Type your question here!

Saturday, July 18, 2015

Potatoes Need to Be Started Early in the Season

Q. I want to plant potatoes here in Vegas. Our season is timed different than others though so there aren't seed potatoes available now for a mid or late July planting. Will standard Yukon Gold, Russett, fingerlings or Sweet Potatoes from the grocery survive here? Or can you suggest where to get some suitable seed potatoes?

A. You are planting too late if you put them in the ground in July. We need to plant Irish potatoes here in late February or early March. Purchase seed potatoes early in the spring. Sweet potatoes are a hot weather crop and need to go in later when soil temperatures are warm, around the first week in late April or early May.

            Any Irish potato can be quartered and used for “seed”. Potato seed are not seeds at all but cut up potato tubers. When cutting potato tubers for seed, make sure each seed piece has at least two “eyes” or “dimples” and plenty of tuber connected to it.
Potato tuber developing on underground rhizome

Sterilize knives used for cutting and allow the cut pieces to “heal” in the refrigerator, moistened, for a few days prior to planting. Warm up seed pieces taken from the refrigerator to room temperature before planting.

I have used potatoes from the grocery stores for seed but you should realize that they are not certified disease free so diseases are more of a potential problem. Purchase organic potatoes for seed since standard potatoes may be treated with a sprout inhibitor. Sprout inhibitors are sometimes applied to keep them from sprouting in storage.
Harvesting potatoes
All of the potatoes you mentioned will grow here including Sweet Potatoes. Consider Red Pontiac and Red La Sota for red skinned potatoes as well as those you mention. Also try blue potatoes such as “Adirondack Blue” as well as fingerlings.

If you’re going to grow potatoes here, make them really special because regular old potatoes are not terribly expensive to purchase. I don’t know of a potato that will not grow here.

Stop Watering Lawns at Night

Q. I read with interest your column in the RJ on watering. Our small lawn seems to be dying in patches. We water 4 days a week for 20 minutes at 11pm.  We regularly feed with Turf Builder Plus and Ironite. What should we do?

Lawn disease of reader.

A. First of all change your watering time to 4 in the morning and finish before sunrise. Never put your lawn to bed at night, wet. You are asking for disease problems if you do.
Most warm weather lawn diseases need about 6 hours of a damp, dark warm environment to get active. After a watering cycle, wait 30 minutes and push a long piece of rebar or screwdriver into the lawn in several locations. Make sure it pushes easily to 10 to 12 inches before you meet much resistance.
If it does, then you are watering deep enough. If not, increase you watering until you can push it that deep. If deeper than this, reduce the minutes to 15 or so and repeat. Break your 20 minute cycle into three shorter cycles totaling 20 minutes and space them about 15 minutes apart. 
This helps prevent puddling and runoff. This fall, rent a core aerifier and punch holes in the lawn. Verify your lawn every three to four years; more often if your lawn gets a lot of foot traffic.
In lawns, nearly any iron product works so you don’t have to spend a lot of money on iron. Not true about other plants.

Lawn Maintenance Companies Should Recycle Clippings Back into the Lawn

Q. I live in a subdivision with 400 townhomes and a fair amount of grass that the HOA maintains. The lawn crew does a couple of things that I question. They keep the grass mowed pretty short; 1-1/2 inches.  Shouldn't they wait until it gets about 3 inches and then cut only 1 inch off?  Wouldn't this minimize evaporation? They are collecting the clippings and discarding them. Wouldn't it be better for the lawn if the clippings fall back on the grass? Doesn't the nitrogen recycle back into the lawn?

