Using Cover Crops in Your Home Garden

Alyssum crop cover flowering

Cover crops and green manures are common in larger scale agriculture, but there is no reason why you can’t adapt and adopt the same sustainable concept on a smaller scale for your home garden. They’re a helpful option for improving soil quality, attracting beneficial insects, and feeding nutrients back into your garden (or your compost bin).

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Benefits of Using Cover Crops

A cover crop is a plant (or plants) which is planted primarily for managing an issue or improving the conditions of your garden. It’s a more common practice for agriculture and larger lifestyle properties, can easily be adopted on a smaller scale at home. Cover crops can be used for many different purposes, depending on the type of plant and the gardener’s plans, including to:

  • Improve soil quality (mulched organic matter, captured nitrogen)
  • Break up compacted soil (deep rooted crops)
  • Reduce erosion (rain, runoff, and/or wind)
  • Suppress weeds
  • Increase beneficial soil microorganisms
  • Control pests and disease
  • Attract beneficial insects

The garden at our current new home has been both loved and neglected over its many years. It has great potential, but isn’t in great condition and patches of soil are actually hydrophobic. Investing soil health has been a big part of our preparation for re-planting. I recently shared some of the DIY soil test techniques that we used to check conditions. Cover crops are one of the tools we’re using to help improve our soil for replanting. 

Selecting Suitable Cover Crop Plants

The right cover crop for your garden will depend on the specific needs of your garden and the conditions in which you’ll be growing.  Here are some factors to consider when planning:

  • Garden needs. Are you trying to address a specific issue or improvement? Not all crops serve the same function for improving or amending soil.
  • Follow-on planting and/or rotation plans. Consider the specific needs of any planned follow-on plantings in terms of nutrients, schedule, diseases or pests, etc.  
  • Duration of cover. Are you planting for the short-term, medium-term, or indefinitely? Do you plan to mulch or naturalise?  If you’re mulching the cover crop and then planting something else, you might want to avoid prolific spreaders, lest your welcome cover become an unwanted weed.
  • Crop time. If you aren’t naturalising the cover, you’ll get maximum benefit from most plants if they are grown until just before seed set, then mulched. What cover plants might suit your seasonal conditions and planting schedule?
  • Decomposition time. If you are mulching in-situ, breakdown time can be particularly important. Some plants decompose faster than others.  If time is of the essence, a tender plant may be better suited even if it’s not as effective at amending soil as sturdier alternatives.
  • Growing season(s), local climate and conditions. As with any plant, choosing suitable varieties for your conditions will give you a better chance of health and growing success.
Lupin plant in flower

Plant Options for Cover Crops

If you aren’t trying to address a specific issue or need, almost any type of plant can be used for general purpose crop cover. Beware of planting anything that has runners, difficult to clear roots, or seeds prolifically throughout it’s cycle, unless you want it to naturalise into a semi-permanent or permanent groundcover or underplanting. Avoid any plants listed as locally invasive species. 

If you’re not sure what might grow in your specific climate or cover cropping season, check growing guides or consult a local seed stockist or nursery. They’ll also sell seeds for common cover crops in your area. Suppliers usually sell the types of seeds used as crop covers in bulk.

Commonly Used Seasonal Cover Crops

Some of the most popular cover crops for commercial agriculture and other large scale growing applications include the following:

  • Alfalfa 
  • Beans 
  • Clover
  • Peas
  • Lentils 
  • Lupin 
  • Mustard
  • Vetch

Cover Crop Uses and Considerations

Alfalfa is usually grown as rapidly composting green manure. It’s cut and tilled back into the soil to add organic matter and nutrients before replanting. Many grasses, grains, and similar plants are easy growing groundcovers and grow good biomass to mulch, but can be difficult to fully clear if you’re a home gardener. Not ideal when you’re ready to replant your garden beds. 

Beans, peas, lentils, lupins, vetch, and other legumes are nitrogen fixing plants, and also help through composting as a green manure to add organic matter and nutrients back into the soil. These are easy popular plants for home gardeners, and many are also edible, if you let them grow long-enough to produce pods before cutting and composting.

Clover is also a nitrogen fixer, soil breaker, and a great host for beneficial soil fungi. But it’s a mental struggle for many gardeners, myself included, to think about adding clover when we spend so much time weeding unwanted clover… Red clover is the common variety for crop covers and pasture mixes. If you’re brave enough to experiment with this as a crop cover, you’ll want to make sure it doesn’t get past flowering before cutting and composting.

Mustard is a green manure crop cover (or companion plant) that gets a special mention as a soil-clensing natural biocontrol to help ward off soil pests, like wireworm. It’s an easy grower with deep soil-conditioning roots and good biomass. Just don’t let it go to seed unless you want it to naturalise…or to make your own mustard! I’m growing it in our kumara and potato beds, and will collect photos for a future post update. Other types of brassicas can also be used as cover crops (or winter rotation edibles), just with less of a soil-clensing effect.

