Forcing Tulips to Bloom on a Precise Date

Q. When should I put tulip bulbs in the fridge so that they bloom on Easter or a few days earlier. Can you please help me? I want a nice table centerpiece.

A. Getting tulips to bloom precisely at Easter is difficult for a homeowner because they frequently do not have enough information about the tulip or a precision growing environment. Commercial growers using greenhouses get plants to bloom precisely on a specific date by selecting known varieties and growing them at precise temperatures.

Some plants like mums and Christmas cactus, require controlling the length of darkness or the application of growth regulating chemicals at specific times. Tulips are a little easier. Most tulip varieties bloom in 4 weeks if the temperature is kept constant at 60F. Plants grow faster or slower depending on temperatures.

Plants grow faster in warm weather and slower in colder temperatures. If tulips are grown ten degrees warmer, 70F, subtract a week. If grown 10 degrees cooler, 50F, add a week. A few varieties may take 5 to 6 weeks to bloom at 60F.

For precision blooming, it’s best to know the variety of tulip being grown and how many weeks it takes to bloom. Some flowering plants require cold temperatures to bloom. We oftentimes have enough outside cold temperatures for tulips during winters in the Las Vegas Valley if they are planted on the north side of a building and in the shade. But it depends on the variety.

 To vernalize tulips (subjecting the bulbs to cold temperatures so they produce flowers) the bulbs are placed in a refrigerator 12 to 14 weeks. They will grow a little bit, slowly, at this temperature. Some varieties of tulip require fewer than 12 to 14 weeks. Some tulip bulbs are available pre-chilled.

 Here is how I would do yours.

• Stick the bulbs in the refrigerator, upright, in slightly moist potting soil for 14 weeks. 
• At the end of 14 weeks, put them at room temperature five weeks before you want them to bloom. If they are growing too fast, grow them colder; put them outside in the shade on the north side of the house to slow them down. When they are back on track, bring them back indoors. 
• Water them when needed but don’t keep the bulb wet. The bulb can’t be dry either. It can lose roots that way. Use a soil moisture meter to judge when to add water. Fertilize lightly once a month with a water soluble fertilizer during warm temperatures. 

No guarantees it will be exactly on the date you want but it will be close.

Using Rock Instead of Wood for Mulch Around Grapes

Q. I am putting in 30 more wine grape vines. I was thinking of using chat, crushed rock, for mulch rather than wood chips. What do you think?

A. The idea of using rock mulch, rather than wood chips, addresses a controversy among wine grape growers. Some growers of high quality wine grapes believe that wine grapes must “struggle” to produce a good quality wine grape. They believe the best wine grapes come from poor soils and a limited water supply.

Jerry Nelson with John Arellano from Duarte Nursery in California

Wine grapes without any kind of mulch growing in raw desert soil near Amargosa Valley, Nevada. Jerry Nelson's vineyard.

The hot desert, with nighttime temperatures around 90° F or more during harvest time, is thought to produce a poor quality wine grape. It is believed that nighttime temperatures should be cooler than this during harvest.

Grape harvesting event I put together for Slow Food Las Vegas at the Gehring Vineyard in Amargosa Valley, Nevada.

Few people believe that a good quality wine grape can come from this type of environment. This may not be true about table grapes. Some of these same producers believe that soils for wine grapes should not be full of nutrients. Adding compost or soil amendments that improve the soil, they believe, produces a grape without intense flavor typical to the variety; a poorer quality grape. I might point out that the flavor attributes of wine grapes is valued much higher than table grapes.

Roger Gehring and I at his orchard in Amargosa Valley, Nevada, several years ago when his vineyard was first established.

The verdict is still out but I believe that wine grapes struggle enough in our climate and soils without additional stress from poor soils and a lack of water. I have seen wine grapes grown in backyards in our climate without soil amendments. The soils around the home, in these cases, was “fill dirt” specified by the contractor. These did, generally, poorly. I have seen wine grapes grown in our climate in native soil, with no organic surface mulch such as wood chips. These did much better. I might point out that in cases like these the soil was a good agricultural desert soil, not “fill dirt”.

Wine grapes at the UNCE MG Orchard in North Las Vegas, Nevada showing 3 to 4 inches of wood chip surface mulch.

I have concerns about growing wine grapes in home landscapes if the home was surrounded with fill dirt. I believe this soil should be amended at the time of planting and the soil surface should be covered with an organic mulch, such as wood chips. I am concerned that applying rock mulch, like chat, to its surface will lead to future problems for wine grapes and many other landscape plants sensitive to poor soils and not intended for our climate.

Viragrow Delivers! : Rejuvenate Soil Mix is Rejuvinated by Mid-January!...

Viragrow Delivers! : Rejuvenate Soil Mix is Rejuvenated by Mid-January!...: Part of my consulting work is with a soil mix company in Las Vegas called Viragrow ( www.Viragrow.com ). When I started with this company ...

