Garden Answers

Soils, Mulches, and Compost

I'm not sure how to start with this clay soil. Will plants grow here?
What do you mean when you say I should "amend" my soil?
Do I need landscaping fabric beneath the bark or rocks?
Should the leaves raked from my yard be composted? How do I compost?
Where do we get our soil tested for PH?
What is a good watering schedule for landscape plants?
Is there any way to get rid of the alkaline that is showing up on the surface?
What can I plant in a large sand pile in the middle of a yard?

Question: I'm new to the Western Slope living in Montrose and am not used to the clay soil here. Can I plant a vegetable garden? I'm not sure how to start or what plants will grow here. Appreciate your help.

Answer: Unfortunately clay soil is a fact of life both here and in Montrose. You should be able to have a vegetable garden, but will need to amend your soil on a regular basis to help your plants grow. I recommend 2" of decomposed materials to start. You can use compost, bark mulch, peat moss, or a combination of any or all of them. Be sure to roto-till as deeply into the soil as you can. This will help with aeration and breaking up the clay somewhat.

Back to the top.

 

Question: I want to plant shrubs, trees and flowers this spring, but am not sure what to do with this clay soil. What do you mean when you say I should "amend" my soil?

Answer: Improving your soil is the best thing you can do for your plants. When I tell folks they should amend their soil, I'm telling them that they need to mix something in that will improve it. Amendments help with water retention, drainage and aeration-each of which helps plant growth. There are a variety of amendments including Sphagnum peat moss, manure, sawdust and manure, barkmulch, and soil pep (an organic forest mulch). Peat moss, barkmulch and soil pep work very well in helping our clay soils. Many folks like to use manure on vegetable gardens. If you do use manure, be sure it is aged (at least 6 months), as fresh manure can actually burn young plants.

The time to amend your soil is before you have a lawn put in. Once the lawn is in, soil improvement can be made only gradually and with considerable cost and difficulty. A thoroughly decomposed organic material like Composted Manure, Barkmulch, or Peat Moss works well in improving our soils. Three to four cubic yards of material should be spread out per 1000 square feet and thoroughly rototilled into the top 4" to 8" of soil. Coarser organic materials (like barkmulch) tend to break up our heavy clays better than finer materials. If your native soil is high in soluble salts, avoid using salty organic amendments like manures. Hope this helps.

Back to the top.

 

Question: I would like to use the decorative bark or mulches you have, but I'm confused. Do I need landscaping cloth beneath the bark, or do the wood products do a good enough job on its own suppressing the growth of weeds and grass?

Answer: You don't need the landscape cloth. In fact, you're better off without it. The bark and mulch will decompose over time, benefiting the soil and plants by enriching the soil. Also, bark chips by themselves will eliminate 90% of your weeds, whereas the decomposed mulch on top of cloth provides a humus layer weeds will thrive in!

Back to the top.

 

Question: I think I finally raked all the leaves from my yard. It seems like a waste to send it to the landfill. Should I keep all that stuff to use for compost? How do I start a compost pile?

Answer: I agree wholeheartedly! Why choke our landfill with plant debris when we can use it in our own yards to enrich our soils-and they need it!

Start with the material you've collected in your yard-leaves, straw, stems and clippings. This is what we call brown matter, high in carbon, low in nitrogen. It should be chopped up. An easy way to do that is to pick up the leaves with your lawn mower. Otherwise, you can try to rent a shredder.

Green matter-nitrogen rich organic material, like lawn clippings and kitchen scraps (no meat!)-is then added to the brown matter at ratio of 1:1. If you don't have enough green matter, you can provide nitrogen with a high nitrogen lawn food like Bookcliff Gardens Choice Lawn Food or ammonium sulfate. It's a good idea to add some old compost, aged manure, or some rich garden soil to introduce the microbes necessary to break down the brown and green matter.

Once you've added your nitrogen source and some microbes, moisten the pile well. Mix the pile monthly by turning with a spading fork or shovel, checking the moisture level. You don't want the pile to dry out and you don't want it soggy either. Water as needed. You'll have a real nice compost in four to six months.

