As professional gardeners and landscapers we are all out frantically trying to work our magic in the green spaces we care for. For some home owners who enjoy working in their yards and want to do things for themselves this can be a frustrating time of knowing there is so much to do but feeling unsure of just what should be getting done.
I thought I would go over the things that I am doing this time of year for people who have requested my help in their gardens. I will discuss the benefits of getting up close and personal with your plants, pruning, fertilizing, and the benefits of horticultural oil sprays. The timing of these activities will primarily be pertinent to people living in zones 5-7.
Spring clean-ups is the name of the game right now. I have my small hand cultivator, my hand rake, and my Felco pruners that were mentioned in my Hand Tool Line-Up post by my side at all times. In the perennial gardens I am going over every inch of every bed. I rake out any remaining leaves and clip off any dead growth on perennials from last season. We had some 80 degree days here this week and a lot of things are coming up so care must now be taken not to damage the new growth on plants like the herbaceous potentilla shown below.
When I have raked out all of the debris I go over the entire bed with a hand cultivator on my hands and knees. This is how you get to know your garden and learn what its’ needs are. Being face to face with your plants will allow you to discover things like: precious seedlings from last year’s foxglove or maybe verbascum that would otherwise have gotten raked up; insect infestations that may have been left until it was too late to prevent the damage; how to recognize the various species you have in the early stages of growth. Learning these these kinds of things is the key to a healthy spirited garden.
The other huge benefits of cultivating your beds is loosening up the soil allowing air back into the areas that have gotten compressed over the past year and eliminating small weeds before they get a chance to get deeply rooted.
Have you ever heard the saying “A farmer’s shadow is the best kind of fertilizer”? It is so true. I am always amazed at the transformation that takes place after I have thoroughly gone over a garden. It seems to look more alive in just a few hours!
It is not too late to prune many shrubs. Below is a list of things that I am typically pruning or shearing right now and how I treat them. I think pruning requires and sort of Zen approach. Take your time and prune lightly at first. You can always prune harder but of course you can’t reverse a hasty, severe cut. Stand back and look at your work as you go along. The shrub will begin to take on a nice, basic, pared down structure that is attractive when you are done. If the pruned shape is nice then the resulting growth probably will be too. If the pruning is hard and ugly then you will probably see something less than desirable when it flushes out.
Hydrangea paniculata and arborescens – These are: the Tardiva types, Pee Gee’s, Limelights, ‘Annabelles’. H. paniculata are very forgiving. You can prune these late summer, fall, winter, or spring. No matter how you prune them they will still bloom, but there are some things you can do to help obtain an attractive plant with a nice overall shape and abundant flowering. Some people have some very elaborate instructions but I try to keep it straight-forward and have achieved good results. Here are a couple of simple rules:
1) You can’t really change their size, just their shape. If the plant is too big you need to move it and put something smaller in like my all time new favorite the ‘Little Lime’ hydrangea shown here
2) If you prune Hydrangea paniculatas hard you will get big shoots with fewer, but larger flowers.
This is my least favorite way to prune these. The cuts in the picture below look hard and severe and they are!! Nothing is really achieved by this method because the new growth will shoot right back to the original height. Because the old wood structure and support has been pruned off they bend and arch under the weight of the huge flowers. You can see the old hard cuts that I consider unsightly and ineffective in this picture and then one year later where I pruned about 12 inches higher.
One year later:
3) If you prune lightly, and by this I mean taking off between 12 and 18 inches all around, you will get new shoots that are shorter( but again, back to the original size) with many more small sized flowers and a bushier, more dense, and I think more attractive appearance.
All of the Rest of the Hydrangeas
How is that for easy! This includes: Mopheads, Lacecaps, Oakleafs. All of these bloom on canes that were formed during the previous season. Some of the varieties like ‘Endless Summer’ will also bloom on growth forming this season but, I basically prune all of these hydrangeas using the following rules:
1) If possible I like to prune these in spring just before they are going to leaf out. The more old growth you leave for the winter and even for early spring the more protection you have to for the already formed flower buds. I have often pruned these too early in the spring only to have a hard frost kill the tips back even further from my cuts and thus loosing all of the flower buds.
