Every spring in most parts of California, the rains come to a stop and a long hot rain free period begins. In these regions summer rains are very rare and, in the rare event that one occurs, it is usually not substantial enough to soak more than a useless 1/2" or so into the soil. I live in such a region at the headwaters of a creek which feeds the Russian river. Like most california creeks in the coastal ranges it is a spawning stream for Salmon and Steelhead. Any water that I don't use goes to feed the creek and keep the baby Salmon and Steelhead alive. If someone doesn't suck up the water which I conserve here when it gets further downstream in order to water their lawn, flush their toilet or irrigate their wine grapes it keeps the Russian River full and cool and livable for these and other fish. I have planted over 100 fruit and nut trees and more are on the way, but there is no way I can irrigate them all. Not only do I like to conserve water but I also don't have much to work with as the spring we use drops to a modest, but so far adequate, 1/2 gallon per minute by the end of the summer in a normal year. A small percentage of trees that require extra water for one reason or another might be irrigated in the future, but the rest will have to make it through the long dry summers using whatever moisture is stored in the soil from the winter rains. I've conceived an idea for a dying mulch system using perennial flower bulbs under fruit and nut trees. If it works the system would provide a permanent solution to soil moisture conservation with a minimal amount of work investment. In addition it will have the added aesthetic value as well as bulbs and flowers which can also be sold to provide additional income.
Imagine this: as the fruit tree loses its leaves in the fall and the rains begin hundreds or thousands of Narcissus bulbs start pushing up leaves from the ground. The leaves grow rapidly with the benefit of the stored energy of the bulbs choking out slower growing weeds completely. In the middle of winter sometime, the ground beneath the tree is a sea of fragrant flowers. In the early summer as the tree is growing rapidly off of the moisture stored in the soil, the Narcissus leaves are withering up and dying in the increasing heat leaving a thick carpet of dead leaves which will protect the surface of the soil from the baking sun and the evaporation of moisture it would bring. Narcissus and another currently favored candidate Amaryllis, are long lived plants dividing into crowded colonies that endure for decades and not unlikely even hundreds of years, so this could be a fairly permanent system.
The options I can see to employing such a system are:
* let everything and anything grow under the trees. Depending on the goals and the site, this might be just fine in some cases, but not in all cases. Grasses are said to be particularly unsuitable as a fruit tree ground cover and we have a lot of perennial grasses that use water through the whole summer.
* weed out some of the more deeply rooted and long lived plants each year to keep the growth restricted to less water hungry plants. I'm not sure I have time to do that for so many trees and certainly know that I don't want to.
* cultivate the soil to kill weeds and leave a layer of tilled up dirt under the trees: This is the so called dirt mulching where the top 4 to 6 inches of soil is kept barren and broken up finely. Its a lot of work, has few other benefits and is ugly. This is an effective method for soil moisture conservation though. Another disadvantage to dirt mulching is that if it is abandoned, the most noxious weeds move in rapidly. Longer established areas of mixed species in a more mature meadow environment tend to keep the thistles, wild lettuce and their ilk mostly out competed.
* Mulch with a layer of some "extra" material like cardboard and wood chips to stifle weeds and prevent water evaporation. This is a lot of work. I use it for tree establishment, but to do it for the life of 100+ trees?... not gonna happen.
* Spray herbicide to kill the vegetation: Really? Sounds nuts to spray herbicide under your food trees.
* Weed torch the weeds: That sounds better than herbicide, but it leaves no vegetative cover on the soil in the winter which is bad news where it rains buckets in the winter. Vegetation generally improves soil, protects it from erosion and can look better than bare soil. this would also leave a caked soil which encourages evaporation of moisture from the soil. Basically, plant cover is good for building and maintaining soil quality and preserving the soil from the destructive effects of sun, rain and wind. Also, bare dirt and mulch don't provide the diversity of life that maintain balance in a healthy system. I'm fairly convinced that, if competition for water and nutrients can be kept within acceptable parameters, fruit trees will grow better in an established ground cover.