Composting isn't for everyone. If you don't want to make your own compost, you can take your leaves and yard waste to the compost facility at the county landfill. There's no charge to drop off organic materials. If you live in the city limits, the city of Grand Junction will pick up leaves you rake into the edge of the street.

Back to the top.

Question: Where do we get our soil tested for PH before we start landscaping? We hear State Universities/Extension services do it.

Answer: The local Extension Office can help you there. You can pick up a mailer from the Tri-River Extension office in Montrose to send a sample over to Fort Collins. They do a complete and very accurate soil test there. It usually takes two or three weeks to get results back. The Extension office in Montrose is at 1001 N. 2nd. Their phone number is 249-3935. Hope this helps.

Back to the top.

 

Question: Could you please tell me what watering schedule you would suggest for landscape plants?

Answer: Well, you've asked a question that's hard to answer in a specific way. The general rules for watering trees and shrubs still apply during the fall. You want to water your plants deeply when you water but do it infrequently, allowing the soil to dry slightly before soaking it again. Now, your watering schedule in the fall will be different than your schedule during the summer. Where most people were watering their trees and shrubs once a week or so during the heat of summer, you should now be thinking about watering anywhere from once every ten days to once a month.

There are a number of factors that will determine your specific schedule: What's the weather like? What's your soil type? Is the area sunny or shady? What kind of soil preparation has or hasn't been done? Is the area mulched? Is there a slope there? When you throw all those different things together you come out with your own watering schedule.

I recommend that people do a little digging in the soil to see what the soil moisture is like. We make lots of assumptions about how wet or dry things are underground without actually looking at the soil. You really don't know until you get underground! I like to use a shovel to check soil moisture. I like to see the soil and feel it to see how wet or dry things are. Some people like to use a probe like a long screwdriver to push into the soil, but, in my opinion, nothing beats actually looking at the soil.

First, make sure that you soak your woody plants deeply when you do water. I like to see water penetration down 12"-18" into the soil. Give your plants a watering, wait an hour or two to let it soak in completely and then dig down several feet away from your plants. The soil should be muddy-wet down at least a foot. Remember that you've just watered—if it's just moist, the water hasn't penetrated down deeply enough.

Next, you want to allow the soil to dry slightly before soaking it well again. This is the frustrating part for many people – they don't know if they're over-watering or under-watering their plants when they have problems. I like to dig down 3"-5" into the soil and check the soil at that depth. There should still be moisture down at that depth but there should be some drying as well. If the soil's dry, you need to water more frequently, if it's still pretty wet, wait a day or two or three and check the soil again. I've found that most people have a pretty good innate sense of when to water or not. If I can get 100 people out digging holes and checking the soil and I ask them "Does this plant need water?" 98 will give me the right answer. I know it's hard to trust yourself, but it's really not that hard!

Now that I’ve given you the general guidelines to follow, here’s how I water my yard. Please take this with a large grain of salt because your yard may be different from mine! I'm watering my lawn about once a week right now (I've been going once every 5 to 10 days depending on the weather). I'm watering my woody trees and shrubs every two or three weeks right now, but I'm stretching it out as things cool down and depending on any rain we get. I water both my lawn and shrubs with pop-up spray heads. They're on different zones so I can water them differently. I run the lawn heads for 40 minutes to give the lawn a good soaking. I run the shrub heads for 60 minutes (actually, I split it up into 2-30 minute runs so the water has a chance to soak in and not run off). This schedule has worked for me for a long time now. I'm telling you how I do it to give you a rough idea of where you should probably be. I know people who water less often than I do and they have beautiful landscapes.

Back to the top.

 

Question: Last spring we landscaped our new yard in a xeriscape design. At that time there was evidence of alkali lying on top of the soil. Now the alkali has seeped through the weed block material and the decorative rock. It looks bad because the decorative rock is now all white. My question is: Is there any way to change the pH of the soil beneath the landscaping to get rid of the alkaline and at the same time dissolve the alkaline that is showing up on and throughout the rocks. The plants that are growing in the areas that seem to have the most alkaline patches are small and yellowed compared to other areas of the yard.