2) I begin by pruning out any dead or broken canes. If the shrubs are a little older I begin removing the chunkiest, knobbiest clusters of canes making sure that there are some nice newer ones that will remain in that space to bloom. If you have a nice healthy hydrangea you will be removing about one third of the oldest canes to allow the plant to have the energy to grow new healthy ones for the coming year. When you make your cuts go down as close to the ground as you can without damaging the other canes. You are aiming for evenly distributed canes the are between 1 and 3 years old.
Here are some not very old Nikko Blue Hydrangeas before pruning:
Here they are after pruning:
3) I do not reduce the height of these unless I absolutely have to. Ideally in late spring after all hard frosts have passed you prune off any dead tips and leave the top with a nice domed shape. If your hydrangea is growing too tall you need to live with it or move it. They will always shoot back to that original height unless they are cut to ground in which case they will not bloom.
Buddleias– I cut these in half and leave them with a nice domed shape.
Knock-Out Roses– I cut these down to 18 inches and remove any dead canes. I used to prune these back about 1/3 like other shrub roses but now, at the advice of my friend Stephanie at Winland’s Complete Landscape Service here in Zanesville, I use some pretty tough love and prune down to between 12 and 18 inches.
Drift Roses– I will be doing a post on these particular roses in the future because I really like them as a filler on the edge of a shrub or perennial border. They are very low maintenance and I simply shear these taking off 1/3 to 1/2 of last year’s growth.
All other Roses– For all other rose types I can not improve upon what the American Rose Society has to offer on their site for all types of rose care. That is where I head for sound advice for pruning, making your own rose food, disease and insect control and winter protection ideas. Here is the link: The American Rose Society
Hypericum– I typically cut these back to 12-18 inches. Carefully cut into branches and look for signs of live tissue. These often appear dead but are not. Hypericum are sometimes treated as perennials in colder zones and can be cut to the ground if the canes all appear dead. It will come back!
Azaleas and Rhododendron– These should get pruned only if needed right after the flowers have gone by in late spring or early summer. Any hard pruning of larger branches or trunks should take place during winter but do not prune the tips at this time or you will lose the flower buds.
Ilex or Holly– If you have chosen holly so that you can enjoy the berries you only have one option. You must prune winter to early spring. Any later and you risk pruning the flower buds off and thus any potential for berries. Obviously pruning in the fall would remove any berries except on the male plants. These you will have planted as pollinators in the spring for the females and since males do not get berries you can prune them in the fall.
If you are just growing hollies for their evergreen quality then you can prune and shear as needed throughout the season. I prefer to leave them with a nice shape by the end of the fall so that in the spring, when they have that wonderful first flush of green growth, they are in good form and you don’t have to do anything to them. I like to enjoy that nice flush for as long as possible.
Ilex glabra or Inkberry– These are not really grown for the ink colored inconspicuous berries. They are a nice native filler evergreen but they can be tricky. These can be sheared as needed but again I try to have them ready in the fall for spring growth. These have a terrible tendency to get leggy and lose their bottom leaves. A few years back I learned that you can prune this plant down to 12 inches to rejuvenate it! I never would have guessed you could do this without killing the shrub but I have done it and it works. Inkberry are VERY slow to leaf out and become even slower to leaf out if you prune them this hard. Be prepared for a dead looking shrub until almost the end of June. Other than that the key with these is organic matter and moisture.
Boxwood– The fate of boxwood is very uncertain with Boxwood Blight beginning to take its toll. I do continue to plant some boxwood purchased from certain reputable nurseries but we would be wise to phase them out of our plans altogether for the time being. As for pruning I am only giving the simplest advice. I never shear or prune these in the spring. You will end up with irregular patches of new growth and they just don’t look nice. IF you desire a more formal look let them get their nice first full flush and then shear them by perhaps mid June. Then shear as needed. Similar to Holly I like to have these looking nice by late fall so that I don’t need to do anything to them that will interfere with that spring growth.
I prefer a more loose looking, hand clipped habit on boxwood and I encourage thinning for almost all varieties. Here is a fantastic link explaining the concept of thinning boxwood and all kinds of other great pruning tips at The Pruning School.
Lilacs– Lightly prune old fashioned Lilacs just after flowering. You can shape and shear these or just dead-head at this time. Lilacs do need to be rejuvenated and bloom best on younger wood up to about 6 years old. Any hard pruning should be done in winter but do NOT prune the tips or you will sacrifice flowers. To maximize flowering on Lilacs you should try to eliminate some of the oldest trunks by pruning them down to the ground. Each winter I recommend picking a couple of old trunks and sacrificing them to encourage new growth.
