Irritating Irrigating - How much water and when?

Unless one wants a yard of sand, rock, and scattered creosote bushes, it takes water and some sort of irrigation system.  My mother loved to go out early in the morning, turn on a faucet and greet the sun, hose in hand, as she watered plants.  I have a much larger yard than she did, and prefer to sleep late.  So I let my automated system do the watering.

The first few years, I asked nursery men and landscapers, lawn maintenance crews and horticulture experts -- How long do I run my lawn sprinklers and how often?  How long do I run the bubblers in my orchard and how often.  Their answer was always, "That depends."  They said that I should observe the plants and I would know when they weren't getting enough water.  So 10 years and many dead plants later, I am just beginning to get the information to  figure it out.  And by the way, most of my plants died from underwatering, not overwatering as the experts predict.  After all, I moved here from a very wet and humid Arkansas, so my tendency was to underestimate supplemental water needs in this windy arid climate.  very time it rains in Barstow, it is amazing how my plants perk up.  And every tine it rains in Barstow, I think that I can turn off my watering system, but that is only true for the lawn and low water plants.  It doesn't rain very often, and when it rains, it doesn't rain very much.  At least not where I live.

What I already knew:
                    1 cu. ft. water = 7.4 gal.
                    1 gal. water = 0.135 cu. ft.
                    1 sq. ft. water  1 inch deep = .62 gal.
                    1 gal. water = 1.62 sq. ft.-in.

What I have learned recently thanks to Dave Palumbo of Rainbird and Victor Valley College:
                    sprinklers spread 1.58" water per sq. ft. per hr. which is 0.98 gph
                    1 bubbler emits 1-2 gpm (gallons of water per minute)
                    1/2" polyethylene irrigation tubing should be limited to 4 gpm,
                           also 1//2" PVC pipe
                               How much it delivers depends on what is connected to it.
                                     e.g. 4 bubblers max
                    1/2" soaker hose delivers 1 gph of water per foot
                               i.e. A 60' foot soaker hose = 1 bubbler,
                                     but delivers the water over a greater area
                     1/2" dripline delivers 0.6 gph or 0.9 gph per inline emitter,
                               The emitters are spaced every 12", 18" or 24"
                               i.e. A 100' dripline with 0.6 gph emitters every 12" = 1 bubbler,
                                    but again over a greater area
                     1/4" irrigation tubing should be limited to 17 gph
                     1/4" soaker tubing delivers 0.33 gph per foot
                     1/4" dripline delivers 0.5 - 0.8 gph from each inline emitter,
                                The emitters are spaced every 6" or 12"
                                 At most 35 emitters can be used

The problem of course is that knowing how much water the irrigation system delivers, still does not tell us how long it should run and how often.  For example, if Barstow averages 4" rain per year, then that is all the water native plants should need, or maybe a little more to perform well if they are close together.  But obviously dumping 4" of water on them on August 12 isn't going to do it.  Nor will giving them 1/3" of water on the first of each month.

It helps to know that trees need the water to reach roots at a 3' depth
                                shrubs                                                   at a 2' depth
                                annual & perennials                             at a 1' depth
                                lawn                                                      at a 0.5' depth
And we need to know whether the soil is sand, loam, or clay.  My soil is sand, but some parts of Barstow have clay.  Water penetrates the different kinds of soil differently.
                                 sand          1" water penetrates 12"
                                 loam         1"                               8"
                                 clay           1"                               4"
So more water must be applied to clay soil to reach a certain depth, than to sandy soil.  But clay soil holds the water longer, so it does not to be applied as frequently.  Also, in clay soil the water spreads almost as far as it penetrates.  In sandy soil it penetrates twice as far as it spreads.  Therefore bubblers or whatever can be farther apart if the soil is clay than if it is sand.  The ideal of course is to build up the soil to where it is all loam.