Pea blossoms in the rain

Growing and Using Cover Crops in the Garden

Seeding a Cover Crop

Crop covers are typically direct seeded. They’re usually low maintenance plants, requiring little care or effort until you are ready to compost them. Since cover crops are commonly used for larger agricultural applications, some might not be the prettiest plants for your home garden. But there are lots of options that you can pick and choose from to suit different needs, including aesthetics if looks are important for the location you’re covering. It might just require a little bit of compromise between nutrient value, function, production, or form.

Controlling Spread

Since they’re usually plants that are easy to direct sow, they’re prone to self-sowing if allowed to set seed. That can have lingering home garden issues. If you don’t want your cover crop to self-sow (whether for maximum nutrient benefit or to control invasive growth), you can trim it, mow it down, or till it into the soil before it starts flowering or setting seed.

Composting for Rotation

Whenever you’re ready to incorporate it back into the soil as compost, you can simply turn or till the plants completely into your garden soil. Ideally, this should be a month or more before you intend to replant the area so things have time to decompose. 

You can also cut and shift it to compost elsewhere, if that’s more suitable for your needs and schedule. You won’t get the in situ compost boost if that was the goal. But if not, no prob! If you already have an ongoing rotation of compost available in your garden, you’ll still be able to feed the beds with that instead. Perhaps with a lot less digging effort, too.

Naturalising Cover Crops

Alternatively, you might want to just let nature take its course and allow your crop cover to self-sow and naturalise longer term. This works well with cottage gardens or free-style underplantings that are intended to draw pollinators to fruiting trees and other special areas or to protect the soil in other ways. It’s not a typical cover crop as such, but we’re loving low-growing underplantings as companions and living mulches in our home garden. Thyme and strawberries are current favourites. Check out our companion planting post for more ideas! 

Close up of a bee on white flowering thyme plant

Crop Cover Experiments and Experiences in Our Garden

Objectives and Considerations

When we first started using cover crops (and this post was first written) our primary crop cover objectives were to improve soil quality, control dust, and support beneficial insects while we get ready to replant the garden. Because of the urban garden situation, looking good was a plus as well. With our cat and dogs, it also had to be pet-friendly and robust. 

Lupin

For our fence/retaining wall border (a significant problem area), we used lupin. Lupins are a leguminous crop cover, adding nitrogen and accumulating phosphorous.  Their long taproot helps to loosen and aerate the soil, which was great in our little patch of trouble. We purchased a non-invasive seed variety, as lupins can be a problem plant in some parts of New Zealand.

They were tolerant of the difficult growing conditions and attractive enough for border planting, especially in an area that isn’t highly visible. The location was behind a rear fence and out of bounds for our pets, which is good since lupin leaves and seeds can be toxic. The flowers also draw pollinators and beneficial insects, which is a nice bonus. If I was replanting that area (as I may in the future), I would probably include other seeds for mixed crop cover planting.

Sweet Alyssum

We used sweet alyssum on bare soil throughout all of the old main garden beds. It was used as a placeholder while we renovated and planned future permanent plantings.  It’s a fast-growing, low (20-30cm) pretty white flowered plant and can be grown all year round in our climate.

Alyssum can be seeded densely to protect soil and suppress weeds, and is great for drawing in beneficial insects. It’s not a usual cover crop, and is more commonly used as an underplanting in orchard settings or elsewhere as a companion plant. It isn’t a great option for adding nutrients and it’s prone to self-seeding, but it was right for us in this particular instance. It looks great(much better than dusty hydrophobic dirt) and was pet-safe, both key considerations. 

As a word of caution, I mowed ours several time to avoid naturalisation, but it still self-seeded. Because it’s relatively pretty little garden plant (unlike some of the more beneficial cover crops), I was ok with that. Be careful though, as it can also spread into paths and other garden spaces. 

Transitioning into Our New Garden

Since this post was first written and shared, we’ve moved yet again. We’re still using cover crops in different forms, depending on the season. They’re being used simply as companion plants or off-season placeholders here at present, which is still a great value-add for the garden, our compost, and the local pollinators and other beneficial insects. And yes, we still have some alyssum self seeding away here at the new place, too.  Haha!

Nature hates a vacuum, and I’d much rather fill empty off-season beds and other bare patches with plants than have the weeds take over. Or the neighbours cats decide it’s a great place for pooping. Naturalised living groundcovers, as noted above, are a new favourites. We’re also using new seasonal cover crops in the edible garden beds through our winter, including kale, daikon, mustard, and more. I’ll update this post with more photos and details in the future.

Using Cover Crops in Your Home Garden

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