If you have ever-blooming Lilacs like ‘Bloomerang’ give them a light clipping after the first big bloom to help promote a better second bloom and then leave them alone until fall. These can be sheared and pruned in fall, winter or early spring.
Spireas, Physocarpus, Weigela – I generally shear all varieties of these these back by one third from the top and leave them with a nice rounded, domed shape. The larger varieties benefit by selectively thinning old wood for rejuvenation and a more attractive controllable shape.
I use compost as a first choice in beds and on lawns for fertilizing. I went over the benefits of this extensively in my post about Get Your Soil In Shape but compost is often not an option.
My first choice in commercial products is the Espoma line of fertilizers. They make one for every situation: Plant-tone, Rose-tone, Holly-tone, Lawn-tone etc. These are slow release fertilizers made of of varying percentages of things like bone meal, blood meal, cottonseed meal, alfalfa seed meal, and corn gluten. I fertilize perennial beds, shrubs, small trees, and lawns with these products. I often will use the Plant-tone for all areas so that I don’t have a bunch of different bags. For the most part I don’t think they are all that different from each other. There is a bit of marketing at work with all of those different types. Check your local garden center for these products and if they don’t have them request them! I often see this being sold only in 5 lb bags which I think is absurd. If you have very much of a lawn or garden you will need at least 25lbs.
I use about 1 cup of fertilizer for a small shrub and 2 cups for larger shrubs. I apply it in a band around the shrub in an area called the drip zone as you can see in the picture below. This is an area away from the base of the plant but just inside of the outer edges of the branches. This is where rain is likely to drip down and help carry the nutrients to the roots of the plant. Then I just work it into the top layer of the soil.
For lawns I highly recommend starting the season off with Espoma Organic Weed Preventer. This is made from 100% corn gluten. Corn gluten is a natural, non-toxic, broad-leaf weed preventer. It will not kill already existing weeds. It will prevent any new ones from germinating. It contains 9 % nitrogen so your lawn gets fertilized at the same time and it is completely safe for children and pets. That is a lot of good stuff in one product!
Because these Espoma products are slow release fertilizers they are safe to put down early. Fast-acting fertilizers, which I do not use, should not be put down until the soil temperatures have reached 50 degrees unless they are specially formulated for cool temperatures or you risk losing the nutrients to…get ready for one of those roll-your-eyes words that spell check doesn’t even know…denitrification. The sloppy definition of denitrification is a loss of the nitrogen due to a lack of oxygen in the soil, excess water, and microbial activity. It is just too early for plant’s roots to be able to take up the nitrogen and other minerals.
At Mission Oaks Gardens we make our own plant food mixes for rhodoendrons, azaleas, and the needier varieties of roses. A good recipe for Rhody food can be found at The American Rhododendron Society and the rose food we make can be found at the American Rose Society.
Spraying with horticultural oil is a critical part of my spring maintenance. Fruit tree growers have traditionally used something called dormant oil in their orchards for an early start on insect and disease control. Just like the name implies it is an oil used when the plants are dormant or before the buds break. Horticultural oil was developed as a much lighter weight oil that mixes with water and can be used during dormancy and during the growing season with out damaging the plants.
An oil spray in the spring can give you a jump on controlling all kinds of problems by doing the following: suffocating insect eggs and insects that it comes into contact with; suffocating fungus and mold spores that are remaining from the previous season; controlling fungus, mold and mildew that is actively growing or spreading. Some examples of the particular diseases you may be familiar with are: powdery mildew; black sooty mold; rust, and black spot.
The best time to apply horticultural oil is on a warm, non-windy, cloudy or partly sunny day. Applying the oil on fully opened leaves on a hot sunny day can cause the leaves to burn a bit. They will recover but it doesn’t look very nice. Ideally pick a time when the night-time temperatures will not be freezing for a few nights. Do not spray flowers or almost open flower buds.
Here are some of the pants I target during my spring application: all hollies; roses; euonymous; rhododendron; azaleas; boxwood; pieris; holly hocks; phlox. Conifers do not like to be coated with horticultural oil so take care not to allow it to drift onto them when you are spraying other plants.
I will talk more on using horticultural oil when we enter the warmer part of the growing season and about some useful formulations for disease control on various plants. For now I highly recommend a spring application. I order Horticultural Oil Insect Spray
made by Monterey from Amazon. The bottle comes with good instructions for how to mix depending on what you are spraying.