The factors that influence irrigation runtime and frequency are: plant type, planting density, climate, microclimate, soil type, time of year, weather, and type of irrigation delivery system.   Rather than go through all of the calclations here, I'm going to give some formulas and  tables for watering that I have worked out.  Take them with a grain of salt and if they work, let me know.  Most of the factors have values that are guesstimates at best, although gesstimates of the experts, not me.

select a value from each category:
     plant water needs                           plant form
     p = 0.2  drought tolerant                f = 0.3  grass
           0.5  moderate water                        0.6  annual or perennial
           0.8  regular water                            1.2  shrub
                                                                    1.9  tree

      type of irrigation
      i =  2.55    gph  sprinkler
           60.0     gph bubbler at 1 gpm
             1.0      gph   soaker hose
             0.6     gph   inline emitter 1/2" dripline
             0.5     gph   inline emitter 1/4" dripline


Assuming each type of irrigation is on a separate valve, then with sandy soil, the runtime for the valve should be

                        T = 60 x  f / i   minutes

This is true year around as the water always needs to penetrate to the root zone of the plant.  Obviously when it is windy, more water is needed and when it is raining, less water is needed.

  T(minutes)          grass         annual        shrub        tree    in sandy soil
sprinkler                   7                14              20             45
bubbler                   0.3             0.6             1.2             1.9
soaker hose            18                36              72            114
1/2" dripline           30               60            120            190
1/4" dripline           36               72            144            228

This table assumes there are enough sprinklers, bubblers, emitters, etc. to cover the area under the plants.

The amount of water a plant needs each month depends on the evapotranspiration rate.  I am using the seasonal rates for Barstow.

     evapotranspiration
     e =   1.67 gal.. per month       cold weather
            4.09 gal.  per month       mild weather
            5.58 gal.  per month        hot weather

Then the frequency of watering is

                         F = e x p / f   times per month
or
                         every 30 / F days

For clay soil the runtime should more or less be doubled and the frequency halved.

  F (regular water)         cold          mild            hot
     (times per month)
grass                                 5             11              15
annual/perennial            3               6                8
shrub                                2              3                 4
tree                                   1              2                 3

New plants should be watered more frequently: new trees or shrubs with the frequence of annuals, and new annuals with the frequency of grass, because the roots have not yet reached the standard depth for the form of plant.

Note - I got my basic information from a course in irrigation at Victor Valley College this Fall.  The formulas and tables are my own.  I have not yet gone through a year using these figures although I am going to do so.  Next year I will let everyone know how they work.

Whatz That? - Barstow agaves & kin

Agaves are native to the Western Hemisphere.  The Old World equivalents are Aloes and Bulbines.  The following list contains the agaves, aloes, and bulbines that I have in my garden in Barstow, most of which are grown in sheltered locations.  The only agave that is recommended by the Sunset Western Gardening Book for Sunset zone 11 is the Agave parryi.  No aloes or bulbines are recommended as they are not thought to be sufficiently winter hardy.  However, I have two bulbines and half a dozen aloes that have survived several winters in a sheltered location.  They are included in the list below..  I have not included pictures of the varieties that are not doing well. But if there is not a picture, do not assume it is doing poorly.  Some of my plants are too small to look much like their mature shape.  Most agaves are marginal for this area, so unless I am assured that they will take both the summer sun and the winter snow, I plant them in areas with some shelter.  Most agaves reproduce by offset.  Then when the mother plant blooms, and subsequently dies, the pups have survived.  Aloes also form offsets.  But aloes do not die when they bloom.  Supposedly a plant can be identified as an aloe or as an agave by the direction the teeth along the sides of the leaves are pointing.  The agave teeth point toward the root and the aloe teeth point toward the tip of the leaf.  I don't find this very helpful as the teeth don't seem to be consistent.

Century Plant/Agave americana
This plant is at the Barstow Public Library.  The extra water from the lawn has helped it grow large quickly.  Mine are a lot smaller and not as pretty.  They don't receive as much water.  The leaves are banded which is unusual for Century Plants, but common for those in Barstow.  I assume they have a common mother plant.