The idea of selecting specific plant under stories is not new at all. People have long used permanent and impermanent plantings under trees to achieve specific goals. Permaculturists are all about this idea referring to the combinations of plants that work well together as plant guilds. In trying to research on the net to see if anyone else has tried the method I've decided to try, I did find reference to using Daffodils and "bulbs" under fruit trees. Unfortunately all the references I could find say the same stuff over and over. The book Gaia's Garden by Toby Hemenway recommends planting bulbs under trees for many of the same reasons I want them but suggests a ring of Daffodils at the trunk and a ring at the drip line only. The remainder in the center is to be filled with plants that serve other purposes such as attracting insects, mining deep into the soil for minerals, and various human uses. That sounds like a neat system but effective gardening, and even more particularly effective permaculture practice, is not about cookie cutter, paint-by-number solutions. To work effectively in a specific environment we have to understand and adapt to that environment. Many permaculture techniques have been developed in areas with summer rains making them inappropriate in this climate. Not to worry, that just means that techniques need to be developed that are specific to climate, site, needs and wants. I'd like to delve into this subject more in the future, but I'd like to get back to the subject at hand so, let me just say... Since working parameters are so widely variable, an effective permaculture strategy won't simply apply a combination of already conceived dogmas and techniques. Building swales or herb spirals or planting understories under trees is not permaculture unless these techniques are integrated with a functional logic that is specific to local working parameters. My working parameters being specific to my site, climate, needs and wants make the ideal plant for tree understories fill the following list of properties:
*Grows vigorously and thickly during the winter to out compete the great majority of grasses, thistles and other less desirable weedy stuff.
*Is compatible with the trees in terms of competition playing friendly and not being overly competitive for nutrients.
*Dies back to the roots early enough in the season to not be overly competitive with the trees for moisture.
*Capable of surviving complete drought through the summer.
*Leaves a thick cover of dead plant material to protect the soil and prevent further moisture loss.
*Is unpalatable to deer and rodents.
*Is long lived- not requiring maintenance after establishment.
*Optionally, but very desirably, provides other services or be useful in some other way as in food, beauty, marketability, bee forage, attractive to beneficial insects etc...
If you know of a perennial plant not mentioned ahead that fits this criteria please let me know. Various non bulbing broad leaved plants do die off early here, but its because they run out of soil water. Given water most broad leaved plants seem to continue growing.
The first plant to come to mind was Narcissus. Here at 1800 feet in coastal N. California the earliest narcissus I have here so far, the double form of the chinese sacred lily, are finishing blooming as of March 3rd and they start blooming as early as January, but usually in February. Other Narcissus varieties and the larger daffodils I have collected come up more slowly, so they probably wouldn't work. There is a difference also in the thickness of the leaves in different narcissus varieties. Some have wide heavy abundant leaves while others have narrow lighter foliage. I obviously want the heavier foliage to out-compete weeds and leave more surface cover as they dry up. I'm collecting more Narcissus of all kinds, but I think the wide leaved Tazetta types are going to be the best. Deer and rodents won't eat Narcissus at all and they are even said to repel voles, though I'm skeptical of that claim. The copious strongly scented flowers provide winter cheer and insect food in the dark days of winter and make good cut flowers for sale. The extra bulbs and flowers could presumably be a potentially valuable sale item. I've collected every bulb I could scrounge up since I got here 4 and a half years ago and I have quite a few of the double chinese type to start my experiment.
One 4 year old Tydemans Late Orange apple tree has been planted to randomly mixed varieties of Narcissus and large Daffodils in a 7 foot ring on about 8 inch centers. The tree is mulched with cardboard and wood chips and holes are punched down through the cardboard to plant the bulbs. I don't have high hopes for this one as many of the varieties are later growing or have narrow foliage, but it will probably help and it will look good anyway.
