Wednesday, March 11, 2015

Fruit tree pruning time

Now that the worst cold winter blasts are hopefully over, dormant season fruit tree pruning should be completed in March prior to bud break. The pruned peach tree in the left foreground looks sparse compared to the unpruned tree to the right. This is as it should be.

Peaches put on a lot of growth and should be pruned hard. They bloom on 1 year old wood and if shoots are left for two years or more, they don't produce fruit. Much of last year's growth should be thinned out to avoid overproduction and allow light into the tree. Excessive fruit production reduces quality and also weighs down branches causing limb breakage.

To balance growth of fruiting wood with peach fruit production, remove one-half to two-thirds of last summer's growth. Space fruiting shoots 6 inches apart remembering to leave long shoots of 12 to 24 inches (they fruit better). On the interior of the tree smaller shoots can be left. Don't worry, you will have plenty of new shoot growth over the season to provide fruiting wood for next year's peach crop.

Little annual pruning is needed on fruiting sour cherries and plums. Bearing apples and pears require a light annual thinning for light penetration. Avoid removal of the short fruiting spurs. Unpruned trees may produce more fruit of lower quality for a few years, that is until growth gets so dense that fruiting on the interior ceases.

Train young trees for a sound structure in the first few years. Then maintain bearing trees with annual pruning for a productive fruit tree.

Friday, January 16, 2015

2014 Gardening Year in Review

Frost apparent on tomato leaves.
The best thing about 2014 was probably the extended growing season with the acknowledgment that many vegetable gardeners had to cope with hail along the way. Even though the first official freeze is recorded as October 3, lows weren't extremely cold on that date nor several times later in the month.

Temperatures dipped only into the low 30's F on Oct 3, 12 and 27 in Denver, well within the ability of frost covers to handle. The weather otherwise was warm enough to keep tomatoes growing late and certainly warm enough for mid-season planted greens and root vegetables to mature nicely.

This all came to an end on November 10 with a low of 13 degrees F followed by subzero F lows the next three nights. These temperatures are way beyond the ability of frost covers to handle and effectively ended the growing season for those using frost protection. True to life in Colorado's high altitude steppe climate, daily highs in the 50's and 60's were recorded the end of the month.

Cherry leaves retained through winter.
The unknown factor about this generally warm late growing season suddenly ended by subzero cold is the possible damage to fruit trees.  The most obvious sign of this now is the retention of leaves on apple, cherry and other fruit (and ornamental) trees. 

The cold obviously interfered with the normal leaf abscission process but less clear is how much damage might have occurred to buds and wood. This won't be fully known until spring when lack of bud break and dead wood will show us the extent of any freeze damage. Lack of gradually cooling weather to promote full development of dormancy can deal a crippling blow to fruit trees exposed to sudden subzero temperatures. Let's hope for the best.

Note for those interested in growing fruit trees, I will be teaching a new fruit tree growing class at Denver Botanic Gardens on March 14. See clickable link to DBG in the 2015 class offerings found in the right column.

Photo credit: Frost on tomato leaves, Leaf retention on cherry - both credit Carl Wilson

Monday, October 13, 2014

Season continues for some gardeners

'Azoychka' yellow tomato Oct 13, 2014
If you were lucky you escaped Oct 12 scattered frosts or covered tender plants and will be rewarded with an extended growing season. We've been in a pattern of cold-hot-cold-hot. This is expected to continue with temperatures again predicted to reach 80 degrees F in a couple days. Life in the high altitude, steppe climate of Denver, Colorado is always a roller coaster ride.

Tomatoes remaining on the vine will continue to ripen and zucchini will continue to grow larger. Just like betting when to plant warm season crops in spring, deciding when to shut down the warm season garden in fall is a challenge. I know some gardeners who have already torn out their gardens. How many more frost "escapes" will us late season garden gamblers have?

Zucchinis Oct 13, 2014
Of course tomatoes still on plants showing some color such as the yellow Azoychkas in the photo above may yet ripen on the vine. The ace in the hole is they are good candidates for picking and ripening indoors if a hard freeze is predicted (overnight temperatures expected to fall into the mid to upper twenties F). Green ones that are small probably won't have a chance but the largest can be harvested and used as fried green tomatoes.
'Bulls Blood' beet and 'Red Russian' kale
Oct 13, 2014

Meanwhile mid-summer planted, cool season crops such as the beets and kale in the photo will tolerate early frosts. The flavor of kale only improves once frosts begin in earnest. This is shaping up to be a year for warm season vegetable harvests to extend late into fall and cool season crops rewarding the savvy gardener with fall harvests as they always do.