A. They should be recycling the clippings back into the lawn and mowing higher. This will require that they use recycling mowers, a special blend of fertilizer with half of its nitrogen in the slow release form and closer lawn management.
Mow tall fescue no closer than 1 1/2 inch at any time and 2 inches is better. This gives them 1/2 inch of growth they can remove safely each mowing. These grass blades contain a lot of fertilizer that end up in the landfill so it is better to recycle them back into the lawn.
If removed clippings are an inch long, this tells me the nitrogen fertilizer applied is excessive. No more than 1/3 to 1/4 of the grass blades should be removed in one cutting. Measuring the average length of clippings is a good way to determine if nitrogen fertilizer is needed by a lawn or not.
Mowing is important for controlling lawn diseases. Grasses are unique because they push growth from the bottom of the blade; the oldest growth is removed when mowing. Old-growth contains more disease problems than the newest growth.
Lawn clippings can and should be returned to the lawn. If they do this successfully they must use recycling mowers and a quality lawn fertilizer. Returning lawn clippings to the lawn substitutes for one fertilizer application every year. Recycling lawn clippings back into the lawn improves its general health because lawn clippings are composted back into the soil, releasing nutrients.
Recycling mowers have a unique blade and a unique deck design that provides greater lift and causes lawn clippings to be “chopped up” more effectively than with traditional mowers. Traditional mowers retrofitted with recycling blades will work but they are not as efficient as recycling mowers.
If a recycling program is done correctly, you will not see any residue from lawn clippings left on the lawn after mowing.
Fertilizers used with recycling mowers are unique. They must have a large percentage of their nitrogen in a slow release form or the fertilizer should be applied in much smaller quantities, more often. Their greater cost is offset because less fertilizer is required.
Where I don’t agree with you is on water conservation. The research is conclusive that lawns mowed higher use more water than lawns mowed shorter. However, lawns with a deeper root system are more drought tolerant. So it is a trade-off.
Lawns that are mowed higher have deeper root systems. This makes them more drought tolerant but they also use more water.
This is misleading because the difference in water use between a closely mowed lawn and one that is mowed taller is not large. It is more important to have an irrigation system that is designed and maintained correctly and water applied when winds are minimal and adjusting your lawn watering schedule monthly during the spring and fall months. Lower water use is tied more closely to management of the lawn and irrigation system, not the root depth of of lawn grasses.
Mowing a lawn higher has other benefits. Lawns mowed taller have deeper roots. Deeper rooting means better drought tolerance. Here is the rub. Improved drought tolerance alone has no relationship to low water use. It could be argued the opposite; they use more water.
Water use of lawns in inches per day as the seasons change in Las Vegas. Months are January=1 and December=12
Bottom line. Lawn maintenance companies should not be bagging lawn clippings but returning them to the lawn using recycling mowers. They must be careful in applying nitrogen to lawns. Over applying nitrogen fertilizers causes lawn recycling programs to fail.

Look For Clues to Spider Mite Damage on Cypress

Q. I have a group of Italian Cypress in my back yard.  I am completely new at this (growing trees and gardening) because I have lived in apartments and condos until recently.  I planted them, they looked very happy, but in early summer my gardener pointed out they were being attacked by spider mites and said I should do something quickly or they will die.  Well, they survived and did not die, and the new growth on top seems to be green but the growth on the bottom is still pretty brown.  I asked at a nursery and was told it will never green up and I have never seen needles fall from the tree, so I suspect he is right (though I am suspicious because nurseries sell trees).  My wife on the other hand is certain that, given a couple of years the problem will go away.  I was going to replace all the trees (they are like 15 feet tall and 3 years old, so they grow very fast) but that is upsetting my wife.  I would like to know who is right, the nursery or my wife (who did grow up around trees).

Readers Italian Cypress
A. I am in the middle on this one. I did look at the original pictures enlarged and it certainly could be spider mite damage. I would be looking for the needles having a "dusty" appearance (tens of thousands dead, cast "skins" of spider mite making a surface "dust" on the foliage. I would also look for perfectly round eggs with a magnifying glass or dissecting scope). Without seeing the branches in person and the extent of the damage it is hard to judge. If the damage has extended all the way into old growth in the interior they will not recover but be permanently brown. If the damage is light and there is some green growth remaining it is possible for them to slowly recover. 

Electron micrograph of spider mite feeding
Take the branches with dried “needles” and bend them strongly. If they are dry and snap they will not recover. If they are supple and do not snap like a dry twig they may recover. That is the best I can tell you. It may not have been spider mites. I would have to see the foliage very closely and inspect it for mite “residues”. Not all spider mites make webbing and some webbing is caused by spiders so seeing webbing alone does not guarantee it is spider mites.
Webbing like this may or may not indicate spider mites are present. Look for other clues too.
During the heat of the summer I would hose down the Italian cypress once  a month or so or after any kind of “dirt” storm. Dirt or dust on the leaves interferes with the natural control of spider mites by predatory mites and beneficial insects. There is a natural “ecosystem” at work on cypress that keeps the bad critters under control. Spraying insecticides or miticides can interrupt this natural control system by killing off the beneficials.

Do not irrigate Italian cypress too frequently. If watered often it can cause root damage and also create the same kind of browning. These are Mediterranean plants and do not tolerate wet soil during warm weather. Water them no more than about once a week if you have a “normal” soil but give them a thorough watering when you do.