A second tree, a four year old Suntan apple, is planted to about 150 of the small double yellow Narcissus. These are planted on eyeballed 8 inch centers and extend out around 9 feet. The soil under this one is mulched with dead leaves for this season to prevent weed growth and conserve moisture this next summer.
I did find this interesting reference indicating definite growing compatibility of Narcissus and fruit trees:
"Apart from the kinds grown for market under the name of "Daffodils" (see p. 26), there are several species, varieties, and hybrids now in commerce, some of them exquisite in shape and colour, and varying in price from a few pence per dozen to several pounds per bulb. The common Poet's Narcissus (N. poeticus), and its variety ornatus, are grown in hundreds of thousands, in the market gardens of Middlesex, Evesham, and other places, beneath fruit trees. They are planted in beds 4-5 ft. wide in rows about 6 in. apart, so that something like a quarter of a million bulbs go to an acre of ground, allowing for pathways, etc. Where the soil is well cultivated and drained, the bulbs live for many years without lifting, and they increase in number at a steady rate. In some places, however, there is a tendency to die out with disease, probably brought about by soil sickness induced by allowing the bulbs to remain for too many years in the same place without lifting. If the flowers happen to come in just at Eastertime a very fair profit may result from the sale of the crop; but if a fortnight sooner or later than Easter the flowers may be a drug on the market, and realize less than 2d. per dozen bunches of twelve flowers. Under fairly good conditions from 40,000 to 50,000 bunches may be reckoned to the acre, and the gross receipts may be anything from £25 to £80. The cost of picking, bunching, packing, and marketing will come to about £15 or £20 per acre, whether the prices realized are good or bad, so that the net profits are difficult to gauge. Taking the average, however, the Poet's or Pheasant's Eye Narcissus may be regarded as a fairly good' catch crop on land that is chiefly engaged in producing fruit. When the newer and finer varieties become more reasonable in price it may be worth the market grower's while to plant some of them on a larger scale. The true poeticus flowers about a month later than its variety ornatus. For special kinds and varieties the reader should consult current bulb catalogues."
from commercial gardening vol 2 John Weathers Gresham Publishing 1913 http://chestofbooks.com/gardening-horticulture/Commercial-Gardening-2/Narcissus.html
Another plant that has caught my attention for this purpose is Amaryllis, the commonest form of which is known as naked ladies. They grow vigorously and very densely and seem to die back and go dormant about the same time as the Narcissus.
Bill the Bulb Baron, who sells Narcissus and Amaryllis bulbs, recommended the Amaryllis over the narcissus saying that he has a hillside of Amaryllis on which no weeds grow because the dense foliage chokes them out. Bill sells mixed hybridized Amaryllis that is seed grown which should provide variation in shape, color and blooming season. That should be refreshing as the standard pink Naked Lady (Amaryllis Belladona) which are so ubiquitous just aren't all that exciting. The potential drawback is that he also says their fleshy roots absorb water all year long. if that's true, they may be incompatible, but I'm going to try them anyway and see what happens. In the Narcissus department, he recommended Early Pearl and Early Cheer. I bought some of each of these narcissus and some mixed Amaryllis choosing in both cases smaller bulbs which will take longer to divide and bloom, but are much cheaper. His prices on small "landscaping" sized bulbs seem as good as, or better than anyone else, with lots of selection. I'm planting most of them in the garden for a couple of years to propagate out as many as I can so that I'll have more to work with when and if I decide to do larger plantings. If the system doesn't work for some un-forseen reason, I'll have lots of pretty flowers around the place and hopefully some floral product for farmers market when I take my surplus winter apples and crafts down. I've also acquired about 360 Naked Lady bulbs some of which I'll be planting under fruit trees on various spacings.
I hope someone else in a similar climate is having the same idea and trying it... or will read this and decide to try it. I did talk to one friend who said that very old apple trees at a place he lived are thriving in a cover of Daffodils. Also Cat (read her comment below) says she knew an orchardist in California who used Narcissus as weed control. And this just in, my neighbor uses Naked Ladies under his olive trees and says they provide a good summer ground cover.