Photo credits: Azoychka tomato, Zucchini, 'Bulls Blood' beet and 'Red Russian' kale all credit Carl Wilson.

Thursday, October 2, 2014

Frost advisory tonight

October 7 is the average date of the first fall freeze in Denver so it should be no surprise that a freeze advisory is issued for tonight, October 2. The earliest fall freeze was September 8 in 1962 and latest November 15 in 1944.

Some of your gardens may have been nipped when it got down to 33 degrees F last month on September 11, particularly those on the northern part of the Front Range (Fort Collins, etc.). Often we have warm temperatures after these episodes as we have had for the rest of September. Indeed, daytime temperatures are predicted to be in the mid 70's by the weekend two days from now and reach the 80's by midweek.

With these short one or two night possibilities of a freeze it is worthwhile to cover frost-tender vegetables such as tomatoes, peppers, squash, etc particularly as we get near the average first fall frost date. Use covers to trap heat stored in the soil around plants as was done in the photo. A sheet of plastic or fabric will serve as long as the material is not too heavy to break down plants.

In the photo, double frost protection was used, probably overkill for this early in the season when it has been warm. A poly frost blanket (thick floating row cover fabric) was thrown over the tomato cages and then plastic placed over top and sealed into the soil to trap heat like an enclosed greenhouse. Clothes pins were used to keep the plastic from flapping in the wind.

Invent your own frost protection cover out of materials you have on hand. Just remember to uncover or at least ventilate the next morning as sun will soon cook plants covered tightly with plastic.

Photo credit: Temporary frost cover over tomato cages - Carl Wilson

Wednesday, July 16, 2014

It's Cherry time

Mature, rarely pruned cherry tree SW Denver
Yields of cherries look reasonable considering the 28 degree F lows we had on May 11 and 12. (See May 12 post on fruit bud damage). Damage at these temperatures was expected to be about 10 percent. Birds also are always a threat and can strip trees of fruit in a few days unless trees are netted.

Tart cherries are hardier than sweet cherries which often winter kill in addition to flower freezing. Sweet cherries are comparable to peaches in this respect.

Recommended tart cherries are 'Montmorency', 'Meteor' and 'Northstar'. If you want to experiment with sweet cherries, try 'Black Tartarian', 'Kansas Sweet' or 'Stella'. Tart cherries are self-fruitful while sweets need a pollinator.

'Montmorency' is the standard tart pie cherry variety that produces a July crop of bright red, firm textured fruit. It is planted in the new (second season this year) "Le Potager" food garden at Denver Botanic Gardens (see photo).

DBG 'Montmorency' cherry
'Meteor' is a very cold-hardy tree growing 12 to 15 feet tall. It develops heavy foliage that can minimize problems with birds. Fruit ripens mid to late July.

'North Star' is a dwarf tree topping out at 10 feet. It sets generally heavy crops of fruit that turn dark red for July harvest.

Note that bush cherries are very hardy and also possibilities. Nanking cherry produces some of the first flowers of spring, can grow to 6 feet and fruit is harvested in July if birds and squirrels don't find it first. Sand cherry is another bush cherry reaching 4 to 5 feet and produces mild-flavored, deep crimson fruit. Both are self-fruitful.

Photo credit: Both Carl Wilson

Thursday, July 3, 2014

Time for mid-summer planting

Vacant mid-summer "real estate"
Although warm season vegetables should be coming along well by now, don't forget about what you want to do with the vacant "real estate" in your garden from previous plantings.

April/May/June harvests of cool season and quick maturing vegetable crops often leave holes in the garden. While there is no problem with leaving ground fallow, do know that if planted before mid-July, a harvest can be gained yet this season. "60 dayers" (vegetables with 60 days to harvest or less) are what to think about planting now. Surprisingly, many cool season vegetables work well. Even though planted in the heat of summer, they will mature in cooler fall weather and be of good quality.

For more specifics on what to do to make a vegetable garden more productive from mid-summer through fall, consider attending my "Follow-on vegetable gardening" class at the Denver Botanic Gardens July 12 (click here for details).

Photo credit: Bare ground from harvest of spring crops - Carl Wilson