Fig Trees Growing in Mojave Desert vs So California are Managed Differently

Q. My Grandfather had fig trees in Southern California. They were the most incredible figs.  He would cut it back to a stump every winter. Every year it would have tons of fruit.  He would pick a lot of it early in order for the other fruit to get big and ripen. He claimed that planting fig trees close to a house caused the roots to grow under the house and cool the roots. His trees were huge.  In the desert of Moapa Valley, we have several fig trees that are old, but they are small, dry, the leaves are burned and they have been stumped, but only every 2 or three years, not every year like my Grandfather did. The trees are fed water with a slow drip system and there is mulch on the ground around the trees.  But the fruits are small and terrible! Many fruits just dry up and drop. They have no shade and are hit with direct heat. Suggestions?

Fig tree being grown without enough water will look like it doesn't have enough, sparse canopy, little new growth and small scorched leaves and will not produce fruit.

A.  Everything I have seen so far regarding figs and the production of fruit in the desert is focused on water. I have grown over 15 varieties of figs over a period of 25 years in the Mohave Desert and all of them have been productive. Problems with the figs are few. 

Dried Fruit Beetle

Dried fruit beetle

The first problem I encountered was the dried fruit beetle. This insect would climb inside the fruit of the figs and cause them to sour. The insect carried with it a bacterial infection of the fruit that caused this problem. If you look at the base of the fig fruit, there is an opening. This opening can be shut or open depending on the variety of fig. Those fig varieties with it open had a bigger problem with the dried fruit beetle than those with fruit openings that are shut. The simple solution is to make sure that fallen fruit and fruit still hanging on the tree after it was mature was collected and put into sealed containers. Dried fruit beetles reproduce in rotting, over mature fruit and spread into soft fruit.

Metallic Green June Beetle

The next problem I had is with the green metallic June beetle. They love fig fruits in particular the white or yellow types like Kadota. They attack and feed on this fruit but the presence is gone in a short time during the summer. I ignore them.

Green June Metallic Beetle

Fig Mosaic Virus

The last problem I have encountered is fig mosaic virus. Not a huge problem but it gets into all of the fig trees eventually. Probably spread by insects from tree to tree. Doesn't hurt the tree and it doesn't hurt the fruit much so I ignore it.

Fig Mosaic Virus

Lack of Water

The really big problem with figs growing in the Mojave Desert is lack of water. Fig trees are big users of water. The tree can grow and look fine with a moderate amount of water. But if there is not enough water the fruits will either drop from the tree early or they will be small and hard, not edible. 

If fig trees get enough water for new growth it is still possible they will not produce a decent crop of figs.

I have had many reports of people growing fig trees with small, hard fruit that are just simply lousy. Until I see something different, I believe this is a lack of water. You can apply small amounts of water daily and still not give the tree enough water for good fruit production. It is not a question of how often the tree is watered but more it is a question of how much water the tree is given in a single application. In the middle of summe middle trees up to 10 or 12 feet tall may require 90 - 100 gallons of water each week. I have found the best way to irrigate fig trees is by filling a basin beneath the tree that is 4 to 6 inches deep, 2 to 3 times each week during the summer. This can be done with the hose or with an irrigation bubbler. If drip emitters are used, there must be enough emitters and they must be on long enough to deliver this amount of water. This could be hours depending upon the number of emitters and their size.

Citrus Pruning Can Be Exception to Most Rules

Q. I have an older Meyer lemon that produces significant amounts of fruit most years.  However, I understand it should be pruned as a tree with one major trunk.  Mine has two trunks and each fork starts just a few inches off the ground. All trunks develop substantial sucker growth.  Should I eliminate all but one trunk or try to prune the suckers each year from all trunks?

Citrus with narrow crotch between two major "trunks"

A. There are always exceptions to rules. Your decision to break the “one trunk rule” depends on the "quality" of the "fork" you're talking about. In most cases, prune it to a single trunk when it is young with scaffold branches originating at about knee height. This may take a few years.You will have problems with that crotch later as it gets heavier and has to hold more fruit. Get rid of the inside one. I know it is large now but it will help later on. Also remove all sucker growth up to about your knees when it gets tall enough.

            There are two reasons for pruning fruit trees. One is for improving its structure. This is called “training”. The other is for improving fruit production. Citrus seldom needs pruning to improve fruit production but it does require pruning when it is young to improve its overall branching structure.

Good structure makes a tree sturdy enough to hold the weight of its limbs and fruit without breaking.

            If the fork does not have a wide angle between two trunks, approximately 60° or more, then remove the weaker of the two. If the angle is too narrow, over time the fork may not be strong enough to support the weight of older branches plus a load of fruit. Citrus, however, has stronger wood than most fruit trees in this regard. It is a judgement call.