I do see some potential problems with this concept:
*The bulbs may still use up too much water before they die off. The whole system is predicated on the working assumption that they won't. Its hard to imagine that it won't be at lest some improvement over random weed cover, but we'll see.
*Planting too close to the tree could create favorable habitat for voles, while planting too far away will leave some area around the trunk unprotected and free to grow large vigorous weeds that will have to be pulled by hand. Hopefully the narcissus will actually repel voles. That would be awesome.
*The flowers and plants will likely be trampled somewhat during winter tree maintenance. I think they will survive, but be less productive of flowers at least. I have a partial solution for this which is to place large stepping stones among the trees before planting the bulbs. I'll start with pieces of old scrap roofing tin and try to replace with stone or broken concrete as I can acquire it. If the stepping stones are large, which I hope they will be, they will also cut down on the number of bulbs needed.
*Trees may not like to grow in dense mats of these bulbs. some diversity would be nice if other plants can be found that will fit the criteria.
*A mulched competition free are might make an ideal habitat for certain perennial weeds here like bindweed, hedge nettle and sheep sorrel, all of which I could see thriving in such an environment if they were to get established.
I'm inclined just now to find more plants that will work and try to make mixed plantings. Mixed plantings seem better in almost every respect, and diversity is almost always a good goal when dealing with living things. It has occurred to me that some plants which do not quite fill the weed choking dense foliage criteria may still survive when mixed in a planting of plants which do meet it. Now I'm thinking that various Allium (onion family) species, Soaproot, native Brodeias and other bulbs might be mixed in for diversity. Garlic grown around tree trunks is said to repel borers which are a big problem here. This assertion is common, but its been my experience that commonness does not make assertions true. In about two years, I should have lots of material to work with and can make various types of plantings to start finding out what works and doesn't. Clearly this is a long term proposition.
One last note, I did read recently in Robert Kourik's book Roots Demystified that some perennial plants will pull extra water from deep in the ground and basically use it to re-hydrate the soil around them during the night which moisture can then be used during the day. If it's true that some plants can recharge the soil on a continual basis like this... and lets make that true to an extent that it is actually useful- as in that they deposit as much or more water than they use... it opens up another realm of possibilities. Along these lines, I might also do an experiment using Kniphophia (aka Red Hot Poker) which is drought tolerant, relatively fast growing, seems deep rooted, stays green all summer, is loved by hummingbirds and chokes out pretty much all smaller plants in its abundant growth. I'm skeptical and hesitant to possibly sacrifice the well being of one of my trees to such an experiment because I'm much more inclined to suspect that the Kniphophia will suck up all the water in the immediate vicinity, but we must sometimes suffer for pseudo-science... or maybe from it...
UPDATE 2/11/11: I've managed to collect a lot of bulbs and put in a number of experimental plantings. I added a couple species to my list of candidates on recommendation and from observation and research. Two are bulbs...
Snow Flakes has bulbs the size of narcissus which form very dense clumps. The flowers are smallish hanging like bells with small green dots at the ends of the petals.
Spanish or English Bluebells are form a dense clump as well. They have a spike of flowers in shades of white to blue.
The other is Oriental Poppies. By all accounts they go dormant by mid summer after flowering. Bees love poppy pollen and they make excellent cut flowers. I have seeds in the mail to me to test it out. A friend suggested this as fitting my criteria for an understory plant and I was quite interested since Cat (see comments below) mentioned a farmer planting poppies as weed control under his trees. Maybe Oriental Poppies are that poppy.
From observation when digging the bulbs, both snowflakes and bluebells seem to grow more densely on the average than the narcissus do and I suspect may be better candidates. I've planted experiments to just amaryllis, just narcissus, mixed narcissus and amaryllis with an assortment of other random native bulbs, narcissus and amaryllis and bluebells and snowflakes and then one that is just Snow flakes, bluebells and poppies. The plantings are not along very scientific lines, but some of the plantings have a "control (ish)" tree next to them for at least some comparison.