Varigated Century Plant/Agave  americana 'marginata'
This plant is at Dana Park.  Mine are much smaller and probably do not receive as much water.

Striped Century Plant/Agave americana mediopicta alba
2'x1' rosette
This is a small plant that offsets readily.  Again mine are smaller and probably receive less water.

Narow-leafed Agave/Agave angustifolia
3'x3' rosette
This plant has a beautiful shape.

Squid Agave/Agave bracteosa
3'x4' clump
One of these looks like a squid.  A clump of them just looks like a clump.

Agave colorata
This agave has grown where it is planted and has produced offsets.  However it does not look very good.  I'm not sure if it gets too much water ot what, so I will plant one of the offet in a drier location.  It is a small cup-shaped greyish plant.





King Ferdinand's Agave/Agave ferdinand-regis

Green Goblet Agave/Agave ferox
3'x3' rosette
A beautiful plant

Threadleaf Agave/Agave filifera
2'x2' rosette
As the name indicates, there are plentiful threads on the leaf margins.

Agave franzosinii
I just bought this one at Cactus Mart in Morongo Basin.  It may be marginal in Barstow, so I am thinking of keeping it in a pot, eventually a big beautiful pot of course.  Given the right conditions it becomes a very large fountain-shaped plant.

Agave gentry 'Jaws'
3'x3' rosette
Like many of my agaves and yuccas, I bought this online from yuccado.com.  Their website gives a lot of information about each plant.






 Gypsum Century Plant/Agave gypsophila
This one also came from Cactus Mart in Morongo Basin.  The people there are very knowledgeable about mature size and hardiness of their plants.  They said it Barstow might be too cold for it, so I will put it in a pot in a sheltered place.




Chisos Agave/Agave harvardiana
Agave neomexicana
Agave ocahui

Agave ovatifolia
This is a new plant for me.  From the pictures I have seen of mature ones, it reaches a fountainlike 5'x5'.






Agave parrasana

Agave parryi 'Cream Spike'
Most of the Agave parryi family are hardy in Barstow, but Yuccado Nursery which sells this, questions the identification and also it's hardiness.  It is a small gem about 5" in diameter, and is beginning to offset.  I have it in a sheltered location.  When it has enough pups that I am ready to divide it, I will try other locations.



Agave parryi var. huachacensis

Parry's Agave/Agave parryi var. parryi
3'x3' rosette
This is one of the most common agaves in nurseries.  It is one of the few recommended by Sunset for zone 11.

Artichoke Agave'Agave parryi var. truncata








Agave potrerana

Maguey de Pulquey/Agave salmiana
4'x3' rosette
offsets readily
The leaves have an attractive striped coloring.

Sharkskin Agave/Agave scabra
2'x3' rosette







Maguey/Agave schidigera 'Durango Delight'

Agave striata 'falcata'
1'x1' rosettes
Although with this plant, I am not sure how to tell a rosette from a clump.  Unlike most agaves, the leaves are stiff and hard rather than succulent.



Sea Urchin, Hedgehog Agave/Agave stricta

Tequila Agave/Agave tequilana
This becomes quite a large plant.  But as it is marginally hardy here, I will keep it in a pot, which will keep it smaller.  The leaves are narrow because it has been in a shady place.




Agave tourmeyana 'Bella'
Utah Agave/Agave utahensis

Queen Victoria Agave/Agave victoria-reginae
When these grow to 2'x3' they are incredible.  However, then they bloom, and like all agaves, die.

Octopus Agave/Agave vilamoriana

Blue Agave/Agave weberii

4'x3' rosette

These are beautiful large rosettes with their rippled leaves.  They grow extremely well here.

Agave x 'Sharkskin Shoes'

Agave ssp 'Mr. Ripple'

Aloes are not winter hardy in Barstow unless they have at least a little protection.  Also most of them are damaged by the summer sun.  So my aloes are either on the east side of walls, or under pine trees.  Unfortunately it is not easy to pick up pine needles that fall around them.

