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Need information? Send your question to Cheryl Moore-Gough, Zone 4's Technical Editor for Horticulture. Cheryl is a past Extension Specialist—Horticulture for the State of Montana, and co-authored five books on gardening with her late husband, Dr. Robert Gough.
Send your questions to Cheryl or mail to the address on our contact page. Please include your city and state, as they may have a bearing on Cheryl's answer.
TREE LEAVES WON'T FALL
My mountain ash leaves and one of my apple tree's leaves still haven't dropped, despite being very brown and dry and going through several high-wind days late last fall and through the winter. I've noticed the same in many other yards in town, particularly those with mountain ash and fruit trees. Why are the leaves still hanging on this late in the winter? Does this indicate any potential problem with the tree's health? For fruit trees, does this indicate a potential problem for flower and fruit production this coming season?
When it comes to leaves falling (or not) in autumn, sometimes we can point to a single weather event, such as a quick, hard freeze, while other times we cannot. Leaf senescence and abscission is a result of a complex of issues, including plant hormones, sometimes juvenility, nutrition, drought ,and weather.
First, let’s talk about leaf abscission. There is a zone of abscission at the base of each leaf’s petiole. During abscission in a “normal” year it is believed that the balance of the plant hormones from each side of the zone stimulates this layer of cells to divide and to dissolve, causing the leaf to be shed cleanly. A protective layer of cork forms on the stem side of the layer.
My first hard freeze in 2011 was September 19, and it put an end to my vegetable garden. Even so, the leaves on the little maple I was given in memory of Bob stayed bright green well into the ensuing Indian summer, while neighboring green ash trees dropped their leaves with a single “foof,” Charlie Brown style. Why the difference? Abscission can be species dependent. Some species’ leaves die in the autumn, but the cells in the abscission layers do not. The process of abscission occurs the following spring, and is similar to the process that takes place in other species in the fall. These are termed marcescent species. But what about non-marcescent species that retain their leaves into the winter? Plant scientists agree it’s complex, and there is no one good reason for it.
The leaves of some species of trees will wilt, die, and be retained as a result of drought while other species shed their leaves as a result of drought, even during the growing season. Trees with leaves that are dropped, or that die prematurely, can indeed be stressed. In the natural scheme of things, woody plants reabsorb nutrients from the leaves as they gradually senesce, so there is a possibility of nitrogen deficiency come spring.
By the way, there are other reasons trees don’t shed their leaves. If your apple trees have retained leaves on individual branches, inspect the buds and bark to be sure fireblight isn’t the culprit.
Amending Soil With Blood Meal
Last summer we installed a 16' x 28' greenhouse. We added topsoil on the crushed granite. It did well considering the late start and I'm learning a lot about greenhouse gardening. I just had the soil tested (MSE in Butte) and the pH is 7.6; lbs/acre = N:22.4, P:886, K:2160. So they recommended N at the rate of 2 lbs/1,000 square feet. My two questions are: should I add 1 pound of blood meal and can/should I till it into the soil?
As you know, analyses of fertilizers vary a bit by manufacturer and I do not know what the nitrogen content is of your particular brand of blood meal. If it is 12%, then you will need to apply about 16 pounds of it per 1000 square feet of soil surface area for the approximate equivalency of 2 pounds of nitrogen over that area. Don't till but rather scratch the meal into the top few inches of soil before planting.
Step Up Leeks
I planted my leeks, onions, and celery seeds on March 5. The onions and leeks are about 3-4+ inches tall now. Would now be a good time to step them up into larger planters? Since they don't grow leaves, it's hard for me to judge when to transplant them.
I suggest you wait a week or two more before stepping up the plants. Be advised that onions and leeks don't take real kindly to transplanting, so be careful not to damage their root systems too much. If you do find the plants getting a bit too tall cut the tops back about half way with a scissors. That will promote stockiness in the plants and keep the tops inbounds. Some folks don't step up onions and leeks at all but grow them in their original clumps, then carefully separate the individual plants just before transplanting to the garden by dipping the clumps in water to loosen the media.
Red Ants
Are red ants harmful to our vegetable garden? How can you get rid of them?
Your question should rightfully be posed to an entomologist, but from personal experience I have not seen red ants eating crops. Rather, their tunneling can sometimes disturb seedling roots and seeds and so they could cause some damage. One non-pesticidal way to get rid of them is to pour boiling water onto their nest, provided it is located well away from your plants. Good luck.
Sweet Corn
My sweet corn is currently tasselling but I don't see any immature ears of corn or silks on the stalks. Why does that happen? I have also planted some later varieties that are not tasselling yet and I'm hoping that there is some way to prevent this from happening to them.
Tasseling (development of the tassels) is a gradual process that takes place over a few weeks, going from tassel formation in the whorl, to tassel emergence, to pollen ripening and shedding (anthesis); I am not sure what stage your tassels are in. Tassels will often appear at some stage of development before the silks show, but by the time the pollen sheds (when a slight brush at the tassel releases dense clouds of yellow pollen) the ears should be in silk. The silk will then receive the pollen, fertilization will take place, and the ears proper will develop. It sounds like you've planted a mid-season to late-season corn that is just beginning to tassel. Wait. If the season cooperates you still might get some great corn. I suggest that next year you try some earlier-ripening varieties like 'Northern Extra Sweet' (67 days), 'Quickie' (57 days), and 'Revelation' (65 days). You will have to see what works best for you.
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