Answer: Actually Sandra, what you have is not a problem with "alkali" but a problem with soluble salts. Though they are somewhat related (most of our salts are alkaline to a degree), these are very different problems. Alkalinity is a measure of the pH of the soil. Almost all of our soils here in Western Colorado are on the alkaline end of the scale with a pH of 7.5 to 8.0. This alkaline pH, however, rarely causes us problems growing plants unless we're trying to grow plants that absolutely demand an acidic soil like Rhododendrons or Blueberries.

Soluble salts, on the other hand, are a pretty common problem here and are more damaging to our plants. Soils on the north side of the Colorado River are underlain with Mancos Shale which is the remnant of an ancient sea which dried up. Think of the Great Salt Lake drying up and how many salts would be left in the soil after the water has evaporated away. Well, it's not quite that bad here, but there are areas in the valley that can really have a problem with those salts.

The only way to get rid of the salts is to physically remove them by leaching the soil with water—a lot of water sometimes! Sometimes you may hear that adding Sulfur or Gypsum will take care of the problem; adding those amendments will only make your salt problem worse! Gypsum is a salt to begin with, making up about 20% of our native salt fraction, so adding Gypsum is just adding more salt to the soil. Sulfur combines with the abundant Calcium in our soils, forming Calcium Sulfate, also known as Gypsum! Sulfur can lower the pH, but that's usually not necessary plus it will spike up salt levels in your soil.

The only way to deal with salts in the soil is to physically remove them by leaching them down deep into the soil where they won't trouble your plants. The first thing we'll recommend is that you amend the soil by adding a good amount of low salt decomposed organic matter and mixing it in well. This will help improve drainage, facilitating the leaching out of the salts. Make sure that the amendment is low in salt to begin with. Manures can be high in salts, and you don’t want to be adding more salt to an already salty soil! Use products like peat moss, composted wood products, or low salt compost.

Next, you have to water deeply and persistently to move those salts down. Salt levels are measured in a scale called millimhos. In a perfect world, your salt levels would be at 4.0 mmho or less. You can take a soil sample down to the Extension office where they can do a quick salt test for you. When leaching out salts, it takes 6 column inches of water to cut your salt levels in half. Let's say for example that your salt levels are at 11 mmho. If you put on 6" of water and let it soak in, you cut your salts in half to 5.5 mmho. Applying six more inches will cut it in half again to 2.75 which is well within the safe zone. That means you have to apply 12" of water to your soil! Think of building a dike around the yard and putting in a couple of fire hoses and filling it up to one foot deep! That's a lot of water!

Now this is a difficult process anytime, but even more so when you have plants growing in the area. Flooding the area with that much water will usually have harmful effects on your plants. I don't have any quick and easy answers for you I'm afraid. The best I can tell you is to concentrate on watering your landscape very deeply and thoroughly. Don't keep the soil constantly wet, but be sure to water very deeply when you do water. You will gradually lower the salts in your soil but it will take some time. The yellowing and stunting of the plants in those bad areas is due to the effects of those high salt levels I’m guessing. Hopefully, you can start to lower the salts in time to save the plants; otherwise, you may be looking at replacing some plants next spring. Wish I had better news for you, but I hope this helps.

Back to the top.

 

Question: What can I plant in a large sand pile in the middle of a yard? The sand pile is on top of regular ground and is surrounded by railroad ties.

Answer: You could grow almost anything on that sand pile provided you do two things. First, amend the soil well by mixing in a lot of decomposed organic matter like compost, Soil Pep, or Peat Moss. I'd figure on mixing it at a ratio of half organic matter and half sand. Second, be sure to water it enough. Though the organic matter will help retain water in the soil better than the plain sand, it will still dry out more quickly than normal and you'll have to be there with the water. I don't know what your watering schedule would be, but I'd guess that you'll have to be soaking your plants once or twice a week.

Back to the top.

 

Bookcliff Gardens
(970) 242-7766
755 26 Road (North 1st at I-70) • Grand Junction, Colorado 81506
Ask the Expert
©2008, Bookcliff Gardens