Lace Aloe/Aloe aristata

4'x4' clump

Desert Aloe/Aloe desertii
2'x1' clumping
yellow flowers on a tall stalk
A friend gave me my start of these.  Soon I had them planted all over the yard.  They grow with almost no water, and are the hardiest aloe I have found.  My identification as Aloe desertii is tentative.  But if that isn't its name, it ought to be.
A. desertii is native to the eastern parts of the Mojave Desert among other places.

Spider Aloe/Aloe humilis

4"x6" cluping
This is another small aloe that forms clumps.

Coral Aloe/Aloe striata
3'x2' offsets
This aloe is edged with pink when it grows in a location with more sun than the ones shown.  However, it will not take full sun in Barstow.  It is easy to grow and easy to propagate.  The bright orange flowers are borne on long stalks.

Karasberg Aloe/ Aloe striata ssp. Karasbergensis
This variety of the Coral Aloe has interesting striped leaves.  I have not decided where to plant mine yet, or if I should leave it in a pot.  It is said to be less hardy than the Coral Aloe.





Aloe vera/Aloe vera

Aloe ssp. 'Blue Elf'
This is a short clumping bluish aloe only about 6" high.  The first one I tried died.  I'm not sure if that was because of the winter cold, so I am trying again.

Bulbine frutescens/Stalked Bulbine
Bulbine latifolia

Most of these plants are on drip irrigation and are watered 10 min. once a week in Summer and 5 min. once every 2-4 weeks in Winter.  The aloes and those agaves which are under my pine trees, I water by hand.

Whatz That? - Barstow yuccas and kin

Yuccas and Nolinas are native to the Western hemisphere.  The Old World equivalents include the Dasylirions, Hesperaloes, and many similar species such as Furcraeas that are houseplants in Barstow because they are not winter hardy here.  Unfortunately nurserymen cannot always distinguish between them.  The following list is those plants that are in my garden.  The second list is additional plants that are recommended by Sunset's Western Gardening Book as growing in zone 11.  I first planted these species ten years ago, and have been planting different varieties ever since.  None of them have been in the ground long enough to show their mature shapes.  Therefore I am including pictures only of those that already have a distinctive shape, or have distinctive coloration. 

Sotol, Green Desert Spoon/Dasylirion acrotriche
All Dasylirions are slow growing, so this one, even though it has been in my garden for a few years, has yet to take on the usual hemispherical shape.

Great Blue Sotol/Dasylirion berlandieri
Here you can see the typical saw-toothed edges of Dasylirion leaves.  Unlike yuccas, the tips of the leaves are not sharp, but the edges are.

Mexican Grass Tree/Dasylirion longissima
Some day this will be a tall column topped with a pompom.  That will probably be past my lifetime.








Green Sotol/Dasylirion texana

Desert Spoon/Dasylirion wheeleri
This is the Dasylirion that is most frequently seen in gardens.









Hesperaloes are grown for the colorful flowers.  To some extent they reseed.
Hesperaloe funifera
Red Yucca/Hesperaloe parviflora               clump, red or yellow flowers


Nolinas are good substitutes for yuccas as they do not have sharp points on the leaves.  The flowers are similar to yuccas but not as pretty.

Nolina funifera
This nolina has threads on the edges of the leaves.









Nolina longifolia                                 6'x6' shrub

Beargrass Tree/Nolina matapensis     
6'x6' shrub
a beautiful fountain-shape plant





Beargrass/Nolina microcarpa              4'x7' clump
Nolina nelsoni                                    12'x6' tree
Parry's Beargrass/Nolina parryi           15'x6' tree

Texas Beargrass/Nolina texana           
5'x5' shrub
This nolina just looks like a messy overgrown clump of grass.  It blooms reliably, but the long stalks of flowers aren't particularly pretty.

Spanish Bayonet/Yucca aloifolia        
10'x5'   clump
flowers nestled in leaves
This yucca requires a little more water than other varieties.  I have all my desert plants on drip irrigation.  The amount of water can be varied by the distance from the source and the button flow controller.  The is one of the yuccas frequently found in nurseries.

