Adrian Higgins gave advice on tending your garden in the spring

Mar 20, 2014

Washington Post gardening columnist Adrian Higgins took questions on how to improve your garden in the spring.

Do old banana skins soaked in water, help roses?

Sorry, some technical issues. Spring is an hour away, so that has to get the sap moving. Banana skins have potassium, which helps roses, certainly. Epsom salts too encourage bushiness and flowering. I wouldn't use bananas skins in an area where you might have nasties like rats or racoons.

Here is a link to Adrian's story about how to send winter packing in your garden, from the cover of today's Local Living.

Our line of 40-yera old Azalaes were over hacked/pruned by amateur gardeners 2 Decembers ago; woody limbs were cut down. Except for mulching, we have done nothing and they bloomed less and are less "full bodied." My wife was in tears them about the hacking, but she seems more able to confront the mess and do something this spring. Any recommendation as to how to revive them? Thank you.

The first thing is to leave them, to allow a new branch structure to emerge. At that point, you can work on deleting some branches to restore a good form. Azalea buds form in late summer for the following spring. The best time to shape them is in May, after flowering. Do not think that someone who prunes your shrubs for money knows what they are doing, btw.

Adrian, I'm not convinced the piles of mulch we lay down each season in this area do much for the health of plants. What do you think of putting down a layer of well composted manure instead? Is that superior to other types of compost? Should I put a thin layer of mulch on top? I have mostly perennial/shrub beds. Thanks and can't wait for "real" Spring.

Repeated layerings of bark or wood mulch actually harm the soil because they produce high levels of manganese. We do it because we are programmed to do so each spring. It is much better for the soil biology to mulch with leaf mold or compost.   

Hello. I fogot to prune my knockout roses last fall. Is it too late to prune them now?

No. Even though roses are beginning to break bud, it's still ok to give them their hard winter prune.

Adrian - Twitter: A month or so ago on twitter you posted that you were starting your leek seeds, so I dutifully ran off bought some seed and started them myself. My question/request is, could you please keep doing that?!?! I'm never quite sure when to start certain things (especially things I haven't grown from seed before like leeks and onions), so having a window into your planting schedule would be very helpful! Hardening off: Do plants care about the temperature when you harden them off or is it all about the intensity of the sun's rays? Obviously you don't want to harden off seedlings when it's below freezing, but what about 45 degrees? I have some broccoli plants that need to be hardened off but when I leave for work, it's in the low to mid 40s (today) and by the time I get home, the temperature is 15 or 20 degrees warmer but I've lost my sun. So my question is will I damage the plants by putting them out when it's cool (40s)? If the answer to that question is, "it doesn't matter", then does that hold for every plant or just the cool season plants? If I can do it for broccoli and lettuce, can i also do it for tomatoes and peppers? Thanks!

OK. Generally, you harden off plants by putting them outside for a week but bring them indoors at night. If a day is really frigid, say below 40, keep them indoors. It is best to put them out in an area that is shaded and protected from wind, say, against an east facing wall or in a screened porch. I have not hardened off yet anything, that will probably be in about a week or more from now. I am starting my tomatoes and peppers now under lights, a bit late, but everything is late this year.

I bought lettuce and strawberry plants from HD a few weeks ago but since it has been so cold with threats (and actual) snow, I've been waiting to plant them. They're starting to wilt. When should I be ok with putting them in the ground?

Harden them off and stick em in. Bit early for lettuce. Just because a merchandizer makes stuff available doesn't mean the timing is right. Beware of basil and tomato plants until mid to late April at the earliest.

I have coneflower, sedums, Arizona blue star and other dreadful looking perennials in my front yard. Is there a good resource I can consult that would tell me when to cut these plants back to the ground? Or maybe I should just leave them as they are?

You could cut them back now, but keep an eye on them: They may be winter killed. You can check by carefully moving some soil around the crown to look for vital buds.

Could you suggest a variety of mahonia that might do well in a north-facing balcony container ?

I've just written that the marginally hardy Soft Caress has taken a hit this winter. The Mahonia bealei is rather coarse and scary, though a nice and fragrant early bloomer.  M. aquifolium is softer, but would need some shade.

I am trying to cultivate a small garden but I am having a hard time ridding it of wild onions. I have been digging each little bulb up by hand but they always seem to reappear! Weed killer does not work.

You either have to be really diligent -- use a fish tail weeder -- or glyphosate will work better if you smash and bruise the foliage first.

