Doug Hack wrote:Today I collected 400 wild bitter almond seeds in a bucket and planted them about every two feet along about 800 feet of perimeter fencing. If even 5 percent of them survive I will have 20 new trees to start my hedgerow/shelter fence. This took about four hours.
Update from this "planting" of four years ago. There are two surviving trees - about three feet high. They have been totally neglected for four years. The very low survival rate I attribute to two things - 1) I did not actually put the seed into the ground, but just put it against the ground or slightly into the surface under a layer of duff. 2) The following Winter was one of the driest on record - less than 10 inches of rain total. I feel like I 'wasted' 400 almond seeds.
If I had repeated this experiment with putting the seeds 2-3 inches into the ground I am sure the survival rate would have been much higher. This would protected the seeds from drying before and in between rains, and also given the seeds some protection from mice. If I had repeated the experiment each year I am sure the results would have been dramatically higher as this past Winter was one of the wettest on record. There is no predicting the rains, but consistency will eventually pay off.
In the meantime I have had excellent germination rates planting in 1 gallon pots and have planted out several almond trees (some now grafted, some yet to be). This is far more time consuming than just planting seeds. An in-between level of inputs with a high probability of sucess might be planting three seeds in a selected spot and then watering that spot until the rains actually start to keep the ground moist.
Here are some observations and thoughts about nitrogen-fixing plants: I have tried planting from seed a variety of clovers, trefoil, vetch and alfalfa. While all sprouted and grew for a while, only purple vetch has persisted and reseeded itself to a reasonable degree over years without attention. It likes to grow on my woven-wire fences, and persists in patches even in areas mostly dominated by tall annual grasses. All of the others needed management (mowing or grazing) and irrigation to persist more than one season.
I have decades of experience with Black Locust trees and I feel they are very valuable as a pioneer soil-improvement tree. Their roots fill the soil over a wide area (up to three or four times the drip line diameter) and they provide plenty of extra nitrogen for other plants. When water stressed in Summer they drop leaves which increases the amount of light for plants under the shade canopy. With regular irrigation a lush lawn will grow under them with no other fertilizer. In my climate most plants grow better under them than in full sun. They are tough and will survive with no irrigation once established a year or two, but growth will be very slow and they will drop nearly all leaves in the summer. If they are grown large with irrigation, and irrigation is stopped, they will die back substantially, looking very bad, but surviving. They have lots of root sprouts and will create thick colonies if allowed to. In my soil (which is shallow and light over thick hardpan) they are unable to sink roots and usually blow over after a few decades. This probably wouldn't be a problem in deeper soils or where allowed to grow very thickly.
I have limited experience with albizia julibrissin (Mimosa or Silk Tree), but I like it very much and it has some advantages over Black Locust. For starters it does not have sharp thorns. It provides an even lighter shade than Black Locust and it will fold it's leaves to save water. It seems to be almost un-killable, fixes substantial nitrogen and (once well established) drops a thick litter of flowers, leaves and seedpods which is an advantage for soil development and a serious disadvantage for manicured yards and patios. The wood decomposes much faster than Black Locust which makes it more useful for chop and drop or any use for decomposing biomass such as hugelkultur. It is a smaller tree at maturity but grows reasonably fast. I haven't noticed colonies of root sprouts (although it resprouts when coppiced). In my climate neither tree is likely to self seed. Both create relatively small seeds with hard seed coats that need scarification and a moist environment to survive and establish. I've had great success by pouring boiling water over the seed and planting those that have swollen up 24 hours later. I am planting Silk Trees in between my fruit and nut trees as nitrogen sources and soil improvers. If they ever get too competitive I will cut them back and use the cuttings as mulch.
I have tried Siberian Pea Tree (or shrub) but it doesn't seem to like the climate here (USDA Zone 9B). It may be too hot for it.
I have also tried Arizona Mesquite. Hand sowing seed into annual grass land did not sprout/survive. Scarification and growing in pots was very successful, but the trees do not seem to thrive once planted out. Maybe my winters are too wet for them? The growth is extremely slow compared with either Black Locust or Silk Tree. I'm not impressed but they may have potential for even hotter and drier climates than mine.
As a shrub I have had good success growing a variety of Ceanothus Arboreous (Owlswood Blue) which is considered to be a nitrogen-fixing plant. I have propagated it from semi-hardwood cuttings (somewhat difficult). It has grown and survived well and seems to get by with a minimum of summer water. I haven't let any go unwatered and I have doubts that it would do well here without some help in the Summer. It has large green leaves that deer, goats and sheep like to eat. It also has beautiful blue flowers in Spring that the bees love. I'm not sure how much nitrogen it actually fixes (it stays very green and grows reasonably fast in poor soil) or shares with other plants.
Not on any list of nitrogen fixing plants is Mulberry. However I have observed it growing amazingly fast and green with very high protein leaves on poor soil. I cannot believe it could possibly do that without fixing nitrogen somehow. I have collected several varieties and I highly recommend them as a pioneer tree. The branches and leaves can be chop and dropped. The fruit is variable but many varieties are very good to eat - and birds love all types! My mulberries keep the birds so well fed that they mostly leave my cherries alone. You can feed the leaves to ruminants (sheep love it!) and chickens. I have propagated it from cuttings, transplanted bird dropped seedlings and grafted it. My observations are that in a hot climate it should be left un-pruned to grow low and wide - shading as much of it's own root zone to the ground as possible. This also makes the fruit easier to reach. The roots are very vigorous and spreading and develop sinkers that I suspect are getting through my hardpan after a few years.
The figs I have propagated from cuttings seem to need a lot of water and haven't produced much fruit yet. I suspect they are not the best adapted to getting by on their own in a hot climate.
I've planted a lot of different varieties of pomegranates (easy from cuttings) and they seem to do very well here. Mine are still very young and I don't know how much water they will need to fruit, but they seem very promising.
I have also planted a lot of varieties of table grapes from cuttings and I am very pleased with the quantity and quality of fruit they produce. They do need to be watered to produce, but they grow very fast, producing lots of leaves (Thompson Seedless leaves are edible), and biomass every year.
My more traditional orchard is doing okay, but it is water-intensive and so far not impressive. This Fall I will collect as many Silk Tree seeds as I can find and start trees to interplant thickly with the fruit trees. I think the extra ground shade and nitrogen will help in three or four years.