Variegated Spanish bayonet/Yucca aloifolia 'marginata'     
10'x10' clump
yellow stripe on edges of leaves









Arkansas Yucca/Yucca arkansana                              2'x2' rosette

Joshua Tree/Yucca brevefolia    
15'x10' tree
flowers raised above leaves
This is a moderately slow grower.  I bought mine 10 years ago with only 3 heads and now it has a dozen or so.  However, that is an effect of watering.  For a number of years I had it on drip irrigation and that caused it to branch out and to offset.  Now it receives no water at all except for what the roots can find.




Silver-edged Yucca/Yucca constricta      clump, white-edged leaves, flowers high, dies after blooming
Soaptree Yucca/Yucca elata        6'x8' tree,  flowers high
Yucca Endlichiana                               tree
Adam's Needle/Yucca filamentosa   3'x5'   flowers high

Yucca filamentosa 'Color Guard'             
 3'x5' rosette
flowers on high stalk
occasional red stripe on leaves

Golden Sword Yucca/Yucca filamentosa 'Golden Sword'  
4'x4' rosette
flowers on high stalk
gold stripe on leaves
I found this plant at Lowe's last month and bought two.




Yucca filifera                      25'x2' tree  flowers hanging

Yucca flaccida 'Gold Sword'          
3'x5' clump
flowers raised above leaves
gold stripe on leaves

Spanish Dagger/Yucca gloriosa              
10'x8'   
flowers raised above leaves
This is the yucca seen all over the Los Angeles area where it is often planted near lawns.  It requires more water than other yuccas.  it is not winter hardy in Barstow, but freezes back and branches when it comes out again.  Mine look messy rather than stately because they have died back so many times.

Variegated Spanish Dagger/Yucca gloriosa 'variegata'     
8'x6' tree
flowers raised above leaves
blooms in Fall
This species must be in a sheltered location as it is marginal in Barstow and will freeze back.



Yucca linearifolia                           5'x5' shrub
Pale Yucca/Yucca pallida            2'x3' cluster
Yucca pallida x rupicola

Weeping Yucca/Yucca recurvifolia           
10' clump of columns
flowers raised above leaves
However mine has been in the ground for 10 years and is simply a clump, not a clump of columns.  It does bloom every Spring.







Yucca recurvifolia 'Gold Ribbons'          4'x4' shrub

Margaritaville Yucca/Yucca recurvifolia 'Hinvargas'
clump
yellow stripe on leaves
The first year I thought this variety was mislabeled as it seemed unexpectedly sensitive to the winter cold, but it perked up with warmer weather.

Blue Yucca/Yucca rigida              
12'x5' rosette
flowers nestled in leaves

Beaked Yucca/Yucca rostrata           
12'x9' column  
flowers on high stalks
After 10 years in the ground, this is a beautiful specimen plant.






Yucca rostrata 'sapphire Skies'
Twisted-leaf Yucca/Yucca rupicola     2'x4' shrub

Mojave Yucca/Yucca schidigera   
16'x10' clump  
flowers nested in leaves
This particular spectacular clump is on the south side of I-15 just beyond Outlet Center Drive.  This native yucca is rarely found in nurseries.  I suppose partly because it is native, and partly because the leaves are stiff and sharp.

Mountain Yucca/Yucca schottii           
20''x5' column  
flowers nestled in leaves
After 10 years in the ground, this plant is still a small clump.

Thompson's Yucca/Yucca thompsoniana 
10'x5' clump
flowers raised above leaves
blooms in Fall

Our Lord's Candle/Yucca whipplei  
3'x6' rosette
flowers raised high
dies after blooming






Chaparral Yucca/Yucca whipplei ssp caespitosa              3'x5' clump, flowers high

All of these pictures are from my garden.  I'm afraid I'm a bit of a collector when it comes to desert plants.  But I try to be a decent landscaper too.