Narrow crotch angles like the top right and left can be problems later on when the tree is expected to hold alot of weight.

            If you are not sure, send me a picture of this fork and I can give you a better opinion. Otherwise, if you think it's wide enough then don't worry about it. With time the sucker growth should stop or at least slow down. Remove suckers by pulling them in early spring rather than cutting them with a shears. If you pull on them when you first see them they will easily pop from the trunk or limb. If you wait too long, they will not.

Why Plants Get Confused Between Spring and Fall

Q. I have daffodils and Dutch iris bulbs shooting out new flowers this last November. Each year they produce leaves in the fall but never flowers. Are they confusing this time of year with spring?  What should I do?

A. This type of oddity, flowering at the wrong time of year, happens with some plants. Sometimes we see it in fruit trees like apples or pears and even grapes. Plants are more in tune to their environment than animals and these environmental clues can sometimes mislead them.

            Plants that originate from temperate climates, climates with seasons, use two major environmental “triggers” to gauge when to flower and produce fruit. These two environmental triggers are cool or cold temperatures and unbroken darkness for long periods. This works great in the spring.

            A primary mission of plants is to survive and produce offspring. Producing flowers will produce fruit that produces seed. Spring flowering, not fall flowering, is extremely important for temperate plants. Flowering in the fall does not give most plants enough time to produce the seed needed for reproduction.

            If one or both triggers are activated at the wrong time the plant may be “tricked” into thinking it’s spring. Every fall the length of nighttime mimics the length of nighttime in the spring. That’s one trigger. If there are unusually cold temperatures in the fall, then both triggers could activate flowering.

What to do? 

Remove the flowers when you see them. Otherwise, leave the plant alone. Flowering in the fall is not a big deal but fall fruit and seed production is a huge drain on plant food supplies needed for next spring.

Steps in Transplanting 15 Ft Pomegranate

Q. What are the proper measures when transplanting a mature 10-15 foot (3.3-5 m) tall pomegranate tree. Once transplanted, what to do that betters the chances of a successful transplant?

A. In a few words, take as much of the roots with it when you move it. That is tough to do by hand and rough on the tree regardless. Use a backhoe or, better yet, a hydraulically operated tree spade. There are a couple of arborists in Las Vegas who own tree spades who could do it for you. A tree spade is by far the best way to move a larger tree.

 See a tree spade in action

            Digging it up and moving it by hand is difficult unless it has been on drip irrigation or prepared for this move one year in advance. A successful transplanting moves as much of the roots as possible to its new location and at the right time of year.

            Now, December through February, is the right time of year. Drip irrigation keeps tree roots closer to the trunk. With rainfall, or a landscape irrigated by sprinklers, tree roots spread wherever there is water up to twice the height of the tree.

            This means a 10-foot tree might, ideally, spread its roots 20 feet from its trunk. Unfortunately, the most important roots to transplant with the tree are roots growing at the outer half of its root spread. That’s not possible.

            Older trees on drip irrigation, or irrigated with a depression around the trunk, have a better chance of survival because more of their roots are close to the trunk. You may not have many options open to you so let’s cover what to do, worst-case scenario.

Reducing canopy size for transplanting. Taken from LE Cook at http://www.lecooke.com/cms/tree-care/care-of-bareroot/358.html

            First, cut the limbs back so they are three or four feet tall.  You must remove at least 1/3 of the tree’s canopy when transplanting. Next, dig a vertical trench around the entire tree deep enough to sever all the roots in the top 18 to 24 inches. This trench should be at least 2 feet from the trunk.

            Dig the new hole for the tree. Dig it twice the width of the trenched hole and about 6 inches deeper. Mix compost with soil taken from the new hole. Use this soil mix when replanting the tree. I am not a huge fan of the product but add Super Thrive to the backfill. It’s relatively cheap insurance.

            Undercut the trenched tree so it moves freely back and forth. It would be perfect if all the soil attached to the roots was moved with the tree. But most of the soil will fall free from the roots in when it is moved. Not perfect but it’s okay.

            Lift the tree from the hole and cut any remaining roots with pruning shears (best) or very sharp shovel. If most of the soil fell from the roots during the transplant, get the tree into its new hole a watered as quickly as possible. Minutes of delay could prove important in the speed of its recovery.

        Begin backfilling around the roots with the soil mix you created and water from a hose at the same time. The soil should be a slurry and fill all of voids around the roots. Filling these soil voids is important.

            Equally important is to stake this tree so it’s roots are immobilized for one growing season. Construct a basin around the tree at least four inches deep and on top of the new hole. Fill this basin after transplanting three times over a period of 1 to 3 days. A good job results in a transplant planted solidly in the ground.

            Water once a week, filling the basin, for the first month. After the first month, water it as you would normally or as needed.