on the foliage. There are also a bunch of non-variegated, blue Agave americana plants in the succulent bed and in the back hill near the compost pile.

A. tequilana

Last, but certainly not least, is a longtime favorite for many of us, Agave tequilana (bottom photo). Native to the state of Jalisco in Mexico, it grows in the wild at altitudes over 1500 meters, so it can take some cold weather. Tequila is made from fermenting the core of this plant after growing it for about 10 years. There is one large, and several small, tequila agaves growing in the succulent bed behind the storm drain. Maybe in ten years’ time we will have the courage to hack them apart and make our own tequila? I don’t think so.

A. attenuata

The spineless A. attenuata is shown at left, growing in the middle front bed. Not all shown, but growing at PG or PRG:

A. americana 
A. americana variegata
A. americana "Lemon Lime"
A. americana medio-picta "Alba" 
A. angustifolia 
A. attenuata 
A. attenuata"Nova"
A. attenuata "Ray Of Light" (since stolen)
A. bracteosa 
A. celsii var. albicans "UCB" (since stolen)
A. colorata
A. decipiens
A. desertii
A. desmetiana "Variegata"
A. filifera
A. franzosinii
A.gentryi "Jaws"

A. gypsophila

A. gypsophila
A. havardiana
A."Joe Hoak"
A. lechuguilla
A. lophantha
A. "Mr. Ripple"
A. murpheyi
A. murpheyi "Engard" - Variegated Hohokam Agave
A. ovata
A. parrasana (probably a hybrid of this species)
A. parryi
A. salmiana ssp. crassispina
A. salmiana 'Green Giant'

A. scabra
A. scaposa (probably)
A. shawii
A. "Sharkskin"
A. sisiliana  
A. tequilana
A. tequilana "Sunrise"
A. weberi "Arizona Star"
A. weberi "Reiner's selection"
A. vilmoriniana (Octopus Agave)
A. vilmoriniana "Stained Glass"

A. weberi "Reiner's selection"