We've a small hedge of these in semi-shade.... they bloom in the winter (although the few flowers are usually almost at ground level) and do need to be trimmed back... but how? When? Or not at all? Thank you!

I've heard that sansanquas have been widely killed this winter. I would wait to see that it is sprouting before doing any pruning at the moment.

Hello Adrian. My neighbor and I share a row of mature and scraggly azaleas that provide little beauty but a soft separation between our front yards that we both appreciate. After trying for a couple of years to revive them with pruning, we've decided to pull them out and start fresh. The question is, with what? Theoretically, mountain laurels would be what we want: glossy dark green foliage year-round, manageable size, lovely flowers. Privacy, but friendly privacy. But the site is exposed, to long days of sun and winter winds. And then there's the challenge of getting these plants happily established. Any suggestions for other plants we should consider?

Mountain laurels are notoriously difficult to establish. I would look into some of the viburnums, both evergreen and deciduous. If you have rich, acidic soil that you can water during droughts, you might also consider some blueberry bushes. 

My chindos, planted just last fall, are looking dreadful. Do I cut them back or wait for spring to hopefully revive them? Spring is coming....isn't it?

Chindo is a tall evergreen viburnum that is marginally hardy here, and I wonder if this winter has actually put paid to them. Again, wait to see how and if the plant regenerates before picking up the shears.

Should I find a way to add more worms to my garden, flower beds, and yard? I know the red wigglers are great for my compost pile but is it worth it to buy some to add to other places? If so, other than a bait shop where can I buy them?

I believe red wigglers don't work in our soil, they're good for compost piles. The best way to attract worms is not to buy any, but to incorporate leaf mold into the soil. They will show up.

Welcome back to Adrian (and, we hope, spring). Our heavily wooded lot is overgrown with ivy and I would like to make some headway against it in order to plant something worth looking at. Back when I owned a lawn mower I used to run that over the ivy and then dig up the roots. But I got rid of the last of the grass-and therefore the lawn mower-years ago. Can you suggest a method of getting rid of ivy that doesn't involve herbicides as I don't want to damage the tree roots underneath?

Thank you. It's great to be back here. English ivy is actually quite easy to remove as it runs along the woodland floor. (Up trees is a bit harder, but still achievable). The snows will make the soil nice and moist, and this will allow the vines to yield. I use very thick leather work gloves and tug up most of it. The stubborn stuff is removed with a garden fork or a mattock.

No question just yet. Just wanted to say, I love your chats and wish they will have you do more.

Merci!

Do you use/recommend heating mats for getting seeds started? Our basement is the only place I have room to start seeds but it's been pretty chilly down there this winter. I sit the flats on old car floor mats and wrap a towel around them, but I'm not sure how much good that does.

Heat mats warm the soil, speed germination and encourage good root development. They are great for lots of things but I have found only really necessary for peppers. (Perhaps eggplant too, but I refuse to grow eggplants. I don't see the point of eggplant).

I appreciate your column so much! In DC there must be many patio gardeners like me with a balcony or large patio who do container gardening. Many such places have mostly shade, as does ours. Last year we found by accident coleus plants do very well. Impatiens, if you can find them do okay. Can you make more suggestions? Would things like ferns or hellebores survive our winters outdoors in pots? Thanks for your help!

I wouldn't grow impatiens until they have found a resistant strain to powdery mildew. Coleus comes in such a range of foliage ornament, that you could almost have a whole garden of them and not be tired. Hellebores can look beautiful in containers, though more as an early spring display, they are perennials of course. You could also try some caladiums, cannas and salvias, which will draw hummingbirds.

How and when to prune smoke brush that has gotten too big for space? Of course want to still promote fantastic blooms.

You could prune them back hard now, and they will grow vigorous and large leafed stems, but you won't have a flower show.  Some gardeners cut them back hard every other year, so at least they have bloom in the second year.

I have several raised beds that have compressed a lot over the past years. Last year I manually tilled (with a shovel) in more soil & amendments. I'm not sure it helped; it certainly was a lot of work and was difficult on the perennials. What should I be doing to keep it from compressing? How do I amend the soil?

Soil naturally compacts over time. The more clay (and flood) the more it will compact. The greatest source of compaction is human feet (other than construction equipment, of course). In beds that are permanent, you can again lay a layer of leafmold in the fall that the worms etc. will incorporate into the soil. If this is done annually, the whole structure of the soil will improve dramatically in time. In my vegetable beds, I spend late winter, early spring digging and amending the soil -- as long as it is not waterlogged. I add organic matter and sand -- I pile it on and then use a garden form to dig it in. I work backwards so that I'm not treading on the freshly dug soil. If you need to improve a perennial bed, the best time to do this is in the early fall, when you can dig and divide the perennials as part of the process.

A report on the radio said that there are only 5 additional days between the first and last frosts. I've been watching carefully for most of my 63 years. I'm a very serious gardener (30 acre farm in Stafford, grow mostly berries and veggies). I have found that, in general, the last first frost in the spring is about 3-4 weeks earlier and the last true killing frost occurs almost a month later in the fall.

I think you're right. The average last frost date in DC used to be April 15, but for years, we didn't have a frost after early March. Outside the Beltway was a different matter. I don't know about this year, it's sort of like a return to the old winters, which is good in a way in that it doesn't encourage early blooming and frost zapping. I think apple and peach growers can't really sleep peacefully until early May, whatever the year.

Do you have any suggestions of where a complete novice should start with planting pots or boxes on a afternoon-sun-lit balcony? I'd love to grow herbs and some vegetables if possible. I'm thinking a few window boxes would work on the balcony railings for flowers, too. Many thanks.

Afternoon sun is good, in that you can grow tomatoes and other heat and sun loving things. The downside is that containers dry out quickly in summer. There are ways to address this, principally by having the largest containers you can manage. Clay pots wick away the moisture, so some gardeners line the inside of them with bubble wrap to reduce this effect. Window boxes are notoriously difficult in a hot climate like ours, they dry out like mad and plants can die over one neglected weekend.

New gardener here. I'm starting my vegetable garden this year and I ordered all my plants online. They ship when it's time to plant them. My onions came when the ground was still covered in snow from a few weeks ago. My potatoes and strawberries came this past Monday - when the ground was covered in snow. It's supposed to be nice this weekend so I'd like to get them in the ground, but I hear more talk of snow next week. Will my plants survive, or should I try to wait before planting?

Make sure the soil is cultivated etc before planting. Before planting the onions, don't water them, store them dry. You could plant them now, along with the strawberry plants. Some gardeners will presprout the potatoes before planting, this reduces the risk of rotting in the soil. The process is called chitting: you can look it up online. I've also become a fan of not cutting up seed potatoes, but chitting and planting them whole.

I had laid down some grass seed right before our big recent snow. Has this cold weather ruined my efforts or can seed survive a freeze?

It'll be ok, slow to germinate. Count on having to rework seeded areas in September.

I have little to no outside space, but do have access to a second-floor balcony that gets quite a bit of sun. I bought an elevated planter that is 19"D x 44 9/10"W x 29 4/5"H and would like to plant some veggies and herbs in it. Because it's not terribly large, what space-saving veggies would work well? I was thinking maybe Tumbling Tom tomatoes and lettuces? Maybe some herbs? If only I had a place to plant berries, I'd be a happy lady. :) (this is the planter: http://www.bjs.com/keter-raised-garden-bed.product.241654?dimId=2001667)

I would sow some mesclun mixes now for harvest through May, and then have some pepper plants ready to stick in. They are really productive in a small area. Tomatoes need a lot of supporting. If you do try a tomato, pick a determinate type, which will stay bushier.

We have a young coral-bark maple in the front yard that the deer have feasted on regularly. In addition last October in the middle of the night, a young buck smashed his antlers agressively against the tree and stripped off most of the bark. Without the bark, is the tree a goner now? Any suggestions for a replacement tree? It will be a focal point and must be able to take direct sun. I loved that coral-bark maple. Thank you very much.

Deer love to rub their antlers on tree trunks that are about two inches in diameter and smooth -- young maples are perfect for that. Whatever you replace it with, I would put some guard around the trunk against rutting. I love paperbark maples, stewartias, and redbuds.

It's a pain to have to haul all those seedlings in little containers indoors at night, then back out the next morning. Then one year I discovered that if I set them all in a wheelbarrow, the job is so much faster.

Great idea. Another tip: If you're getting creaky in the joints, replace that heavy old wheelbarrow with a smaller one. Well, I have to dash, but will be back here regularly during the spring. Thanks for all your questions.

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Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his recent story on seeds for the home gardener and follow him on Twitter.
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